The use of products from CO_2 photoreduction for improvement of hydrogen evolution in water splitting

摘要

CuO/TiO_2 photocatalysts were prepared and shown to enhance the rate of CO_2 photoreduction and the production of total organic carbon (TOC), including HCOOH, HCHO and CH_3OH. Resulting TOC could act as electron donors for enhancing visible light hydrogen evolution from Pt/TiO_2 photocatalysts. The impacts on CO_2 photoreduction were investigated including the effect of Cu dopant, pH, irradiation time and using Na_2SO_3 as a sacrificial agent, and those on hydrogen evolution was also studied including TOC concentration and Pt doping. The CO_2 photoreduction mechanisms with respect to pH and CO_2 reduction potentials were discussed. CuO/TiO_2 and Pt/TiO_2 photocatalysts were characterized by X-ray diffraction, Raman spectroscopy and diffuse reflection UV-vis spectrophotometry. Both photocatalysts showed a visible light response in comparison with pure TiO_2. The photocatalytic experiments and FT-IR spectra indicated that photo-product desorption was the rate-limiting step in the CO_2 photoreduction.