Facile fabrication of a novel BiPO4 phase junction with enhanced photocatalytic performance towards aniline blue degradation

Photocatalytic degradation of multiple-organic-pollutant under visible light by graphene oxide modified composite: degradation pathway, DFT calculation and mechanism

Wastewater containing antibiotics, organic dyes, and waterborne bacteria is a severe threat to human health and the environment. Amoxicillin has a slow metabolism rate in humans. Methylene blue is mutagenic and carcinogenic. In addition, Salmonella causes serious diarrhea. In this study, an effective 2D/2D photocatalyst with excellent elimination of these pollutants was fabricated by combining graphene oxide (GO), Bi2WO6, BiPO4 and Ag species. GO was applied at varying loading contents (0.8, 1.6, 2.4, 3.2 wt%) to improve the properties of the photocatalyst toward the removal of representative pollutants. The chemical structures, morphology, light absorption and charge mobility were investigated by different GO loading samples. The results indicated that when the wt% of GO was 2.4%, the photocatalyst showed excellent photocatalytic properties and removal rates for typical pollutants. Amoxicillin and methylene blue were mineralized into CO2, H2O, and small molecules, while Salmonella was disinfected with excellent photocatalytic efficiency. Furthermore, the possible photodecomposition pathways of amoxicillin and methylene blue were proposed by DFT calculations and intermediates identified by LCMS. The mechanism of the photocatalytic process was investigated by radical trapping experiments, ESR spectroscopy, and Motty-Schottky plots. The free radicals could be produced constantly during the photocatalytic process, leading to mineralization of amoxicillin and methylene blue, and disinfection of Salmonella. In this work, a new perspective on GO modified Bi2WO6 with different loading contents and the degradation pathways of antibiotics and dyes was proposed.

Defect physics of intrinsic point defects in BiPO4 photocatalysts: a hybrid functional study

In this work, the intrinsic point defect properties of bulk BiPO4 under different growth conditions are intensively investigated and explored using first-principles hybrid functional calculations. It is found that Bi vacancies and O vacancies are the primary native defects in BiPO4. Under O-poor conditions, BiPO4 acts as an intrinsic insulator because the O vacancy defects (donor) and the Bi vacancy defects (acceptor) compensate for each other. Under Bi-poor conditions, good p-type conductivity is observed in BiPO4, which affirms the observed p-type conductivity behavior in experiments. Bi vacancies in BiPO4 are very shallow, which make it an excellent acceptor and are mostly responsible for the p-type character. In addition, it is found that the primary Bi vacancy defects of BiPO4 hardly affect its electronic structure and optical absorption spectrum regardless of the charge states. In contrast, the neutral O vacancy defects in BiPO4 introduce an impurity energy level near the VBM and induce a new optical absorption peak at around 370 nm. Furthermore, the O vacancies should be favorable for enhancing the production and separation efficiencies of the photo-generated electrons and holes in BiPO4. While Bi vacancies easily provide p-type carriers, simultaneously, they could become the active sites for the photocatalytic reactions because of their dominant -3 charge state. Therefore, understanding the defect physics in BiPO4 photocatalysts is believed to be beneficial for more research in developing BiPO4 or BiPO4-based photocatalysts.

Bismuth and Vanadium-Substituted Yttrium Phosphates for Cool Coating Applications

Luminescent yttrium phosphate is engineered into an environmentally benign near infrared (NIR) reflective yellow pigment by the substitution of bismuth and vanadium metals in the host lattice. A series of YP_(1-x)V _x O₄ (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.4), Y_(1-y)Bi _y PO₄ (y = 0.1 and 0.3), and Y_(1-y)Bi _y P_(1-x)V _x O₄ (x = y = 0.2, 0.4, and 0.6) were prepared by the precipitation method. Secondary phase was noticed at x = 0.2 and y = 0.2 while substituting vanadium and bismuth, respectively, due to high ionic radii of the dopant ions. Co substitution of vanadium and bismuth in the YPO₄ lattice enhanced both NIR reflectance and yellow color of all the fabricated materials. XPS spectra proved the presence of trivalent bismuth and pentavalent vanadium in Y_0.4Bi_0.6P_0.4V_0.6O₄. Due to the substitution effect, a more defined morphology was noticed, which enhanced the scattering co-efficient of the fabricated materials; hence, the NIR reflectance of the materials was increased from 68% (YPO₄) to 83% (Y_0.4Bi_0.6P_0.4V_0.6O₄). Chemical and thermal stability test of Y_0.4Bi_0.6P_0.4V_0.6O₄ confirmed the color and strength of the designed pigment. With good yellow hue (b* = +56.06), high NIR solar reflectance (R* = 83%), and good stability, Y_0.4Bi_0.6P_0.4V_0.6O₄ can act as an environmentally benign cool yellow pigment.

