Photocatalytic Partial Oxidation of Methane on Palladium-Loaded Strontium Tantalate

Partial oxidation of methane (POM) to syngas is a credible approach to utilize natural gas resources effectively. However, the high reaction temperature required in thermocatalysis decreases the cost-performance ratio. A scheme for photocatalytic POM is proposed using palladium (Pd) nanoparticles loaded onto strontium tantalate (Sr2Ta2O7), an ultrawide-bandgap (UWBG) semiconductor. UV irradiation initiates POM at temperatures lower than 423 K and promotes the reaction efficiency below 873 K as compared with the dark conditions. The photogenerated hot carriers that arise from the d to s interband excitation of Pd drive the photocatalytic reaction, rather than the bandgap excitation of the semiconductor support. It is demonstrated that the combination of a UWBG semiconductor and metal nanoparticles is conducive to the migration and separation of hot carriers. The suppressed activities of frequently used wide-gap semiconductors such as TiO2 loaded with Pd are attributed to the competition between bandgap excitation in semiconductors and interband excitation in metal nanoparticles.