High visible light photocatalytic performance of V and Mo doped CuO/ZnO composites: integration between doping and p-n heterojunction

Efficient, fast, and stable visible light photocatalysts composed of V and Mo-doped CuO/ZnO composites (p-n heterojunction) were realized for photodegradation of methylene blue (MB) and crystal violet (CV) dyes. Pure, 6 wt% V, and Mo-doped CuO/ZnO composites were synthesized by a precipitation technique. The X-ray diffraction results clearly verified the formation of the desired phases and ratios of CuO and ZnO components as well as confirming the actual incorporation of V⁴⁺ and Mo⁶⁺ ions into their lattices. Optically, V and Mo ions have a strong effect on the absorption ability of CuO/ZnO catalyst towards visible light radiation by reducing the band gap energy of ZnO from 3.12 to 2.96 and 2.87 eV, respectively. The surface area of the pure CuO/ZnO was increased from 12 to 22 and 23 m² g⁻¹ due to V and Mo ions doping, respectively. The photocatalytic results demonstrate that the Mo-doped CuO/ZnO composite exhibits superior photodegradation characteristics with high efficiency towards MB and CV pollutants. In 45 min, Mo-doped CuO/ZnO catalyst shows a photo-removal efficiency of 98–99% for 20 ppm MB and CV dyes (100 mL, catalyst dose 0.04 g). Besides, this catalyst possesses a high efficiency (95–99%) for three cycles towards 20 ppm CV solution. The integration between Mo⁶⁺ doping and p-n heterojunction leads to remarkable photocatalytic characteristics including high visible light absorption, large surface area, and high separation of charge carriers through trapping by Mo⁶⁺ ions and p-n interface contact between CuO and ZnO particles.