Hydrogen fuel cell: description, characteristics, operating principle, photo. Hydrogen energy: the beginning of a long journey
A fuel cell is a device that efficiently produces heat and direct current through an electrochemical reaction and uses a hydrogen-rich fuel. Its operating principle is similar to that of a battery. Structurally, the fuel cell is represented by an electrolyte. What's so special about it? Unlike batteries, hydrogen fuel cells do not store electrical energy, do not require electricity to recharge, and do not discharge. The cells continue to produce electricity as long as they have a supply of air and fuel.
Peculiarities
The difference between fuel cells and other electricity generators is that they do not burn fuel during operation. Due to this feature, they do not require high-pressure rotors and do not emit loud noise or vibration. Electricity in fuel cells is generated through a silent electrochemical reaction. The chemical energy of the fuel in such devices is converted directly into water, heat and electricity.
Fuel cells are highly efficient and do not produce large amounts of greenhouse gases. The emission product during cell operation is a small amount of water in the form of steam and carbon dioxide, which is not released if pure hydrogen is used as fuel.
History of appearance
In the 1950s and 1960s, NASA's emerging need for energy sources for long-term space missions provoked one of the most critical challenges for fuel cells that existed at that time. Alkaline cells use oxygen and hydrogen as fuel, which are converted through an electrochemical reaction into byproducts useful during space flight - electricity, water and heat.
Fuel cells were first discovered at the beginning of the 19th century - in 1838. At the same time, the first information about their effectiveness appeared.
Work on fuel cells using alkaline electrolytes began in the late 1930s. Cells with nickel-plated electrodes under high pressure were not invented until 1939. During World War II, fuel cells consisting of alkaline cells with a diameter of about 25 centimeters were developed for British submarines.
Interest in them increased in the 1950-80s, characterized by a shortage of petroleum fuel. Countries around the world have begun to address air and environmental pollution in an effort to develop environmentally friendly ways to generate electricity. Fuel cell production technology is currently undergoing active development.
Operating principle
Heat and electricity are generated by fuel cells as a result of an electrochemical reaction involving a cathode, anode and an electrolyte.
The cathode and anode are separated by a proton-conducting electrolyte. After oxygen enters the cathode and hydrogen enters the anode, a chemical reaction is started, resulting in heat, current and water.
Dissociates on the anode catalyst, which leads to the loss of electrons. Hydrogen ions enter the cathode through the electrolyte, while electrons pass through the external electrical network and create a direct current, which is used to power the equipment. An oxygen molecule on the cathode catalyst combines with an electron and an incoming proton, ultimately forming water, which is the only product of the reaction.
Types
The choice of a specific type of fuel cell depends on its application. All fuel cells are divided into two main categories - high temperature and low temperature. The latter use pure hydrogen as fuel. Such devices typically require processing of primary fuel into pure hydrogen. The process is carried out using special equipment.
High temperature fuel cells don't need this because they convert fuel at elevated temperatures, eliminating the need for hydrogen infrastructure.
The operating principle of hydrogen fuel cells is based on the conversion of chemical energy into electrical energy without ineffective combustion processes and the transformation of thermal energy into mechanical energy.
General concepts
Hydrogen fuel cells are electrochemical devices that produce electricity through highly efficient "cold" combustion of fuel. There are several types of such devices. The most promising technology is considered to be hydrogen-air fuel cells equipped with a proton exchange membrane PEMFC.
The proton-conducting polymer membrane is designed to separate two electrodes - the cathode and the anode. Each of them is represented by a carbon matrix with a catalyst deposited on it. dissociates on the anode catalyst, donating electrons. Cations are conducted to the cathode through the membrane, but electrons are transferred to the external circuit because the membrane is not designed to transfer electrons.
An oxygen molecule on the cathode catalyst combines with an electron from the electrical circuit and an incoming proton, ultimately forming water, which is the only product of the reaction.
Hydrogen fuel cells are used to manufacture membrane-electrode units, which act as the main generating elements of the energy system.
Advantages of Hydrogen Fuel Cells
Among them are:
- Increased specific heat capacity.
- Wide operating temperature range.
- No vibration, noise or heat stain.
- Cold start reliability.
- No self-discharge, which ensures long-term energy storage.
- Unlimited autonomy thanks to the ability to adjust energy intensity by changing the number of fuel cartridges.
- Providing virtually any energy intensity by changing the hydrogen storage capacity.
- Long service life.
- Quiet and environmentally friendly operation.
- High level of energy intensity.
- Tolerance to foreign impurities in hydrogen.
Scope of application
Due to their high efficiency, hydrogen fuel cells are used in various fields:
- Portable chargers.
- Power supply systems for UAVs.
- Uninterruptible power supplies.
- Other devices and equipment.
Prospects for hydrogen energy
The widespread use of hydrogen peroxide fuel cells will only be possible after the creation of an effective method for producing hydrogen. New ideas are required to bring the technology into active use, with high hopes placed on the concept of biofuel cells and nanotechnology. Some companies have relatively recently released effective catalysts based on various metals, at the same time information has appeared about the creation of fuel cells without membranes, which has made it possible to significantly reduce the cost of production and simplify the design of such devices. The advantages and characteristics of hydrogen fuel cells do not outweigh their main disadvantage - high cost, especially in comparison with hydrocarbon devices. The creation of one hydrogen power plant requires a minimum of 500 thousand dollars.
How to assemble a hydrogen fuel cell?
You can create a low-power fuel cell yourself in a regular home or school laboratory. The materials used are an old gas mask, pieces of plexiglass, an aqueous solution of ethyl alcohol and alkali.
The body of a hydrogen fuel cell is created with your own hands from plexiglass with a thickness of at least five millimeters. The partitions between the compartments can be thinner - about 3 millimeters. Plexiglas is glued together with a special glue made from chloroform or dichloroethane and plexiglass shavings. All work is carried out only with the hood running.
A hole with a diameter of 5-6 centimeters is drilled in the outer wall of the housing, into which a rubber stopper and a glass drain tube are inserted. Activated carbon from the gas mask is poured into the second and fourth compartments of the fuel cell housing - it will be used as an electrode.
Fuel will circulate in the first chamber, while the fifth is filled with air, from which oxygen will be supplied. The electrolyte, poured between the electrodes, is impregnated with a solution of paraffin and gasoline to prevent it from entering the air chamber. Copper plates with wires soldered to them are placed on the coal layer, through which the current will be drained.
