While the validity of this reaction has been proven to be effective through electrochemical means, the efficiency and selectivity still need to be improved to make it a cost-effective solution for the rural communities most affected by groundwater pollution. Specifically, a slightly acidic electrolyte solution has improved the selectivity of nitrate reduction to ammonia. While earlier studies had focused on the bulk pH role on selectivity, very few studies have tried to elucidate the role of interfacial pH on selectivity. Previous work done by our group has developed a protocol to measure the interfacial pH (10 nm from the electrode surface) by performing ATR–SEIRAS and reported the drastic swings in pH that were particularly dramatic in the first minute.
Our FTIR with rapid scanning capabilities allows us to track these dynamic and swift changes in interfacial pH. We performed calibration between 1 to 13 pH using a phosphate buffer system, recording a spectrum for every 0.2 pH increment. The ratio of the peak areas from the calibration data at known pH values is then used to identify the in situ pH under reaction conditions. The pH was measured before and after each in situ experiment at 0.1 V vs. the reversible hydrogen electrode (VRHE) to ensure reproducibility. These insights into interfacial pH dynamics have paved the way for future work to improve the selectivity of electrochemical nitrate reduction. This will advance the development of cleaner, more efficient ammonia production methods to benefit both the environment and vulnerable communities.