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.