Light-promoted activation of oxygen and carbon monoxide for low-temperature catalytic oxidation

Molecular oxygen (O 2 ) activation is a critical step in the low-temperature catalytic oxidation of carbon monoxide (CO). Photocatalysis is a facile way to activate O 2 to superoxide radicals under mild conditions. Photothermal catalysis, which integrates the photocatalysis of semiconductors and the thermocatalysis of noble metals, has arisen as an appealing strategy to achieve low-temperature catalytic oxidation. Here, we report that Pd/PdO/CeO 2 shows that the temperature of 90% CO conversion dropped by 30°C–50°C under irradiation. The apparent activation energy reduces from 64.6 kJ ⋅ mol −1 to 44.6 kJ ⋅ mol −1 . Pd/PdO/TiO 2 and Pd/PdO/Al 2 O 3 are prepared and compared to understand the underlying mechanism. The results reveal that photocatalysis is vital in lowering the apparent activation energy besides the photothermal effect. The photo-generated electrons promote O 2 activation to generate the superoxide anion. The hole can activate the adsorbed CO on the PdO. These active species are beneficial for lowering the CO oxidation temperature.