Highly selective conversion of methane to oxygenates with O2 as a green oxidant remains a great challenge. It is still difficult to suppress the generation of COx (x=1, 2) as undesired by-products due to unavoidable overoxidation reaction. Hence, tungsten-doped (W-doped) TiO2 photocatalysts were designed with a tunable band structure for photocatalytic oxidation of methane to C1 oxygenates using O2 at low temperature (30 °C). The W-doping effectively modified the electronic and band structure of pristine TiO2 to enhance photocatalytic performance. Liquid oxygenates productivity could reach as high as 12.2 mmol g-1 with high selectivity of 99.4 %. Moreover, COx selectivity was effectively decreased from 21.2 % over TiO2 to 0.6 % for W-doped catalyst. Detailed characterizations further disclosed that W-doping not only enhanced light absorption, but also promoted the separation of photo-generated carriers to improve methane conversion. This work provides new insights into the design of highly efficient photocatalysts for methane oxidation.
Keywords: methane; oxidation; oxygenates; photocatalysis; titanium dioxide.
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