Theoretical study of hybridized heterojunction structure for highly efficient bifunctional water electrolysis

Abstract

The alternative energy industry that can potentially solve the global environmental problems caused by excessive consumption and depletion of fossil fuels is attracting much attention. Electrochemical catalysts are the core material in the alternative energy industry. In the process of many studies being conducted to improve the performance of existing catalysts, the first principles calculation method based on the density functional theory (DFT) is It has become an essential tool for understanding the interaction of reactants and reaction mechanisms. This tool is essential for the development of high-efficiency, earth-rich bifunctional electrocatalysts that demonstrate oxygen evolution (OER) or hydrogen evolution (HER) activity and stability in the same electrolyte for industrial hydrogen production. Among noble metal-free transition metal-based electrocatalysts, Co- and Mo-based sulfides have received considerable interest for OER and HER applications due to their abundance of electrochemically active sites and favorable electrical composition for fast charge transfer. Here, we report on the catalytic activity of a theoretical model of a bifunctional hybrid CoS/MoS2 catalyst for water electrolysis. We preferentially established the CoS/MoS2 heterojunction structure using CoS(0 0 1) and MoS2 surfaces to explore enhanced HER and OER catalytic activity in hybrid CoS/MoS2 systems. Considering the lattice mismatch between the two surface structures, all possible heterojunction structures were constructed such that minimal strain was applied to the two surface structures. The calculated catalytic activity results show that the CoS/MoS2 structure has significantly lower HER and OER overpotentials of (0.03 V and 0.39 V) and outperforms the pure catalytic (CoS, MoS2) and S defect systems. It was confirmed that this is due to the one-way electron transfer effect that can simultaneously activate the oxidation/reduction reaction of CoS/MoS2 and the synergistic effect due to a specific transformation when the two surface structures are combined in terms of geometrical properties. In conclusion, we argue that the performance of the CoS/MoS2 heterostructure catalyst is competitive with that of the conventional Pt and RuO2 catalysts used for HER and OER, respectively.