Photocatalytic highly selective generation of HCHO by TiO<sub>2</sub> nanosheets

Under mild conditions, selective conversion of methane to C1 chemicals, such as HCHO, CH₃OH, etc, is a very attractive CH₄ conversion pathway. At present, in order to improve the yield of liquid oxygenates, most methane oxidation is carried out under pressurized conditions, which results in a large number of products without obvious selectivity. To overcome this shortcoming, this study was carried out at room temperature and pressure without any oxidant. By adjusting the crystal facet of anatase TiO₂, the TiO₂-001 nanosheets were prepared by hydrothermal method, and the single liquid oxygenate HCHO 767 μmol/(g·h) with selectivity of 83.3% and C1 liquid oxygenate (HCHO+CH₃OH) with selectivity of 100%. Various characterization methods (TEM, XRD, XPS, EPR) confirmed that the exposure of the crystal facet of TiO₂-001 and the high surface hydroxyl group (Ti-OH) could promote the generation of ·OH, optimize the reaction path, and promote the highly selective generation of HCHO. This work is of great significance for controlling free radical species and generating single liquid oxygenates with high selectivity.