Gas-fed photoelectrochemical reactions sustained by phosphotungstic acid as an inorganic surface electrolyte

Abstract

Gas-fed photoelectrochemical (PEC) system with a porous photoelectrode and proton-exchange membrane (PEM) has the potential to produce hydrogen from water vapour and activate methane at room temperature. To effectively drive gas-phase PEM-PEC reactions, porous photoelectrodes should be coated with a solid electrolyte of perfluorinated sulfonic acid (PFSA) ionomers. However, fluorocarbon-based ionomers were not chemically stable in vapour-fed PEC systems. Herein, we report that polyoxometalate, an inorganic proton-conducting material, may be employed as the surface electrolyte of a WO₃ porous photoelectrode for vapour-fed water splitting and methane activation under visible light irradiation. We demonstrate that the porous WO₃ photoanode modified with phosphotungstic acid (H₃PW₁₂O₄₀) induces PEC reactions, including the oxygen evolution reaction and methane conversion, under gas feeding. Additionally, we demonstrated improved durability by using the inorganic surface electrolyte.