Photocatalytic conversion of greenhouse gases (CO2 and CH4) using copper phthalocyanine modified TiO2

• Photoconversion of (CO2+CH4) in a gas-phase reactor under visible light was studied.
• Cu-phthalocyanine modified TiO2 (CuPc/TiO2) coated on mesh was used as photocatalyst.
• The photoconversion for CO2 and CH4 under visible light were 14% and 18%, respectively.
• However, the conversions under unmodified TiO2 and visible light were zero, approximately.
• According to final gas products of photoconversion a mechanism was proposed.

In the present study, the direct photoconversion of carbon dioxide and methane in an appropriate gas-phase batch reactor under visible light was investigated. In the photocatalytic reaction system copper phthalocyanine (CuPc) modified titanium dioxide (CuPc/TiO2) photocatalyst that was coated on stainless steel mesh was used. The morphology of CuPc/TiO2 photocatalysts were characterized using XRD, SEM, FTIR and UV–vis analyses, and photoreduction products were identified using GC-TCD, GC–MS and FTIR in gas medium. The results of SEM have shown limited presence of CuPc on TiO2 surface, also the results of UV–vis have shown that the absorbance spectra of titania extended to visible spectral region. The results of photocatalytic activity have shown the conversion of 14% and 18% for CO2 and CH4 under modified TiO2 and visible light, respectively. However, the conversions of CO2 and CH4 under unmodified TiO2 and visible light were zero, approximately. Based on GC–MS and FTIR analyses, final products of conversion were characterized to be formate and acetate derivatives, and a mechanism involving the photoactivation of both TiO2 and CuPc sensitizer is proposed.