Effective CO2 Capture and Selective Photocatalytic Conversion into CH3OH by Hierarchical Nanostructured Photocatalysts GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg

Abstract

The attenuation of greenhouse gases especially CO2 as one of the main causes of global warming and its conversion into valuable materials are among the challenges that must be met in the 21st century. For this purpose, hierarchical ternary and quaternary hybrid photocatalysts based on graphene oxide, TiO2, Ag2O, and Arginine have been developed for combined CO2 capture and photocatalytic reductive conversion to methanol under visible and UV light irradiation. The material’s bandgap energy was estimated from diffuse reflectance spectra (DRS) Tauc analysis algorithm. Structural and morphological properties of the synthesized photocatalysts were studied using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM). The calculated band for GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg were 3.18 eV and 2.62 eV respectively. This reduction in the bandgap showed that GO-TiO2-Ag2O-Arg has a significant visible light photocatalytic ability. The investigation of CO2 capture for the designed catalyst shown that GO-TiO2-Ag2O-Arg and GO-TiO2-Ag2O have high CO2 absorption capacity (1250 and 1185 mmol g-1 respectively at 10 bar and 273 K under visible light). The amount of methanol produced by GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg was 8.154 µmol. gcat-1.h-1 and 5.1 µmol. gcat-1.h-1 respectively. The main advantages of this study are the high efficiencies and selectivity of catalysts toward methanol formation. The reaction mechanism to understand the role of hybrid photocatalysts for CO2 conversion is deliberated. In addition, these catalysts remain stable during the photocatalytic process and can be used repeatedly, and enlightening for environmental researches.