Clean Power from Hydrogen
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) directly into electricity through a pair of redox reactions.
How a Hydrogen Fuel Cell Works (PEM Fuel Cell)
Components: Anode, cathode, and an electrolyte membrane (a Proton Exchange Membrane, or PEM).
Reaction at the Anode (-): Hydrogen gas (H₂) is supplied to the anode. A catalyst (usually platinum) splits the H₂ into protons (H⁺) and electrons (e⁻).
2H₂ → 4H⁺ + 4e⁻
Movement: The protons (H⁺) pass through the electrolyte membrane to the cathode. The electrons (e⁻) cannot pass through the membrane, so they are forced to travel through an external circuit, creating an electric current that can power a device.
Reaction at the Cathode (+): Oxygen from the air is supplied to the cathode. The electrons from the external circuit and the protons from the membrane combine with oxygen to form water, which is the only byproduct.
O₂ + 4H⁺ + 4e⁻ → 2H₂O
Overall Reaction: 2H₂ + O₂ → 2H₂O + Electricity + Heat
The Hydrogen Economy
The hydrogen economy is a proposed system of delivering energy using hydrogen.
Concept: Use clean, renewable electricity (from solar or wind) to produce hydrogen gas via the electrolysis of water (the reverse of the fuel cell reaction). Then, use that hydrogen as a clean, portable energy carrier to power vehicles (with fuel cells) or generate electricity when needed.
Advantages and Challenges
Advantages:
Zero Emissions at Point of Use: The only byproduct is water.
High Efficiency: Fuel cells can be more efficient than internal combustion engines.
Energy Security: Hydrogen can be produced domestically from various sources (including water).
Challenges:
Production: Most hydrogen today is produced from natural gas, which releases CO₂. Clean production via electrolysis is currently expensive.
Storage: Storing hydrogen safely and compactly on a vehicle is a major technological hurdle (it's either a high-pressure gas or a cryogenic liquid).
Infrastructure: A whole new infrastructure of hydrogen production plants and fueling stations would need to be built.