To study the NO3R reactivity on the different electrocatalysts, we constructed a Cu(111), Zn(101) and Zn93Cu7(101) surface slab models (as confirmed by XRD) followed by the assessment of their surface coverages under experimental conditions, as depicted in Figure . For Cu(111), DFT simulations predict 75 % of the fcc sites to be covered by H atoms, while all the bridge positions on Zn(101) and Zn93Cu7(101) are occupied by H. Taking these surface terminations as the catalyst resting state, the electroreduction of NO to N2, NH2OH and NH3 was then explored via a series of proton-coupled electron transfer (PCET) steps, as reported elsewhere. Furthermore, at each step, the hydrogenation of both the N and O atoms were considered, as well as all the possible adsorption sites for each reaction intermediate (see Tables and).