Although NO 3 -is highly soluble in comparison to gaseous N2, it's transport to the catalyst surface, as well as that of proton sources, can appreciably impact measured rates and product distribution . The regime under which kinetic effects dominate will be a balance between catalyst surface area (dispersion), reaction rate of NO3RR, rate of competing HER (also consuming protons), convection, and diffusion. Researchers should consider the impact of mass transport by e.g. comparing performance at different stir or flow rates. In cases where mass transport effects might not be avoidede.g. considering low NO 3 -concentrations at high overpotentialscare should be taken to fully report sufficient information (including the exposed catalyst surface area and catholyte volume) for reproducibility and catalyst comparison.