bounds approaching -0.8 VRHE. Reduction of adsorbed nitrate (quasi-equilibrated with electrolyte concentration) to nitrite has been determined to be the rate-limiting step for NO3RR in acidic and alkaline electrolytes. Therefore, the observed decrease in jPeak could be caused by irreversibly adsorbed hydrogen, originating from phosphate deprotonation or directly from water dissociation, competing with nitrate adsorption and subsequent reduction. Cu foil NO3RR activity