BiOxCly/BiOmBrn/BiOpIq/GO quaternary composites: Syntheses and application of visible-light-driven photocatalytic activities

Photocatalytic Degradation of Crystal Violet on Cu, Zn Doped BiVO4 Particles

Fabrication of codoped photocatalysts is a developing area of research. Herein, we explore the visible light photocatalytic properties of Cu, Zn codoped BiVO4 particles. Doping lower valent cations (Cu and Zn) makes the BiVO4 surface more acidic and enables us to target the basic crystal violet (CV) dye. The adopted hydrothermal protocol of synthesis results in the formation of Cu-Zn codoped monoclinic BiVO4 particles. Undoped monoclinic BiVO4, prepared by the same protocol, showed significant formation of oxygen vacancies. XPS analyses confirm the coexistence of Cu2+/Cu+ and Zn2+ dopants. Increased dopant percentage reduced oxygen vacancies. XRD indicates that Cu2+/Cu+ or Zn2+ dopants generally substitute Bi3+ in BiVO4. All photocatalysis activities for CV degradation are reported under near-neutral pH conditions. A typical codoped BiVO4 photocatalyst with 1% Zn and 2% Cu demonstrated the best CV degradation photocatalytic activity. The activity of this Zn, Cu codoped photocatalyst is better than that of pure, Zn-doped, and Cu-doped BiVO4 samples. Active species trapping experiments indicated the possible photocatalysis mechanism. The photocatalysts exhibited appropriate recyclability and photostability.

Enhanced photocatalytic performance of Bi2O2CO3/Bi4O5Br2/reduced graphene oxide Z-schemehe terojunction via a one-pot room-temperature synthesis

Bi2O2CO3(BOC)/Bi4O5Br2(BOB)/reduced graphene oxide (rGO) Z-scheme heterojunction with promising photocatalytic properties was synthesized via a facile one-pot room-temperature method. Ultra-thin nanosheets of BOC and BOB were grown in situ on rGO. The formed 2D/2D direct Z-scheme heterojunction of BOC/BOB with oxygen vacancies (OVs) effectively leads to lower negative electron reduction potential of BOB as well as higher positive hole oxidation potential of BOC, showing improved reduction/oxidation ability. Particularly, rGO is an acceptor of the electrons from the conduction band of BOC. Its dual roles significantly improve the transfer performance of photo-induced charge carriers and accelerate their separation. With layered nanosheet structure, rich OVs, high specific surface area, and increased utilization efficiency of visible light, the multiple synergistic effects of BOC/BOB/rGO can achieve effective generation and separation of the electron-holes, thereby generating more •O2- and h+. The photocatalytic reduction efficiency of CO2 to CO (12.91 µmol/(g·hr)) is three times higher than that of BOC (4.18 µmol/(g·hr)). Moreover, it also achieved almost 100% removal of Rhodamine B and cyanobacterial cells within 2 hours.

Broad Spectral Response FeOOH/BiO2-x Photocatalyst with Efficient Charge Transfer for Enhanced Photo-Fenton Synergistic Catalytic Activity

In this work, to promote the separation of photogenerated carriers, prevent the catalyst from photo-corrosion, and improve the photo-Fenton synergistic degradation of organic pollutants, the coating structure of FeOOH/BiO2-x rich in oxygen vacancies was successfully synthesized by a facile and environmentally friendly two-step process of hydrothermal and chemical deposition. Through a series of degradation activity tests of synthesized materials under different conditions, it was found that FeOOH/BiO2-x demonstrated outstanding organic pollutant degradation activity under visible and near-infrared light when hydrogen peroxide was added. After 90 min of reaction under photo-Fenton conditions, the degradation rate of Methylene Blue by FeOOH/BiO2-x was 87.4%, significantly higher than the degradation efficiency under photocatalysis (60.3%) and Fenton (49.0%) conditions. The apparent rate constants of FeOOH/BiO2-x under photo-Fenton conditions were 2.33 times and 3.32 times higher than photocatalysis and Fenton catalysis, respectively. The amorphous FeOOH was tightly coated on the layered BiO2-x, which significantly increased the specific surface area and the number of active sites of the composites, and facilitated the improvement of the separation efficiency of the photogenerated carriers and the prevention of photo-corrosion of BiO2-x. The analysis of the mechanism of photo-Fenton synergistic degradation clarified that ·OH, h+, and ·O2- are the main active substances involved in the degradation of pollutants. The optimal degradation conditions were the addition of the FeOOH/BiO2-x composite catalyst loaded with 20% Fe at a concentration of 0.5 g/L, the addition of hydrogen peroxide at a concentration of 8 mM, and an initial pH of 4. This outstanding catalytic system offers a fresh approach to the creation and processing of iron-based photo-Fenton catalysts by quickly and efficiently degrading various organic contaminants.

