2.4. Analysis of the Photocatalytic Activities

The photocatalytic performance of ZnO/CdSe–CC for the degradation of methylene blue (MB) in aqueous solutions at different times was assessed using ultraviolet-visible (UV-Vis) spectrophotometry. CC, ZnO–CC, and ZnO/CdSe–CC were cut into 5 × 5 cm² samples. After weighing, the average mass of CC and ZnO–CC was 0.32 g and 0.42 g, respectively. Therefore, we speculated that the weight difference between ZnO–CC and CC was the ZnO powder loaded on CC. The 5 × 5 cm² CC, ZnO–CC, ZnO/CdSe–CC heterostructure samples, and 0.1 g ZnO powder were immersed in 50 mL MB aqueous solution (10 mg/L) and stirred for 40 min in the dark to obtain an adsorption–desorption equilibrium. An 800 W xenon lamp was used to irradiate the aqueous solution at room temperature. In the adsorption–desorption equilibrium and photocatalytic process, the rotating speed of the magnetic stirring device was maintained at 150–200 rpm. The degradation efficiency was calculated using Equation (1), where C_t and C₀ represent the concentrations of degraded MB at different illumination times and initial MB concentrations, respectively [21]. At the end of each cycle, the samples were washed several times and dried thoroughly before being placed in 50 mL fresh MB solution.