BiOI Photocatalysts Research Articles

Heterojunction photocatalyst for organic degradation: Superior photocatalytic activity through the phase and interface engineering

Semiconductor-based heterostructure photocatalyst attracts extensive attention because of its excellent interface charge transfer/separation ability. Here, the β-Bi2O3/CeO2 heterostructure photocatalysts are fabricated via a simple mechanochemical couple with thermal decomposition strategy. The introduction of CeO2 can not only stabilize the phase of β-Bi2O3 but also construct a heterojunction at the interface, resulting in the improved visible light response capability and efficient transfer and separation of photo-generated charges. Besides, the increased specific surface area and pore volume increase the active sites to accelerate the adsorption and mass transfer process. As a result, the β-Bi2O3/CeO2 heterostructure photocatalyst shows remarkably enhanced photocatalytic performance towards malachite green (MG) degradation under visible-light irradiation compared with the Bi2O3 and CeO2. The degradation efficiency of MG over the optimized β-Bi2O3/CeO2 heterostructure reaches up to 97.5% after 2 h of visible-light irradiation. This work provides a new approach for the rational design of heterojunction photocatalyst combined with phase and interface engineering and opens up a potential avenue for efficient application of Bi2O3 photocatalyst for efficient energy conversion.

Synthesis, characterization, and visible-light-induced photocatalytic activity of powdered semiconductor oxides of bismuth and zinc toward degradation of Alizarin Red S.

Semiconductor oxides of bismuth and zinc have been synthesized using modified sol-gel method and sol-combustion method, respectively. The synthesized catalysts were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. The photocatalytic activity of Bi2 O3 and ZnO was evaluated for the degradation of Alizarin Red S (ARS), as a model pollutant, at 20mg/L level in water under visible light irradiation. The percentage of photocatalytic degradation was determined using UV-vis spectrophotometer. The photocatalytic results revealed that Bi2 O3 and ZnO could effectively degrade 73% and 53% of ARS, respectively, within 13hr under visible light illumination, indicating that synthesized Bi2 O3 is a better photocatalyst than ZnO. Photodegradation of ARS with Bi2 O3 and ZnO is remarkably influenced by change in pH of the dye solution, and pH 8 was found to be the most favorable for maximum removal of ARS in case of both Bi2 O3 (75%) and ZnO (58%) photocatalyst. PRACTITIONER POINTS: Photocatalytic degradation of ARS dye depends on pH of the solution. Calcination temperature influences the crystallite size of prepared semiconductor oxides of bismuth and zinc. Bi2 O3 shows better photocatalytic degradation efficiency than ZnO under visible light illumination.

Fabrication of metal-doped BiOI/MOF composite photocatalysts with enhanced photocatalytic performance

An octahedron-like metal-organic framework (MOF) was successfully synthesized by the ultrasound irradiation synthesis method. Meanwhile, a novel visible-light-driven Cu-doped BiOI/MOF composite photocatalyst was also synthesized by the microwave irradiation. MOFs, a new class of porous crystalline materials, have attracted tremendous attention considering their broad applications because MOF possesses the repeated crystalline structures and thereby improving the harvest of solar energy and transportation of charge carriers. In this article, the result has revealed that the appropriate modification of BIOI by incorporating MOF and copper could reach the maximum hydrogen yield under visible light irradiation. The hydrogen evolution for 10% v/v lactic acid and 0.30 g L−1 of 3In/BiOI/4MOF composite photocatalyst had the maximum of 269.1 μmol h−1 g−1 for 6 h. However, as the overall time in a course of irradiation is prolongated until 48 h, 3Cu/BiOI/4MOF has the higher hydrogen evolution efficiency (7685.2 μmol) than that of 3In/BiOI/4MOF. Therefore, this study has substantially demonstrated to enhance the photocatalytic efficiency of BiOI photocatalyst using MOF and copper modified BiOI.

