Regulating catalytic kinetics in nanoclimbing-wall-like NiO/NiCoP hybrids for enhanced overall water splitting

Abstract

Developing integrated cost-efficient bifunctional electrocatalysts with unique architecture comparable to noble metals is greatly desirable for efficient electrocatalytic water splitting. Herein, a highly active NiO/NiCoP hybrid catalyst on nickel foam (NiO/NiCoP/NF) with a unique nanoclimbing-wall structure is constructed, which is believed to simultaneously improve electron transfer efficiency and catalytic activity. The resultant NiO/NiCoP/NF exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH, featuring low overpotentials of 92 and 216 mV at 10 mA cm⁻². A two-electrode system based on NiO/NiCoP/NF‖NiO/NiCoP/NF requires as low as 1.56 V to deliver a current density of 10 mA cm⁻². Theoretical calculations and in situ Raman characterization reveal that the positive synergy between NiCoP and NiO endows NiO/NiCoP/NF with accelerated HER and OER kinetics. Moreover, a high solar-to-hydrogen (STH) conversion efficiency ofs up to 12.40% is obtained by using NiO/NiCoP/NF as both the cathode and anode in a solar-driven water splitting system. This work provides a promising strategy for the construction of an innovative bifunctional electrocatalyst for efficient overall water splitting and the establishment of a synergistic catalytic mechanism.