Synthesis of Zn _x Cd_1–x S Solid Solution Porous Spheres as Efficient Visible-Light Driven Photocatalysts

A series of Zn _x Cd_1–x S (ZCS) solid solution photocatalysts (x = 0.0, 0.33, 0.5, 0.67, 0.8 and 1.0) was directly fabricated by a simple wet chemistry route for the first time. The results revealed that the as-prepared ZCS solid solutions had wurtzite structure with various chemical compositions. With increasing Zn content, the ZCS morphology transformed from irregular aggregates to porous spheres accompanied by the reduction and homogenization of building block sizes; the band gaps were continuously adjusted from 2.2 to 3.1 eV; the specific surface area (AAS) increased from 4.2 to 93.3 m²/g. The photocatalytic activities in degradation of refractory reactive brilliant red (X3B) under visible light irradiation were also dependent on the photocatalyst compositions and all showed much higher activity than that of commercial product CdS (CP-CdS). Among them, the sample Zn_0.8Cd_0.2 S, with the lowest content of Cd, exhibited the highest photoactivity. The higher activity of Zn_0.8Cd_0.2 S may be attributed to the synergistic effect of its demonstrated doping levels of N species, appropriate band gap and the special porous spherical morphology. No apparent deactivation was observed for N-doped Zn_0.8Cd_0.2 S after being reused for six times.