Bismuth Molybdate Research Articles

Layered Double Hydroxide-Bismuth Molybdate Hybrids toward Water Remediation via Selective Adsorption of Anionic Species.

The steady release of anthropogenic toxins into the biosphere is compromising water security globally. Herein, CoAl layered double hydroxide, a clay-like layered material with a cationic surface charge, was organically modified and used to template the growth of Bi2MoO6. The resulting nanohybrid selectively removed the anionic dye methyl orange from aqueous solution and showed an enhancement of greater than 300% in the maximum adsorptivity (1.95 mmol/g) compared to modified CoAl layered double hydroxide (0.42 mmol/g). Interestingly, the observed improvement in adsorption occurs without any significant increase in the surface area of the hybrids. Furthermore, these hybrids exhibit increased broadband visible light absorption, and their photoactivity is slightly improved compared to CoAl layered double hydroxide. This study demonstrates that composites of clay-like materials with Aurivillius oxides are promising sorbent materials for water decontamination and photocatalytic antifouling membranes and shows that the synthetic strategy that was first established with an anionic layered silicate nanoclay can be generalized to other ionic layered materials.

PH-induced structural evolution, photodegradation mechanism and application of bismuth molybdate photocatalyst

In this work, we have elucidated the pH-induced structural evolution of bismuth molybdate photocatalyst based on a hydrothermal synthesis route. With increasing the pH value of precursor solution, pure Bi2MoO6 was synthesized at pH 2–5, Bi2MoO6-Bi4MoO9 mixture was obtained at pH 7–9, pure Bi4MoO9 was obtained at pH 11, and pure α-Bi2O3 was derived at pH 13. The as-derived samples mainly present particle-like shapes but with different particle sizes (except the observation of Bi2MoO6 nanowires in sample S-pH9). The photocatalytic performances between the samples were compared via the degradation of methylene blue (MB) under irradiation of simulated sunlight. The Bi2MoO6 sample synthesized at pH 2 exhibited the highest photodegradation performance (η(30 min) = 89.8 %, kapp = 0.05007 min−1) among the samples. The underlying photocatalytic mechanism and degradation pathways of MB were systematically analyzed. Moreover, the photodegradation performance of the Bi2MoO6 photocatalyst was further evaluated at different acidic-alkaline environments as well as in degrading various color and colorless organic pollutants, which provides an important insight into its practical application.

A facile synthesis route and photo-catalytic properties of mixed-phase bismuth molybdate

The polymorphs (α – Bi2Mo3O12, β – Bi2Mo2O9, γ – Bi2MoO6) of bismuth molybdate (BMO) exhibit photo-catalytic activity. Among them, the β phase exhibits good photo electrochemical (PEC) performance but suffers from stability issues. In this work, mixed-phase BMO compounds were synthesized using a facile co-precipitation route. The processed BMO showed a band gap of 2.46 eV. The sample with predominantly γ-BMO (γ – Bi2MoO6) with lower α and β content exhibited better photo-electrochemical performance with a photocurrent density of 1.12 μA/cm2 and lower charge transfer resistance compared to the BMO-1 sample with a larger amount of α and β phases. Both the samples displayed n-type conductivity and excellent photoresponse under chopped illumination.

Microwave-assisted rapid synthesis of bismuth molybdate with enhanced oxidative desulfurization activity

In this work, six different bismuth molybdate catalysts were synthesized by a fast microwave-assisted hydrothermal method. By adjusting the pH in the preparation process, the morphology and structure of the synthesized catalysts can be modified, and the transition of Bi2MoO6 crystals to Bi3.2Mo0.8O7.5 crystals can be selectively achieved. The sample prepared at pH 1, BMO-1, exhibited excellent activity for oxidizing sulfur compounds in fuel oil at 60 °C with a molar hydrogen peroxide to sulfur ratio of four, achieving removal rates of dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene of 99.71%, 99.68%, and 77.95%, respectively. When recycling the catalyst seven times, the removal rate of dibenzothiophene still reached 98.07%. A probable mechanism for the oxidative desulfurization process was proposed. This work not only offers a high-efficiency, method for the rapid preparation of bismuth molybdate catalysts but also extends the application of this catalyst in the field of deep oxidative desulfurization.

