Zeolitic imidazolate framework-67 derived cobalt-based catalysts for water splitting

Developing novel electrocatalysts for efficient active hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial in improving water splitting efficiency. Derivatives of cobalt-based zeolitic imidazolate framework-67 (ZIF-67) have received extensive research and application interest due to the abundant metal-atom incorporation, highly porous structure, good electrical conductivity, efficient mass transfer, and excellent multifunctional catalysis in electrocatalytic reactions. ZIF-67-derived Co-based electrocatalysts exhibit superior intrinsic activity for electrochemical water splitting, which is attributed to the proper binding energy of Co with hydrogen and oxygen. In this review, we summarized the structural features of ZIF-67 and several important ZIF synthesis methods, especially solvothermal and hydrothermal methods. Then, we reviewed the recent research efforts toward developing advanced Co-based electrocatalysts (oxides/sulfides/phosphides/selenides) based on ZIF-67 for highly efficient water splitting with a focus on the influence of the composition and structure engineering (porous, hollow, and hierarchical structure) of ZIF-67 derivatives. Some techniques to improve the stability in acid electrolytes have been emphasized in terms of coordination environments and morphology structures. Furthermore, the bottleneck steps of ZIF-67 derivatives for the HER and OER are discussed combined with key performance-related parameters to provide insights into the role of composition and structure engineering. Finally, this review concludes the development trend of ZIF derivatives and our perspectives on their opportunities and challenges as potential water splitting electrocatalysts.