Photocatalytic CO2 Reduction to CH4 and Dye Degradation Using Bismuth Oxychloride/Bismuth Oxyiodide/Graphitic Carbon Nitride (BiOmCln/BiOpIq/g-C3N4) Nanocomposite with Enhanced Visible-Light Photocatalytic Activity

The use of visible-light-driven photocatalysts in wastewater treatment, photoreduction of CO2, green solar fuels, and solar cells has elicited substantial research attention. Bismuth oxyhalide and its derivatives are a group of visible-light photocatalysts that can diminish electron–hole recombination in layered structures and boost photocatalytic activity. The energy bandgap of these photocatalysts lies in the range of visible light. A simple hydrothermal method was applied to fabricate a series of bismuth oxychloride/bismuth oxyiodide/grafted graphitic carbon nitride (BiOmCln/BiOpIq/g-C3N4) sheets with different contents of g-C3N4. The fabricated sheets were characterized through XRD, TEM, SEM-EDS, XPS, UV-vis DRS, PL, and BET. The conversion efficiency of CO2 reduction to CH4 of BiOmCln/BiOpIq of 4.09 μmol g−1 can be increased to 39.43 μmol g−1 by compositing with g-C3N4. It had an approximately 9.64 times improvement. The photodegradation rate constant for crystal violet (CV) dye of BiOmCln/BiOpIq of k = 0.0684 can be increased to 0.2456 by compositing with g-C3N4. It had an approximately 3.6 times improvement. The electron paramagnetic resonance results and the quenching effects indicated that 1O2, •OH, h+, and •O2− were active species in the aforementioned photocatalytic degradation. Because of their heterojunction, the prepared ternary nanocomposites possessed the characteristics of a heterojunction of type II band alignment.

Construction of Ag2CO3/BiOBr/CdS ternary composite photocatalyst with improved visible-light photocatalytic activity on tetracycline molecule degradation

Photocatalytic degradation was considered as a best strategy for the removal of antibiotic drug pollutants from wastewater. The photocatalyst of ABC (Ag₂CO₃/BiOBr/CdS) composite synthesized by hydrothermal and precipitation method. The ABC composite used to investigate the degradation activity of tetracycline (TC) under visible light irradiation. The physicochemical characterization methods (e.g. scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), ultraviolet visible spectroscopy (UV), photoluminescence (PL) and time resolved photoluminescence (TRPL) clearly indicate that the composite has been construct successfully that enhances the widened visible light absorption, induces charge transfer and separation efficiency of electron - hole pairs. The photocatalytic activity of all samples was examined through photodegradation of tetracycline in aqueous medium. The photocatalytic degradation rate of ABC catalyst could eliminate 98.79% of TC in 70 min, which is about 1.5 times that of Ag₂CO_3, 1.28 times that of BiOBr and 1.1 times that of BC catalyst, respectively. The role of operation parameters like, TC concentration, catalyst dosage and initial pH on TC degradation activity were studied. Quenching experiment was demonstrated that ·OH and O₂^·- were played a key role during the photocatalysis process that was evidently proved in electron paramagnetic resonance (EPR) experiment. In addition, the catalyst showed good activity perceived in reusability and stability test due to the synergistic effect between its components. The mechanism of degradation of TC in ABC composite was proposed based on the detailed analysis. The current study will give an efficient and recyclable photocatalyst for antibiotic aqueous pollutant removal.