Highly response and humidity-resistant gas sensor based on polyaniline-functionalized Bi2MoO6 with UV activation

The bismuth molybdate (Bi2MoO6) has shown great application potential in the field of gas sensing owing to its abundant Lewis acid sites, suitable energy band and unique layered structure. In this work, a room temperature, highly response, selectivity and humidity-resistant NH3 gas sensor based on the Bi2MoO6/Polyaniline (BMO/PANI) nanocomposite was successfully developed by an in-situ chemical oxidative polymerization process. The obtained samples were characterized by X-ray diffractometer, UV–vis diffuse reflectance spectra, Transmission electron microscopy, X-ray photoelectron spectroscopy, etc. A series of gas-sensing properties studies were conducted with the assistance of UV light, which indicate that UV light illumination could significantly enhance the response of the prepared BMO/PANI sensor and short recovery time (71s). Additionally, the sensor also demonstrated excellent selectivity, repeatability, long-term stability, and moisture resistance. These outstanding characteristics of the sensor are attributed to the dramatic increase of surface state density upon activation by the UV light and the distinctive heterogeneous interface strengthens the interfacial charge transfer.

Redox regulation of photocatalytic nitrogen reduction reaction by gadolinium doping in two-dimensional bismuth molybdate nanosheets

Photocatalytic nitrogen reduction can achieve sustainable NH3 synthesis at room temperature and pressure, which is a more sustainable technology than the classical Haber-Bosch process. Herein, based on the ability of Gd3+ ions to capture and release electrons, a novel Gd-doped 2D Bi2MoO6 nanosheet photocatalyst for nitrogen reduction with in-built Gd3+ redox center was designed and prepared. The results showed that Gd3+ doping can increase the number of reaction sites by increasing the specific surface area of 2D Bi2MoO6, and promote the separation and transfer of photogenerated carriers by forming in-built Gd3+ redox centers. The visible-light-driven nitrogen reduction performance of Gd-Bi2MoO6 was obviously improved, and the average yield of NH3 was 300.15 μmol g-1 h−1, which was about 5.8 times that of pure Bi2MoO6. Theoretical calculations showed that the Gd3+ redox centers can also control the formation of *NHNH to regulate the nitrogen reduction reaction, which greatly reduces the free energy of the whole nitrogen reduction reaction, thus effectively accelerating the conversion of N2 to NH3. The significance of this work is to prove that the lanthanide ion Gd3+ can be used to regulate the nitrogen reduction reaction of 2D catalyst and enhance the performance of nitrogen reduction reaction.

A sustainable approach for the synthesis of bismuth molybdate by continuous flow method using custom design reactor and their photocatalytic application for environmental remediation

A sustainable approach for the synthesis of bismuth molybdate by continuous flow method using custom design reactor and their photocatalytic application for environmental remediation

Tuning product selectivity in nitrobenzene reduction over a single Bi2MoO6 photocatalyst in one pot: Mechanisms and roles of reaction compositions

Poor product selectivity of metal oxide photocatalysts is one of crucial issues limiting their application in photocatalytic organic synthesis particularly when multiple parallel reactions as well as several intermediates and products are involved, as in the reduction of nitrobenzene (NB) in this present study. Accordingly, catalyst modification is often needed. Herein, we first demonstrate that without catalyst modification it is feasible to control product selectivity over a single bismuth molybdate photocatalyst to selectively prepare three different valuable compounds including aniline (AN), azobenzene (AZO) and azoxybenzene (AZX) with high efficacy. Two widely used bismuth molybdate photocatalysts, namely Bi2MoO6 and Bi4MoO9, were studied and compared. Bi2MoO6 offers better visible-light-driven photocatalytic performance than Bi4MoO9 partly due to its narrow band gap energy and efficient charge carrier separation and transfer as evidenced from UV–vis DRS, EIS, and transient photocurrent studies. The roles of hydrazine hydrate, alcohol solvent, and KOH additive on the transfer hydrogenation of NB were examined and their concentrations were optimized to solely obtain the three different products with excellent selectivity (>98%). Based on UV–vis DRS and Mott-Schottky analysis, the band energy level of Bi2MoO6 and plausible reactions at solid–liquid interface are proposed. The capability to control product selectivity over a single photocatalyst in one pot demonstrated in this work would make the process more practical especially for continuous flow photochemical systems.

