Nitrogen-doped 2D MXene-based catalysts: Synthesis, properties and applications for electrochemical hydrogen production

Designing advanced materials with a trade-off between overall electrocatalytic efficiency and economic cost for electrochemical hydrogen production is crucial to overcoming the current energy crisis and environmental issues. On the more 10-year journey since the discovery, transition-metal carbides/nitrides nanosheets (MXenes) have increasingly attracted attention as potential materials toward hydrogen/oxygen evolution reactions (HER/OER) because of their unique physical and chemical characteristics, but the layered restacking and low intrinsic electrochemical activity are dragging them out water-splitting technology. Doping MXenes with nitrogen atoms has recently been introduced as a facile but efficient strategy to accelerate the HER/OER efficiency by the optimization of electronic structure, surface terminations, and adsorption/desorption energies of intermediates on pristine MXenes. However, a comprehensive evaluation of the doping mechanism and content-structure-performance relationship of N-doped 2D MXene-related catalysts is still lacking. Thus, we herein systematically summarize synthetic strategies, theoretical calculations, properties, and applications of nitrogen-doped 2D MXenes for the HER and OER to give more fundamental insights into physicochemical characteristics of nitrogen-doped 2D MXenes to further design next-generation catalysts for the electrochemical hydrogen production and other applications.