The assembled hydrogen fuel cell is charged with vodka diluted with water in a 1:1 ratio. Caustic potassium is carefully added to the resulting mixture: 70 grams of potassium dissolve in 200 grams of water.
Before testing a hydrogen fuel cell, fuel is poured into the first chamber and electrolyte into the third. The reading of a voltmeter connected to the electrodes should vary from 0.7 to 0.9 volts. To ensure continuous operation of the element, spent fuel must be removed, and new fuel must be poured through a rubber tube. By squeezing the tube, the fuel supply rate is adjusted. Such hydrogen fuel cells, assembled at home, have little power.
FUEL CELL
electrochemical generator, a device that provides direct conversion of chemical energy into electrical energy. Although the same thing happens in electric batteries, fuel cells have two important differences: 1) they function as long as the fuel and oxidizer are supplied from an external source; 2) the chemical composition of the electrolyte does not change during operation, i.e. The fuel cell does not need to be recharged.
See also BATTERY SUPPLY .
Operating principle. The fuel cell (Fig. 1) consists of two electrodes separated by an electrolyte, and systems for supplying fuel to one electrode and oxidizer to the other, as well as a system for removing reaction products. In most cases, catalysts are used to speed up a chemical reaction. The fuel cell is connected by an external electrical circuit to a load that consumes electricity.
In the one shown in Fig. In a fuel cell with an acidic electrolyte, hydrogen is fed through a hollow anode and enters the electrolyte through very fine pores in the electrode material. In this case, hydrogen molecules decompose into atoms, which, as a result of chemisorption, each giving up one electron, turn into positively charged ions. This process can be described by the following equations:
Hydrogen ions diffuse through the electrolyte to the positive side of the cell. Oxygen supplied to the cathode passes into the electrolyte and also reacts on the surface of the electrode with the participation of a catalyst. When it combines with hydrogen ions and electrons that come from the external circuit, water is formed:
Fuel cells with an alkaline electrolyte (usually concentrated sodium or potassium hydroxides) undergo similar chemical reactions. Hydrogen passes through the anode and reacts in the presence of a catalyst with hydroxyl ions (OH-) present in the electrolyte to form water and an electron:
At the cathode, oxygen reacts with water contained in the electrolyte and electrons from the external circuit. In successive stages of reactions, hydroxyl ions are formed (as well as perhydroxyl O2H-). The resulting reaction at the cathode can be written as:
The flow of electrons and ions maintains the balance of charge and matter in the electrolyte. The water formed as a result of the reaction partially dilutes the electrolyte. In any fuel cell, some of the energy from a chemical reaction is converted into heat. The flow of electrons in an external circuit is a direct current that is used to do work. Most reactions in fuel cells produce an emf of about 1 V. Opening the circuit or stopping the movement of ions stops the fuel cell from operating. The process occurring in a hydrogen-oxygen fuel cell is, by its nature, the reverse of the well-known electrolysis process, in which water dissociates when electric current passes through the electrolyte. Indeed, in some types of fuel cells the process can be reversed - by applying a voltage to the electrodes, water can be decomposed into hydrogen and oxygen, which can be collected on the electrodes. If you stop charging the cell and connect a load to it, such a regenerative fuel cell will immediately begin to operate in its normal mode. Theoretically, the dimensions of a fuel cell can be as large as desired. However, in practice, several cells are combined into small modules or batteries, which are connected either in series or in parallel.
Types of fuel cells. There are different types of fuel cells. They can be classified, for example, by the fuel used, operating pressure and temperature, and the nature of the application.
Hydrogen fuel cells. In this typical cell described above, hydrogen and oxygen are transferred to the electrolyte through microporous carbon or metal electrodes. High current density is achieved in elements operating at elevated temperatures (about 250 ° C) and high pressure. Cells that use hydrogen fuel, produced by processing hydrocarbon fuels such as natural gas or petroleum products, are likely to see the most widespread commercial use. By combining a large number of elements, you can create powerful energy systems. In these installations, the direct current generated by the elements is converted into alternating current with standard parameters. A new type of elements capable of operating on hydrogen and oxygen at normal temperatures and pressures are elements with ion-exchange membranes (Fig. 2). In these cells, instead of a liquid electrolyte, a polymer membrane is located between the electrodes, through which ions pass freely. In such elements, air can be used along with oxygen. The water formed during operation of the cell does not dissolve the solid electrolyte and can be easily removed.
Elements for hydrocarbon and coal fuels. Fuel cells, which can convert the chemical energy of widely available and relatively inexpensive fuels such as propane, natural gas, methyl alcohol, kerosene or gasoline directly into electricity, are the subject of intense research. However, no significant success has yet been achieved in the creation of fuel cells operating on gases obtained from hydrocarbon fuels at normal temperatures. To increase the reaction rate of hydrocarbon and coal fuels, it is necessary to increase the operating temperature of the fuel cell. Electrolytes are molten carbonates or other salts, which are enclosed in a porous ceramic matrix. The fuel is "split" inside the cell to produce hydrogen and carbon monoxide, which support the current-generating reaction in the cell. Elements operating on other types of fuel. In principle, reactions in fuel cells do not have to be oxidation reactions of conventional fuels. In the future, other chemical reactions may be found that will allow efficient direct generation of electricity. In some devices, electrical energy is obtained by oxidizing, for example, zinc, sodium or magnesium, from which consumable electrodes are made.
Efficiency. Converting the energy of conventional fuels (coal, oil, natural gas) into electricity has until now been a multi-stage process. Burning fuel to produce the steam or gas needed to run a turbine or internal combustion engine, which in turn drives an electric generator, is not a very efficient process. Indeed, the coefficient of energy utilization of such a transformation is limited by the second law of thermodynamics, and it is unlikely to be significantly raised above the existing level (see also HEAT; THERMODYNAMICS). The fuel energy utilization factor of the most modern steam turbine power plants does not exceed 40%. For fuel cells there is no thermodynamic limitation on energy efficiency. Existing fuel cells convert 60 to 70% of the fuel's energy directly into electricity, and fuel cell power plants using hydrogen from hydrocarbon fuels are designed to be 40 to 45% efficient.
Applications. Fuel cells may become a widely used source of energy in transport, industry and households in the near future. The high cost of fuel cells has limited their use to military and space applications. Anticipated applications for fuel cells include portable power sources for military applications and compact alternative power sources for solar-powered low-Earth satellites in long shadow orbits. The small size and weight of fuel elements made it possible to use them in manned flights to the Moon. Fuel cells aboard the three-person Apollo spacecraft were used to power onboard computers and radio communications systems. Fuel cells can be used to power equipment in remote areas, for off-road vehicles, such as in construction. When combined with a DC electric motor, the fuel cell will be an efficient source of vehicle propulsion. Widespread use of fuel cells requires significant technological progress, reduction in their cost and the ability to effectively use cheap fuel. If these conditions are met, fuel cells will make electrical and mechanical energy widely available throughout the world.