Statistical optimization of process conditions for photocatalytic degradation of phenol with bismuth molybdate photocatalyst

Statistical optimization of process conditions for photocatalytic degradation of phenol with bismuth molybdate photocatalyst

Selective oxidation of biomass‐based 5‐hydroxymethylfurfural to 2,5‐diformylfuran catalyzed by multicomponent molybdenum‐based catalyst

AbstractBACKGROUNDOn the way to convert biomass‐derived products as a renewable and environment‐friendly source to high‐value added chemicals, one great challenge is the effective control of selectivity in the reaction. Here, we contribute a heterogeneous catalysis method for selective transformation of biomass‐based 5‐hydroxymethylfurfural (HMF) into 2,5‐diformylfuran (DFF) via multicomponent bismuth molybdate catalyst. The influence of the different pH value on the catalytic activity of the catalyst were investigated. In addition, to evaluate the catalytic performance of the catalyst in the selective oxidation of HMF, a variety of important reaction parameters such as the reaction temperature, catalyst amount, atmosphere, and solvent were examined.RESULTSThe catalyst prepared with pH value in the range of 1–2 exhibits the optimal catalytic activity in the selective aerobic oxidation of the hydroxy group of HMF. As a result, the target compound of DFF could be obtained with excellent yield (99%) and high selectivity (> 99%) in the presence of 0.25 mg Co9Fe3BiMo12O51 (pH = 1–2) in DMSO at 130 °C under O2 atmosphere. In addition, the catalyst Co9Fe3BiMo12O51 could be reused several times without a significant loss of its catalytic activity.CONCLUSIONIn this work, a heterogeneous catalytic approach to oxidizing HMF to DFF using Co9Fe3BiMo12O51 as catalyst and molecular oxygen as oxidant was established. The O2 temperature‐programmed desorption (O2‐TPD) characterization indicated that the pH value of co‐precipitation obviously affected the oxygen mobility and storage capacities in the catalysts, which is related to the catalytic performance in the selective aerobic oxidation. © 2022 Society of Chemical Industry (SCI).

Bismuth molybdate photocatalyst for the efficient photocatalytic degradation of tetracycline in water under visible-light irradiation

Based on a solvothermal method using Bi2MoO6 (BMO) as the raw material, a novel BiOCl BMO photocatalyst with a flower-like spherical structure was synthesized. The photocatalytic activity of this catalyst was evaluated using a Xe lamp (λ ≥ 420 nm) to simulate sunlight. The crystal structure, morphology, and photochemical characteristics of the BiOCl–BMO photocatalyst were characterized by X-ray diffractometry, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, Raman spectroscopy, photoluminescence measurements, and electrochemical impedance spectroscopy. Under visible-light irradiation, 50 mg BiOCl–BMO with a BiOCl/BMO mass rate of 0.06 degraded 97.23% of a tetracycline (TC) hydrochloride solution (50 mL, 10 mg/L) within 100 min, with a mineralization rate of 81.22%. Free-radical capture experiment revealed that the •OH, •O2−, h+, and e− species (and in particular •OH and •O2−) promoted TC degradation. Furthermore, the active free radicals and TC photodegradation intermediates were identified, and the mechanism and degradation pathways of TC photodegradation by the heterojunction structures were proposed. This study describes an efficient catalyst for the removal of TC from water and introduces a new approach that could be applied in the design of other Bi-based photocatalysts with excellent photocatalytic properties. At the same time, the developed system is of great significance for the efficient removal of TC from aqueous environments.

Photocatalytic Degradation of Orange G Dye by Using Bismuth Molybdate: Photocatalysis Optimization and Modeling via Definitive Screening Designs.

In the current study, Bismuth molybdate was synthesized using simple co-precipitation procedure, and their characterization was carried out by various methods such as FT-IR, SEM, and P-XRD. Furthermore, the photocatalytic degradation of Orange G (ORG) dye using synthesized catalyst under visible light irradiation was studied. Response surface Method was used for the optimization of process variables and degradation kinetics evaluated by modeling of experimental data. Based on the experimental design outcomes, the first-order model was proven as a practical correlation between selected factors and response. Further ANOVA analysis has revealed that only two out of six factors have a significant effect on ORG degradation, however ORG concentration and irradiation time indicated the significant effects sequentially. Maximum ORG degradation of approximately 96% was achieved by keeping process parameters in range, such as 1 g L−1 loading of catalyst, 50 mg L−1 concentration of ORG, 1.4 mol L−1 concentration of H2O2 at pH 7 and a temperature of 30 °C. Kinetics of ORG degradation followed the pseudo first order, and almost complete degradation was achieved within 8 h. The effectiveness of the Bi2MoO6/H2O2 photo-Fenton system in degradation reactions is due to the higher number of photo-generated e- available on the catalyst surface as a result of their ability to inhibit recombination of e- and h+ pair.

