Technologies　for　industrial　pollutant　purification　and　hydrogen　(H2)　production　via　water　reduction　are　effective　for　environmental　management　but　are　often　energy-intensive,　costly,　and　result　in　direct/indirect　carbon　emissions.　Here,　we　report　a　formaldehyde-water　fuel　cell　that　uses　formaldehyde　as　fuel　and　the　hydrogen　evolution　reaction　(HER)　as　the　cathode　reaction,　converting　pollutant　at　the　anode　into　valuable　chemicals　while　simultaneously　producing　H2　at　the　cathode　through　water　reduction,　and　generating　electricity　without　any　carbon　emissions.　The　anodic　formaldehyde　1-electron　oxidation　reaction　(FOR-1)　produces　formate　and　H2,　enabling　fuel　cell　to　simultaneously　and　equimolarly　generate　H2　fuel　at　both　cathode　and　anode.　For　each　1　Nm3　H2　generated,　38.5　mol　of　formate　and　0.062　kWh　of　electricity　are　produced.　Experiments　and　simulations　indicate　that　the　weak　intrinsic　reactivity　of　hydrogen　on　Cu　among　various　catalysts　prevents　excessive　oxidation　of　formaldehyde,　ensuring　the　selectivity　of　FOR-1.　The　innovative　fuel　cell,　coupling　HER　with　a　low　oxidation　potential　half-reaction,　offers　an　energy-free　alternative　for　water　reduction　and　pollutant　treatment.　©　2025