Basal Plane Passivation of Ti 3 C 2 T x MXenes Through Prussian Blue Analogue Nanoparticles Anchoring for Efficient and Selective Electrochemical Ammonia Synthesis

Abstract

ABSTRACT Two‐dimensional (2D) MXene‐based materials have emerged as promising electrocatalysts for aqueous nitrogen fixation. However, their performance is limited by inactive basal planes, weak N 2 adsorption, and hydrophilic surface terminations that hinder N 2 binding and promote the competing hydrogen evolution reaction (HER). Herein, we report basal‐plane activation of Ti 3 C 2 T+ MXenes via decoration with Prussian blue analogue (PBA) nanoparticles. The PBA nanoparticles mask hydrophilic surface groups, suppress HER, and enhance N 2 adsorption. Strong synergistic interactions between PBA nanoparticles and the Ti 3 C 2 T x matrix significantly boost electrocatalytic nitrogen reduction reaction (ENRR) activity, while MXenes provide mechanical robustness and chemical stability to the PBAs. The degree of basal plane activation and synergism is tuned by varying the transition metal centers in PBAs and by controlling MXene surface termination in the composites. The PBA metal centers regulate N 2 adsorption strength and stabilization of reaction intermediates, whereas MXene terminations control proton accessibility and electron transfer, collectively dictating ENRR selectivity. Owing to favorable d‐orbital interactions, FeHCF/Ti 3 C 2 T x delivers the highest NH 3 yield rate of 106 µg mg cat −1 h −1 (91 µg cm −2 h −1 ), whereas CuHCF/F‐Ti 3 C 2 achieves the highest Faradaic efficiency of 95% at ‐0.2 V.