Cooperation between inside and outside of TiO2: Lattice Cu+ accelerates carrier migration to the surface of metal copper for photocatalytic CO2 reduction

TiO2 has been extensively used for CO2 reduction while the low carrier transport efficiency still impedes its practical application. In the present work, Cu/Cu+ fabricated Ti3+/TiO2 (Cu/Cu+@TiO2) was prepared via in situ ionothermal method and acts as a highly selective catalyst for photocatalytic reduction of CO2. Abundant Cu+-O valences were formed inside the lattice of TiO2 to enhance the carrier transport efficiency, and the metal copper outside on the surface are the active sites for CO2 reduction. The synergistic effect between outside Cu and inside Cu+ in Cu/Cu+@TiO2 has dramatically increased the electron carrier density. More importantly, the photogenerated electrons in Cu/Cu+@TiO2 can be 100 % utilized for CO2 reduction aided by the hydroxyl group on the surface and no H2 evolution was detected. Density functional theory calculations also confirm the role of Cu+-O bridge with a higher charge density at the Cu site in the lattice of TiO2. This work will provide new insights into increasing photocatalytic efficiency for CO2 reduction by traditional photocatalyst like TiO2.