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Developing high‐efficiency bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to realize low‐cost water splitting is the premise for large‐scale production of hydrogen. The catalytic activity of an electrocatalysts greatly depends on its composition and structure. In this work, we report the preparation of hollow CoS2/MoS2 heterostructure using ZIF‐67 as the precursor. The ratio of Co and Mo are optimized to maximize the synergy of CoS2 and MoS2, due to their specific catalytic activity for OER and HER. The optimized CoS2/MoS2 exhibits good bifunctional catalytic activity in view of its low overpotentials for HER (170 mV) and OER (270 mV), as well as small cell voltage of 1.66 V for overall water splitting. This work provides a facile strategy to controllable fabrication of efficient bifunctional electrocatalysts for renewable energy applications. [ABSTRACT FROM AUTHOR]

Benefiting from the high electrochemical surface area brought by the 2D nanosheet structure, MoS2 has received great research attention for the hydrogen evolution reaction (HER). Recently, it has been demonstrated that by constructing a transitional metal sulfide–MoS2 heterostructure, the HER performance of the MoS2-based catalysts can be further improved. It is even possible to obtain bifunctional catalysts for both HER and oxygen evolution reaction (OER) due to the synergistic effect of the different components in the composite, the electronic effect to enable an efficient electron transfer and appropriate binding energy for the intermediates of the electrocatalytic reactions, and the surface defects on the interface of the heterostructures. Herein, we review the recent progress on the construction of the transitional metal sulfide–MoS2 heterostructure for water splitting based on non-self-supporting and self-supporting catalysts. The surface and interface parameters of the heterostructures are discussed in detail to reveal the key roles of the hybrid structures for energy conversion. We also pay special attention to the theoretical simulations based on first principles to clarify the relationships between the electrochemical performance and structure parameters. Finally, the prospects and challenges of the transition metal sulfide–MoS2 heterostructures for water splitting in the future are proposed to prompt the reasonable design of transition metal sulfide–MoS2 heterostructures for full water splitting. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) have attracted increasing research interests owing to their unique electronic structures, quantum size effects and maximum utilization rate of atoms. Metal organic frameworks (MOFs) are good candidates to prepare SACs owing to the atomically dispersed metal nodes in MOFs and abundant N and C species to stabilize the single atoms. In addition, the distance of adjacent metal atoms can be turned by adjusting the size of ligands and adding volatile metal centers to promote the formation of isolated metal atoms. Moreover, the diverse metal centers in MOFs can promote the preparation of dual‐atom catalysts (DACs) to improve the metal loading and optimize the electronic structures of the catalysts. The applications of MOFs derived SACs and DACs for electrocatalysis, including oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, carbon dioxide reduction reaction and nitrogen reduction reaction are systematically summarized in this Review. The corresponding synthesis strategies, atomic structures and electrocatalytic performances of the catalysts are discussed to provide a deep understanding of MOFs‐based atomic electrocatalysts. The catalytic mechanisms of the catalysts are presented, and the crucial challenges and perspectives are proposed to promote further design and applications of atomic electrocatalysts. [ABSTRACT FROM AUTHOR]