Mn doping promotes deep surface reconstruction of CoP nanosheet arrays to drive efficient water splitting†

Abstract

Among the non-precious metal electrocatalysts, transition metal phosphides (TMPs) show the greatest promise, but their activity and stability still fall short of expectations. Therefore, in order to improve the catalytic activity of TMPs, doping of heteroatoms with different electronegativities becomes one of the best methods. In this study, Mn₁₀-doped CoP (the molar amount of Mn accounts for 10% of the total molar amount of metal salts) nanosheet arrays were successfully loaded on coal-based carbon nanofibers (CNFs) via electrodeposition and low-temperature phosphating. Experimentally, the generated electrocatalyst Mn₁₀-CoP@CNFs demonstrated remarkable catalytic activity at 10 mA cm⁻² in 1 M KOH solution, which only needed overpotentials of 62 mV and 230 mV for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. In situ Raman spectroscopy was used to explore the active intermediates present under catalytic conditions. The results showed that the incorporation of Mn into CoP promoted the formation of the active layered intermediate CoOOH, thus improving the performance of the OER. Prominently, at a current density of 10 mA cm⁻², the catalyst also exhibited durability of more than 80 hours and an extremely low voltage of 1.537 V when it was used as the full hydrolysis catalyst. This study provides a general approach for the production of high-performance and effective catalysts for water splitting.