There are many sources of error in the simulation besides the adsorbate binding energies, such as neglected heat transfer e↵ects, di↵usion limitations, coverage e↵ects, and describing the multifaceted catalyst nanoparticles as a pristine (111) or (211) slab. Even a perfect method for predicting the energies is unlikely to perfectly capture the physical system. Because BEEF-vdW is a Bayesian estimation based approach, the uncertainty can be estimated with 2000 perturbations on the exchange-correlation functional. A Gaussian distribution was constructed with the 2000 energy ensemble, and the 2 of this distribution was used as the uncertainty for the DFT calculations. The DFT uncertainties were calculated for the gas-phase species used in the hypothetical reaction in Equation 3, the slabs, and the adsorbates. The uncertainties were then propagated through Eq. 7 to calculate the binding energy uncertainty. BEEF-vdW was trained using diverse data sets representing bonding in both chemical and condensed matter systems, so the uncertainty of adsorption systems tends to be overestimated. As such, a factor of 0.683, employed in prior studies, was used to correct the binding energy uncertainty. It should be noted for the DFT uncertainties that the BEEF-vdW functional does not go beyond the generalized gradient approximation for any of the ensemble calculations, and as such is blind to errors and o↵sets inherent in this functional family. While a truly comprehensive error study would ascend further up Jacob's ladder, to include other functional families, this was deemed impractical for the current study.