Electronic structure engineering on two-dimensional (2D) electrocatalytic materials for oxygen reduction, oxygen evolution, and hydrogen evolution reactions

Two-dimensional (2D) materials with the conservation of 2D configuration are excellent candidates for fundamental energy conversion and storage research and potential candidate for commercial applications. In this regard, this comprehensive review highlights the recent advances in the electronic structure tuning of 2D materials such as carbon/graphene, metal chalcogenides, metal oxides/hydroxides, MXenes, toward electrocatalytic energy conversions such as oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). First, this review offers a systematic summary of the classification, controllable synthesis, and formation mechanism of 2D nanomaterials. Later, the strategies for tuning the electronic structure of 2D nanomaterials, and further their impact on electrocatalytic properties are summarized, namely doping, defect engineering, temperature effect, composite and heterostructure formation. The recent development of electrocatalysts with novel nanosheets structures and compositions were discussed deeply. The understandings of the correlation between the electronic nature, activity and the shape, size, composition, and synthesis methods were summarized. Finally, some personal perspectives on future challenges of this research field will also be presented.