Deciphering Cation-Stabilized *NO <sub>2</sub> at the Molecular Level in Electrocatalytic Nitrate Reduction
Ru-Yu Zhou, Shisheng Zheng, Rui Ma, Yao-Hui Wang, Mengting Zhao, Chongyuan Zhai, Dong Jin-Chao, Feng Pan, Jian-Feng Li
Abstract
Electrochemical nitrate reduction (NO 3 RR) offers a sustainable pathway for ammonia (NH 3 ) production, yet its advancement is limited by a lack of molecular-level understanding of interfacial reaction dynamics. Here, we unravel a synergistic interfacial mechanism for rational catalyst design based on cooperative interfacial modulation. By integrating in situ Raman spectroscopy with multiscale simulations, we uncover a cation-mediated stabilization mechanism of the key *NO 2 intermediate on atomically defined Au single-crystal surfaces. We demonstrate that electrolyte cations play a critical role in modulating the local electric field and stabilizing *NO 2 via interfacial coordination, thereby controlling its interfacial reactivity and subsequent transformation. Armed with this insight, we employ Sn heteroatom modification to achieve dual-function optimization. The electronic interaction between Sn and Au weakens *NO 2 adsorption, lowering the hydrogenation barrier, while the altered interfacial water structure facilitates proton transfer through a reinforced hydrogen-bond network. This synergistic modulation leads to enhanced NH 3 selectivity and suppressed hydrogen evolution. Our findings highlight a paradigm shift from an active-site-centric catalyst design to an integrated approach that considers the entire electrochemical interface, where electronic, ionic, and solvent effects are concurrently tuned. This work provides both molecular-level mechanistic insights and a generalizable strategy for designing advanced electrocatalysts for NO 3 RR and broader proton-coupled electron transfer reactions.