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Fuel Cells
World B — Acids, Bases & Solutions
VS
R25.01 Continuous Feed
- Batteries store chemical energy (closed system).
- Fuel cells convert continuous external fuel (open system).
- Never "dies" as long as fuel is supplied.
R25.02 The Hydrogen Anode
- $H_2$ gas enters and hits a platinum catalyst.
- Oxidation occurs: $H_2 \rightarrow 2H^+ + 2e^-$.
- Splits into protons and electrons.
R25.03 The PEM
- Proton Exchange Membrane (Solid electrolyte).
- Selectively permeable.
- Allows $H^+$ through, blocks $e^-$.
R25.04 The Oxygen Cathode
- $O_2$ enters from the air.
- Reduction occurs: $O_2 + 4H^+ + 4e^- \rightarrow 2H_2O$.
- The only byproduct is pure liquid water.
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R25.05 Electron Pathway
- Blocked by the PEM, electrons must take an external route.
- This forced detour creates the electrical current.
- Powers external devices before reaching the cathode.
R25.06 Thermodynamic Efficiency
- Combustion wastes massive energy as heat (Carnot limit).
- Fuel cells convert chemical energy *directly* to electricity.
- Can achieve 60-80% efficiency.
R25.07 Mobility & Space
- Powered the Apollo space missions (providing power + drinking water).
- Fuel Cell Electric Vehicles (FCEVs).
- Fast refueling compared to battery EVs.
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H₂
H₂O
R25.08 Green Hydrogen Nexus
- Solar/Wind power + Electrolysis = Green $H_2$.
- Fuel Cell converts $H_2$ back to electricity + Water.
- A perfectly circular, zero-carbon energy economy.