Which one of the following is the exhaust pipe emission from Fuel Cell Electric Vehicles, powered by hydrogen ?
- (a) Hydrogen peroxide
- (b) Hydronium
- (c) Oxygen
- (d) Water vapour ✓ UPSC's answer
Why the answer is (d)
• A hydrogen fuel-cell vehicle combines hydrogen from its tank with oxygen from the air in a proton-exchange-membrane fuel cell; the reaction produces electricity to drive the motor, with water as the only chemical product.
• The exhaust is therefore water vapour (and some warm air), making FCEVs zero-emission at the tailpipe — option (d).
• Hydrogen peroxide and hydronium ions may appear transiently in electrochemistry but are not emitted.
• Oxygen is consumed, not emitted.
• Toyota's Mirai and Hyundai's Nexo are commercial examples; India's National Green Hydrogen Mission is piloting such buses.
Why the other options are wrong
- (a) Hydrogen peroxide
- Hydrogen peroxide is not the product of the fuel-cell reaction.
- (b) Hydronium
- Hydronium is an intermediate ion, not an exhaust emission.
- (c) Oxygen
- Oxygen is consumed by the fuel cell, not emitted.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2024, held on 16 June 2024. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.