Homologous heterostructures of Ni/NiFeO Mott–Schottky for alkaline water electrolysis

Abstract

Effective and economical bifunctional catalysts for electrochemical water splitting to produce H₂ are in high demand. The design of Mott–Schottky junctions by integrating metal nanoparticles with metal oxides has emerged as an effective method to boost the catalyst performance. Herein, a 3D homologous heterostructure Ni/NiFeO was synthesised by direct calcination of NiFe-LDH under a N₂ atmosphere. The Ni/NiFeO catalyst exhibits exceptional activity with minimal overpotentials of 98 mV@10 mA cm⁻² for the hydrogen evolution reaction and 284 mV@10 mA cm⁻² for the oxygen evolution reaction, and remarkable stability under 500 mA cm⁻² over 50 h. An overall water-splitting electrolyzer based on Ni/NiFeO can drive 10 mA cm⁻² at 1.60 V with long-term stability. Theoretical calculations confirm that metal Ni can improve the conductivity and optimize hydrogen adsorption. The formation of *OOH on the Ni/NiFeO heterostructure exhibits a much lower energy barrier of 3.20 eV, as compared to 4.66 eV on pure NiFeO. This reduction is attributed to the heterointerfaces within the Ni/NiFeO, which modulate the electronic structure and regulate the electron transfer pathways, thereby optimising the adsorption and desorption of reaction intermediates. This work provides a feasible strategy for the preparation of efficient electrochemical catalysts for water splitting.