Rational Design of Bifunctional CoS2/MoS2 Catalysts with Abundant Heterointerfaces for Efficient Overall Water Splitting.

Developing low-cost, highly efficient bifunctional non-noble-metal catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for the application of overall water splitting. Herein, we report the rational design of a CoS2/MoS2 heterostructure with abundant interfaces by a facile two-step hydrothermal strategy. Owing to its unique three-dimensional structure with rich channels, the CoS2/MoS2 assembly provides a large amount of electrochemically active surface area and charge transfer pathways. In addition, the electron transfer from CoS2 to MoS2 at the interfaces not only enhances the conductivity of MoS2 but also optimizes the adsorption of intermediates in both the HER and OER processes. More importantly, MoS2 and CoS2, serving as the active centers for HER and OER, respectively, work in synergy to jointly promote the splitting of water molecules. Consequently, the optimized CoS2/MoS2-0.1 (where "0.1" represents the Co/Mo molar ratio) electrocatalyst exhibits excellent bifunctional performance with small overpotentials of 127 mV for HER and 252 mV for OER at 10 mA cm-2, as well as good stability for 24 h. In addition, a low cell voltage of 1.61 V is required to achieve the current density of 10 mA cm-2 toward overall water splitting by assembling CoS2/MoS2-0.1 into a two-electrode electrolyzer.