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The large-scale application of clean electrochemical energy storage and conversion systems such as water-splitting devices and Zn–air batteries greatly depends on the development of low-cost and highly efficient electrocatalysts. Transitional metal sulfides (TMSs) have gained great research interest owing to their high intrinsic catalytic activity, adjustable electronic structures, and various crystal structures and phases. Meanwhile, metal–organic frameworks (MOFs) are ideal precursors for the preparation of TMSs due to the diverse metal nodes, organic ligands, topologies, and morphologies of MOFs. In addition, MOFs could act as hosts for the incorporation of guest molecules, which could further expand the metal types of TMSs. In this review, the recent progress of MOF-derived TMS electrocatalysts for hydrogen evolution reactions (HERs), oxygen evolution reactions (OERs) and oxygen reduction reactions (ORRs) are summarized. After a brief introduction to the reaction mechanisms, the preparation strategies, structures, catalytic performances, and catalytic mechanisms of the TMSs are discussed to give readers a comprehensive understanding of this prosperous field. The strategies such as nanostructure engineering, interface engineering and heteroatom doping used to improve the performance of the electrocatalysts are discussed in each section. In addition, bifunctional catalytic performances of the catalysts for overall water splitting and rechargeable Zn–air batteries are illustrated. Furthermore, challenges and opportunities for the future development of this field are proposed. We expect this review could provide guidelines for the design and fabrication of TMSs, and initiate more efforts and new discoveries in this emerging research area. [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]