Defect-driven MXenes for enhanced electrocatalytic nitrogen reduction: a first-principles and microkinetic study.
The electrocatalytic nitrogen reduction reaction (ENRR) offers a sustainable pathway for ammonia synthesis under mild conditions, yet its practical implementation is hindered by poor N2 activation efficiency and the lack of a clear structure-activity relationship for rational catalyst design. Herein, we systematically investigate the electrocatalytic performance of vacancy-engineered M2CT2 (M = Ti, Nb, and Mo; T = O, S, Cl, and Br) MXenes for the ENRR using well-defined density functional theory calculations combined with microkinetic modeling. Our results demonstrate that surface vacancies significantly modulate the local electronic structure of MXenes, thereby promoting N2 adsorption and activation. The results demonstrated that the ENRR proceeded on VT-M2CT2 through the distal pathway according to free energy calculations. A novel descriptor, Ψ, based on the valence of the transition metal and the lattice constant, is proposed to establish a quantitative structure-activity relationship, enabling rapid screening of high-performance catalysts. Among the candidates, vacancy-engineered Ti2CBr2 exhibits outstanding ENRR activity, as further validated by microkinetic analysis. This work provides a universal strategy for the design of defect-mediated MXene catalysts and paves the way for the development of efficient ENRR electrocatalysts.