In Situ Construction of BiO(ClBr)(1-x)/2Ix-n Solid Solution with Appropriate Surface Iodine Vacancies for Synergistically Boosting Visible-Light Photo-Oxidation Capability

A proposed BiO(ClBr)_(1-x)/2I_x-n solid solution containing abundant iodine vacancies has been constructed through a facile solvothermal treatment strategy. Fascinatingly, the iodine-vacancy BiO(ClBr)_(1-x)/2I_x-n solid solution exhibits an outstanding visible-light photocatalytic degradation property for the environmentally hazardous pollutants of methyl orange, tetracycline, and phenol solutions, which is credited to the synergistic effect of iodine vacancies and the solid solution. By manipulating the molar ratios of Cl, Br, and I, the band structure of the solid solution attained is controlled, enabling the samples to maximize the harvest of visible light and to possess strong oxidation features. More importantly, the construction of iodine vacancies is bound to modulate the local surface atomic structure and promotes the efficiency of the separation of photogenerated carriers. Given these, the microstructure and physicochemical and photoelectrochemical properties of the photocatalysts are fully characterized in a series. In addition, the iodine-vacancy BiO(ClBr)_(1-x)/2I_x-n solid solution has a stable crystal structure that permits favorable recyclability even after multiple cycles of degradation. This study sheds light on the significance of the simultaneous existence of vacancy and the solid solution for the enhanced performance of photocatalysts and opens up new insights for sustainable solar-chemical energy conversion.

Effective photodegradation of rhodamine B and levofloxacin over CQDs modified BiOCl and BiOBr composite: Mechanism and toxicity assessment

In this contribution, carbon quantum dots (CQDs) modified 3D-flower like BiOX (X = Cl, Br, I) photocatalyst were successfully prepared via a facile mechanical compounding method. The crystal structure, surface composition, morphologies, optical properties and photocatalytic activities were investigated in detail. The photocatalytic activity of the as-obtained photocatalyst were evaluated by degradation of rhodamine B (RhB) and Levofloxacin (LEV) under near IR-UV-vis light irradiation, the CQDs/BiOX composite displayed enhanced photocatalytic activity as compared with individual BiOX materials. The CQDs/BiOX composite had the outstanding light harvesting and electron transfer ability because of the ordered ultrathin nanosheet structure of the BiOX, the formation of metal Bi under photoinduction, and the synergistic effects between CQDs and pure BiOX. Antibacterial activity and effects on Rye seeds growth of the LEV degradation intermediate were also researched. Reactive-species-trapping experiments exhibited that h⁺ and O₂^- were the active reactive species during photodegradation process. This work provided an effective and simple strategy for designing QDs modified Bi-rich oxyhalides in organic pollutant containing wastewater treatment.

Photoreduction of carbon dioxide and photodegradation of organic pollutants using alkali cobalt oxides MCoO2 (M = Li or Na) as catalysts

The recycling of lithium batteries should be prioritized, and the use of discarded alkali metal battery electrode materials as photocatalysts merits research attention. This study synthesized alkali metal cobalt oxide (MCoO₂, M = Li or Na) as a photocatalyst for the photoreduction of CO₂ and degradation of toxic organic substances. The optimized NaCoO₂ and LiCoO₂ photocatalysts increased the photocatalytic CO₂-CH₄ conversion rate to 21.0 and 13.4 μmol g^-1 h^-1 under ultraviolet light irradiation and to 16.2 and 5.3 μmol g^-1 h^-1 under visible light irradiation, which is 17 times higher than that achieved by TiO₂ P25. The rate constants of the optimized reactions of crystal violet (CV) with LiCoO₂ and NaCoO₂ were 2.29 × 10^-2 and 4.35 × 10^-2 h^-1, respectively. The quenching effect of the scavengers and electron paramagnetic resonance in CV degradation indicated that active O₂^•-, ¹O₂, and h⁺ play the main role, whereas ^•OH plays a minor role for LiCoO₂. The hyperfine splitting of the DMPO-^•OH and DMPO-^•CH₃ adducts was a_N = 1.508 mT, a_Hβ = 1.478 mT and a_N = 1.558 mT, a_Hβ = 2.267 mT, respectively, whereas the hyperfine splitting of DMPO^+• was a_N = 1.475 mT. The quenching effect also indicated that active O₂^•- and h⁺ play the main role and that ^•OH and ¹O₂ play a minor role for NaCoO₂. The hyperfine splitting of the DMPO-^•OH and DMPO^+• adducts was a_N = 1.517 mT, a_Hβ = 1.489 mT and a_N = 1.496 mT, respectively. Discarded alkali metal battery electrode materials can be reused as photocatalysts to address environmental pollution.

