We specifically employed variational and fixed-node diffusion Monte Carlo (FNDMC) methods , with the latter providing high-accuracy many-body electronic structure calculations by projecting the ground state from an initial trial wave function and effectively capturing electron correlation within the fixed-node approximation . Although the polynomial scaling of FNDMC (N with the number of particles) historically limited its application in surface chemistry due to high computational cost, recent advancements in codes like QMCPACK , used in this study, along with GPU acceleration, have significantly improved its practicality. Techniques such as finite-size corrections and extrapolation methods further improve the efficiency of FNDMC for catalytic systems. All computational details, including the DFT and QMC setups, are provided in the Supporting Information. Datasets for energies and structures are available at catalysishub.org . Input files for all calculations were generated using the Nexus workflow management system .