Effect of pH on the Electrochemical Reduction of Nitrate on Metallic Copper

The electrochemical reduction of nitrate (NO 3 − ) presents a promising route for wastewater treatment and nitrogen cycle restoration. In this work, we investigate the influence of pH on the electrochemical nitrate reduction reaction (NO 3 RR) using metallic copper as a model catalyst. We systematically examine pH effects within the range of 4.4 to 9.3 through electrochemical experiments, such as on line differential electrochemical mass spectrometry (DEMS) and in situ Fourier transform infrared (FTIR) spectroscopy. Our findings reveal that the NO 3 RR mechanism is highly dependent on the electrolyte pH, dictating the rate‐determining step and the formation of reaction intermediates. Under mildly acidic conditions (pH 4.4), NO formation is favored, while at mildly alkaline pH (9.3), byproducts such as N 2 O and N 2 H 4 emerge due to lower proton concentration that hinders oxygenated intermediate hydrogenation. In situ FTIR spectroscopy reveals local pH alkalinization during NO 3 RR, shifting phosphate equilibria and influencing reaction selectivity. These insights emphasize the critical role of electrolyte pH in tuning product distribution and reaction pathways. Our work highlights the importance of electrolyte engineering for optimizing electrochemical nitrate reduction, contributing to sustainable nitrogen management strategies.