Improved the Light Adsorption and Separation of Charge Carriers to Boost Photocatalytic Conversion of CO2 by Using Silver Doped ZnO Photocatalyst

Abstract

This work developed a strategy to enhance the photocatalytic activity of ZnO by doping it with silver nanoparticles (Ag) to improve the light adsorption and separation of charge carriers, which further increases the conversion of CO2. The loading of Ag over ZnO (Ag-ZnO) was confirmed by characterization methods (SEM, XRD, and XPS), and the photocatalytic activities of Ag-ZnO were significantly enhanced. As the result, the production rates of CO and CH4 by doped Ag-ZnO were 9.8 and 2.4 µmol g−1 h−1, respectively. The ZnO that had the production rate of CO was 3.2 µmol g−1 h−1 and it is relatively low for the production of CH4 at around 0.56 µmol g−1 h−1. The doping of Ag over ZnO displayed a high conversion rate for both CO and CH4, which were 3 and 4.2 times higher than that of ZnO. The doped Ag-ZnO photocatalyst also had high stability up to 10 cycles with less than 11% loss in the production of CO and CH4. The improvement of photocatalytic activities of Ag-ZnO was due to the Ag doping, which enhanced the light adsorption (400–500 nm) and narrowed band gap energy (2.5 eV), preventing the charge carrier separation. This work brings an efficient photocatalyst for CO2 conversion in order to reduce carbon dioxide concentration as well as greenhouse gas emissions.