Adapting Stringent Electrochemical Nitrogen Reduction Protocols for Catalysts with Ultralow Production Rates

Despite extensive research, an active, selective, and stable electrocatalyst for the electrochemical nitrogen reduction reaction (eNRR) in aqueous media remains elusive. Model catalytic architectures provide a valuable platform for testing active sites and compositions, understanding reaction mechanisms, and optimizing surfaces based on scaling relationships. However, current eNRR testing protocols, designed for high-surface-area catalysts, are often incompatible with the ultralow production rates typical of these materials, limiting insights into critical structure–activity relationships. This study adapts eNRR protocols to model catalysts, enabling reliable activity evaluation through rigorous control experiments. We systematically address sources of ammonia contamination and losses, assess trap effectiveness, and evaluate reactor configurations and electrochemical parameters while examining ammonia detection accuracy via ion chromatography and colorimetry. To demonstrate protocol robustness, we applied it to three thin-film catalysts─two transition metal oxynitrides (ZrON/Si and VON/Si) and a transition metal carbide (WC/Si)─and a high-surface-area Ru catalyst on nitrogen-doped carbon support (Ru/N–C). Results indicate that three of the four catalysts do not produce statistically significant ammonia, with the potential exception of vanadium oxynitride, where genuine eNRR activity may be present. Importantly, these adapted protocols enable the reliable detection of production rates as low as 3 pmol cm–2 s–1, advancing accurate and reproducible eNRR performance assessments.