Photo reduction ofCO2to methanol viaTiO2photocatalyst

Abstract

Greenhouse gas such asCO2is the primary cause of global warming. Alternative energy source should be provided without producing moreCO2, such as solar energy. One of the best routes to remedyCO2is to transform it to hydrocarbons using photo reduction. In our study,CO2was photocatalytically reduced to produce methanol using a Hg lamp with wavelength 365 nm in a steady-state optical-fiber photo reactor. The optical-fiber photo reactor, comprised of near 120 Cu/TiO2-coated fibers, was designed and assembled to transmit and spread light uniformly inside reactor.TiO2film was coated on optical fiber using dip-coating method. Titania and Cu-loaded solutions were prepared by a thermal hydrolysis method. The thickness of Cu/TiO2film was 53 nm and consisted of very fine spherical particle with diameter of near 14 nm. The XRD spectra indicated the anatase phase of allTiO2and Cu/TiO2films. The wavelength of absorption edge was on 367 nm, equivalent to near 3.3 eV. Most active Cu species onTiO2surface wereCu2Oclusters, and played an important role for the formation of methanol. The methanol yield increased with UV irradiative intensity. Photo activity increased with increasing Cu loadings. Maximum methanol rate was 0.45μmole/g-cat•hr using 1.2 wt%-Cu/TiO2catalyst under 16 W /cm2irradiation, 1.3 bar pressure ofCO2, and 5000 seconds mean residence time. Higher than 1.2 wt% Cu loading gave less rate of methanol yield because of the masking effect ofCu2Oclusters on the surface of TiO2.