Ultrathin RuO2/Bi2WO6 and PtO2-Pt/Bi2WO6 heterojunction nanosheets toward efficient photocatalytic CO2 reduction under visible light irradiation

Ultrathin RuO2/Bi2WO6 and PtO2-Pt/Bi2WO6 heterojunction nanosheets with superior (001) crystal planes were successfully constructed by combining a hydrothermal process with photo-deposition technique, which present efficient photocatalytic reduction of CO2 into CO and CH4 under visible light irradiation. Under the irradiation of 420 nm monochromatic light, the apparent quantum yield (AQY) of RuO2/Bi2WO6 reached to 0.21 %, which was about 1.2 times that of PtO2/Pt-Bi2WO6 (0.17 %) and 1.9 times that of pristine Bi2WO6 (0.11 %), respectively. After decorated RuO2 or PtO2-Pt QDs on Bi2WO6 nanosheets to form local heterojunctions including a type II p-n heterojunction RuO2/Bi2WO6 or PtO2/Bi2WO6, as well a Schottky junction Pt/Bi2WO6, RuO2/Bi2WO6 exhibited a higher photocatalytic activity and selectivity of CH4 evolution (33.95 %) than PtO2-Pt/Bi2WO6 (20.9 %), due to the synergetic effect of following factors including enhanced absorption of visible light, improved separation efficiency of charge carrier, reduced charge transfer resistance, enlarged reduction drive ability of photo-induced electrons, accelerated surface catalytic reaction kinetics, and improved specific surface and pore volume. This work provides guidance for designing and developing novel Bi2WO6-based photocatalysts for selective photocatalytic CO2 reduction into target reaction.