Quantifying Nitrate Reduction to Ammonia Performance on Metal Foam Electrodes

Abstract Electrochemical nitrate reduction reaction (NO ₃ RR) has emerged as a promising strategy for sustainable ammonia (NH ₃ ) synthesis and the remediation of nitrate‐contaminated wastewater. However, the catalytic pathways for NO ₃ RR vary across different catalyst surfaces, which in turn affects the kinetics and selectivity of product formations. Therefore, it is necessary to establish a unified performance quantification for NO ₃ RR among commonly used catalysts. In this work, transition metal‐based foam electrodes—iron, cobalt, nickel, and copper, which are widely used as catalysts or substrates due to their excellent conductivity, high specific surface area and catalytic activity are systematically evaluated and compared to enable quantitative comparison of catalytic performance. Through comprehensive characterization of NO ₃ RR performance metrics, a standardized evaluation framework is established. Furthermore, advanced in situ optical imaging reveals the dynamic evolution of NH ₃ , intermediate nitrite, and hydrogen bubbles during NO ₃ RR, uncovering critical mechanistic insights and guiding the subsequent targeted loading and modification of catalysts. In addition, the zinc‐nitrate battery performance based on foam electrodes is also standardized and unified.