Unlocking the Critical Role of Noncovalent Interactions Between Alkali Metal Cations and Nitrate in Promoting the Reduction of Nitrate to Ammonia

Abstract The electrochemical nitrate reduction reaction (NO 3 − RR) is widely investigated for sustainable ammonia (NH 3 ) production from NO 3 − pollutants. Alkali metal cations (AM + ) in the electrolyte often greatly impact electrocatalytic performance; however, the role of AM + in the NO 3 − RR remains unclear. Here, we first investigate the influence of AM + on the Cu‐catalyzed NO 3 − RR, revealing an activity increase trend of Li + < Cs + < Na + < K + , which is inconsistent with the local electric field and proton transfer rate increase trend of Li + < Na + < K + < Cs + , hinting that the presence of other important factors governs the NO 3 − RR activity. Intriguingly, Ab initio molecular dynamic (AIMD) simulations uncover that Na + , K + , and Cs + with relatively soft solvation shells could be partially desolvated and then coordinate with NO 3 − via a short‐range electrostatic interaction, thereby boosting the rate determining step (RDS), that is the conversion of NO 3 − to NO 2 − . Notably, K + with suitable NO 3 − interaction strength has higher ability to boost the RDS than Na + and Cs + with too weak and strong strength, respectively. Our results highlight that the short‐range electrostatic interaction strength of AM + /NO 3 − is a crucial factor to determine the NO 3 − RR activity.