Graphene-doped CuO (rGO-CuO) nanocomposites with flower shapes were prepared by an improved solvothermal method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and UV–visible spectroscopy. The active species in the degradation reaction of rGO-CuO composites under ultrasonic irradiation were detected by electron paramagnetic resonance. On the basis of comparative experiments, the photodegradation mechanisms of two typical dyes, Rhodamine B (Rh B) and methyl orange (MO), were proposed. The results demonstrated that the doped CuO could improve the degradation efficiency. The catalytic degradation efficiency of rGO-CuO (2:1) to rhodamine B (RhB) and methyl orange (MO) reached 90% and 87% respectively, which were 2.1 times and 4.4 times of the reduced graphene oxide. Through the first-principles and other theories, we give the reasons for the enhanced catalytic performance of rGO-CuO: combined with internal and external factors, rGO-CuO under ultrasound could produce more hole and active sites that could interact with the OH· in pollutant molecules to achieve degradation. The rGO-CuO nanocomposite has a simple preparation process and low price, and has a high efficiency of degrading water pollution products and no secondary pollution products. It has a low-cost and high-efficiency application prospect in water pollution industrial production and life.

Photocatalytic reduction of CO₂ is considered as a kind of promising technologies for solving the greenhouse effect. Herein, a novel hybrid structure of g-C₃N₄/ZnO/Ti₃C₂ photocatalysts was designed and fabricated to investigate their abilities for CO₂ reduction. As demonstration, heterojunction of g-C₃N₄/ZnO can improve photogenerated carriers' separation, the addition of Ti₃C₂ fragments can further facilitate the photocatalytic performance from CO₂ to CO. Hence, g-C₃N₄/ZnO/Ti₃C₂ has efficiently increased CO production by 8 and 12 times than pristine g-C₃N₄ and ZnO, respectively. Which is ascribed to the photogenerated charge migration promoted by metallic Ti₃C₂. This work provides a guideline for designing efficient hybrid catalysts on other applications in the renewable energy fields.