An aqueous Zn-polyoxometalate battery for decoupled hydrogen production from alkaline water electrolysis

Abstract

Decoupled water electrolysis is a feasible technique for the large-scale production of high-purity H₂, in which heteropolyacids are attractive electron-coupled proton buffers. An aqueous Zn-phosphomolybdic acid battery is designed for the simultaneous generation of reduced phosphomolybdic acid and electricity. The reported Zn-phosphomolybdic acid battery possesses an open circuit voltage of ∼1.50 V, and the coulombic efficiency of the Zn-phosphomolybdic acid battery can remain at a high level (>90%). Furthermore, the reduced phosphomolybdic acid can be used as an active electron-coupled proton buffer for efficient decoupled hydrogen production from alkaline water electrolysis in the presence of highly dispersed ultrafine Pt nanoparticles (∼2.0 nm) on nickel–cobalt hydroxide nanosheets at a low Pt loading (0.4 mg cm⁻²) as a free-standing electrode.