Exploring the CO2 Reduction Reaction Mechanism on Pt/TiO2 with the Ambient-Pressure X-ray Photoelectron Spectroscopy
Publication
Intensive efforts have been devoted to exploring the CO2 reduction reaction (CO2RR) mechanism to get valuable high-level hydrocarbons under mild reaction conditions. Herein, the investigation of thermocatalytic CO2RR on a metallic oxide-supported catalyst (Pt-TiO2) is conducted by utilizing the surface and chemical-state sensitive ambient pressure X-ray spectroscopy together with the mass spectroscopy. It is revealed that CO2 is first chemisorbed on surface in the form of CO2δ- by capturing electrons from Pt, while the introduction of H2 induces the formation of various intermediates species, such as HCOO, sp3 carbon, and CHxO. Subsequently, CO is discovered after the dissociation of the HCOO species from the reversed water-gas shift reaction, and CH4 is eventually formed after the further hydrogenation of CHxO. Importantly, increasing the concentration of H2 and the overall reactant pressure considerably improves the CO2 activation and the selectivity of CH4, while excessive H2 does not bring any more apparent enhancement of CO2RR on Pt-TiO2. Ultimately, the optimized concentration of H2 is proposed to be 1:2 in the reactant mixture, and the manipulation of methane product selectivity is also realized. Thus, our report might shed valuable insights on the fundamental understanding of CO2 conversion mechanism based on the metallic-oxide catalyst.
