Operando Tracking of Atomic Hydrogen Dynamics and Lifetime Extension for Nitrate-to-Ammonia Electroreduction

Nitrate (NO3-) contamination in aquatic environments poses a significant threat to ecosystems and public health. The electrochemical nitrate reduction reaction (eNO3RR) represents a promising remediation approach, yet its efficiency is generally compromised by the rapid dimerization of atomic hydrogen (H*) into H2. In this work, we established a strategy that leverages hydrogen spillover to prolong the lifetime of H* intermediates and thereby benefits the overall reaction. Specifically, protons were first reduced to H* on NiOx sites, followed by the rapid H* spillover onto a Bi metallene support that facilitates NO3- adsorption and reduction. In situ UV-vis spectroscopy provided direct evidence to understand hydrogen spillover dynamics, and transient current measurements further quantified a 5-fold increase in H* lifetime. This work demonstrated a design principle to enhance the eNO3RR through stabilizing short-lived H* and presented a quantitative methodology to evaluate the hydrogen spillover behavior within the electrochemical realm.