Defect and non-metallic doping co-engineering in two-dimensional transition-metal carbide-based electrocatalysts for renewable energy conversion

As an emerging member of the two-dimensional (2D) material family, MXenes have gained significant attention for electrocatalysis because of their unique physical and chemical properties; however, their practical performance is often restricted by nanosheet restacking and inherently low intrinsic activity. To address these challenges, defect and non-metallic doping co-engineering are of interest as efficient strategies to improve the electrocatalytic performance of 2D MXenes. We herein comprehensively and critically discuss theoretical and experimental advances involved in the mechanism, characteristics, fabrication strategies, and applications of defect and doping co-engineered MXene-based materials for electrochemical reactions. Furthermore, the synergistic effects of defects and non-metallic dopants on the electronic structure, adsorption/desorption energies of intermediates, and possible electrocatalytic mechanism on 2D MXene-based materials are highlighted. Current challenges and prospects of defect and doping co-engineered MXene-based electrocatalysts are discussed. This review aims to elucidate the nature of defect and non-metallic doping co-engineering in MXenes, offering valuable insights for designing advanced MXene-based electrocatalysts.