Basal Plane Passivation of Ti3C2Tx MXenes Through Prussian Blue Analogue Nanoparticles Anchoring for Efficient and Selective Electrochemical Ammonia Synthesis.

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 N2 adsorption, and hydrophilic surface terminations that hinder N2 binding and promote the competing hydrogen evolution reaction (HER). Herein, we report basal-plane activation of Ti3C2T+ MXenes via decoration with Prussian blue analogue (PBA) nanoparticles. The PBA nanoparticles mask hydrophilic surface groups, suppress HER, and enhance N2 adsorption. Strong synergistic interactions between PBA nanoparticles and the Ti3C2Tx 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 N2 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/Ti3C2Tx delivers the highest NH3 yield rate of 106 µg mgcat -1 h-1 (91 µg cm-2 h-1), whereas CuHCF/F-Ti3C2 achieves the highest Faradaic efficiency of 95% at -0.2 V.