Based on the above experimental results and previous NO3R studies that revealed a significantly stronger adsorption of reaction intermediates on Cu compared to Zn, we posited four possible (not excluding) reasons for the different behavior observed with the Zn-Cu alloy electrocatalysts: (1) Cu has a stronger surface adsorption of NO3 -than Zn and therefore facilitates the electrochemical NO3R at lower potentials; (2) Cu favors the further electroreduction of *NH2OH to NH3, instead of the chemical reaction with cyclohexanone to give oxime; (3) introducing Cu into Zn creates a more porous surface morphology and thus leads to NO3R lower potentials; (4) pure Zn is disadvantaged by the competing NO3R pathway towards N2, rather than NH2OH or NH3. The difference in surface morphology for Zn, Cu and Zn93Cu7 is supported by SEM images (Figure ) and the measurements of the electrochemical active surface area (ECSA, Figure ). Hence, we next carried out further experimental and theoretical studies to prove the other three possible reasons.