Visible-light-driven 3D Bi5O7I/BiOCl microsphere with enhanced photocatalytic capability: Performance, degradation pathway, antibacterium and mechanism

It is well known that both of the separation efficiency of photogenerated carriers and the response capability to visible light remarkably affect the photocatalytic performance. In the present work, a 3D microsphere of Bi₅O₇I/BiOCl heterojunction catalyst was synthetised. The synergy of Bi₅O₇I and BiOCl not only significantly enhances the transfer rate and separation efficiency of carriers, but also heightens light absorption capacity. As-prepared Bi₅O₇I/BiOCl (40 wt% BiOCl) has a higher degradation efficiency on doxycycline hydrochloride (DC) (90 min, 83.0%) and super high inhibition rate (90 min, 99.92%) on Escherichia coli under visible light, compared to the two monomers. Pollutants DC is finally decomposed into CO₂, H₂O and small molecule intermediates by generated h⁺, •OH and •O₂^-. The effects of reactive radicals follow the order of •OH radicals > h⁺ radicals ≫ •O₂^- and e^- radicals. The possible structures of intermediates and four possible degradation pathways involved were also discussed. In addition, As-synthetised Bi₅O₇I/BiOCl has preferable reusability and excellent chemical stability. Biological toxicity experiments also verify that Bi₅O₇I/BiOCl is a green and environmentally friendly composite material. This strategy provides a green, low-toxic way for the application of traditional type II heterojunction in the fields of environmental remediation and photocatalysis.

Recent advancement in Bi5O7I-based nanocomposites for high performance photocatalysts

Bi₅O₇I belongs to the family of bismuth oxyhalides (BiOX, X = Cl, Br, I), having a unique layered structure with an internal electrostatic field that promotes the separation and transfer of photo-generated charge carriers. Interestingly, Bi₅O₇I exhibits higher thermal stability compared to its other BiOX member compounds and absorption spectrum extended to the visible region. Bi₅O₇I has demonstrated applications in diverse fields such as photocatalytic degradation of various organic pollutants, marine antifouling, etc. Unfortunately, owing to its wide band gap of ∼2.9 eV, its absorption lies mainly in the ultraviolet region, and a tiny portion of absorption lies in the visible region. Due to limited absorption, the photocatalytic performance of pure Bi₅O₇I is still facing challenges. In order to reduce the band gap and increase the light absorption capability of Bi₅O₇I, doping and formation of heterostructure strategies have been employed, which showed promising results in the photocatalytic performance. In addition, the plasmonic heterostructures of Bi₅O₇I were also developed to further boost the efficiency of Bi₅O₇I as a photocatalyst. Here, in this review article, we present such recent efforts made for the advanced development of Bi₅O₇I regarding its synthesis, properties and applications. The strategies for photocatalytic performance enhancement have been discussed in detail. Moreover, in the conclusion section, we have presented the current challenges and discussed possible prospective developments in this field.

Polyvinyl pyrrolidone-coordinated ultrathin bismuth oxybromide nanosheets for boosting photoreduction of carbon dioxide via ligand-to-metal charge transfer

Photoreduction of CO₂ to useful ingredients remains a great challenge due to the high energy barrier of CO₂ activation and poor product selectivity. Herein, Polyvinyl pyrrolidone (PVP) coordinated BiOBr was synthesized by a facile chemical precipitation method at room temperature. The CO₂ photoreduction behaviors of PVP coordinated BiOBr were evaluated with H₂O without sacrificial agent under the simulated sunlight. The evolution rates of CO and CH₄ are 263.2 µmol g^-1h^-1 and 3.3 µmol g^-1h^-1, which are 8 times and 2 times higher than those of pure BiOBr respectively. Furthermore, the coordination of PVP on BiOBr surface enhances greatly the selectivity of product CO, which is close to 100%. Loading PVP onto BiOBr could not only induce and stabilize the oxygen vacancy, but also increase the charge density of BiOBr via the ligand to metal charge transfer (LMCT), which could be beneficial to the adsorption and activation of CO₂ molecule. The photoreduction mechanism of CO₂ for PVP coordinated BiOBr was proposed based on the improved charge density of BiOBr by the experimental results and Density functional theory (DFT) calculations. This finding provides a new pathway to boost the conversion efficiency and selectivity for the activation of CO₂ photoreduction and new molecule insights into the role of PVP in photocatalysis.

