<p>The electrocatalytic nitrate reduction reaction (NO₃RR) has emerged as a promising approach for sustainable nitrogen management, enabling the selective conversion of nitrate into targeted nitrogen-containing compounds, such as ammonia and hydroxylamine. However, the efficiency and selectivity of the NO₃RR are highly dependent on the physicochemical properties of the electrocatalysts, necessitating a standardized and comprehensive characterization protocol. Here we provide a detailed methodology for the structural, chemical, electronic and electrochemical characterization of the materials used in the NO₃RR. We outline procedures for evaluating catalyst morphology, composition and redox states, as well as methodologies for quantifying reaction products to determine nitrate conversion efficiency and selectivity. To track catalyst evolution and reaction pathways under reaction conditions, we present real-time monitoring strategies that capture structural changes, key reaction intermediates and electronic transformations associated with chemical bond formation and cleavage. In addition, we incorporate theoretical calculations to comprehensively evaluate the reaction pathways and their interplay with the electronic structures of electrocatalysts, providing deeper mechanistic insights into the reaction kinetics, active site evolution and selectivity-determining factors. This Protocol is designed for researchers in electrocatalysis, environmental chemistry and energy conversion, offering a reproducible workflow for catalyst assessment. The step-by-step methodology ensures reliable data collection and interpretation, enabling direct comparisons across different catalysts and facilitating the development of more efficient NO₃RR catalysts. The entire workflow requires ~8–10 days, depending on sample preparation and measurement duration.</p>