Highly efficient hydrogen evolution from water electrolysis using nanocrystalline transition metal phosphide catalysts

Abstract

Nanocrystalline transition metal phosphides (CoP and Ni₂P) were successfully synthesized by a simple calcination method by using transition metal hydroxides and NaH₂PO₂ as raw materials. Their catalytic activities for the hydrogen evolution from water electrolysis were evaluated with silicotungstic acid as an electron-coupled-proton buffer, whereby hydrogen and oxygen could be produced separately. It was found that the CoP sample showed higher catalytic activity (32 mmol min⁻¹ g⁻¹) and good stability (12 h) as compared to the Ni₂P sample, and its catalytic activity could rival that of the commercial Pt/C catalyst. The electrochemical results revealed that CoP had high cathodic current and small charge transfer resistance, which further suggested it was indeed an efficient noble metal-free catalyst for hydrogen evolution from water electrolysis.