Controlled hydrothermal synthesis of BiOxCly/BiOmBrn/g-C3N4 composites exhibiting visible-light photocatalytic activity

The first systematic synthesis of bismuth oxychloride/bismuth oxybromide/graphitic carbon nitride (BiO_xCl_y/BiO_mBr_n/g-C₃N₄) nano-composites used a controlled hydrothermal method. The structure, morphology and characteristic of BiO_xCl_y/BiO_mBr_n/g-C₃N₄ photocatalyst were measured by XRD, UV-vis-DRS, FT-IR, FE-TEM, FE-SEM-EDS, PL, BET, HR-XPS and EPR. Under visible light irradiation, the photodegradation activity was evaluated for the decolorization of crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) in aqueous solution. The catalytic performance showed that, when using sample BB2C1-4-250-30 wt% g-C₃N₄ composite as a photocatalyst, the best reaction-rate-constant (k) was 0.071 h^-1. It was 1.5 times higher than the k value of BB2C1-4-250 as a photocatalyst. From the scavenging effect of various scavengers, the results of EPR showed that reactive OH was the main scavenger, while O₂^-, h⁺ and ¹O₂ were the second scavenger in CV degradation. In this study, a possible photodegradation mechanism was proposed and discussed. In this work, our method of BiO_xCl_y/BiO_mBr_n/g-C₃N₄ preparation could be used for future mass production and the BiO_xCl_y/BiO_mBr_n/g-C₃N₄ composite materials could be applied to the environmental pollution control in future.

Peroxymonosulfate activation through 2D/2D Z-scheme CoAl-LDH/BiOBr photocatalyst under visible light for ciprofloxacin degradation

The synergistic effect between photocatalytic and peroxymonosulfate (PMS) activation has been widely applied in the field of sewage treatment. In this work, we synthesized a two-dimensional/two-dimensional (2D/2D) CoAl-LDH/BiOBr Z-scheme photocatalyst via a simple method. Then, multiple detection results demonstrated that CoAl-LDH was successfully anchored onto BiOBr, as well as formed an intimate interaction. Moreover, the photocatalytic degradation performance of the catalysts/PMS/vis system had been explored under several conditions (e.g., different catalyst doses, PMS doses, anions and pollutants). The 8 wt% CoAl-LDH/BiOBr composite exhibited the highest degradation efficiency (96%) of ciprofloxacin (CIP). In addition, radicals quenching experiments and electron paramagnetic resonance (EPR) indicated that •O₂- and ¹O₂ were the primary radicals for CIP degradation. The photoelectrochemical measurement and photoluminescence (PL) confirmed that 8 wt% CoAl-LDH/BiOBr exhibited the highest separation and transfer rate of charge carriers. The liquid chromatography-mass spectrometer (LC-MS) analysis revealed that oxidation of the piperazine ring and defluorination were the main CIP degradation pathways. Density functional theory (DFT) calculation, including the laplacian bond order (LBO) and Fukui index, which was consistent with the results of LC-MS. This study explained the superiority of the synergistic effect between photocatalysis and PMS activation on the degradation of pollutants.

