Aryl sulfur ligand-modulated silver catalysts with tailored binding affinity for selective nitrate-to-ammonia conversion.

Abstract

Manipulating the selectivity-determining step in the hydrogenation of nitrogen-containing intermediates is critical to achieving high ammonia selectivity in electrocatalytic nitrate reduction. Here, we propose a molecular interface engineering strategy that functionalized with thiol-anchored aromatic ligands to regulate the interfacial binding affinity and activation of key nitrogen-containing intermediates on silver nanocube surfaces. By systematically varying the electronic properties of the substituents, we identify 4-(methylthio)benzaldehyde as the most effective ligand, increasing the ammonia Faradaic efficiency from 50.8% to 98.9% and achieving a yield rate of 14,366.1 μg h^-1 cm_geo^-2 at -0.63 V versus reversible hydrogen electrode. In situ electrochemical characterizations combined with theoretical simulations further reveal that 4-(methylthio)benzaldehyde modification promotes the activation of weakly hydrogen-bonded water molecules and accelerates the hydrogenation of *HNO intermediates. This targeted modulation of interfacial binding affinity offers an effective strategy for selectivity control in electrocatalytic nitrate reduction. The enhanced performance is further validated in a membrane electrode assembly electrolyser, underscoring the practical viability of this molecular design strategy for selective nitrate conversion.