In this paper, ZnO/NiO composites rich in oxygen vacancies are prepared by the solvothermal method and reduction method. In the test, through the use of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and electron paramagnetic resonance (EPR), we effectively prove the existence of phase, morphology and oxygen vacancies in the material. Through the photocatalysis test and gas sensitivity test, it is found that 10% Ni doped OZN-10 has the best photocatalytic activity and gas sensitivity characteristics. The degradation rate of methylene blue (MB) was 98%. The gas sensitivity test shows that OZN-10 has good selectivity, good response performance (3000 ppm, 27,887%) and excellent response recovery time (response time: 50 s, recovery time: 5–7 s) for saturated NH₃ gas at standard atmospheric pressure (101.325 KPa) and room temperature (25 °C). The synergistic effect of oxygen vacancy as the center of a trap and p–n heterojunction forming an electric potential field at the interface is explained, and the mechanism of improving photocatalysis and gas sensitivity is analyzed. This work will provide an innovative vision for dual-performance oxygen vacancy modification of heterojunctions through photocatalysis.

Solar-driven nano-semiconductor catalysts have shown great potential in solving environmental pollution and energy issues. They convert solar energy into chemical energy, release strong oxidizing hydroxyl radicals (OH·), and thoroughly degrade organic pollutants. However, these photocatalysts in turn may also damage some organic carriers. Therefore, we have used graphite phase carbon nitride (g-C ₃ N ₄ ) as the isolation layer to prevent the carrier polyester fiber (PET) from being oxidized by zinc oxide (ZnO). ZnO-g-C ₃ N ₄ @PET composite has been prepared by hydrothermal method, photoluminescence results indicated that ZnO-g-C ₃ N ₄ @PET has a low photo-generated charge recombination rate, while g-C ₃ N ₄ improves the visible light response of the composite and exhibits an obvious photocatalytic enhancement effect. In the experiment of degrading methylene blue (MB), the degradation efficiency of ZnO-g-C ₃ N ₄ @PET composite has been significantly improved compared with ZnO@PET and g-C ₃ N ₄ @PET alone. In addition, the prepared photocatalyst also has good reusability and still maintains a high degradation rate after five cycles of tests. In the end, a possible mechanism and a pathway of photocatalytic degradation of MB were proposed. All in all, this is a feasible way to build a highly efficient, environmentally friendly and sustainable supported photocatalyst.

The effect of Ce doping on the structural and optical properties of BiFeO ₃ nanoparticles via sol–gel method is reported. All samples were a pure phase with perovskite structure. The EDX results show the doped samples contain Bi, Fe, O and Ce elements. The vibrational properties of samples were studied using Raman spectroscopy. Photoluminescence shows an intense peak at 398 nm, the peak strength enhanced greatly and had redshift with the increase of Ce doping concentration. UV–vis results show the samples have a broad absorption band in the range of 500–600 nm. The bandgaps decrease with the concentration increase of Ce doping. It indicates the as‐prepared BiFeO ₃ can be used as visible light catalyst.

Recently, the use of semiconductor-based photocatalytic technology as an effective way to mitigate the environmental crisis attracted considerable interest. Here, the S-scheme BiOBr/CdS heterojunction with abundant oxygen vacancies (Vo-BiOBr/CdS) was prepared by the solvothermal method using ethylene glycol as a solvent. The photocatalytic activity of the heterojunction was investigated by degrading rhodamine B (RhB) and methylene blue (MB) under 5 W light-emitting diode (LED) light. Notably, the degradation rate of RhB and MB reached 97% and 93% in 60 min, respectively, which were better than that of BiOBr, CdS, and BiOBr/CdS. It was due to the construction of the heterojunction and the introduction of Vo, which facilitated the spatial separation of carriers and enhanced the visible-light harvest. The radical trapping experiment suggested that superoxide radicals (·O₂⁻) acted as the main active species. Based on valence balance spectra, Mott-Schottky(M-S) spectra, and DFT theoretical calculations, the photocatalytic mechanism of the S-scheme heterojunction was proposed. This research provides a novel strategy for designing efficient photocatalysts by constructing S-scheme heterojunctions and introducing oxygen vacancies for solving environmental pollution.