Microwave-assisted synthesis of high efficient α-Fe2O3/BiOI composites and its performance in photocatalytic degardation of organic pollutants

Herein, we prepare novel composites of α-Fe2O3/BiOI photocatalysts by one step microwave hydrothermal process. The SEM and TEM characterization results suggest microsphere shaped of BiOI with α-Fe2O3 nanoparticles decorated on the surface of BiOI nanosheets. According to the results of UV-vis DRS measurements, α-Fe2O3/BiOI exhibited more visible light adsorption. The composite exhibited the highest photoactivity for decomposition of methyl orange (MO) and antibiotics tetracycline (Tc) superior to that of the pure α-Fe2O3 and BiOI in the visible light. The degradation rate constant is 2.3 times and 2.0 times higher than that of pure BiOI and α-Fe2O3 under the same conditions for degradation MO and Tc respectively. The photodegradation performances of α-Fe2O3/BiOI composites were also investigated under different light sources irradiation. Based on the analysis results of radical capture experiment, the enhanced photocatalytic efficiency of α-Fe2O3/BiOI photocatalyst can be mainly indentified to be the dominant active species of hole (h+) and superoxide radical(O2−).

Highly efficient Bi2O3/MoS2 p-n heterojunction photocatalyst for H2 evolution from water splitting

The design of p-n heterojunction photocatalysts to overcome the drawbacks of low photocatalytic activity that results from the recombination of charge carriers and narrow photo-response range is promising technique for future energy. Here, we demonstrate the facile hydrothermal synthesis for the preparation of Bi2O3/MoS2 p-n heterojunction photocatalysts with tunable loading amount of Bi2O3 (0–15 wt%). The structure, surface morphology, composition and optical properties of heterostructures were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–visible absorption spectroscopy, Brunauer-Emmett-Teller (BET) surface area, photoluminescence (PL), electrochemical impedance spectroscopy (EIS). Compare to pure Bi2O3 and MoS2, the Bi2O3/MoS2 heterostructures displayed significantly superior performance for photocatalytic hydrogen (H2) production using visible photo-irradiation. The maximum performance for hydrogen evolution was achieved over Bi2O3/MoS2 photocatalyst (10 μmol h−1g−1) with Bi2O3 content of 11 wt%, which was approximately ten times higher than pure Bi2O3 (1.1 μmol h−1g−1) and MoS2 (1.2 μmol h−1g−1) photocatalyst. The superior performance was attributed to the robust light harvesting ability, enhanced charge carrier separation via gradual charge transferred pathway. Moreover, the increased efficiency of Bi2O3/MoS2 heterostructure photocatalyst is discussed through proposed mechanism based on observed performance, band gap and band position calculations, PL and EIS data.

Iodine-Deficient BiO1.2 I0.6 Coupling with Bi2 O3 for Degradation of Volatile Organic Compounds under Simulated Sunlight Irradiation.

A photocatalyst with a high separation efficiency of carriers is crucial for the photocatalytic efficient decomposition of volatile organic compounds (VOCs). In this work, a new iodine-deficient BiO1.2 I0.6 /Bi2 O3 photocatalyst was developed through a solvothermal approach coupled with thermal decomposition. The 2 wt % BiO1.2 I0.6 /Bi2 O3 sample demonstrated optimal photocatalytic activity for the degradation of toluene, achieving a 55.1 % mineralization ratio under 8 h of irradiation, which was 14.9 and 2.1 times higher than those of BiO1.2 I0.6 and Bi2 O3 , respectively. Compared with BiO1.2 I0.6 and Bi2 O3 , 2 wt % BiO1.2 I0.6 /Bi2 O3 exhibited the weakest fluorescence band, highest photocurrent density, and lowest impedance; thus suggesting that Bi2 O3 compounded by 2 wt % BiO1.2 I0.6 distinctly promoted the separation efficiency of carriers. The hydroxyl radical (. OH) was the main active species, apart from holes, for the photocatalytic degradation of toluene.

