5.2.2 Fuel Cells

Fuel cells are electrochemical devices that generate electricity by utilising an external supply of fuel and an oxidant, such as oxygen or air. One commonly used fuel in fuel cells is hydrogen.

Fuel Cell Operation

Fuel cells work through an electrochemical process. The fuel, such as hydrogen, is supplied to the anode (negative electrode) of the fuel cell, while the oxidant, usually oxygen or air, is supplied to the cathode (positive electrode). The fuel undergoes oxidation at the anode, releasing electrons, while the oxidant undergoes reduction at the cathode, consuming electrons. The overall reaction produces a potential difference, generating electricity.

Hydrogen Fuel Cell

In a hydrogen fuel cell, the overall reaction involves the oxidation of hydrogen and the reduction of oxygen to produce water. At the anode, hydrogen gas is split into protons (H⁺) and electrons (e-). The protons move through an electrolyte, while the electrons travel through an external circuit, creating an electric current. At the cathode, oxygen gas combines with the protons and electrons to form water. The overall reaction is:

• Anode: 2H₂ → 4H⁺ + 4e^-
• Cathode: O₂ + 4H⁺ + 4e^- → 2H₂O
• Overall: 2H₂ + O₂ → 2H₂O

Advantages of Hydrogen Fuel Cells:

Hydrogen fuel cells offer several advantages compared to rechargeable cells and batteries.

• They can provide a continuous supply of electricity as long as the fuel and oxidant are available.
• Fuel cells are highly efficient, converting a significant portion of the fuel's energy into electricity.
• They also produce only water as a by-product, making them environmentally friendly.

Half Equations in a Hydrogen Fuel Cell (HT only):

At the anode, the oxidation of hydrogen produces protons (H⁺) and electrons (e^-). At the cathode, the reduction of oxygen combines protons and electrons to form water. The half equations are:

• Anode: H₂ → 2H⁺ + 2e^-
• Cathode: O₂ + 4H⁺ + 4e^- → 2H₂O

Conclusion

Understanding fuel cells, such as hydrogen fuel cells, provides insights into their potential as a clean and sustainable energy technology. It also encourages critical thinkingThe ability to effectively analyse and evaluate arguments. about their advantages and limitations in comparisonIdentifying similarities and/or differences between texts. to other energy storage and conversionThe act of changing someone's religion. systems.