Exploring the Catalytic Properties of Unsupported and TiO₂-Supported Cu₅ Clusters: CO₂ Decomposition to CO and CO₂ Photoactivation

In this work, we explore the decomposition of CO₂ on unsupported and TiO₂-supported Cu₅ clusters via computational modeling, using both finite cluster and periodic slab structures of the rutile TiO₂(110) surface. While the energy needed for C?O bond breaking is already significantly reduced upon adsorption onto the unsupported metal catalyst (it drops from 7.8 to 1.3 eV), gas desorption before bond activation is still the inevitable outcome due to the remaining barrier height even at 0 K. However, when the Cu₅ cluster itself is supported on TiO₂, reactant and product adsorption is strongly enhanced, the barrier for bond breaking is further reduced, and a spontaneous decomposition of the molecule is predicted. This finding is linked to our previous work on charge-transfer processes in the Cu₅-TiO₂ system triggered by solar photons, since a combination of both phenomena at suitable temperatures would allow for a photoinduced activation of CO₂ by sunlight.