The detection of the NH2OH intermediate proved very challenging in the presence of cyclohexanone because of the extremely fast nucleophilic addition of NH2OH to the ketone. Therefore, we set out to perform electrochemical NO3R experiments with the different Zn/Cu catalysts in the absence of cyclohexanone to confirm the formation of NH2OH. As shown in Figure , similar trends of lower potentials and higher FE towards NH3 were observed as the Cu content increased, consistent with hypothesis 1 that Cu facilitates electrochemical NO3R. More importantly, pure Zn and Zn93Cu7 were found to produce NH2OH at 100 mA/cm 2 with FEs of 12±3% and 3±1%, respectively (detection of NH2OH in solution is shown in Figure ). The formation of NH2OH, and its subsequent release into the electrolyte solution, were also evidenced at other current densities for Zn93Cu7 (Figure ). In contrast, the other electrocatalysts with higher Cu contents did not yield any detectable amount of NH2OH, indicating that this intermediate can be further reduced to NH3 on Cu-rich catalysts, whereas on Zn-rich catalysts (i.e. pure Zn and Zn93Cu7) the NH2OH intermediate can desorb from the surface and accumulate in the solution to a detectable concentration.