Synergism between {111} and {100} Crystal Facets on Cu₂O for Boosted Photothermal Catalysis

Cu2O with different morphologies (Cu2O–C (Cube), Cu2O–CB (Cuboctahedra), and Cu2O–O (Octahedra)) was synthesized to investigate the effect of crystal planes for the photothermal catalytic oxidation of toluene. It was found that the order of catalytic activity was as follows: Cu2O–CB > Cu2O–O > Cu2O–C. The H2-TPR and XPS results showed that the {111} facets were more susceptible to oxidation, and the oxidized structure was more difficult to reduce. The combination of {100} and {111} on Cu2O–CB showed a synergistic effect between the oxidation and reduction cycle. Moreover, the {100} facets showed high electron–hole separation efficiency, which could promote the formation of •O2– species. In-situ DRIFTS results provided a comprehensive reaction pathway: toluene was oxidized to form benzyl alcohol or benzaldehyde and then subsequently oxidized to benzoic acid and ultimately converted to CO2 and H2O. All these results provided a fundamental understanding of the effect of the crystal plane on the photothermal catalysis reaction.