MXene Nanoarchitectonics: Defect-Engineered 2D MXenes towards Enhanced Electrochemical Water Splitting

2D MXenes-based nanoarchitectures are being actively explored for electrocatalytic water splitting because they possess physical and physiochemical properties that enhance catalytic activity toward the hydrogen evolution reaction and oxygen evolution reaction. This review systematically summarizes current strategies involved in defect engineering, including introducing atomic vacancies and active edges, and doping with metal and non-metal atoms, which have been employed to achieve high-efficiency MXenes-based catalysts. The electronic structures, optimized adsorption/desorption energies of the intermediates, and possible catalytic mechanisms resulting from various defects are disclosed based on combined experimental results and theoretical calculations. Current challenges and future opportunities for the mechanistic investigation and practical application of defective MXenes-based catalysts are proposed. This report aims to reveal the nature of defective MXenes electrocatalysts and to provide valuable guidelines for designing defective MXenes-based nanoarchitectures for various catalytic reactions.