IGCSE›Cambridge IGCSE Chemistry›Mind mapsHydrogen-Oxygen Fuel CellsCambridge IGCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat it isMakes electricity directly from hydrogen and oxygenFuel is not burnedWater is the only chemical productSame overall reaction as hydrogen combustionEnergy comes out as electrical, not heatCharge flowElectrons flow round the external circuitThis flow of electrons is the currentIons move through the electrolyteIon movement completes the circuitHalf-equationsOxidation (electron loss) at the hydrogen electrodeReduction (electron gain) at the oxygen electrodeElectrons lost equal electrons gainedSame pattern as electrolysis, run in reverseFuel cellshydrogen and oxygenH2O2AdvantagesNo carbon dioxide or pollutants from the vehicleCan be more efficient than a combustion engineCombustion engines waste more energy as heatDisadvantagesHydrogen is hard and costly to storeHighly flammable and bulky as a gasFew refuelling stationsMaking hydrogen needs energy, often from fossil fuelsExam tipsSay: electricity with water as the only productOxidation is at the hydrogen electrode, not oxygenMention hydrogen storage in disadvantages