See also ENERGY RESOURCES.
LITERATURE
Bagotsky V.S., Skundin A.M. Chemical current sources. M., 1981 Crompton T. Current sources. M., 1985, 1986
Collier's Encyclopedia. - Open Society. 2000 .
See what "FUEL CELL" is in other dictionaries:
FUEL CELL, ELECTROCHEMICAL CELL for directly converting the oxidation energy of fuel into electrical energy. Suitably designed electrodes are immersed in the ELECTROLYTE and fuel (eg hydrogen) is supplied to one... Scientific and technical encyclopedic dictionary
A galvanic cell in which the redox reaction is maintained by a continuous supply of reagents (fuel, such as hydrogen, and oxidizing agent, such as oxygen) from special reservoirs. The most important component... ... Big Encyclopedic Dictionary
fuel cell- A primary element in which electrical energy is generated through electrochemical reactions between active substances continuously supplied to the electrodes from the outside. [GOST 15596 82] EN fuel cell cell that can change chemical energy from... ... Technical Translator's Guide
Direct methanol fuel cell Fuel cell is an electrochemical device similar to but different from a galvanic cell... Wikipedia
The US has several initiatives aimed at developing hydrogen fuel cells, infrastructure and technology to make fuel cell vehicles practical and fuel efficient by 2020. More than one billion dollars have been allocated for these purposes.
Fuel cells generate electricity quietly and efficiently, without polluting the environment. Unlike energy sources that use fossil fuels, the byproducts of fuel cells are heat and water. How does this work?
In this article we will briefly look at each of the existing fuel technologies today, as well as talk about the design and operation of fuel cells, and compare them with other forms of energy production. We'll also discuss some of the obstacles researchers face in making fuel cells practical and affordable for consumers.
Fuel cells are electrochemical energy conversion devices. A fuel cell converts chemicals, hydrogen and oxygen, into water, generating electricity in the process.
Another electrochemical device that we are all very familiar with is the battery. The battery has all the necessary chemical elements inside itself and converts these substances into electricity. This means that the battery eventually dies and you either throw it away or charge it again.
In a fuel cell, chemicals are constantly fed into it so that it never “dies.” Electricity will be generated as long as chemicals enter the element. Most fuel cells in use today use hydrogen and oxygen.
Hydrogen is the most abundant element in our Galaxy. However, hydrogen practically does not exist on Earth in its elemental form. Engineers and scientists must extract pure hydrogen from hydrogen compounds, including fossil fuels or water. To extract hydrogen from these compounds, you need to expend energy in the form of heat or electricity.
Invention of fuel cells
Sir William Grove invented the first fuel cell in 1839. Grove knew that water could be split into hydrogen and oxygen by passing an electric current through it (a process called electrolysis). He suggested that in reverse order it would be possible to obtain electricity and water. He created a primitive fuel cell and called it gas galvanic battery. After experimenting with his new invention, Grove proved his hypothesis. Fifty years later, scientists Ludwig Mond and Charles Langer coined the term fuel cells when trying to build a practical model for generating electricity.
The fuel cell will compete with many other energy conversion devices, including gas turbines in urban power plants, internal combustion engines in cars, and all kinds of batteries. Internal combustion engines, like gas turbines, burn different types of fuel and use the pressure created by the expansion of gases to perform mechanical work. Batteries convert chemical energy into electrical energy when needed. Fuel cells must perform these tasks more efficiently.
The fuel cell provides DC (direct current) voltage that can be used to power electric motors, lights and other electrical appliances.
There are several different types of fuel cells, each using different chemical processes. Fuel cells are usually classified according to their operating temperature And typeelectrolyte, which they use. Some types of fuel cells are well suited for use in stationary power plants. Others may be useful for small portable devices or for powering cars. The main types of fuel cells include:
Polymer exchange membrane fuel cell (PEMFC)
PEMFC is considered as the most likely candidate for transport applications. PEMFC has both high power and relatively low operating temperatures (ranging from 60 to 80 degrees Celsius). Low operating temperatures mean fuel cells can quickly warm up to begin generating electricity.
Solid oxide fuel cell (SOFC)
These fuel cells are most suitable for large stationary power generators that could power factories or cities. This type of fuel cell operates at very high temperatures (700 to 1000 degrees Celsius). High temperature poses a reliability problem because some fuel cells can fail after a few on-off cycles. However, solid oxide fuel cells are very stable during continuous operation. In fact, SOFCs have demonstrated the longest operating life of any fuel cell under certain conditions. The high temperature also has the advantage that the steam produced by the fuel cells can be sent to turbines and generate more electricity. This process is called cogeneration of heat and electricity and improves overall system efficiency.
Alkaline fuel cell (AFC)
It is one of the oldest designs for fuel cells, having been in use since the 1960s. AFCs are very susceptible to contamination as they require pure hydrogen and oxygen. In addition, they are very expensive, so this type of fuel cell is unlikely to be put into mass production.
Molten-carbonate fuel cell (MCFC)
Like SOFCs, these fuel cells are also best suited for large stationary power plants and generators. They operate at 600 degrees Celsius so they can generate steam, which in turn can be used to generate even more energy. They have a lower operating temperature than solid oxide fuel cells, which means they do not require such heat-resistant materials. This makes them a little cheaper.
Phosphoric-acid fuel cell (PAFC)
Phosphoric acid fuel cell has potential for use in small stationary power systems. It operates at a higher temperature than a polymer exchange membrane fuel cell, so it takes longer to warm up, making it unsuitable for use in automobiles.
Direct methanol fuel cell (DMFC)
Methanol fuel cells are comparable to PEMFC in terms of operating temperature, but are not as efficient. Additionally, DMFCs require quite a large amount of platinum as a catalyst, which makes these fuel cells expensive.
Fuel cell with polymer exchange membrane
Polymer exchange membrane fuel cell (PEMFC) is one of the most promising fuel cell technologies. PEMFC uses one of the simplest reactions of any fuel cell. Let's look at what it consists of.
1. A node – negative terminal of the fuel cell. It conducts electrons that are released from hydrogen molecules, after which they can be used in an external circuit. It has engraved channels through which hydrogen gas is distributed evenly over the surface of the catalyst.
