A fuel cell is an electrochemical device that converts the chemical energy of a fuel directly into electricity. The main components of a fuel cell for electricity generation are as follows:
Anode: This is the negative electrode of the fuel cell, where the fuel is introduced. Typically, hydrogen gas is used as the fuel, although other fuels like methanol can also be employed. At the anode, the fuel is split into protons and electrons through a process called electrochemical oxidation.
Cathode: This is the positive electrode of the fuel cell, where oxygen (from the air) is introduced. The oxygen combines with the protons and electrons from the anode in a process called electrochemical reduction.
Electrolyte: The electrolyte is a special material that separates the anode and cathode while allowing the flow of ions between them. It plays a crucial role in facilitating the ion exchange between the anode and cathode, which is essential for the generation of electricity. There are different types of electrolytes used in different types of fuel cells, such as proton exchange membrane (PEM), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), etc.
Proton Exchange Membrane (PEM): Some fuel cells, like PEM fuel cells, have a separate proton exchange membrane that conducts protons while blocking the electrons. It ensures that only ions can pass through, forcing the electrons to travel through an external circuit, generating electricity.
Bipolar Plates: These plates are located on either side of the fuel cell stack and serve as current collectors. They distribute the reactant gases (hydrogen and oxygen) across the surface of the anode and cathode, and they also collect the electrical current generated within the fuel cell.
Fuel Delivery System: This system is responsible for delivering the fuel (hydrogen, for example) to the anode of the fuel cell at a controlled rate.
Air Delivery System: It supplies the required oxygen or air to the cathode of the fuel cell.
Cooling System: Fuel cells generate heat during the electrochemical reactions. A cooling system is essential to maintain the fuel cell at an optimal operating temperature and prevent overheating.
Stack: A fuel cell stack is an assembly of multiple individual fuel cells connected in series or parallel. Stacks are used to achieve the desired voltage and power output for practical applications.
End Plates: These plates provide structural support and help in sealing the fuel cell.
When hydrogen is used as the fuel, the overall electrochemical reaction in a hydrogen fuel cell is as follows:
Anode (oxidation reaction): H2 (hydrogen) → 2H+ (protons) + 2e- (electrons)
Cathode (reduction reaction): 1/2O2 (oxygen) + 2H+ (protons) + 2e- (electrons) → H2O (water)
The electrons flow through an external circuit from the anode to the cathode, generating electricity, while the protons move through the electrolyte. At the cathode, the protons, electrons, and oxygen combine to form water. This process is continuous as long as there is a supply of fuel and oxygen, providing a sustainable source of electricity.