With important metrics in the field including FE and selectivity, direct identification and quantification of products is necessary. This requires separating the anode and cathode via a membrane that allows for ion transport but prevents NO3RR products from re-oxidizing at the anode. Crossover of products to the anolyte compartment is possible even using such membranes , however, and should be explicitly measured. In some scenarios like RDE measurements focusing on reaction rates for samples with known product distribution, a cell single volume cell may be used if counter electrode reactions do not impact the cathode performance. The electrochemical potential at the counter electrode should be explicitly measured to ensure the reactions taking place do not influence catalytic performance in either reactor geometry (as could e.g. oxidative dissolution at the counter). We note that oxygen, either from ambient or produced at a counter electrode, reduces more readily than NO 3 -and should be removed from the solution by sparging with an inert gas. We suggest doing so with Ar, rather than N2, to enable possible N2 detection.