2.TO athode - positive terminal of the fuel cell, also has channels for distributing oxygen over the surface of the catalyst. It also conducts electrons back from the catalyst's external circuit, where they can combine with hydrogen and oxygen ions to form water.
3.Electrolyte-proton exchange membrane. This is a specially treated material that conducts only positively charged ions and blocks electrons. With PEMFC, the membrane must be hydrated in order to function properly and remain stable.
4. Catalyst is a special material that promotes the reaction of oxygen and hydrogen. It is typically made from platinum nanoparticles applied very thinly to carbon paper or fabric. The catalyst has a surface structure such that maximum surface area of the platinum can be exposed to hydrogen or oxygen.
The figure shows hydrogen gas (H2) entering the fuel cell under pressure from the anode side. When an H2 molecule comes into contact with platinum on the catalyst, it splits into two H+ ions and two electrons. The electrons pass through the anode, where they are used in external circuitry (doing useful work, such as turning a motor), and return to the cathode side of the fuel cell.
Meanwhile, on the cathode side of the fuel cell, oxygen (O2) from the air passes through the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative charge. This negative charge attracts two H+ ions across the membrane, where they combine with an oxygen atom and two electrons coming from the external circuit to form a water molecule (H2O).
This reaction in a single fuel cell produces only about 0.7 Volts. To raise the voltage to a reasonable level, many individual fuel cells must be combined to form a fuel cell stack. Bipolar plates are used to connect one fuel cell to another and undergo oxidation to reduce potential. The big problem with bipolar plates is their stability. Metal bipolar plates can be corroded, and by-products (iron and chromium ions) reduce the efficiency of the fuel cell membranes and electrodes. Therefore, low temperature fuel cells use light metals, graphite, and composites of carbon and thermoset (a thermoset is a kind of plastic that remains solid even when exposed to high temperatures) in the form of a bipolar sheet material.
Fuel cell efficiency
Reducing pollution is one of the main goals of a fuel cell. By comparing a car powered by a fuel cell to a car powered by a gasoline engine and a car powered by a battery, you can see how fuel cells could improve the efficiency of cars.
Since all three types of cars have many of the same components, we will ignore this part of the car and compare the useful actions up to the point where mechanical energy is produced. Let's start with the fuel cell car.
If the fuel cell is powered by pure hydrogen, its efficiency can be up to 80 percent. Thus, it converts 80 percent of the energy content of hydrogen into electricity. However, we still have to convert electrical energy into mechanical work. This is achieved by an electric motor and an inverter. The efficiency of the motor + inverter is also approximately 80 percent. This gives an overall efficiency of approximately 80*80/100=64 percent. Honda's FCX concept vehicle reportedly has 60 percent energy efficiency.
If the fuel source is not in the form of pure hydrogen, then the vehicle will also need a reformer. Reformers convert hydrocarbon or alcohol fuels into hydrogen. They generate heat and produce CO and CO2 in addition to hydrogen. They use various devices to purify the resulting hydrogen, but this purification is insufficient and reduces the efficiency of the fuel cell. So the researchers decided to focus on fuel cells for vehicles powered by pure hydrogen, despite the challenges associated with hydrogen production and storage.
Efficiency of a gasoline engine and a battery-electric car
The efficiency of a car powered by gasoline is surprisingly low. All heat that is exhausted or absorbed by the radiator is wasted energy. The engine also uses a lot of energy to drive the various pumps, fans and generators that keep it running. Thus, the overall efficiency of a gasoline automobile engine is approximately 20 percent. Thus, only about 20 percent of gasoline's thermal energy content is converted into mechanical work.
A battery-powered electric vehicle has fairly high efficiency. The battery is approximately 90 percent efficient (most batteries generate some heat or require heating), and the motor + inverter is approximately 80 percent efficient. This gives an overall efficiency of approximately 72 percent.
But that's not all. In order for an electric car to move, electricity must first be generated somewhere. If it was a power plant that used a fossil fuel combustion process (rather than nuclear, hydroelectric, solar or wind power), then only approximately 40 percent of the fuel consumed by the power plant was converted into electricity. Plus, the process of charging a car requires converting alternating current (AC) power to direct current (DC) power. This process has an efficiency of approximately 90 percent.
Now, if we look at the whole cycle, the efficiency of an electric vehicle is 72 percent for the vehicle itself, 40 percent for the power plant, and 90 percent for charging the vehicle. This gives an overall efficiency of 26 percent. Overall efficiency varies significantly depending on which power plant is used to charge the battery. If the car's electricity comes from a hydroelectric power plant, for example, the electric car's efficiency will be approximately 65 percent.
Scientists are researching and improving designs to continue improving the efficiency of the fuel cell. One new approach would be to combine fuel cell and battery-powered vehicles. A concept vehicle powered by a hybrid powertrain powered by a fuel cell is being developed. It uses a lithium battery to power the car while the fuel cell recharges the battery.
Fuel cell vehicles are potentially as efficient as a battery-powered car that is charged from a power plant that does not use fossil fuels. But achieving this potential in a practical and accessible way can be difficult.
Why use fuel cells?
The main reason is everything related to oil. America must import nearly 60 percent of its oil. By 2025, imports are expected to rise to 68%. Americans use two-thirds of oil daily for transportation. Even if every car on the street were a hybrid car, by 2025 the US would still need to use the same amount of oil that Americans consumed in 2000. In fact, America consumes a quarter of all the oil produced in the world, although only 4.6% of the world's population lives here.
Experts expect oil prices to continue rising over the next few decades as cheaper sources dwindle. Oil companies must develop oil fields in increasingly difficult conditions, which will increase oil prices.
Concerns extend far beyond economic security. A lot of money coming from the sale of oil is spent on supporting international terrorism, radical political parties, and the unstable situation in oil-producing regions.
The use of oil and other fossil fuels for energy produces pollution. It is best for everyone to find an alternative to burning fossil fuels for energy.
Fuel cells are an attractive alternative to oil dependence. Instead of polluting, fuel cells produce clean water as a by-product. While engineers have temporarily focused on producing hydrogen from various fossil sources such as gasoline or natural gas, renewable, environmentally friendly ways to produce hydrogen in the future are being explored. The most promising, naturally, will be the process of producing hydrogen from water
Oil dependence and global warming are an international problem. Several countries are jointly involved in promoting research and development for fuel cell technology.
It is clear that scientists and manufacturers have a lot of work to do before fuel cells become an alternative to modern methods of energy production. Yet, with worldwide support and global cooperation, a viable fuel cell power system could become a reality within just a couple of decades.
