Wavelength Effect on Photocatalytic Reduction of CO2 by Ag/TiO2 Catalyst

Abstract

Photocatalytic reduction of CO 2 by water was performed in the presence of a Ag/TiO 2 catalyst under illumination by lamps with different wavelengths (254, 365, and 400 nm). The yields of the main products (methane and methanol) were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp. This was because the electron-hole generation rate increased with increasing energy of irradiation (decreasing wavelength) and there were higher densities of electron states at higher energies in TiO 2 . The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst. The energy of the electrons excited by visible light (400 nm) was too low for CO 2 photocatalytic reduction. A Ag/TiO 2 catalyst was used under illumination of different wavelengths for CO 2 photocatalytic reduction by water. Methane and methanol yields were higher with 254 nm light than with 365 nm light while no products were observed with 400 nm light.