Zn1-xCdxS Solid Solutions with Controlled Bandgap and Enhanced Visible-Light Photocatalytic H2-Production Activity

Photocatalytic hydrogen (H-2) production from water splitting under visible light irradiation is considered to be an attractive way to solve the increasing global energy, crises in modern life. In this study, highly efficient photocatalytic H-2 production without the assistant of a cocatalyst was achieved using Znl(1-x)Cd(x)S solid solutions' as the visible-light-driven photocatalysts and a mixed Na2S and Na2SO3 aqueous solution as the sacrificial reagent. The Zn1-xCdxS samples were prepared by a simple zinc-cadmium-thiourea (Zn-Cd-Tu) complex thermolysis method using thiourea zinc acetate (Zn(Ac)(2)), and cadmium acetate (Cd(Ac)(2)) as the precursors The obtained Zn1-xCdxS solid solutions feature a small crystallite size and precisely controllable band structure, which are beneficial for the photocatalysis. When the Zn/Cd molar ratio is 1:1, the prepare Zn0.5Cd0.5S sample exhibits highest H-2-production rate of 7.42 mmol.h(-1).g(-1), exceeding that of the pure CdS and ZriS samples by more than 24 and 54 times, respectively, and even muck higher than that of optimal Pt-loaded CdS. This high photocatalytic H-2-production activity is attributed predominantly to enough visible-light absorption capacity and suitable conduction band potential of the Zn0.5Cd0.5S solid solution which is further evidenced from the related theory calculations on the band structures of the Zn1-xCdxS solid solutions. Moreover, the calculation on the Mulliken populations of Zn, Cd, and S toms for the first time provides new insight into the deep understanding of the chemical shifts of element binding energies for the Zn1-xCdxS solid solutions and the designing of new ternary photocatalytic materials.