Novel synthesis of Z-scheme α-Bi2O3/g-C3N4 composite photocatalyst and its enhanced visible light photocatalytic performance: Influence of calcination temperature

Construction of novel g-C3N4 coupled efficient Bi2O3 nanoparticles for improved Z-scheme photocatalytic removal of environmental wastewater contaminant: Insight mechanism

Recently, the major environmental pollution produced by the release of wastewater in liquid type is one of the most extensive forms of foremost pollution in water ecosystems. In this article, the Bi₂O₃/g-C₃N₄ nanocomposite with a direct Z-scheme was effectively obtained by a facile hydrothermal system. The crystal structures, surface morphology, chemical composition, and the optical belongings of the as-obtained composite catalysts were examined by Power XRD, FT-IR spectra, High-resolution XPS spectra, FE-SEM images with EDX spectra, High-resolution TEM images, UV-Vis DRS, and PL spectra respectively. Furthermore, the photocatalytic performance was assessed by the degradation of aqueous Rhodamine B (Rh B) dye under visible-light exposure. The Bi₂O₃/g-C₃N₄ composite photocatalysts (PCs) showed the maximum photo-degradation efficiency through a rate constant value of 0.0149 min^-1, which is 4.9 and 5.3 folds superior to Bi₂O₃, and GCN, respectively. The better GBO2 nanocomposite PCs showed a superior photocatalytic degradation performance (>82%) of aqueous Rh B dye after five successive recycles. Moreover, based on these outcomes of the radical scavenging test, a direct and effective Z-scheme photocatalytic charger transfer mechanism was also projected. Finally, the reusability of the as-obtained Bi₂O₃/g-C₃N₄ nanocomposite has better stability and reusability, which was a favourable applicant for wastewater handling.

Photocatalytic degradation of reactive brilliant blue KN-R by Ti-doped Bi2O3

In this study, different compositions of Ti-doped Bi₂O₃ photocatalytic materials were prepared by chemical solution decomposition method. It was used to degrade reactive brilliant blue KN-R, and then characterized by XRD, SEM, UV-vis DRS, XPS, photocurrent, and other detection methods. The results show that when the catalyst dosage is 1.0 g/L and the initial concentration of reactive brilliant blue KN-R is 20 mg/L, the degradation rate of pure Bi₂O₃ to reactive brilliant blue KN-R is 75.30%; the Ti doping amount is 4% (4Ti/Bi₂O₃), 4Ti/Bi₂O₃ had the best degradation effect on reactive brilliant blue KN-R, and the degradation rate could reach 93.27%. When 4Ti/Bi₂O₃ was reused for 4 times, the degradation rate of reactive brilliant blue KN-R only decreased by 6.91%. Doping Ti can inhibit the growth of Bi₂O₃ grains, making the XRD peak of Ti/Bi₂O₃ material wider. The pure Bi₂O₃ particles are larger and the surface is smooth. With the increase of Ti doping content, the surface of Ti/Bi₂O₃ material grows from roughness to nanofibrous Bi₄Ti₃O₁₂. The visible light absorption performance and electron separation and transfer ability of Bi₂O₃ are significantly improved by doping Ti ions. The band gap is reduced from 2.81 to 2.75 eV. In conclusion, doping Ti enhances the visible light absorption and electron separation and transfer capabilities of Bi₂O₃, reduces the band gap, and improves the surface morphology, which makes Bi₂O₃ have higher photocatalytic performance.

Visible-light driven p-n heterojunction formed between α-Bi2O3 and Bi2O2CO3 for efficient photocatalytic degradation of tetracycline

To improve the efficiency of photocatalytic oxidative degradation of antibiotic pollutants, it is essential to develop an efficient and stable photocatalyst. In this study, a polymer-assisted facile synthesis strategy is proposed for the polymorph-controlled α-Bi₂O₃/Bi₂O₂CO₃ heterojunction retained at elevated calcination temperatures. The p-n heterojunction can effectively separate and migrate electron-hole pairs, which improves visible-light-driven photocatalytic degradation from tetracycline (TC). The BO-400@PAN-140 photocatalyst achieves the highest pollutant removal efficiency of 98.21% for photocatalytic tetracycline degradation in 1 h (λ > 420 nm), and the degradation efficiency was maintained above 95% after 5 cycles. The morphology, crystal structure, and chemical state of the composites were analysed by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Ultraviolet-visible diffuse reflection, transient photocurrent response, and electrochemical impedance spectroscopy were adopted to identify the charge transfer and separation efficiency of photogenerated electron-hole pairs. The EPR results verified h⁺ and ˙OH radicals as the primary active species in the photocatalytic oxidation reactions. This observation was also consistent with the results of radical trapping experiments. In addition, the key intermediate products of the photocatalytic degradation of TC over BO-400@PAN-140 were identified via high-performance liquid chromatography-mass spectrometry, which is compatible with two possible photocatalytic reaction pathways. This work provides instructive guidelines for designing heterojunction photocatalysts via a polymer-assisted semiconductor crystallographic transition pathway for TC degradation into cleaner production.

