AuPd/3DOM-TiO2 catalysts for photocatalytic reduction of CO2: High efficient separation of photogenerated charge carriers

Abstract

The photocatalytic conversion of CO2 and H2O into value-added chemicals using sunlight is significant to solve energy crisis and environmental problems. In this work, a series of novel bifunctional catalysts of core-shell structured AuPd nanoparticles decorated 3DOM TiO2 (AuPd/3DOM-TiO2) w were successfully fabricated via a facile one-pot method of gas bubbling-assisted membrane reduction (GBMR). AuPd/3DOM-TiO2 catalysts show uniform 3D ordered macroporous structure, and the slow photon effect of 3DOM-TiO2 as a photonic crystal can enhance light-harvesting efficiency. AuPd nanoparticles are highly dispersed on the surface of 3DOM-TiO2 carrier. Since bimetallic AuPd nanoparticles with the relatively low Fermi level have good capacity of trapping electron, they can efficiently promote the separation of photogenerated electron-hole pairs in TiO2. The AuPd/3DOM-TiO2 catalysts exhibit excellent photocatalytic activity for CO2 reduction with H2O to CH4 under light irradiation. Among the studied catalysts, Au3Pd1/3DOM-TiO2 catalyst exhibits the highest photocatalytic activity and selectivity for CO2 reduction, e.g., its formation rate of CH4 is 18.5μmolg−1h−1 and its selectivity to CH4 production by CO2 reduction is 93.9%. The possible mechanism of AuPd/3DOM-TiO2 catalysts for photocatalytic CO2 reduction is also proposed, and it would guide further design and synthesis of high efficient photocatalysts for CO2 reduction with H2O.