Solar driven CO hydrogenation on transition metal doped ZnO cluster.

Photocatalytic hydrogenation of carbon dioxide (CO) to produce value-added chemicals and fuel products is a critical routine to solve environmental issues. However, developing photocatalysts composed of earth-abundant, economic, and environmental-friendly elements is desired and challenging. Metal oxide clusters of subnanometer size have prominent advantages for photocatalysis due to their natural resistance to oxidation as well as tunable electronic and optical properties. Here, we exploit 3d transition metal substitutionally doped ZnO clusters for CO hydrogenation under ultraviolet light. By comprehensive ab initio calculations, the effect of the dopant element on the catalytic behavior of ZnO clusters is clearly revealed. The high activity for CO hydrogenation originates from the distinct electronic states and charge transfer from transition metal dopants. The key parameters governing the activity and selectivity, including the d orbital center of TM dopants and the energy level of the highest occupied molecular orbital for the doped ZnO clusters, are thoroughly analyzed to establish an explicit electronic structure-activity relationship. These results provide valuable guidelines not only for tailoring the catalytic performance of subnanometer metal oxide clusters at atomic precision but also for rationally designing non-precious metal photocatalysts for CO hydrogenation.