Nitrogen reduction reaction is the conversion of dinitrogen (N₂) into ammonia or related nitrogen-containing products, most often studied as a six-proton, six-electron process driven electrochemically or photocatalytically at ambient temperature and pressure ^[1]. Because the N₂ triple bond is among the strongest in small molecules, and because the adsorbed N₂H, NH₂ and NH₃ intermediates bind either too weakly or too strongly on most metal surfaces, the attainable rate is constrained by the scaling relations that link their adsorption energies ^[2]. Rates and Faradaic efficiencies are therefore usually low, and in aqueous electrolytes most of the applied current is consumed by hydrogen evolution rather than by ammonia formation ^[1]. Reported ammonia yields for metal, carbon-based and single-atom catalysts span several orders of magnitude, and the electrolyte, cell geometry and applied potential shift the measured value substantially; alkali-metal and nitrate or nitrite impurities can also contribute to the detected ammonia, so quantitative control experiments are required ^[3]. Catalysts examined to date range from transition metals and their nitrides to metal-free carbon materials, and no single material has yet combined high selectivity, high current density and long-term stability ^[4]. Standardised procedures for ammonia quantification have accordingly become part of how the field reports performance, including isotope labelling with ¹⁵N₂ and rigorous blank measurements ^[5].