Controllable Syntheses, Crystal Structure Evolution, and Photoluminescence of Polymorphic Zirconium Oxyfluorides

Precise synthesis of polymorphic phases with similar components but distinct crystal structures is one of the key problems in inorganic chemistry. In this work, we report a fluorination method adopting ZrO₂ as the starting material and NH₄F as the fluoridation agent that can afford multiphases in the Zr-O-F system, including Zr₇O₉F₁₀, Zr₃O₂F₈, ZrO_0.46F_3.08, ZrO_0.33F_3.33, β-ZrF₄, NH₄Zr₂F₉, and NH₄ZrF₅. A preliminary phase formation diagram was established as a function of the fluorination temperature (T), reaction time (t), and F/Zr ratio after systematic optimization of the preparation conditions. Among the as-obtained phases, the detailed crystal structures of Zr₇O₉F₁₀ and ZrO_0.33F_3.33 were refined based on the powder X-ray diffraction patterns. As the F/O ratio increases, the crystal structures of Zr-O-F phases transform gradually from an anion-deficient α-UO₃-related structure of Zr₇O₉F₁₀ to an anion-excess ReO₃-related structure of ZrO_0.33F_3.33. At last, we also prepared Ti-doped ZrO₂, Zr₇O₉F₁₀, ZrO_0.46F_3.08, and ZrO_0.33F_3.33 to study the host-lattice-dependent photoluminescence properties of zirconium oxyfluorides. The four materials show distinct photoluminescence in the UV and visible regions due to different local coordination environments of Zr/Ti. This work demonstrates the low-temperature fluorination method as an efficient route to phase-selective polymorphic metal oxyfluorides, which can be employed in further structure-property relationship studies.

Energizing periodic mesoporous organosilica (PMOS) with bismuth and cerium for photo-degrading methylene blue and methyl orange in water

This work reported an efficient catalyst to reduce the organic pollutants by using an energetic periodic mesoporous organosilica (PMOS) supported with bismuth (Bi-PMOS) and cerium (Ce-PMOS). PMOS support was designed through co-condensation of sodium silicate and 3-methacryloxypropyltrimethoxysilane on polysorbate templates. The resultant PMOSs were fabricated with bismuth and cerium oxides to formulate Bi-PMOS and Ce-PMOS, respectively. These materials showed photo-degradations of methylene blue (MB, 74.7% and 41.1% with Bi-PMOS and Ce-PMOS, respectively) and methyl orange (MO, 53.2% and 39.4% with Bi-PMOS and Ce-PMOS, respectively). Such efficient photo-degradations were attributed to the precise doping of metallic nodes of Bi₂ O₃ and CeO₂ on the porous structure of PMOS with high surface area. The results also showed that Bi and Ce were more effective in PMOS support for photo-degradation of dyes as the support provides more lifetime to photo-generated electron-hole pairs than other materials. Moreover, active reusability and high degradation efficiencies of Bi-PMOS and Ce-PMOS proved them better analytical tools to reduce organic pollutants under visible lights. PRACTITIONER POINTS: The oxides of bismuth and cerium have impressive photocatalytic characteristics. New material energizing mesoporous organosilica with bismuth and cerium for photo-degradation of methylene blue and methyl orange in water. The use of an efficient catalyst to reduce the organic pollutants by using an energetic periodic mesoporous organosilica (PMOS) supported with bismuth (Bi-PMOS) and cerium (Ce-PMOS).

Visible-light-driven photocatalysis of carbon dioxide and organic pollutants by MFeO2 (M = Li, Na, or K)

In recent years, lithium-containing ceramic materials have attracted considerable research attention as high-temperature adsorbents of carbon dioxide. The recycling of electrode materials from spent lithium-ion batteries for use as photocatalysts in recovering CO₂ and degrading organic pollutants is worthy of exploration. Solid, magnetic ferrite-containing photocatalysts are easily separated from reaction solutions by using magnetic devices. Solid catalysts (e.g., LiFeO₂, LiFe₅O₈, NaFeO₂, and K₂Fe₂O₄) were prepared through the calcination of Fe₂O₃ and M₂CO₃. CO₂ was photoreduced and crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) were photodegraded under visible light irradiation. The optimized K₂Fe₂O₄ photocatalyst increased the rate of photocatalytic conversion from CO₂ to methane at 20.9 µmol g^-1 h^-1. The catalytic efficiency indicated that the optimized reaction rate constants of CV with LiFeO₂, NaFeO₂, and K₂Fe₂O₄ were 2.98 × 10^-1, 5.32 × 10^-1, and 4.36 × 10^-1 h^-1, respectively. The quenching effect achieved through the use of various scavengers and the electron paramagnetic resonance in CV degradation revealed the substantial contribution of the reactive superoxide anion radical O₂^- and the minor roles of h⁺ and the OH radical. Its usefulness in the synthesis of solid-base catalyst MFeO₂ is promising for environmental control and relevant applications, particularly in solar energy manufacturing.