Augmenting the Photocatalytic Performance of Direct Z-Scheme Bi2O3/g-C3N4 Nanocomposite

Huge demands for photocatalytically efficient visible-light-induced catalysts have spurred widespread interest in building adaptable heterojunctions. Here, we used in situ thermal polymerization to synthesise the Z-scheme Bi2O3/g-C3N4 heterojunction. The optical, structural, chemical, compositional and photocatalytic behaviours of the samples were analysed through various analytical techniques and photocatalytic methylene blue (MB) dye degradation reaction. Among the various ratios of Bi2O3/g-C3N4 heterojunction composites, the 1:1 ratio showed improved visible-light-induced catalytic activity, which attained 91.2% degradation efficiency after 120 min of visible-light exposure. The dye degradation efficiency was calculated under various environmental conditions by varying the dye concentration, solution pH and catalyst dosage. A improved Z-scheme photocatalytic mechanism was proposed in light of the results. A potential mechanism was suggested to explain the photocatalytic activity, and trapping experiments supported it. Last but not least, this strategy might be helpful to prepare the heterojunction photocatalyst for the degradation of organic pigments.

Research Progress on Graphitic Carbon Nitride/Metal Oxide Composites: Synthesis and Photocatalytic Applications

Although graphitic carbon nitride (g-C3N4) has been reported for several decades, it is still an active material at the present time owing to its amazing properties exhibited in many applications, including photocatalysis. With the rapid development of characterization techniques, in-depth exploration has been conducted to reveal and utilize the natural properties of g-C3N4 through modifications. Among these, the assembly of g-C3N4 with metal oxides is an effective strategy which can not only improve electron-hole separation efficiency by forming a polymer-inorganic heterojunction, but also compensate for the redox capabilities of g-C3N4 owing to the varied oxidation states of metal ions, enhancing its photocatalytic performance. Herein, we summarized the research progress on the synthesis of g-C3N4 and its coupling with single- or multiple-metal oxides, and its photocatalytic applications in energy production and environmental protection, including the splitting of water to hydrogen, the reduction of CO2 to valuable fuels, the degradation of organic pollutants and the disinfection of bacteria. At the end, challenges and prospects in the synthesis and photocatalytic application of g-C3N4-based composites are proposed and an outlook is given.

Use of an ultraviolet light-activated persulfate process to degrade humic substances: effects of wavelength and persulfate dose

Natural organic matter (NOM), commonly found in surface and ground waters, form disinfection by-products in drinking water. Generally, advanced oxidation processes (AOPs) featuring hydrogen peroxide are used to treat water; however, sulfate radical recently has been used to treat recalcitrant organics, because it is associated with a higher oxidation potential and more effective removal than hydroxyl radicals. Hence, in this research, we evaluated persulfate oxidation efficiency in terms of reductions in humic substance levels and investigated the degradation mechanism. The results showed that ultraviolet-activated persulfate effectively treated humic substances compared with hydrogen peroxide and direct irradiation. Treatment was dose and wavelength dependent; higher persulfate concentrations or shorter UV wavelengths were more effective for treating humic substances as high concentration sulfate radicals were created. The degradation mechanism was similar to that of hydrogen peroxide. Aromatic and chromophore components were more susceptible to degradation than were lower molecular weight components, being initially decomposed into the latter, reducing UV₂₅₄ absorbance and the SUVA₂₅₄. Lower molecular weight materials were eventually degraded to end products: NPOC levels fell. And we also treated the inflow of a drinking water treatment plant with persulfate, and humic substances were effectively removed.

Facile synthesis of layered Co(OH)2 deposited g-C3N4 for activating peroxymonosulfate to degrade organic pollutants

Layered Co(OH)2 deposited g-C3N4 is found to be highly active in the activation of peroxymonosulfate (PMS) for pollutant removal.