Nitrate contamination, primarily from agricultural runoff and industrial discharge, poses environmental risks, as wastewater treatment effluents can contain up to 30 mg/L of nitrate. Addressing this issue through the electrochemical nitrate (NO3⁻) reduction (NO3R) to ammonia (NH3) presents a sustainable approach to ammonia production while mitigating nitrate pollution in wastewater. 

While catalyst activity is important, the interfacial microenvironment controls reaction kinetics, intermediate stabilization, ion transport, and consequently the activity and selectivity of NO₃RR. Among the most influential factors are the identities and concentrations of cations present in solution, which are unavoidable in practical wastewater systems. 

In this study, we systematically investigate the impact of common alkaline cation species, Li+, Na+, K+ and Cs+, on the electrochemical reduction of nitrate to ammonia in acidic medium. Nitrite and ammonia were quantified by UV–Vis spectroscopy with calibration curves prepared in the corresponding background electrolyte for each cation condition. Assays were automated using an Opentrons liquid-handling system. Hydrogen was quantified by GC. Preliminary results reveal a volcano shaped trend of ammonia Faradaic efficiency on alkali cation ionic radius, with Na⁺, Li+, and K+ exhibiting varying trends in NH3 selectivity.