Surface engineering assisted CoNiP nanosheet arrays for electrochemical overall water splitting

Abstract

Electrochemical overall water splitting is a green, environmentally friendly, and efficient hydrogen production method that involves two half-reactions: the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Due to the slow reaction kinetics of the OER and HER, electrochemical overall water splitting often requires a higher potential than the theoretical value, resulting in significant energy loss. Here, we report that a hybrid catalyst synthesized using cobalt oxyhydroxide (CoOOH) nanoparticles and 2D metallic CoNiP nanosheets on a conductive carbon fiber paper (CoNiP/CoOOH-CFP) shows significantly enhanced overall water splitting activity in alkaline electrolytes. The high activity of CoNiP/CoOOH-CFP may be due to the dual-function mechanism used in this hybrid catalyst, in which CoOOH promotes the adsorption and dissociation of water, thereby providing protons for the subsequent hydrogen evolution reaction on CoNiP and reducing the free energy of the oxygen evolution reaction. It is worth noting that our self-made alkaline electrolytic cell assembled with CoNiP/CoOOH-CFP as a dual-function catalyst can achieve a water splitting current density of 20 mA cm⁻² at a low battery voltage of 1.732 V. When a bias voltage of 1.73 V was applied, the performance of the hybrid catalyst remained unchanged after a 50 hour working cycle, indicating its good stability.