In this study, we used state-of-the-art QMC methods to investigate the site-specific adsorption (binding) energies of CO* and H* on the copper (111) surface, along with the selectivity-limiting steps involving CHO* and COH* intermediates, which are the key species in CO reduction reactions (CORR) . Precise energies for these intermediates remain under debate , with little to no experimental data available. The chemisorption of CO* and H* on copper are prototypical adsorption processes on transition metal surfaces, extensively studied experimentally and theoretically . These species are treated as computational benchmarks for this study and for understanding key adsorption processes that influence selectivity in reduction pathways .