Gas-Phase Photoelectrocatalysis Mediated by Oxygen Ions for Uphill Conversion of Greenhouse Gases

The present study reports a gas-phase photoelectrochemical (GPEC) system in which photoanode and photocathode materials are coated on each side with a pellet of the oxygen-ion conductor yttria-stabilized zirconia (YSZ), where light irradiation is feasible on both sides. As a model gas-phase reaction, we chose dry reforming of methane (DRM), which converts greenhouse gases into valuable syngas. Consequently, the stoichiometric DRM reaction proceeded in our GPEC system, indicating that the oxygen ions in a YSZ pellet act as mediators to link the redox reactions. It was also noted that UV light irradiation on the anodic side was more effective than that on the cathodic side, suggesting that the photogenerated holes in the anodic YSZ side activate methane molecules, while photogenerated electrons are injected into Rh nanoparticles to cause carbon dioxide reduction in the cathodic side. Our GPEC system converts greenhouse gases into valuable syngas by light irradiation.