ZIF-67-derived CuCo2S4@CoS2 as an efficient bifunctional electrocatalyst for overall water splitting

Abstract

Non-precious metal sulfide bifunctional electrocatalysts with high efficiency for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hold great promises in the overall water splitting field. In this study, a hybrid bifunctional catalyst CuCo₂S₄@CoS₂ was fabricated by synthesizing CuCo₂S₄ with ZIF-67 as a template and externally modified with CoS₂. The CuCo₂S₄@CoS₂ catalyst exhibited improved alkaline oxygen evolution and hydrogen evolution activities with the overpotentials of 261 mV@10 mA cm⁻² and 153 mV@10 mA cm⁻², respectively. The three-dimensional interconnected nanosheet stacked structure, high conductivity of CuCo₂S₄, and strong interfacial interactions endowed the hybrid CuCo₂S₄@CoS₂ catalyst with enhanced HER and OER performance due to rich electrocatalytic active sites, fast diffusion pathways for reactants and intermediates, and reduced kinetic barriers. An electrolytic cell using CuCo₂S₄@CoS₂ as both cathode and anode required a cell voltage of 1.61 V, along with good long-term stability, to deliver a current of 10 mA cm⁻², suggesting a promising bifunctional electrocatalyst for overall water splitting.