Visible-light-driven selective oxidation of methane to methanol on amorphous FeOOH coupled m-WO3

• Published in: Fuel (Guildford) Vol. 266; p. 117104
• Main Authors: Yang, Juan, Hao, Jingyi, Wei, Jianping, Dai, Jun, Li, Yao
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.04.2020; Elsevier BV
• Subjects: Amorphous FeOOH; Catalysts; Catalytic activity; Catalytic converters; Conduction; Conduction bands; Direct conversion; Dispersion; Electron paramagnetic resonance; Electron spin; Electron spin resonance; Free radicals; Hydrogen peroxide; Hydroxyl radicals; Irradiation; Light irradiation; Methane; Methanol; Methyl radicals; Optimization; Oxidants; Oxidation; Oxidizing agents; Photoelectric effect; Photoelectric emission; Photoelectrons; Photoluminescence; Photons; Radiation; Selectivity; Silica; Silicon dioxide; Solar energy; Spin resonance; Visible-light-driven; WO3; Methane; WO3; Amorphous FeOOH; Visible-light-driven; Methanol
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.117104

[Display omitted] •Amorphous FeOOH/m-WO3 photocatalysts are synthesized by using silica KIT-6 template.•FeOOH/m-WO3 show improved visible-light catalytic activity for CH4 partial oxidation.•CH3OH selectivity reaches 91.0% on 1.98% FeOOH/m-WO3 in the presence of 1.5 mM H2O2.•Enhanced catalytic activity is due to efficient electron migration from WO3 to FeOOH.•Main active species and catalytic mechanism for CH4 selective oxidation are proposed. Direct conversion of methane into value-added fuels or chemicals under ambient conditions remains a great challenge. Constructing solar-energy-driven catalytic systems is considered as a promising strategy, but the conversion efficiency and products selectivity are still low, especially for producing alcohol derivatives. Herein, to promote the photocatalytic activity of methane partial oxidation to methanol, a series of FeOOH/m-WO3 consisting of ordered mesoporous WO3 (m-WO3) and highly dispersed amorphous FeOOH were synthesized by using KIT-6 silica as hard template. The prepared FeOOH/m-WO3 catalysts exhibit dramatically improved visible-light catalytic activities toward selective oxidation methane into methanol in the presence of H2O2. A methane conversion rate of 238.6 μmol·g−1·h−1 is achieved over the optimal 1.98% FeOOH/m-WO3, which is 3 times higher than that of pristine m-WO3 (79.2 μmol·g−1·h−1). Moreover, a methanol production rate of 211.2 μmol·g−1·h−1 with a selectivity of 91.0% is obtained on the optimum catalyst under 4 h visible-light irradiation. Significantly, the greatly improved methane conversion and methanol production can be attributed to efficient electron migration from the conduction band of m-WO3 to highly dispersed FeOOH, evidenced by in-situ XPS analysis, transient photocurrent response and photoluminescence spectra. Furthermore, based on radicals trapping experiments and electron spin resonance (ESR) results, methane is primarily activated by photoholes accumulated on the valence band of m-WO3 to generate methyl radicals (·CH3) and the produced hydroxyl radicals (·OH) via decomposing H2O2 by photoelectrons on FeOOH surface are predominant oxidant for methanol generation. Desired methanol is selectively produced via radicals reaction between ·CH3 and ·OH.