Increasing the active sites and intrinsic activity of transition metal chalcogenide electrocatalysts for enhanced water splitting

Electrochemical water splitting has been regarded as a promising technique for facilitating the conversion of sustainable energy. To realize the large-scale application of water electrolysis, it is urgent and imperative to develop low-cost, earth-abundant, high-efficient, and stable electrocatalysts to substitute noble-metal-based catalysts. Among the various nonnoble-metal-based electrocatalysts, transition metal chalcogenides (TMCs) have attracted considerable attention in recent years in the field of electrochemical water splitting because of their unique structural and electronic properties. Nevertheless, the limited number of active sites as well as sluggish electrochemical kinetics severely impede their electrochemical performances. Some valid strategies, such as increasing the number of active sites and enhancing the intrinsic activity of each active site via extrinsic and intrinsic modifications, have been consequently adopted to enhance electrochemical activities. Herein, a comprehensive overview of the developed strategies in optimizing the electrocatalytic activities of TMCs is reviewed. A unique emphasis is placed on the promising strategies to regulate the electronic structures of TMCs by surface vacancy/defect, heteroatom doping, strain regulation, phase transition, and heterostructure engineering. Moreover, the intrinsic mechanistic analyses of the electronic structure, intermediate adsorption, and coordination environment are also presented via theoretical simulation and advanced characterization techniques. Remaining challenges and future perspectives for the further development of promising water-splitting systems are discussed, too.