# Recent Advances and Applications of Semiconductor Photocatalytic Technology
## 5 Methods for Improving Photocatalytic Efficiency
### Semiconductor Compound  
A semiconductor composite photocatalyst is realized by two types of band-matched semiconductors. The methods for achieving semiconductor recombination include simple combinations, doping, multilayer structure, and out of phase combination. The essence of semiconductor blending to improve the photocatalytic performance is that photogenerated electrons or holes generated by a semiconductor move to the conduction band or the valence band of another semiconductor to separate photogenerated electrons and holes, thus effectively suppressing the recombination of carriers [252]. [PERSON] et al. [267] combined a single-dimensional cadmium sulfide (CdS) nanowire with a TiO\({}_{2}\) nanoparticle by a hot solvent method to form a catalyst for a core-shell structure. In photocatalysis  
Figure 6: Block diagram of (**A**) mono metal or bimetallic (both) TiO\({}_{2}\) modification and (**B**) bimetallic TiO\({}_{2}\) modification (seq) [263]. experiments, cadmium sulfide/titanium dioxide (CdS/TiO\({}_{2}\)) photocatalysts can completely decompose methyl orange, methylene blue, and rhodamine B, and the photocatalytic decomposition time is only 2-3 min. [PERSON] et al. [268] prepared a nanorod FeVO\({}_{4}\)-TiO\({}_{2}\) composite catalyst by the coprecipitation method. In the NO gas conversion experiment, the decomposition rate of NO by the nanorod FeVO\({}_{4}\)-TiO\({}_{2}\) composite catalyst was more than 1.5 times that of the nanoparticle FeVO\({}_{4}\)-TiO\({}_{2}\) composite catalyst. [PERSON] et al. [269] prepared a MoSe\({}_{2}\)-TiO\({}_{2}\) composite photocatalyst by using a hot solvent method. Cr\({}^{6+}\) ions were reduced by using pure MoSe\({}_{2}\), pure TiO\({}_{2}\), and complex MoSe\({}_{2}\)-TiO\({}_{2}\) as the photocatalysts. After 120 min of visible light irradiation, the reduction rate of Cr\({}^{6+}\) by pure MoSe\({}_{2}\) and pure TiO\({}_{2}\) was only 61% and 2%, respectively, while the conversion rate of composite catalyst MoSe\({}_{2}\)-TiO\({}_{2}\) was as high as 91%. [PERSON] et al. [270] prepared a zirconium dioxide-titanium dioxide (ZrO\({}_{2}\)-TiO\({}_{2}\)) composite semiconductor photocatalyst by the sol-gel method. In the research of industrial printing and dyeing wastewater purification, there is a relationship between the degradation rate of pollutants and the radiation time, pH, sewage concentration, and catalyst concentration. The concentration of organic pollutants, especially, has the greatest influence on the degradation rate of pollutants. [PERSON] et al. [271; 272] reported the use of wet chemical methods to synthesize large-sized porous InVO\({}_{4}\) spheroids and large-sized porous g-C\({}_{3}\)N\({}_{4}\) particles. Next, nano-TiO\({}_{2}\) particles were composited on the surfaces of InVO\({}_{4}\) and g-C\({}_{3}\)N\({}_{4}\) to obtain a semiconductor composite material having a large size, porosity, and narrow band gap. Experiments show that, in addition to improving the quantum effect of the material, the semiconductor composite material also increases the specific surface area of the material. Higher specific surface areas provide more reactive sites, thereby extending the lifetime of photogenerated electron-hole pairs. In multicomponent modified TiO\({}_{2}\), as compared to one-component modified TiO\({}_{2}\), different components can be combined with one another such that the catalyst has different degrees of improvement in light absorption performance and electron-hole separation efficiency. [PERSON] et al. [273] used photoreduction deposition and chemical bath deposition to prepare Pt and CdS nanoparticles on co-modified TiO\({}_{2}\) nanotubes. The decomposition rate of methyl orange dye with Pt and CdS co-modified TiO\({}_{2}\) nanotubes reached 91.9% under visible light. The decomposition rate of methyl orange fueled by a pure TiO\({}_{2}\), Pt/TiO\({}_{2}\), and CdS/TiO\({}_{2}\) single composite catalyst is much lower than 91.9%.