Density Functional Theory (DFT) simulations were performed using the Vienna Ab initio Simulation Package, VASP 5.4.4 and the Perdew, Burke, and Ernzerhof (PBE) functional . In addition, we utilized the DFT-D2 method to incorporate van der Waals (vdW) corrections, employing our reparametrized C 6 coefficients specifically tailored for metallic systems . Core electrons were described using Projected Augmented Wave (PAW) pseudopotentials , while valence electrons were expanded using plane waves with a basis set cutoff energy of 450 eV. such that the cation donates its extra electron to the surface . The gas phase energies of CO 2 and CO were corrected to match with the corresponding NIST reaction energies of formation from CH 4 (g) . Implicit solvation was included through the VASPsol method and the entropies for the adsorbed species were calculated using the Harmonic Oscillator approximation with all the frequencies below 50 cm -1 set to be 50 cm -1 . Computational Hydrogen Electrode (CHE) approximation was used to correct the free energy of intermediates with respect to potential and pH. Activation barriers were assessed using the Climbing Image Nudged Elastic Band (CI-NEB) method . To create the intermediate images between the initial and final states, we employed the Image Dependent Pair Potential (IDPP) method . Grand Canonical formalisms for Ag(111)-K + system was introduced using VASP-sol++ , by assuming an ion concentration of 1 M and the hydrated diameter of K + to be 6.62 Å . More details about how the Grand Canonical formalism has been incorporated in the microkinetic model can be found in the Supporting Information section 1.1.6.