Heterojunction of CoMoO4/SrTiO3 as efficient electrocatalysts for hydrogen evolution reaction and oxygen evolution reaction in alkaline media

Abstract

Developing efficient and cost-effective bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by modulation of the electronic states is critical for sustainable hydrogen production. In this study, we engineered a heterojunction between CoMoO4 (CMO) and SrTiO3 (STO). The p-n junction between CMO and STO tunes their electronic structure and redistributes the surface charges. The positive charge induced by the p-n junction offers greater adsorption of hydroxyls on the surface of the electrocatalysts. The optimized 60 % CMO/STO heterojunction exhibited the most promising bifunctional activity, achieving the lowest overpotential of 102 mV for HER and 280 mV for OER in alkaline media. Electrochemical studies revealed that the 60 % CMO/STO shows the highest double-layer capacitance (Cdl) and the largest electrochemically active surface area (ECSA), indicating superior charge transfer and active site availability. Moreover, based on work functions, the enhanced electron transfer and optimized hydroxyl ions adsorption due to the position charge distribution result in superior HER and OER performance. Additionally, it demonstrates the smallest Tafel slope, highlighting its enhanced reaction kinetics. This work highlights the role of heterojunction and interfacial electron transfer descriptors for enhanced OER and HER performance of the p-n junction, providing a venue to design a new electrocatalytic system for bifunctional activities.