An Atypical Heterojunction in Favor of Conversion of CO2 and Sunlight into C2H4.

Current heterojunction semiconduction assemblies, including type I, II, Z-Scheme, and S-Scheme constructures, enable the utilization of longer-wavelength sunlight for photocatalytic conversions. However, such benefits are often achieved at the expense of either the redox potentials of the conduction and valence bands or the quantum yield due to additional electron-hole recombination across the heterojunction interface. Herein, an atypical type II heterojunction constituted of Au/TiO2/MFU-4l is reported that demonstrates outstanding catalytic performance in photocatalytic reduction of carbon dioxide (CO2) to ethylene (C2H4) through tuning up-converting of holes in MFU-4l component raised from full-spectrum solar irradiation. Anchored to the edge of cube MFU-4l with a TiO2 cover layer, aurum ions (Au+)supported by aurum (Au) nanoparticles enables such a reverse hole-transfer event through leveraging the Ti-O-•-Au+/0-•-O-Zn potential, which significantly accelerates the hole-dominated oxidative desaturation of C-C intermediates from CO2 reduction into C═C bond products. The catalyst efficiently converts CO2 to C2H4 with more than 90% selectivity and a yield of 107.0 µmol g-1 h-1 under simulated sunlight. Electron paramagnetic resonance (EPR) experiments directly observe the holes formed in visible-light excited MFU-4l moiety of Au/TiO2/MFU-4l that are fused into TiO2 component's holes, thereby generating more hydroxyl radicals (•OH) than that TiO2 is excited alone under ultraviolet (UV) carbon dioxide (CO2) light of the same intensity.