CO Photoreduction on Metal Oxide Surface Is Driven by Transient Capture of Hot Electrons: Quantum Dynamics Simulation.

The most critical bottleneck in CO photoreduction lies in the activation of CO to form an anion radical, CO, or other intermediates by the photoexcited electrons, because CO has a high-energy lowest unoccupied molecular orbital (LUMO). Taking rutile TiO(110) as a prototypical surface, we use time-dependent nonadiabatic molecular dynamics simulations to reveal that the excitation of bending and antisymmetric stretching vibrations of CO can sufficiently stabilize the CO LUMO below the conduction band minimum, allowing it to trap photoexcited hot electrons and get reduced. Such vibrational excitations occur by formation of a transient CO adsorbed in an oxygen vacancy. CO can trap the hot electrons for nearly 100 fs and dissociate to form CO within 30-40 fs after the trapping. We propose that the activation of the CO bending and antisymmetric stretching vibrations driven by hot electrons applies to other CO reduction photocatalysts and can be realized by different techniques and material design.