All density functional theory (DFT) calculations were performed using the Vienna Ab initio Simulation Package (VASP) interfaced with the Atomic Simulation Environment (ASE) . DFT calculations in conjunction with the computational hydrogen electrode (CHE) model were used to determine intermediate adsorption energies of the urea and formamide formation pathways. Core electrons were described using PAW pseudopotentials , and valence electrons were expanded as planewaves up to a kinetic energy cutof of 500 eV. The electron exchange and correlation interactions were accounted for using the revised Perdew-Burke-Ernzerhof (RPBE) exchange-correlation functional by Hammer and Nørskov . Solvation effects were incorporated using a continuum solvation model as implemented in VASP (VASPsol) . A (3 × 3 × 1) Monkhorst-Pack 52 k-point mesh was used to sample the Brillouin zone. Adsorbate binding energies were calculated using a 3 x 3 x 3 supercell with the bottom two layers fixed and the top layer free to relax with the adsorbate. Geometries were considered to be optimized after the maximum force on each unconstrained atom fell below 0.05 eV/Å. The transition states for the two C-N bond formation reactions were estimated using a constrained one-dimensional bondlength scan at constant potential as described and benchmarked in our previous publications . Briefly, the bond length is varied over a series of 25 images spanning the initial state (e.g. *CO + *NO) to the final state (e.g. *CONO). At each image, the C-N bond length is constrained and the geometry optimized at constant potential with respect to this constraint. The adsorption-free energies, ΔG of the reaction intermediates are calculated using the expression (ΔGads = ΔEads + ΔZPE -TΔS), where ΔE is the difference in electronic energy of the adsorbed species, ΔZPE is the difference in zero-point energies, and ΔS is the change in entropy of the adsorbed species with respect to the catalyst surface. The ZPE and entropies S were calculated using the Harmonic Oscillator approximation, which assumes that adsorbed molecules vibrate harmonically and have only vibrational degrees of freedom. The reaction mechanisms for the various elementary steps and further details of the simulation cell can be found in the supplementary material.