The fully converged vacuum FNDMC calculations reveal that the COH* intermediate binds most strongly at the FCC and HCP hollow sites on the Cu(111) surface, slightly less strongly at the bridge site, and weakest at the top site (Figure ). In contrast, the CHO* intermediate binds strongest at the top site, less strongly at the bridge site, and weakest at the FCC/HCP hollow sites (Figure ). The adsorption energies for CHO* across all adsorption sites differ by less than 0. The FNDMC results revealed exceptionally weak binding of COH* to the Cu(111) surface, which would suggest it is less likely to be a favorable intermediate in the CORR.