Recent progress on bismuth oxyiodide (BiOI) photocatalyst for environmental remediation

There are huge prospects for environmental remediation using semiconductor photocatalysts that decompose toxic pollutants under the illumination of light. This review article offers an outline of the applications of BiOI photocatalyst for the efficient decomposition of pollutants exist in the aqueous ecosystem. In addition, methods for synthesizing and modifying BiOI are emphasized to provide strategies for improving their photocatalytic activity. Furthermore, recent research progress and future predictions for BiOI photocatalyst are also summarized. This review will offer vision into the fabrication of novel and highly active BiOI-based photocatalysts in a green manner at low operational cost.

Comparative photocatalytic behavior of photocatalysts (TiO2, SiC, Bi2O3, ZnO) for transformation of glycerol to value added compounds

Four types of semiconductors were used as photocatalyst to convert glycerol to other value added compounds at identical testing condition in the presence of H2O2 as the electron acceptor. The results demonstrated that the band gap energy affected the photocatalytic activity of glycerol than the crystallite size and textural property of the utilized photocatalyst. The SiC, Bi2O3 and ZnO achieved almost complete glycerol conversion at 8 h of reaction time, which was significantly higher than that of TiO2. Similar types of products, including dihydroxyacetone, glyceraldehyde, glyceric acid, glycolic acid and formic acid, were generated via all explored photocatalysts. Interestingly, one additional compound known as glyoxylic acid, an important intermediate of organic chemicals, used in medicine, spices, pesticides, paint, paper and food, was produced via Bi2O3. The reaction mechanism and the pathways of photocatalytic conversion of glycerol via Bi2O3 were proposed. Finally, the reusability of Bi2O3 photocatalyst was explored.

Exploration and crystal phase engineering from bismuthinite ore to visible-light responsive photocatalyst of Bi2O3

Semiconductor photocatalysts have attracted considerable research attention because of their extensive range of applications in eliminating hazardous environmental pollutants. Herein, a compact process was introduced to prepare Bi2O3 photocatalyst from bismuthinite ore. This new process is simplified by eliminating the preparation of pure bismuth salts solutions or bismuth ingots compared with the traditional process and beneficial to the controllable preparation of Bi2O3. The synthesized samples were characterized by various analytical techniques and their photocatalytic performance was evaluated by photocatalytic degradation rhodamine B (RhB) under visible-light irradiation. Among the as-prepared photocatalysts, β-Bi2O3 exhibited much higher photocatalytic activities than α and δ-Bi2O3 for degradation of RhB. The much better photocatalytic activities of β-Bi2O3 was considered to be closely related to its smaller band gap, higher crystallinity and unique crystal structures. Given this, this work might open up a potential avenue for the large-scale preparation of Bi2O3 photocatalyst for advanced photocatalysis systems.

Enhanced photocatalytic performance of metal silver and carbon dots co-doped BiOI photocatalysts and mechanism investigation.

The photocatalytic technology provides a promising and effective strategy for the transformation and degradation of contaminants. Herein, we accurately fabricated a novel ternary photocatalyst, namely, metal silver (Ag) and carbon dots (CDots) co-doped BiOI nanocomposite (Ag/CDots/BiOI) via the reduction method with ionic liquids 1-butyl-3-methylimidazolium iodine ([Bmim]I) at room temperature. The morphologies and microstructures showed the Ag and CDots were uniformly loaded on the surface of BiOI, forming a ternary system. The characterization results implied that an intense interaction was formed between Ag and CDots on the BiOI, which could achieve the broad spectrum utilization of visible light and boosted the photocatalytic performances. The 0.9-Ag/2-CDots/BiOI (0.9 wt% of Ag, 2 wt% of CDots) presented the highest photocatalytic activity with ~ 100% in 4-Chlorophenol, 68.8% in mineralization, and 87.4% in dechlorination in 6 h under visible light illumination. The enhanced photocatalytic activity could be ascribed to the surface plasmon resonance effect of Ag, the up-converted photoluminescence (PL) properties of CDots, and the electron transfer properties of both Ag and CDots. Moreover, a possible photocatalytic reaction mechanism was discussed in detail by band structure analysis and radical scavenger quenching experiments. This study provides a promising approach for promoting the utilization efficiency for solar energy and sustainable environmental remediation.