Fuel cell is an electrochemical device similar to a galvanic cell, but differs from it in that the substances for the electrochemical reaction are supplied to it from the outside - in contrast to the limited amount of energy stored in a galvanic cell or battery.
Rice. 1. Some fuel cells
Fuel cells convert the chemical energy of fuel into electricity, bypassing ineffective combustion processes that occur with large losses. They convert hydrogen and oxygen into electricity through a chemical reaction. As a result of this process, water is formed and a large amount of heat is released. A fuel cell is much like a battery that can be charged and then use the stored electrical energy. The inventor of the fuel cell is considered to be William R. Grove, who invented it back in 1839. This fuel cell used a sulfuric acid solution as an electrolyte and hydrogen as a fuel, which was combined with oxygen in an oxidizing agent. Until recently, fuel cells were used only in laboratories and on spacecraft.
Rice. 2.
Unlike other power generators, such as internal combustion engines or turbines powered by gas, coal, fuel oil, etc., fuel cells do not burn fuel. This means no noisy high-pressure rotors, no loud exhaust noise, no vibrations. Fuel cells produce electricity through a silent electrochemical reaction. Another feature of fuel cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.
Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only emissions from fuel cells are water in the form of steam and a small amount of carbon dioxide, which is not released at all if pure hydrogen is used as fuel. Fuel cells are assembled into assemblies and then into individual functional modules.
Fuel cells have no moving parts (at least not within the cell itself) and therefore do not obey Carnot's law. That is, they will have greater than 50% efficiency and are especially effective at low loads. Thus, fuel cell vehicles can become (and have already proven to be) more fuel efficient than conventional vehicles in real-world driving conditions.
The fuel cell produces a constant voltage electric current that can be used to drive the electric motor, lighting, and other electrical systems in the vehicle.
There are several types of fuel cells, differing in the chemical processes used. Fuel cells are usually classified by the type of electrolyte they use.
Some types of fuel cells are promising for use in power plants, while others are promising for portable devices or to drive cars.
1. Alkaline fuel cells (ALFC)
Alkaline fuel cell- This is one of the very first elements developed. Alkaline fuel cells (AFC) are one of the most studied technologies, used since the mid-60s of the twentieth century by NASA in the Apollo and Space Shuttle programs. On board these spacecraft, fuel cells produce electrical energy and potable water.
Rice. 3.
Alkaline fuel cells are one of the most efficient cells used to generate electricity, with power generation efficiency reaching up to 70%.
Alkaline fuel cells use an electrolyte, an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The potassium hydroxide concentration may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in SHTE is the hydroxyl ion (OH-), moving from the cathode to the anode, where it reacts with hydrogen, producing water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxyl ions there. As a result of this series of reactions taking place in the fuel cell, electricity and, as a by-product, heat are produced:
Reaction at the anode: 2H2 + 4OH- => 4H2O + 4e
Reaction at the cathode: O2 + 2H2O + 4e- => 4OH
General reaction of the system: 2H2 + O2 => 2H2O
The advantage of SHTE is that these fuel cells are the cheapest to produce, since the catalyst needed on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. In addition, SHTEs operate at relatively low temperatures and are among the most efficient.
One of the characteristic features of SHTE is its high sensitivity to CO2, which may be contained in fuel or air. CO2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SHTE is limited to enclosed spaces, such as space and underwater vehicles; they operate on pure hydrogen and oxygen.
2. Molten carbonate fuel cells (MCFC)
Fuel cells with molten carbonate electrolyte are high temperature fuel cells. The high operating temperature allows the direct use of natural gas without a fuel processor and low calorific value fuel gas from industrial processes and other sources. This process was developed in the mid-60s of the twentieth century. Since then, production technology, performance and reliability have been improved.
Rice. 4.
The operation of RCFC differs from other fuel cells. These cells use an electrolyte made from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of ion mobility in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). Efficiency varies between 60-80%.
When heated to a temperature of 650°C, the salts become a conductor for carbonate ions (CO32-). These ions pass from the cathode to the anode, where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electric current and heat as a by-product.
Reaction at the anode: CO32- + H2 => H2O + CO2 + 2e
Reaction at the cathode: CO2 + 1/2O2 + 2e- => CO32-
General reaction of the element: H2(g) + 1/2O2(g) + CO2(cathode) => H2O(g) + CO2(anode)
The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. The advantage is the ability to use standard materials (stainless steel sheets and nickel catalyst on the electrodes). The waste heat can be used to produce high pressure steam. High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures requires a long time to achieve optimal operating conditions, and the system responds more slowly to changes in energy consumption. These characteristics allow the use of fuel cell installations with molten carbonate electrolyte under constant power conditions. High temperatures prevent damage to the fuel cell by carbon monoxide, “poisoning,” etc.
Fuel cells with molten carbonate electrolyte are suitable for use in large stationary installations. Thermal power plants with an electrical output power of 2.8 MW are commercially produced. Installations with output power up to 100 MW are being developed.
3. Phosphoric acid fuel cells (PAFC)
Fuel cells based on phosphoric (orthophosphoric) acid became the first fuel cells for commercial use. This process was developed in the mid-60s of the twentieth century, tests have been carried out since the 70s of the twentieth century. The result was increased stability and performance and reduced cost.
Rice. 5.
Phosphoric (orthophosphoric) acid fuel cells use an electrolyte based on orthophosphoric acid (H3PO4) at concentrations up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, so these fuel cells are used at temperatures up to 150-220 °C.
The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in proton exchange membrane fuel cells (PEMFCs), in which hydrogen supplied to the anode is split into protons and electrons. Protons travel through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are sent through an external electrical circuit, thereby generating an electric current. Below are reactions that generate electric current and heat.
Reaction at the anode: 2H2 => 4H+ + 4e
Reaction at the cathode: O2(g) + 4H+ + 4e- => 2H2O
General reaction of the element: 2H2 + O2 => 2H2O
The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. With combined production of heat and electricity, the overall efficiency is about 85%. In addition, given operating temperatures, waste heat can be used to heat water and generate atmospheric pressure steam.
The high performance of thermal power plants using fuel cells based on phosphoric (orthophosphoric) acid in the combined production of thermal and electrical energy is one of the advantages of this type of fuel cells. The units use carbon monoxide with a concentration of about 1.5%, which significantly expands the choice of fuel. Simple design, low degree of electrolyte volatility and increased stability are also advantages of such fuel cells.
