A　formaldehyde-phosphomolybdic　acid　battery　is　designed　to　simultaneously　achieve　the　production　of　reduced　phosphomolybdic　acid　with　electricity　and　hydrogen　generation,　in　which　CuxO　nanowire　arrays　in-situ　grown　on　Cu　foam　is　used　as　an　efficient　porous　electrode　for　the　H-2　production　from　the　electrooxidation　of　formaldehyde.　And　the　reduced　polyoxometalate　can　further　act　as　an　electron-coupled　proton　buffer　for　the　decoupled　hydrogen　production　from　water　electrolysis.　The　reported　battery　possesses　an　open　circuit　voltage　of　about　0.95　V　with　a　peak　power　density　of　8.0　mW　cm(-　2).　Multiple　discharge　experiments　reveal　that　the　Faradaic　efficiency　for　the　hydrogen　production　from　anodic　formaldehyde　oxidation　is　sustained　at　similar　to　100%,　and　a　repeatable　current　density　curve　of　the　hydrogen　production　with　a　theoretical　maximum　coulombic　efficiency　of　100%　can　be　achieved　by　oxidizing　the　reduced　phosphomolybdic　acid,　suggesting　a　good　stability　of　the　reported　cell　device　for　dual-decoupled　hydrogen　production.