Photoelectrochemical C-H activation of methane to methyl radical at room temperature

Herein, we report a continuous gas-fed photoelectrochemical (PEC) system with a proton exchange membrane for CH 4 activation at ambient temperature and pressure. We found that both water splitting and steam reforming of CH 4 were induced over oxide photoanodes. When the CH 4 concentration was low, O 2 and CO 2 were formed on titanium oxide (TiO 2 ) and tungsten trioxide (WO 3 ) photoanodes under ultraviolet light irradiation. We also found that visible light enhanced CH 4 activation and ethane (C 2 H 6 ) formation over the WO 3 photoanode. When the CH 4 concentration increased, O 2 formation was suppressed, with increasing production rates of CO 2 , C 2 H 6 , and CO. Under optimised conditions, the selectivity of C 2 H 6 reached 57% on a carbon basis over the WO 3 photoanode under visible-light irradiation. The production of C 2 H 6 implies the formation of methyl radicals during the CH 4 gas-fed PEC process. We also demonstrated the PEC coupling of ethane to n -butane and the visible-light-induced oxidation of CH 4 without external bias. Visible light illumination induced CH 4 oxidation over a WO 3 photoanode. The production of C 2 H 6 implies the formation of methyl radicals through photoelectrochemical activation of methane.