Thermal power plants with electrical output power of up to 400 kW are commercially produced. Installations with a capacity of 11 MW have passed appropriate tests. Installations with output power up to 100 MW are being developed.
4. Proton exchange membrane fuel cells (PEMFC)
Proton exchange membrane fuel cells are considered the best type of fuel cells for generating power for vehicles, which can replace gasoline and diesel internal combustion engines. These fuel cells were first used by NASA for the Gemini program. Installations based on MOPFC with power from 1 W to 2 kW have been developed and demonstrated.
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The electrolyte in these fuel cells is a solid polymer membrane (a thin film of plastic). When saturated with water, this polymer allows protons to pass through but does not conduct electrons.
The fuel is hydrogen, and the charge carrier is a hydrogen ion (proton). At the anode, the hydrogen molecule is split into a hydrogen ion (proton) and electrons. Hydrogen ions pass through the electrolyte to the cathode, and electrons move around the outer circle and produce electrical energy. Oxygen, which is taken from the air, is supplied to the cathode and combines with electrons and hydrogen ions to form water. The following reactions occur at the electrodes: Reaction at the anode: 2H2 + 4OH- => 4H2O + 4eReaction at the cathode: O2 + 2H2O + 4e- => 4OH Overall cell reaction: 2H2 + O2 => 2H2O Compared to other types of fuel cells, fuel cells with a proton exchange membrane produce more energy for a given volume or weight of the fuel cell. This feature allows them to be compact and lightweight. In addition, the operating temperature is less than 100°C, which allows you to quickly start operation. These characteristics, as well as the ability to quickly change energy output, are just a few that make these fuel cells a prime candidate for use in vehicles.
Another advantage is that the electrolyte is a solid rather than a liquid. It is easier to retain gases at the cathode and anode using a solid electrolyte, so such fuel cells are cheaper to produce. With a solid electrolyte, there are no orientation issues and fewer corrosion problems, increasing the longevity of the cell and its components.
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5. Solid oxide fuel cells (SOFC)
Solid oxide fuel cells are the highest operating temperature fuel cells. The operating temperature can vary from 600°C to 1000°C, allowing the use of different types of fuel without special pre-treatment. To handle such high temperatures, the electrolyte used is a thin solid metal oxide on a ceramic base, often an alloy of yttrium and zirconium, which is a conductor of oxygen ions (O2-). The technology of using solid oxide fuel cells has been developing since the late 50s of the twentieth century and has two configurations: planar and tubular.
The solid electrolyte provides a sealed transition of gas from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (O2-). At the cathode, oxygen molecules from the air are separated into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen, creating four free electrons. The electrons are sent through an external electrical circuit, generating electric current and waste heat.
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Reaction at the anode: 2H2 + 2O2- => 2H2O + 4e
Reaction at the cathode: O2 + 4e- => 2O2-
General reaction of the element: 2H2 + O2 => 2H2O
The efficiency of electrical energy production is the highest of all fuel cells - about 60%. In addition, high operating temperatures allow for the combined production of thermal and electrical energy to generate high-pressure steam. Combining a high-temperature fuel cell with a turbine makes it possible to create a hybrid fuel cell to increase the efficiency of generating electrical energy by up to 70%.
Solid oxide fuel cells operate at very high temperatures (600°C-1000°C), resulting in significant time required to reach optimal operating conditions and the system being slower to respond to changes in energy consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels resulting from gasification of coal or waste gases, etc. The fuel cell is also excellent for high power applications, including industrial and large central power plants. Modules with an electrical output power of 100 kW are commercially produced.
6. Direct methanol oxidation fuel cells (DOMFC)
Direct methanol oxidation fuel cells They are successfully used in the field of powering mobile phones, laptops, as well as to create portable power sources, which is what the future use of such elements is aimed at.
The design of fuel cells with direct oxidation of methanol is similar to the design of fuel cells with a proton exchange membrane (MEPFC), i.e. A polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. But liquid methanol (CH3OH) oxidizes in the presence of water at the anode, releasing CO2, hydrogen ions and electrons, which are sent through an external electrical circuit, thereby generating an electric current. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.
Reaction at the anode: CH3OH + H2O => CO2 + 6H+ + 6eReaction at the cathode: 3/2O2 + 6H+ + 6e- => 3H2O General reaction of the element: CH3OH + 3/2O2 => CO2 + 2H2O The development of such fuel cells has been carried out since the beginning of the 90s s of the twentieth century and their specific power and efficiency were increased to 40%.
These elements were tested in the temperature range of 50-120°C. Because of their low operating temperatures and the absence of the need for a converter, such fuel cells are a prime candidate for use in mobile phones and other consumer products, as well as in car engines. Their advantage is also their small size.
7. Polymer electrolyte fuel cells (PEFC)
In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which conduction water ions H2O+ (proton, red) attaches to a water molecule. Water molecules pose a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and at the outlet electrodes, which limits the operating temperature to 100°C.
8. Solid acid fuel cells (SFC)
In solid acid fuel cells, the electrolyte (CsHSO4) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the SO42 oxyanions allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two electrodes that are tightly pressed together to ensure good contact. When heated, the organic component evaporates, exiting through the pores in the electrodes, maintaining the ability of multiple contacts between the fuel (or oxygen at the other end of the element), the electrolyte and the electrodes.
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9. Comparison of the most important characteristics of fuel cells
Fuel cell type | Operating temperature | Power generation efficiency | Fuel type | Scope of application |
Medium and large installations |
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Pure hydrogen | installations |
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Pure hydrogen | Small installations |
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Most hydrocarbon fuels | Small, medium and large installations |
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Portable installations |
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Pure hydrogen | Space researched |
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Pure hydrogen | Small installations |
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10. Use of fuel cells in cars
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In modern life, chemical sources of current surround us everywhere: these are batteries in flashlights, batteries in mobile phones, hydrogen fuel cells, which are already used in some cars. The rapid development of electrochemical technologies may lead to the fact that in the near future, instead of gasoline-powered cars, we will be surrounded only by electric vehicles, telephones will no longer discharge quickly, and each home will have its own fuel cell electric generator. One of the joint programs of the Ural Federal University and the Institute of High-Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences is devoted to increasing the efficiency of electrochemical storage devices and generators of electricity, in partnership with which we are publishing this article.
Today, there are many different types of batteries, which can become increasingly difficult to navigate. It is not obvious to everyone how a battery differs from a supercapacitor and why a hydrogen fuel cell can be used without fear of harming the environment. In this article we will talk about how chemical reactions are used to generate electricity, what is the difference between the main types of modern chemical current sources, and what prospects open up for electrochemical energy.
