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 center dot- 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.

Automated summary

The activation of CO2 is a crucial step in its photoreduction to valuable chemicals. Previous studies suggested two pathways, either CO2 accepting a photoelectron to form CO2•- radical or accepting two photoelectrons and a proton to form HCOO- anion on TiO2(110) surface. However, we reveal a new mechanism in which CO2 is directly cleaved to CO and adsorbed O2- anion triggered by two photoelectrons. This new mechanism is more favorable than the previously proposed pathways. Moreover, the deficiency of photoelectrons on the catalyst surface may explain the low efficiency of CO2 photoreduction.