CePMo12O40/TiO2 catalysts for photocatalytic oxidation of methane to value-added organic oxygenates

Methane is the main component of natural gas. The effective activation of C-H bond of methane to synthesize value-added compounds under mild conditions is attractive. Compared to the most investigated noble metal catalysts (such as Au, Pd, and Rh), rare earth metal catalysts possess stronger oxidizing activity. Herein, we report the first synthesis of Ce cation-based phosphomolybdic salt (CePMo12O40) with a simple milling method. Furthermore, CePMo12O40-based TiO2 catalyst (CePMo/TiO2) exhibited excellent catalytic performance for selective conversion of methane, achieving high yield (5618.5 mu mol/g(cat)) of organic oxygenates (CH3OOH, HCOOH, and HCHO) using O-2 as an oxidant in water at 150 degrees C under 1.5G sunlight irradiation for 2 hours. It was found that the yield of total produced organic oxygenates over CePMo/TiO2 is 119% larger with 1.5G sunlight light irradiation than that without the light irradiation. In addition, the introduction of CePMo into TiO2 increased its photocatalytic activity for organic oxygenates by 11%. The isotope-labeling evaluation revealed that both H2O and O-2 participated the oxidation of methane into CH3OOH, HCOOH, and HCHO. This work provides the first example of rare earth POM-based photocatalysts for conversion of methane into liquid oxygenates.

Automated summary

This study presents a rare earth POM-based photocatalyst CePMo/TiO2 for efficient conversion of methane into organic oxygenates. CePMo/TiO2 exhibits excellent catalytic performance under 1.5G sunlight irradiation and the addition of CePMo enhances the photocatalytic activity of TiO2 for organic oxygenates.