Facile synthesis of Zn-rich (GaN)_1-x(ZnO)_x solid solutions using layered double hydroxides as precursors

(GaN)_1-x(ZnO)_x solid solutions are potential photocatalysts for water splitting and environmental decontamination under visible light. Solid solutions prepared by the traditional method are not effective because of their low Zn content (x < 0.5). Here, we show that Zn-rich solid solutions (∼0.5 < x < ∼0.8) are readily prepared by the nitridation of layered double hydroxides (LDHs) containing Zn²⁺ and Ga³⁺ ions, and that the Zn content is easily adjusted by changing the Zn/Ga ratio of the LDH precursors. The band gap of (GaN) _1-x(ZnO)_x decreases gradually from 2.60 eV at x = 0.46 to 2.37 eV at x = 0.81. The Zn-rich solid solutions absorb strongly above 500 nm, and these solutions loaded with 1 wt% Pt are found to be efficient for photoreducing Cr⁶⁺ ions under visible light.