MXene Electrocatalysts for Selective Nitrogen Reduction Reaction‐to‐Ammonia Production: Surface Chemistry, Electronic Framework, and Design Principles

The electrochemical nitrogen reduction reaction (eNRR) is considered a promising approach to sustainable ammonia production compared with the Haber–Bosch process. However, eNRR remains significantly hindered by the extreme stability of the N≡N bond, slow proton‐coupled electron transfer (PCET), and the kinetically favored hydrogen evolution reaction (HER), which collectively reduce ammonia yield and Faradaic efficiency. MXenes represent a unique class of 2D transition‐metal carbides, nitrides, and carbonitrides, distinguished by chemically versatile transition‐metal active sites, defect‐rich structures, tunable surface terminations, and metallic conductivity. These properties enable unprecedented tuning of N 2 adsorption, interfacial charge redistribution, orbital hybridization, and adsorption energetics, enabling selective N 2 activation while minimizing competing proton reduction. This review provides a critical overview of the design principles of MXene‐based electrocatalysts for selective ammonia synthesis. The distinctive contribution of this review is to systematically link MXene composition, vacancy engineering, heteroatom doping, single‐atom anchoring, and assembling MXene heterostructures to their effects on electronic structure, adsorption free‐energy landscapes, NRR pathways, and HER suppression. Particular emphasis is placed on understanding catalytic selectivity in terms of the underlying mechanism and structure–activity relationships, derived through advanced operando characterization, density functional theory, and emerging machine‐learning‐assisted catalyst discovery.