Chemistry as a source of electricity
First, let's figure out why chemical energy can be used to generate electricity at all. The thing is that during redox reactions, electrons are transferred between two different ions. If the two halves of a chemical reaction are separated in space so that oxidation and reduction take place separately from each other, then it is possible to make sure that an electron that leaves one ion does not immediately get to the second, but first passes along a path predetermined for it. This reaction can be used as a source of electric current.
This concept was first implemented in the 18th century by the Italian physiologist Luigi Galvani. The action of a traditional galvanic cell is based on the reduction and oxidation reactions of metals with different activities. For example, a classic cell is a galvanic cell in which zinc is oxidized and copper is reduced. Reduction and oxidation reactions take place at the cathode and anode, respectively. And to prevent copper and zinc ions from entering “foreign territory”, where they can react with each other directly, a special membrane is usually placed between the anode and cathode. As a result, a potential difference arises between the electrodes. If you connect electrodes, for example, to a light bulb, then current begins to flow in the resulting electrical circuit and the light bulb lights up.
Galvanic cell diagram
Wikimedia commons
In addition to the materials of the anode and cathode, an important component of the chemical current source is the electrolyte, inside which the ions move and at the border of which all electrochemical reactions take place with the electrodes. In this case, the electrolyte does not have to be liquid - it can be either a polymer or ceramic material.
The main disadvantage of a galvanic cell is its limited operating time. As soon as the reaction completes (that is, the entire gradually dissolving anode is completely consumed), such an element will simply stop working.
AA alkaline batteries
Rechargeable
The first step towards expanding the capabilities of chemical current sources was the creation of a battery - a current source that can be recharged and therefore reused. To do this, scientists simply proposed using reversible chemical reactions. Having completely discharged the battery for the first time, using an external current source, the reaction that took place in it can be started in the opposite direction. This will restore it to its original state so that the battery can be used again after recharging.
Car lead acid battery
Today, many different types of batteries have been created, which differ in the type of chemical reaction that occurs in them. The most common types of batteries are lead-acid (or simply lead) batteries, which are based on the oxidation-reduction reaction of lead. Such devices have a fairly long service life, and their energy intensity is up to 60 watt-hours per kilogram. Even more popular recently are lithium-ion batteries based on the oxidation-reduction reaction of lithium. The energy intensity of modern lithium-ion batteries now exceeds 250 watt-hours per kilogram.
Li-ion battery for mobile phone
The main problems of lithium-ion batteries are their low efficiency at low temperatures, rapid aging and increased risk of explosion. And due to the fact that lithium metal reacts very actively with water to form hydrogen gas and oxygen is released when the battery burns, spontaneous combustion of a lithium-ion battery is very difficult to use with traditional fire extinguishing methods. In order to increase the safety of such a battery and speed up its charging time, scientists propose a cathode material that prevents the formation of dendritic lithium structures, and add substances to the electrolyte that cause the formation of explosive structures and components that ignite in the early stages.
Solid electrolyte
As another less obvious way to increase the efficiency and safety of batteries, chemists have proposed not limiting chemical current sources to liquid electrolytes, but creating a completely solid-state current source. In such devices there are no liquid components at all, but a layered structure of a solid anode, a solid cathode and a solid electrolyte between them. The electrolyte simultaneously performs the function of a membrane. Charge carriers in a solid electrolyte can be various ions, depending on its composition and the reactions that take place at the anode and cathode. But they are always small enough ions that can move relatively freely throughout the crystal, for example, H + protons, lithium ions Li + or oxygen ions O 2-.
Hydrogen fuel cells
The ability to recharge and special safety measures make batteries much more promising sources of current than conventional batteries, but still each battery contains a limited amount of reagents, and therefore a limited supply of energy, and each time the battery must be recharged to restore its functionality.
To make a battery “endless,” you can use as an energy source not the substances that are inside the cell, but fuel specially pumped through it. The best choice for such fuel is a substance that is as simple in composition as possible, environmentally friendly and available in abundance on Earth.
The most suitable substance of this type is hydrogen gas. Its oxidation by atmospheric oxygen to form water (according to the reaction 2H 2 + O 2 → 2H 2 O) is a simple redox reaction, and the transport of electrons between ions can also be used as a current source. The reaction that occurs is a kind of reverse reaction to the electrolysis of water (in which, under the influence of an electric current, water is decomposed into oxygen and hydrogen), and such a scheme was first proposed in the middle of the 19th century.
But despite the fact that the circuit looks quite simple, creating an efficiently operating device based on this principle is not at all a trivial task. To do this, it is necessary to separate the flows of oxygen and hydrogen in space, ensure the transport of the necessary ions through the electrolyte and reduce possible energy losses at all stages of work.
Schematic diagram of the operation of a hydrogen fuel cell
The circuit of a working hydrogen fuel cell is very similar to the circuit of a chemical current source, but contains additional channels for supplying fuel and oxidizer and removing reaction products and excess supplied gases. The electrodes in such an element are porous conductive catalysts. A gaseous fuel (hydrogen) is supplied to the anode, and an oxidizing agent (oxygen from the air) is supplied to the cathode, and at the boundary of each electrode with the electrolyte, its own half-reaction takes place (hydrogen oxidation and oxygen reduction, respectively). In this case, depending on the type of fuel cell and the type of electrolyte, the formation of water itself can occur either in the anode or in the cathode space.
Toyota hydrogen fuel cell
Joseph Brent / flickr
If the electrolyte is a proton-conducting polymer or ceramic membrane, an acid or alkali solution, then the charge carrier in the electrolyte is hydrogen ions. In this case, at the anode, molecular hydrogen is oxidized to hydrogen ions, which pass through the electrolyte and react with oxygen there. If the charge carrier is the oxygen ion O 2–, as in the case of a solid oxide electrolyte, then oxygen is reduced to an ion at the cathode, this ion passes through the electrolyte and oxidizes hydrogen at the anode to form water and free electrons.
In addition to the hydrogen oxidation reaction, it has been proposed to use other types of reactions for fuel cells. For example, instead of hydrogen, the reducing fuel can be methanol, which is oxidized by oxygen to carbon dioxide and water.
Fuel cell efficiency
Despite all the advantages of hydrogen fuel cells (such as environmental friendliness, virtually unlimited efficiency, compact size and high energy intensity), they also have a number of disadvantages. These include, first of all, the gradual aging of components and difficulties in storing hydrogen. It is precisely how to eliminate these shortcomings that scientists are working on today.
