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/CeO2 shows that the temperature of 90% CO conversion dropped by 30 degrees C-50 degrees C under irradiation. The apparent activation energy reduces from 64.6 kJ.mol(-1) to 44.6 kJ . mol(-1). Pd/PdO/TiO2 and Pd/PdO/Al2O3 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.