Band structure-controlled solid solution of Cd_{1 - x}Zn_x S photocatalyst for hydrogen production by water splitting

A series of Cd_{1 - x} Zn_x S (x = 0-0.92) photocatalysts were prepared by coprecipitation method and were calcined at 723 K under N₂ atmosphere. X-ray diffraction patterns results showed that the solid solution of Cd_{1 - x} Zn_x S were formed between ZnS and CdS. UV-Vis spectra indicated that the absorption edges of Cd_{1 - x} Zn_x S were red-shifted as the value of x decreased. The band gaps of the photocatalysts were estimated to be between 2.20-3.12 eV (x = 0-0.92) from the onsets of the absorption edges and almost showed linear variation with x increasing. The position of conduction band for solid solution is shifted towards more negative potential as compared to that of CdS. The hydrogen productions of Cd_{1 - x} Zn_x S (x = 0-0.92) by splitting water photocatalytically under ultraviolet and visible light irradiation were carried out in an inner-irradiation type reactor. The results indicated that the photocatalyst of Cd_0.62 Zn_0.16 S has the highest rate of hydrogen evolution with the quantum efficiency of 2.17% and 0.60% under ultraviolet and visible light irradiation, respectively. It has been considered that the crystallite size, (1 0 1) plane and band gap for the Cd_{1 - x} Zn_x S solid solutions have a strong influence on the efficiency of hydrogen production capability for water splitting.