It is currently proposed to increase the efficiency of fuel cells by changing the composition of the electrolyte, the properties of the catalyst electrode, and the geometry of the system (which ensures the supply of fuel gases to the desired point and reduces side effects). To solve the problem of storing hydrogen gas, materials containing platinum are used, for saturation of which, for example, graphene membranes.
As a result, it is possible to achieve an increase in the stability of the fuel cell and the lifetime of its individual components. Now the coefficient of conversion of chemical energy into electrical energy in such elements reaches 80 percent, and under certain conditions it can be even higher.
The enormous prospects of hydrogen energy are associated with the possibility of combining fuel cells into entire batteries, turning them into electric generators with high power. Already, electric generators running on hydrogen fuel cells have a power of up to several hundred kilowatts and are used as power sources for vehicles.
Alternative electrochemical storage
In addition to classical electrochemical current sources, more unusual systems are also used as energy storage devices. One of such systems is a supercapacitor (or ionistor) - a device in which charge separation and accumulation occurs due to the formation of a double layer near a charged surface. At the electrode-electrolyte interface in such a device, ions of different signs are lined up in two layers, the so-called “double electric layer,” forming a kind of very thin capacitor. The capacity of such a capacitor, that is, the amount of accumulated charge, will be determined by the specific surface area of the electrode material, therefore, it is advantageous to take porous materials with a maximum specific surface area as a material for supercapacitors.
Ionistors are record holders among charge-discharge chemical current sources in terms of charge speed, which is an undoubted advantage of this type of device. Unfortunately, they also hold the record for discharge speed. The energy density of ionistors is eight times less compared to lead batteries and 25 times less than lithium-ion batteries. Classic “double-layer” ionistors do not use an electrochemical reaction as their basis, and the term “capacitor” is most accurately applied to them. However, in those versions of ionistors that are based on an electrochemical reaction and charge accumulation extends into the depth of the electrode, it is possible to achieve higher discharge times while maintaining a fast charge rate. The efforts of supercapacitor developers are aimed at creating hybrid devices with batteries that combine the advantages of supercapacitors, primarily high charging speed, and the advantages of batteries - high energy intensity and long discharge time. Imagine in the near future a battery-ionistor that will charge in a couple of minutes and power a laptop or smartphone for a day or more!
Despite the fact that now the energy density of supercapacitors is still several times less than the energy density of batteries, they are used in consumer electronics and for engines of various vehicles, including the most.
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Thus, today there are a large number of electrochemical devices, each of which is promising for its specific applications. To improve the efficiency of these devices, scientists need to solve a number of problems of both fundamental and technological nature. Most of these tasks are being carried out within the framework of one of the breakthrough projects at the Ural Federal University, so we asked Maxim Ananyev, director of the Institute of High-Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences, professor of the Department of Electrochemical Production Technology of the Institute of Chemical Technology of the Ural Federal University, to talk about the immediate plans and prospects for the development of modern fuel cells .
N+1: Are there any alternatives to the currently most popular lithium-ion batteries expected in the near future?
Maxim Ananyev: Modern efforts of battery developers are aimed at replacing the type of charge carrier in the electrolyte from lithium to sodium, potassium, and aluminum. As a result of replacing lithium, it will be possible to reduce the cost of the battery, although the weight and size characteristics will increase proportionally. In other words, with the same electrical characteristics, a sodium-ion battery will be larger and heavier compared to a lithium-ion battery.
In addition, one of the promising developing areas for improving batteries is the creation of hybrid chemical energy sources based on combining metal-ion batteries with an air electrode, as in fuel cells. In general, the direction of creating hybrid systems, as has already been shown with the example of supercapacitors, will apparently in the near future make it possible to see chemical energy sources on the market with high consumer characteristics.
The Ural Federal University, together with academic and industrial partners in Russia and the world, is today implementing six mega-projects that are focused on breakthrough areas of scientific research. One of such projects is “Advanced technologies of electrochemical energy from chemical design of new materials to new generation electrochemical devices for energy conservation and conversion.”
A group of scientists from the strategic academic unit (SAE) of the UrFU School of Natural Sciences and Mathematics, which includes Maxim Ananyev, is engaged in the design and development of new materials and technologies, including fuel cells, electrolytic cells, metal-graphene batteries, electrochemical energy storage systems and supercapacitors.
Research and scientific work are carried out in constant cooperation with the Institute of High Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences and with the support of partners.
Which fuel cells are currently being developed and have the most potential?
One of the most promising types of fuel cells are proton-ceramic elements. They have advantages over polymer fuel cells with proton exchange membrane and solid oxide elements, since they can operate with a direct supply of hydrocarbon fuel. This significantly simplifies the design of a power plant based on proton-ceramic fuel cells and the control system, and therefore increases operational reliability. True, this type of fuel cell is currently historically less developed, but modern scientific research allows us to hope for the high potential of this technology in the future.
What problems related to fuel cells are currently being addressed at the Ural Federal University?
Now UrFU scientists, together with the Institute of High-Temperature Electrochemistry (IVTE) of the Ural Branch of the Russian Academy of Sciences, are working on the creation of highly efficient electrochemical devices and autonomous power generators for applications in distributed energy. The creation of power plants for distributed energy initially implies the development of hybrid systems based on an electricity generator and a storage device, which are batteries. At the same time, the fuel cell operates constantly, providing load during peak hours, and in idle mode it charges the battery, which can itself act as a reserve both in case of high energy consumption and in case of emergency situations.
The greatest successes of UrFU and IVTE chemists have been achieved in the development of solid-oxide and proton-ceramic fuel cells. Since 2016, in the Urals, together with the State Corporation Rosatom, the first in Russia production of power plants based on solid oxide fuel cells has been created. The development of Ural scientists has already passed “full-scale” tests at the gas pipeline cathodic protection station at the experimental site of Uraltransgaz LLC. The power plant with a rated power of 1.5 kilowatts worked for more than 10 thousand hours and showed the high potential for the use of such devices.
Within the framework of the joint laboratory of UrFU and IVTE, the development of electrochemical devices based on a proton-conducting ceramic membrane is underway. This will make it possible in the near future to reduce the operating temperatures for solid-oxide fuel cells from 900 to 500 degrees Celsius and to abandon the preliminary reforming of hydrocarbon fuels, thus creating cost-effective electrochemical generators capable of operating under the conditions of the developed gas supply infrastructure in Russia.
Alexander Dubov