AQA 3.1.11.2 · OCR A 5.2.3 · Year 13
Fuel cells, storage cells and rechargeable cells
See what happens during discharge, reverse a rechargeable cell correctly, and use unfamiliar fuel-cell data without memorising chemistry your board does not require.
Primaryreactants stored insidenot normally rechargeable
Rechargeablereaction reversed electricallyexternal energy on charge
Fuel cellfuel + oxidant suppliedruns while supplies continue
Commercial cell lab
Track the electron flow through each cell
AQA and OCR A
Learn the chemistry your board actually asks for
Same principle
During spontaneous discharge, oxidation releases electrons at the negative electrode and reduction consumes them at the positive electrode. Rechargeable cells reverse the chemistry using an external electrical supply.
Examiner-report traps
These mistakes recur because the ideas are easy to blur together
Calling a fuel cell rechargeable because it can keep operating.
Saying air supplies hydrogen; air supplies the oxidant, usually oxygen.
Writing the discharge equation again when the question asks about recharging.
Forgetting to cancel H2O, OH− or other identical species after combining half-equations.
Assuming a commercial voltage must equal E°cell even under non-standard conditions.
Calling hydrogen automatically carbon-neutral without considering how the hydrogen was produced.