A facile synthesis of Ag3PO4/BiPO4 p-n heterostructured composite as a highly efficient photocatalyst for fluoroquinolones degradation

Ag₃PO₄/BiPO₄ heterojunction photocatalysts with an intergrowth structure composed of sphere-shaped Ag₃PO₄ and nanorod BiPO₄ were synthesized via a facile combination of solvothermal method and in-situ deposition process. They exhibit enhanced photocatalytic activities under sunlight irradiation, and the heterojunction composite with the 10 wt% loading amounts of Ag₃PO₄ presented the highest photocatalytic activities against norfloxacin (NFX), ofloxacin (OFXL) and ciprofloxacin (CIP), with high degradation efficiencies of 94.7%, 95.4% and 92.1%, respectively. Additionally, the Ag₃PO₄/BiPO₄ photocatalyst demonstrates outstanding structural and photocatalytic stability. The superior performance was attributed to the effective charge transfer across the p-n heterojunction interface and the enhancement of light absorption. This work provides a new insight into the development of novel BiPO₄-based heterojunction composites and meets the remediation for contaminated aqueous environment.

Enhanced solar-light-driven photocatalytic properties of novel Z-scheme binary BiPO4 nanorods anchored onto NiFe2O4 nanoplates: Efficient removal of toxic organic pollutants

Global environmental problems have been increasing with the growth of the world economy and have become a crucial issue. To replace fossil fuels, sustainable and eco-friendly catalysts are required for the removal of organic pollutants. In this study, nickel ferrite (NiFe₂O₄) was prepared using a simple wet-chemical synthesis, followed by calcination; bismuth phosphate (BiPO₄) was also prepared using a hydrothermal method. Further, NiFe₂O₄/BiPO₄ nanocomposites were prepared using a hydrothermal technique. Numerous characterization studies, such as structural, morphology, surface area, optical, photoluminescence, and photoelectrochemical investigations, were used to analyze NiFe₂O₄/BiPO₄ nanocomposites. The morphology analysis indicated a successful decoration of BiPO₄ nanorods on the surface of NiFe₂O₄ nanoplate. Further, the bandgap of the NiFe₂O₄/BiPO₄ nanocomposites was modified owing to the formation of a heterostructure. The as-prepared NiFe₂O₄/BiPO₄ nanocomposite exhibited promising properties to be used as a novel heterostructure for tetracycline (TC) and Rhodamine B (RhB) removal. The NiFe₂O₄/BiPO₄ nanocomposite degrades TC (98%) and RhB (99%) pollutants upon solar-light irradiation within 100 and 60 min, respectively. Moreover, the trapping experiments confirmed the Z-scheme approach of the prepared nanocomposites. The efficient separation and transfer of photogenerated electron-hole pairs rendered by the heterostructure were confirmed by utilizing electrochemical impedance spectroscopy, photocurrent experiments, and photoluminescence. Mott-Schottky measurements were used determine the positions of the conduction and valence bands of the samples, and the detailed mechanism of photocatalytic degradation of toxic pollutants was projected and discussed.

Ultrafast conversion of carcinogenic 4-nitrophenol into 4-aminophenol in the dark catalyzed by surface interaction on BiPO4/g-C3N4 nanostructures in the presence of NaBH4

The heterogeneous catalytic conversion of pollutants into useful industrial compounds is a two-goals at once process, which is highly recommended from the environmental, economic, and industrial points of view.

One-pot fabrication of BiPO4/Bi2S3 hybrid structures for visible-light driven reduction of hazardous Cr(VI)

For the first time, a novel BiPO₄/Bi₂S₃ heterostructures with different morphologies have been fabricated through a facile and rapid one pot precipitation route followed by anion-exchange strategy for the photoreduction of toxic Cr(VI) to harmless Cr (III). The hybrid structures systematically investigated using XRD, FE-SEM, EDS, TEM, HRTEM, XPS, FT-IR, UV-vis DRS, and PL. Changing the solvent type has a significant role for controllable morphologies of BiPO₄/Bi₂S₃ hybrid as well as the catalytic activity. The BiPO₄/Bi₂S₃ hybrid synthesized in diethylene glycol (DEG) performed the highest reduction efficiency of Cr(VI) within 20 min, compared with pure hexagonal phase of BiPO₄ under visible light. The rate constant for BiPO₄/Bi₂S₃ synthesized in DEG found to be 20.3 times larger than that for pure BiPO₄. In addition, the presence of tartaric acid as hole scavenger could enhance the Cr(VI) reduction efficiency to 97.9%. No significant decrease in the catalytic efficiency after recycling up to four cycles. This promising study could present a significant approach towards Cr(VI) photoreduction from water through the novel BiPO₄/Bi₂S₃ photocatalyst.