Activation of CO₂ by Direct Cleavage Triggered by Photoelectrons on Rutile TiO₂(110)

The initial activation of the inert CO2 is a key step in its photoreduction to valuable chemicals. This process was proposed to proceed mainly by CO2 accepting a photoelectron to form a CO2•- radical or by CO2 accepting two photoelectrons and a proton to form the HCOO- anion on the prototypical rutile TiO2(110) surface. Here, we reveal a new mechanism, in which CO2 is directly cleaved to CO and the adsorbed O2- anion under the trigger of two photoelectrons, by using density functional theory calculations with the HSE06 hybrid functional. The newly revealed mechanism is more favorable than the two previously proposed pathways. Furthermore, our results show that the deficiency of photoelectrons on the catalyst surface is a potential reason for the current low efficiency of CO2 photoreduction.