Surface Oxophilicity Driven ^*N Pathway Tuning for Selective Nitrate Electroreduction to Nitrogen.

Abstract

Electrochemical reduction of nitrate to nitrogen (N₂) offers a sustainable pathway to close the nitrogen cycle and mitigate nitrate pollution. However, for Cu, Co, and other transition-metal catalysts, high N₂ selectivity has mainly relied on breakpoint chlorination, which consumes large amounts of chlorine and poses secondary contamination risks. Here, we introduce a surface-oxophilicity strategy to steer the ^*N pathway, thereby enhancing both catalytic efficiency and intrinsic nitrogen selectivity. Among oxophilicity-modified Pd, Sn doping emerged as the optimal configuration. The resulting PdSn metallene aerogels achieve remarkable NO₃ ^--N conversion (∼97%) and N₂ selectivity (∼99%), together with long-term stability (>600 h) and broad tolerance to variable nitrate concentrations. In situ characterization and theoretical analyses reveal that Sn-induced oxophilicity strengthens nitrogen-oxygen intermediate adsorption, ensuring sufficient ^*N availability for N-N coupling while elevating the hydrogenation barrier of ^*N → ^*NH, thus suppressing NH₃ formation. Integrated into a Zn-NO₃ ^- battery and a customized gas-integrated flow electrolyzer, the catalyst enables efficient nitrate removal and nearly complete N₂ selectivity, offering a promising platform for sustainable nitrogen recycling and energy conversion.