Substrate Vibrations as Promoters of Chemical Reactivity on Metal Surfaces

Studies exploring how vibrational energy (E_vib) promotes chemical reactivity most often focus on molecular reagents, leaving the role of substrate atom motion in heterogeneous interfacial chemistry underexplored. This combined theoretical and experimental study of methane dissociation on Ni(111) shows that lattice atom motion modulates the reaction barrier height during each surface atom’s vibrational period, which leads to a strong variation in the reaction probability (S₀) with surface temperature (T_surf). State-resolved beam-surface scattering studies at T_surf = 90 K show a sharp threshold in S₀ at translational energy (E_trans) = 42 kJ/mol. When E_trans decreases from 42 kJ/mol to 34 kJ/mol, S₀ decreases 1000-fold at T_surf = 90 K, but only 2-fold at T_surf = 475 K. Results highlight the mechanism for this effect, provide benchmarks for DFT calculations, and suggest the potential importance of surface atom induced barrier height modulation in heterogeneously catalyzed reactions, particularly on structurally labile nanoscale particles and defect sites.