In-situ preparation of molybdenum trioxide-silver composites for the improved photothermal catalytic performance of cyclohexane oxidation.

The selective catalytic oxidation of cyclohexane has important theoretical and practical application value. However, high conversion rate and high selectivity are difficult to achieve simultaneously by conventional catalytic system. In this work, blue molybdenum trioxide (MoO3) nanorods with oxygen vacancies were prepared by hydrothermal method using hydrated molybdic acid as a precursor under the reduction of formic acid, and in-situ produced MoO3-silver (MoO3-Ag) composites were further used in the photothermal catalytic oxidation of cyclohexane with high conversion and high selectivity using dry air as oxidant. The results showed that the best conversion rate of cyclohexanone and cyclohexanol (KA oil) could reach 8.6% with the selectivity of 99.0%. The excellent catalytic performance of MoO3-Ag composites can be attributed to the significantly increased visible and near-infrared light absorption caused by the plasma resonance effect of Ag nanoparticles and oxygen vacancies, and the prevented charge recombination by MoO3-Ag Schottky heterojunction. This work provides new reference solutions for the design and preparation of high-performance photothermal catalysts for the selective oxidation of hydrocarbons.

High-performance silver nanoparticles coupled with monolayer hydrated tungsten oxide nanosheets: The structural effects in photocatalytic oxidation of cyclohexane.

The photocatalytic properties of silver nanoparticles (Ag NPs) coupled with tungsten oxide (WO3) nanocrystals are investigated to understand structural effects of the WO3 nanocrystals in selective oxidation of cyclohexane (CyH). The photocatalytic activity of monolayer hydrated WO3 nanosheet - Ag nanoparticle composites (WO3 NSs-Ag NPs) is 1.3 times higher than that of WO3 nanocube - Ag nanoparticle composites (WO3 NCs-Ag NPs). The highest cyclohexane conversion of 40.2% with cyclohexanol and cylohexanone (KA oil) selectivity of 97.0% is achieved by the photocatalyst of WO3 NSs-Ag NPs under solar-light irradiation at room temperature. The WO3 NSs-Ag NPs shows good photocatalytic stability without evident decline of catalytic activity after ten cycles. The improved photocatalytic activity in the oxidation of cyclohexane by WO3 NSs-Ag NPs is mainly due to the facilitated generation of high-reactive hydroxyl radical (OH), which is caused by the enhanced light absorption by surface plasmon resonance (SPR) effect of Ag NPs, and the effective charge transfer on the surface of WO3 monolayer structure. The design and structural analysis of the WO3 NSs-Ag NPs in this research may provide a novel approach for the further development of high-performance photocatalyst.