Time-Resolved Raman Spectroscopy of Nitrate Electroreduction Reveals Dynamic Interfacial Adsorbate Evolution

Nitrate electroreduction offers a pathway for coupling wastewater remediation with sustainable ammonia production, yet its mechanistic details under operating conditions remain poorly understood. In this work, we directly resolve the dynamic evolution of nitrate-derived intermediates at electrified interfaces, addressing a key limitation in understanding dynamic reaction pathways. We employ time-resolved surface-enhanced Raman spectroscopy (TR-SERS) to monitor the interfacial behavior of NO3– and NO2– during nitrate reduction on roughened silver electrodes and observe potential-dependent vibrational shifts attributed to systematic changes in adsorption modes under increasingly cathodic potentials. Density functional theory calculations further support the vibrational assignments and provide insight into preferred binding motifs across the applied potential range. By tracking the time evolution of adsorbates, this approach provides insights into the sequence of adsorption and transformation steps on silver. The combined experimental and computational analysis contributes to a molecular-level understanding of nitrate electroreduction and provides a framework for probing dynamic reaction intermediates in nitrogen conversion electrocatalysis.