The Quantum Monte Carlo (QMC) methods now offer a balance between computational feasibility and accuracy in surface chemistry. Despite its limited applications to date, QMC has successfully addressed discrepancies where density functional theory (DFT) falls short. For example, QMC has accurately predicted CO adsorption on both metal oxides like MgO(001) and transition metals . It has also been successfully applied in studying the dissociative chemisorption of H 2 on metal surfaces . These successes highlight the potential of the QMC methods to provide valuable insights into adsorption energies and mechanisms, addressing complex accuracy challenges critical to heterogeneous catalysis, where DFT remains the primary computational tool . Furthermore, data from QMC calculations can aid in the development of improved DFT functionals for catalysis.