Oxygen and sulfur dual vacancy engineering on a 3D Co3O4/Co3S4 heterostructure to improve overall water splitting activity

Abstract

Electrochemical water splitting is a highly efficient approach for realizing industrial hydrogen production. Nonetheless, electrocatalysts suffer from low efficiency and high energy consumption. Herein, a novel vacancy engineering strategy for the fabrication of a Ni foam-supported Co₃O₄/Co₃S₄ heterojunction with rich O and S dual vacancies (DV-Co₃O₄/Co₃S₄@NF) is proposed. The oxygen vacancy optimizes the electron distribution on the spinel surface and reduces the energy barrier for the adsorption of OH* free radicals. Meanwhile, the sulfur vacancy provides highly active sites for H* adsorption, thanks to the exposed active edge of spinel, leading to enhanced hydrogen evolution reaction (HER) performance. Benefiting from the synergistic effect of O and S dual vacancies, the DV-Co₃O₄/Co₃S₄@NF exhibits outstanding electrocatalytic activity for both the OER and HER with small overpotentials of 99 and 26 mV at 10 mA cm⁻², respectively. Moreover, as the bifunctional electrocatalyst for overall water splitting (OWS), the DV-Co₃O₄/Co₃S₄@NF requires only a low cell voltage of 1.52 V to obtain a large current density of 20 mA cm⁻², and the cell voltage remains basically unchanged for more than 200 h. More importantly, the DV-Co₃O₄/Co₃S₄@NF acting as both the anode and the cathode was assembled into a cell, powered by a single self-assembled 1.5 V AA battery device, which is very suitable for the needs of industrial hydrogen production. This work provides theoretical and pragmatic guidelines for the development and mechanism exploration of electrocatalysts.