Phase transformation and heterojunction construction of bismuth oxyiodides by grinding-assisted calcination in the presence of thiourea and their photoactivity

Bismuth-rich oxyhalides are promising photocatalysts due to their special layered structure and adjustable band gap energy. In this work, a series of bismuth oxyiodides were fabricated by grinding-assisted calcination in the presence of thiourea, where grinding-induced mechanical force could accelerate the decomposition reaction and thiourea could prohibit the crystal particles from growing due to coordination action. The combined effect of grinding and thiourea could decrease the temperature of phase transformation of bismuth oxyiodides. Among these, heterojunction Bi4O5I2/Bi5O7I containing uniform flower-like microspheres assembled by ultra-thin nanosheets exhibited the highest photocatalytic activity and favorable stability for the degradation of the antibiotic tetracycline under visible light irradiation. This work could provide a good reference for the design of bismuth-rich oxyhalide heterojunction for photocatalytic applications.

A facile synthesis of bismuth oxychloride-graphene oxide composite for visible light photocatalysis of aqueous diclofenac sodium

In this study, bismuth oxychloride/graphene oxide (BiOCl-GO) composite was fabricated by facile one pot hydrothermal method. The pure BiOCl and BiOCl-GO composite was characterized by X-ray diffraction, Transmission electron microscopy X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance spectroscopy. The synthesized composite was then assessed for photocatalytic degradation of diclofenac sodium (DCF) in visible as well as direct solar light and UV irradiation. Results indicated that the photocatalytic removal efficiency of DCF was significantly affected by dose of catalysts, pH value and source of light. The results reveled that degradation efficiency of BiOCl-GO for DCF reduced from 100 to 34.4% with the increases in DCF initial concentration from 5 mg L^-1 to 25 mg L^-1. The solar light degradation of DCF using BiOCl-GO was achieved with apparent rate constant 0.0037 min^-1. The effect of scavengers study revealed that superoxide ions and holes were mainly responsible for DCF degradation. The regeneration study indicates that BiOCl-GO composite can be successfully recycled up to the five cycles. The study revealed the effectiveness of one pot hydrothermal method for the fabrication of BiOCl-GO composite.

Bismuth-rich bismuth oxyiodide microspheres with abundant oxygen vacancies as an efficient photocatalyst for nitrogen fixation

A combined bismuth-rich and defect introduction strategy was used to prepare the H-Bi₅O₇I with abundant oxygen vacancies, which can effectively yield ammonia under visible light without any organic scavengers or noble-metal cocatalysts.

Bi4O5I2/nitrogen-doped hierarchical carbon (NHC) composites with tremella-like structure for high photocatalytic performance

BiOI is a visible photocatalyst towards organic pollutant. In this work, biomass waste (withered typha grass) was used to fabricate nitrogen-doped hierarchical carbon (NHC) by an one-step carbonization route. Then NHC provided a good carrier to load the BiOI semiconductor materials by a green simple co-precipitation method, after adding NaOH solution, the irregular microspheres BiOI/NHC was gradually etched by OH^- to form the tremella-like Bi₄O₅I₂/NHC. The well-defined tremella-like Bi₄O₅I₂/NHC invested adequate interface and high particular surface range (S_BET: 66 m² g^-1), which is higher than pure BiOI (22 m² g^-1) and Bi₄O₅I₂ (17 m² g^-1). Multiple synergistic effects, such as high S_BET can give more dynamic destinations, the special tremella-like structure can assimilate more reflected occurrence light of other nanosheets, low I content can increase the conduction/valence band gap of semiconductor materials and NHC can act as an electron acceptor, making as-prepared Bi₄O₅I₂/NHC composite ideal candidates for photocatalysis. The degradation rate of Bi₄O₅I₂/NHC reaches up to 87.4% of methyl orange in 2 h, which is about 2 times higher than BiOI and Bi₄O₅I₂. Therefore, this work gives a technique to link NHC derived from biomass waste to Bi₄O₅I₂ with highly-efficiency photocatalytic performance.