Sono-solvothermal design of nanostructured flowerlike BiOI photocatalyst over silica-aerogel with enhanced solar-light-driven property for degradation of organic dyes

In this study, in order to scrutiny the effect of adding Silica Aerogel to the BiOI for evaluation of photocatalytic performance, BiOI-Silica Aerogel with different percentages of Silica Aerogel (10, 20 and 30%) was synthesized by Sono-solvothermal method. In order to determine the physical, chemical and optical characteristics of synthesized photocatalysts, XRD, FESEM, EDX-dot mapping, FTIR, BET-BJH, UV–vis DRS and pHpzc have been used. The results of the characterization techniques showed that adding Silica Aerogel had a significant effect on physicochemical properties of BiOI. Photocatalytic activity of the samples was measured by degradation of organic pollutants such as Methylene Blue, Acid Orange 7 and Rhodamine B under visible light. From experimental data, it was also found that the amount of Silica Aerogel impressed photocatalyst performance. The best photocatalytic performance was obtained by adding 20% Silica Aerogel to BiOI. Furthermore, the effect of operational parameters such as pH, concentration of MB on the activity of BiOI(80)-SA(20) composite was evaluated. The results showed that MB at pH = 9 and a 0.5 g dosage of BiOI(80)-SA(20) had the highest removal percentage (96.5%) in 120 min. Finally, after 4 cycles, only 9.7% of the photocatalytic activity declined.

Selective oxidation of cyclohexane to cyclohexanol by BiOI under visible light: Role of the ratio (1 1 0)/(0 0 1) facet

The development of semiconductors capable of photocatalytic activity under visible light is very important, because such materials are potentially useful for performing photocatalytic conversion under solar illumination. However, these processes are frequently unselective because they involve the production of free radicals. Reports suggest that the selectivity of the photocatalytic processes may be adjusted through modification of the structural parameters of the semiconductor photocatalysts by the preferential exposure of certain crystalline planes.The present work focuses on the relationship between the preferential exposure of the (1 1 0) and (0 0 1) facets of bismuth oxyiodide and the cyclohexanol produced by the photocatalytic oxofunctionalization of cyclohexane. For this purpose, four bismuth oxyiodide photocatalysts (BiOI-4, BiOI-6, BiOI-10, and BiOI-12) were synthesized at different pH levels and characterized (via X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, and the Brunauer–Emmett–Teller surface area). All BiOI photocatalysts showed higher selectivity for cyclohexanol. Additionally, a linear dependence between the cyclohexanol yield and peak intensity (1 1 0)/(0 0 1) ratio was established and related to the relative amount of hydroxyl radicals formed in the photocatalytic system.

A Bi/BiOI/(BiO)2CO3 heterostructure for enhanced photocatalytic NO removal under visible light

Narrow-band BiOI photocatalysts usually suffer from low photocatalysis efficiency under visible light exposure because of rapid charge recombination. In this work, to overcome this deficiency of photosensitive BiOI, oxygen vacancies, Bi particles, and Bi2O2CO3 were co-induced in BiOI via a facile in situ assembly method at room temperature using NaBH4 as the reducing agent. In the synthesized ternary Bi/BiOI/(BiO)2CO3, the oxygen vacancies, dual heterojunctions (i.e., Bi/BiOI and BiOI/(BiO)2CO3), and surface plasmon resonance effect of the Bi particles contributed to efficient electron-hole separation and an increase in charge carrier concentration, thus boosting the overall visible light photocatalysis efficiency. The as-prepared catalysts were applied for the removal of NO in concentrations of parts per billion from air in continuous air flow under visible light illumination. Bi/BiOI/(BiO)2CO3 exhibited a highly enhanced NO removal ratio of 50.7%, much higher than that of the pristine BiOI (1.2%). Density functional theory calculations and experimental results revealed that the Bi/BiOI/(BiO)2CO3 composites promoted the production of reactive oxygen species for photocatalytic NO oxidation. Thus, this work provides a new strategy to modify narrow-band semiconductors and explore other bismuth-containing heterostructured visible-light-driven photocatalysts.

