Hybrid acid/alkali electrolysis toward industrial-scale H2 generation and sulfite oxidation conversion.

[Display omitted] • A hypotoxic molten-salt-assisted method was developed to synthesize Co 2 P (t-Co 2 P). • The t-Co 2 P can spontaneously transform into CoOOH in alkaline solutions. • The t-Co 2 P can effectively electrocatalysis acidic hydrogen evolution reaction. • CoOOH can effectively electrocatalysis alkaline sulfite (SO 3 2–) oxidation. • A hybrid acid-alkali electrolyzer was built for H 2 generation and sulfite removal. Co 2 P has been widely applied in a variety of applications yet still faces challenges in implementing hypotoxic and large-scale synthesis. We here report a scalable synthetic route to produce tussock-like nanostructured Co 2 P (t-Nano Co 2 P), which exhibits high-performance electrocatalytic properties toward acidic hydrogen evolution reaction (HER). Such t-Nano Co 2 P can evolve to CoOOH nanoplates that show excellent electrocatalytic activity for sulfite oxidation reaction (SOR) in alkaline solution. The findings encourage us to construct a hybrid acid/alkali electrolyzer with t-Nano Co 2 P and its CoOOH derivative as catalysts of acidic cathode for HER and alkaline anode for SOR, respectively, which performs excellently with capability of synchronous generation of H 2 and sulfate in an industrial-level rate at a relatively low applied voltage. The proof-of-concept electrolyzer, by virtue of the viability of scalable synthesis and high-production yield, holds great promise for co-production of H 2 and sulfate in an energy-effective and environmentally-friendly manner. [ABSTRACT FROM AUTHOR]