Vibration-driven reaction of CO2 on Cu surfaces via Eley–Rideal-type mechanism

Understanding gas–surface reaction dynamics, such as the rupture and formation of bonds in vibrationally and translationally excited (‘hot’) molecules, is important to provide mechanistic insight into heterogeneous catalytic processes. Although it has been established that such excitation can affect the reactions occurring via dissociative mechanisms, for associative mechanisms—in which the gas-phase reactant collides directly with a surface-adsorbed species—only translational excitation has been observed to affect reactivity. Here we report a bond-formation reaction that is driven by the vibrational energy of reactant molecules and occurs via an (associative) Eley–Rideal-type mechanism, in which the reaction takes place in a single collision. Hot CO 2 in a molecular beam is found to react with pre-adsorbed hydrogen atoms directly on cold Cu(111) and Cu(100) surfaces to form formate adspecies. The vibrational energy of CO 2 is more effective at promoting the reaction than translational energy, the reaction rate is independent of the surface temperature and the experimental results are consistent with density functional theory calculations. Vibrational and translational energies have previously been observed to promote reactions at surfaces occurring via dissociative mechanisms. Now, it has been shown that the reaction of CO 2 with surface-adsorbed atomic hydrogen—which occurs via an associative (Eley–Rideal-type) mechanism—can be driven by vibrationally exciting CO 2 .