Construction of BiOF/BiOI nanocomposites with tunable band gaps as efficient visible-light photocatalysts

A series of BiOF/BiOI heterojunction composites photocatalysts has been prepared via a simple coprecipitation method and characterized by using UV–vis (UV–vis) diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller for determination of the specific surface area and porosity (BET), high resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The enhanced photocatalytic activity for removal of the pharmaceutical compound Diclofenac Potassium commercially available as Voltfast sachets under visible light irradiation was demonstrated by comparing heterojunction prepared composites photocatalysts with that of pure BiOF and BiOI photocatalysts prepared under the same conditions. Based on the experimental conditions, the highest activity was achieved for the composite contains 40% BiOF and 60% BiOI showing comparable activities to that of pure BiOI. To the best of our knowledge, this study is the first to report the preparation of BiOF/BiOI composites photocatalysts and their use in the photocatalytic removal of Diclofenac Potassium from aqueous solution.

Photocatalytic degradation kinetics of unsymmetrical dimethylhydrazine in aqueous solution by Fe3+ doped Bi2O3

The Fe3+ doped Bi2O3 photocatalyst was prepared by sol-gel method. The photocatalytic degradation experiment was carried out using unsymmetrical dimethylhydrazine (UDMH) simulated wastewater as the target pollutant. The results showed that Fe3+ doping significantly improved the degradation efficiency of UDMH with an optimum doping concentration of 2.0%. The reaction kinetics study indicated that the reaction was heterogeneously catalyzed and the kinetic fitting results were consistent with pseudo first-order reaction kinetics model. According to the results of linear fitting, the kinetic reaction rate constant of Fe3+ doped Bi2O3 (2.0%) was the largest, about 1.9 times as much as that of undoped Bi2O3. Finally, a possible mechanism was proposed to explain the enhanced photocatalytic activity.

F127-assisted hydrothermal preparation of BiOI with enhanced sunlight-driven photocatalytic activity originated from the effective separation of photo-induced carriers

BiOI photocatalyst with remarkably enhanced sunlight-driven photocatalytic performance was prepared by a facile hydrothermal approach with the assistance of EO106PO70EO106 (F127). Brunauer -Emmett-Teller (BET), X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectra (DRS), surface photovoltage spectroscopy (SPS) and electron spin-resonance (ESR) spectra were employed to study the samples. The level of O2− was investigated using nitrotetrazolium blue chloride (NBT)-O2− exclusive reaction. The results show that F127 dramatically promotes the specific area parameters, enhances the separation efficiency of photo-induced carriers and surface hydroxyl content as well as expedites the formation of O2−. The photocatalytic activities of two photocatalysts for decomposition of methyl orange (MO) were evaluated. The photocatalytic activity of F127-BiOI is more than twice of that of BiOI.

Multifunctional property exploration: Bi4O5I2 with high visible light photocatalytic performance and a large nonlinear optical effect.

Exploration of the versatility of materials is very important for increasing the utilization of materials. Herein, we successfully prepared Bi4O5I2 powders via a facile solvothermal method. The Bi4O5I2 photocatalyst exhibited significantly higher photocatalytic activity as compared to the common BiOI photocatalyst in the degradation of methyl orange, methylene blue and rhodamine B under visible light irradiation. Especially, for the degradation of methyl orange, the photocatalytic activity of Bi4O5I2 is about 10 times that of BiOI. Moreover, Bi4O5I2 exhibits an extremely high second harmonic generation response of about 20 × KDP (the benchmark) estimated by the unbiased ab initio calculations. The coexisting multifunction of Bi4O5I2 is mainly because of the increased dipole moment due to the stereochemical activity of lone pairs that promotes separation and transfer of photogenerated carriers, then enhances the photocatalytic activity and results in a high second harmonic generation response. This indicates that Bi4O5I2 may have good potential applications in photocatalytic and nonlinear optical fields.

