Hydrothermal synthesis Zn_xCd_(1-x)S solid solution coupled with TiO2 nanotubes film for photocatalytic hydrogen production

摘要

The photocatalytic splitting of water into H2 would be an environmentally friendly way of producing clean and renewable hydrogen on a large scale. Since the first photocatalysis of water was demonstrated by Fujishima and Honda, various photocatalysts for H2 production have been studied. Take the solar spectrum into consideration, the ultraviolet(UV) irradiation only account for 4% of the solar spectrum, which severely limits their practical application. Over the last few years, considerable effort has been made to improve visible light response of catalysts, metal sulfide are regarded as good candidates for visible-light photocatalysts. Among them, ZnS and CdS are the most often applied for photocatalytic H2 production. CdS has its excellent properties in that the band gap (2.3eV) corresponds well with the spectrum of sunlight and the conduction band edge is more negative than the H2O/H2 redox potential. However the narrow band gap and the proper band position are no guarantee of high potential for reduction of water to H2. the shortcomings such as its photocorrosion and the need to employ noble metals as co-catalysts prohibiting its wide usage. ZnS is another metal sulfide extensively studied for H2-production. However, its large band gap limits the range of light effective for photocatalytic activity. Therefore, numerous efforts have been focused on making solid solutions with CdS and ZnS in order to shift the absorption edge of ZnS into the visible light range . The recently reported solid solution photocatalysts about Cd_(1-x)Zn_xS, showed excellent performance for photocatalytic hydrogen production under visible light irradiation because of their controllable band structures and high quantum yield. However, in the application of these nanoparticles, there exist difficulties in the separation and the recycle of the particles. Therefore, film catalysts and the immobilization of solid solution attract more and more attentions.