Hexagonal Zn1-xCdxS (0.2 ≤ x ≤ 1) solid solution photocatalysts for H2 generation from water

A series of hexagonal Zn1-xCdxS photocatalysts with variable composition (0.2 <= x <= 1) is synthesized by a solvothermal method. XPS spectra of Zn 2p and Cd 3d regularly shift upon changing the composition of Zn1-xCdxS samples, due to the difference in the Mulliken atomic charges of Zn, Cd, and S. The photocatalytic activity of the samples for H-2 evolution from water was tested under visible-light irradiation (lambda >= 420 nm) without a cocatalyst; the Zn0.4Cd0.6S sample exhibited the highest photocatalytic H-2 evolution rate, which was about 81 mL h(-1) g(-1). Under irradiation with a 368 nm LED, the H-2 evolution rate decreased with increasing Cd fraction in the Zn1-xCdxS solid solution. By comparing the crystallinity, surface area, valence/conduction band positions, absorption spectra and fluorescence lifetimes, we conclude that the photocatalytic activity is related to the balance between the absolute positions of the valence/conduction bands and light absorption ability of the Zn1-xCdxS photocatalysts.