Preparation of interstitial carbon doped BiOI for enhanced performance in photocatalytic nitrogen fixation and methyl orange degradation

Carbon-doped BiOI (C-BiOI) photocatalysts were successfully synthesized via a hydrothermal method with Bi(NO3)3·5H2O, KI, and glucose as raw materials for the first time. The synthesized samples had excellent photocatalytic activities in the degradation of methyl orange (MO) and the reduction of N2 to NH3. To reveal the origin of the superior photoactivity, the C-BiOI was examined by multi techniques, including N2-adsorption, XRD, SEM, TEM, Raman, XPS, DRS, PL, EIS and transient photocurrent response. The characterization results indicated that the carbon clusters entered the interlayers of BiOI crystal during preparation. The doped carbon interfered the lattice periodicity and generated vacancies in the BiOI structure, resulting in the decreased band gap and increased efficiency in charge separation, both of which could significantly hasten the photocatalytic reaction. Additionally, the introduced carbon affected the morphology of BiOI and increased its specific surface area, which may also benefit the photocatalytic process. The carbon content was crucial to the promotion effect. Under visible light, the optimized carbon-doped BiOI (C-BiOI-2) presented an MO degradation rate of 0.136 min−1, which was 4.44 times higher than that of pure BiOI. However, for the photocatalytic N2 fixation, due to the contribution of surface carbon in N2 adsorption, the C-BiOI sample containing higher carbon content (C-BiOI-3) displayed superior performance than C-BiOI-2. The NH3 generation rate under simulated sunlight reached 311 μmol g−1 h−1, which was about 3.7-fold of that of BiOI. This work may shed some insight into the designing and understanding of carbon-doped semiconductor photocatalysts.

Preparing BiOI photocatalyst for degradation of methyl blue in wastewater

Photocatalytic oxidation on semiconductors is a green and friendly route to deal with environmental issues. Herein, a novel C/BiOIdefect photocatalyst was prepared by one-step hydrothermal method, and this nanocomposite exhibited excellent photocatalytic degradation performance under visible light irradiation. The substantially increased visible light absorption and separation of photoinduced carriers were attributed to the high photocatalytic performance. Moreover, the C/BiOIdefect also shows outstanding adsorption capacity and photochemical stability, which are also extremely important for practical application.

Effect of preparation method on the structure and photocatalytic performance of BiOI and Bi5O7I for Hg0 removal

This paper presents a study on the effect of preparation method on the structure and photocatalytic activities of BiOI and Bi5O7I photocatalysts for elemental mercury (Hg0) removal in a wet bubbling reactor. Two visible-light-driven BiOI photocatalysts (BiOI-HAc and BiOI-EG) via either glacial acetic acid (HAc) coprecipitation or ethylene glycol (EG) hydrothermal synthesis as well as their derivative samples (Bi5O7I-HAc and Bi5O7I-EG) were synthesized, respectively. The photocatalysts were characterized by N2 adsorption-desorption analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoelectrochemical measurement and electron spin resonance (ESR) techniques. The results showed that Bi5O7I-HAc and BiOI-EG exhibited superior Hg0 removal performances in comparison with BiOI-HAc and Bi5O7I-EG, and Bi5O7I-HAc photocatalyst possessed much better activity on SO2 resistance and wider reaction temperature scope than BiOI-EG. The enhancement in Hg0 removal efficiency can be attributed to the appearance of plenty of adsorbed oxygen, efficient photoinduced carrier separations and their special band gap structures. The photoexcited O2− and h+ played key roles in the process of Hg0 removal.