MXene-Based Oxygen Electrocatalysts: Mechanistic Insights, Property Tuning Strategies, and Prospects toward Practical...

MXene delivers promising features that are highly compatible with oxygen electrocatalysis, such as excellent electroconductivity, high specific surface area, superhydrophilicity, and tailorable chemically functionalized surfaces, thus being recognized as the ideal platform for developing high-performance catalysts for practical applications in industrial devices. A comprehensive understanding of oxygen catalytic mechanism on MXene ontology and a systematic refining of the general principles toward various physicochemical property regulation strategies are, respectively, the basis and effective alleyway to hitting the target, yet it is currently insufficient and need to be further explored in-depth. Herein, the fundamental effects of MXene on oxygen catalytic activity are sorted out thoroughly, and on this basis, the current mainstream strategies for tuning the property of MXene-based electrocatalysts are classified into four categories, including anion-tuning, cation-tuning, defect/vacancy regulation, and heterometallic dual-site collaboration, where the intrinsic mechanism of each strategy affecting the structure-activity relationship of catalysts is revealed accordingly. Particularly, the indispensability of advanced in situ characterizations in establishing the dynamic process of oxygen electrocatalysis, including real-time structural evolution and reaction pathways is emphasized. Finally, the latest advances of MXene-based electrocatalysts are reviewed from the viewpoint of the metal-support interactions effect, along with forward-looking perspectives on addressing the present thorny challenges.