The lowest energy ECH mechanism (see Supplementary Materials for details), depicted in Fig. , begins with the adsorption of AP on the different metal coverages, which lies parallel to the surface at ca. 3.5-4 Å, interacting through the 𝜋-system. Because of the physisorbed nature of this intermediate (*AP, Fig. ), the range of the calculated binding energies is very narrow, i.e. from -0.01 (Ag) to 0.14 (Cu) eV (Fig. ), and therefore, the binding energy of *AP cannot be taken as a good descriptor for the ECH process. Hence, we next modelled the hydrogenation of *AP, which can occur either at the C or O atoms of the carbonyl group. According to simulations, the hydrogenation at the O is thermodynamically more favorable on all the metals except Ag and Cu, which favor the hydrogenation at the C (see Supplementary Materials). This latter mechanism, however, is hindered by an energy barrier of ca. +2.0 eV (Supplementary Figure ), rendering this pathway very unlikely at ambient experimental conditions. On the other hand, the hydrogenation of the carbonyl O in *AP leads to the intermediate *APHᐧ. This species has a radical character delocalized over the aromatic ring, as confirmed by the magnetic moments obtained in the DFT simulations (see Supplementary Materials), which contributes to lower the energy of this intermediate. Interestingly, this second step is endergonic on all the investigated metals, i.e. Au (+0.16) < Ag (+0.39) < Cu (+0.49) < Pt (+0.52) < Ni (+0.79) (Fig. ), and correlates well with the respective ΔGH values obtained in the surface coverage analysis shown in Fig. . Specifically, the formation of *APHᐧ becomes less favorable with more negative values of ΔGH, as we envisioned for ECH catalysts operating in alkaline media. Once *APHᐧ is formed, the H surface vacancy is regenerated (*H), followed by the hydrogenation at the C atom to yield the final product, *1-PEA. This step is highly exergonic on all the cathodes, i.e. Au (-0.80) < Ag (-0.77) < Cu (-0.58) < Pt (-0.08) < Ni (-0.07) (Fig. ). Finally, the H coverage is regenerated (*H) again, and 1-PEA desorbs from the metal surface, closing the catalytic cycle.