Evaluating PBE-D3/M06 for copper-catalyzed carbon chemistry: Kinetic barriers and mechanistic insights

Accurate prediction of activation barriers is essential for reliable mechanistic modeling of copper-catalyzed carbon conversion reactions yet remains challenging for conventional density functional theory. Here, we evaluate a hybrid PBE-D3/M06 approach for reaction kinetics on low-index Cu(100), Cu(110), and Cu(111) surfaces. Benchmarking against experimental barriers for seven representative elementary reactions shows that PBE-D3/M06 achieves near-chemical accuracy, with a mean absolute error and root mean square error of 0.06 eV, substantially outperforming PBE and RPBE. The method also reproduces embedded CASPT2 trends for C–C coupling on Cu(111), correctly identifying COH*–CHO* coupling as both kinetically and thermodynamically preferred. Applied to CO2 hydrogenation to methanol on Cu(111), PBE-D3/M06 indicates that the formate-mediated pathway is favored, with HCOOH* hydrogenation as the rate-determining step. This work suggests that PBE-D3/M06 is a promising framework for modeling elementary steps in copper-catalyzed carbon chemistry.