Asia chemical profile: Propylene

Robert K. Grasselli was a pioneer in the development and commercialization of catalysts for propene oxidation to acrolein and ammoxidation to acrylonitrile, products that today are produced at the level of over 10 billion pounds per year. The catalysts used for both processes are contain bismuth molybdates augmented by up to seven additional elements used to attain high activity, selectivity, and stability. The importance of propene oxidation and ammoxidation has stimulated considerable interest in understanding the mechanism and kinetics of these processes and the particular role of catalyst composition and structure in defining catalyst activity and selectivity. Virtually all of this work has been carried out using bismuth molybdates, primarily α-Bi2Mo3O12. The objective of this paper is to review the findings of experimental studies and illustrate how theoretical studies based on density functional theory provide additional insights that support deductions drawn from experiments and, more importantly, provide information that cannot be accessed experimentally.

Superoxide anion and singlet oxygen dominated faster photocatalytic elimination of nitric oxide over defective bismuth molybdates heterojunctions

Establishing an ideal photocatalytic system with efficient reactive oxygen species (ROS) generation has been regarded as the linchpin for realizing efficient nitric oxide (NO) removal and unveiling the ROS-mediated mechanism. In this work, a novel oxygen-deficient 0D/1D Bi3.64Mo0.36O6.55/Bi2MoO6 heterojunctions (BMO-12-H) were successfully synthesized under the enlightenment of clarified crystal growth mechanism of bismuth molybdates. Because of the synergies between defect-engineering and heterojunction-construction, BMO-12-H demonstrated improved photoelectrochemical properties and O2 adsorption capacity, which in turn facilitated the ROS generation and conversion. The enhancement of •O2– and 1O2 endowed BMO-12-H with strengthened NO removal efficiency (59%) with a rate constant of 12.6*10-2 min−1. A conceivable NO removal mechanism dominated by •O2– and 1O2 was proposed and verified based on the theoretical calculations and in-situ infrared spectroscopy tests, where hazardous NO was oxidized following two different exothermic pathways: the •O2–-induced NO → NO3– process and the 1O2-induced NO → NO2 → NO3– process. This work offers a basic guideline for accelerating ROS generation by integrating defect-engineering and heterojunction-construction, and provides new insights into the mechanism of efficient NO removal dominated by •O2– and 1O2.

Surface-layer bromine doping enhanced generation of surface oxygen vacancies in bismuth molybdate for efficient photocatalytic nitrogen fixation

The oxygen vacancy (Ov) in photocatalysts plays a significant role for N2 fixation, but effective and simple means for creation of Ov are in urgent demand. Herein, surface-layer Br doping was confirmed to create massive surface Ov in Bi2MoO6 in a solvothermal process, with the product (BMO-Br-Ov) exhibiting remarkably enhanced N2 chemisorption and activation, photoinduced charge separation, and thus photocatalytic N2 fixation, compared with bulk Bi2MoO6, with an apparent quantum yield at 420 nm reaching 0.52% in pure water and 2.56% in the methanol aqueous solution. The charge separation enhancement benefits from the Ov introduced defect level and Br doping and surface Ov modification induced band-level difference between the surface and the inside in BMO-Br-Ov that leads to fabrication of the surface/inside homojunction. This work provides a simple way to create surface Ov in Bi2MoO6 and may direct Ov creation in other Bi-based photocatalysts for efficient N2 fixation.

Removal of pollutants via synergy of adsorption and photocatalysis over MXene-based nanocomposites

The MXene-based nanocomposites comprised by multi-layered Ti3C2-MXene (ML-Ti3C2) nanosheets and transition metal oxide (TMO) nanomaterials, i.e. zinc oxide (ZnO), bismuth molybdate (Bi2MoO6) and tin dioxide (SnO2), were prepared in this work. After loading ML-Ti3C2 MXene, the contact angle of oleophobic ZnO, Bi2MoO6, and SnO2 for oil drop decreases to 98°, 62°, and 75°, respectively. The improvement of lipophilicity of the composites is conducive to the adsorption of water-soluble organic pollutants. Coupling of MXene enhances the adsorption capacity of the composite catalyst for pollutants. The adsorption capacities of ZnO/ML-Ti3C2, SnO2/ML-Ti3C2 and Bi2MoO6/ML-Ti3C2 for methylene blue (MB) molecules are 155 mg/g, 163 mg/g and 152 mg/g, respectively. The adsorption of MB on ML-Ti3C2 based nanocomposites follows the Langmuir model, indicating that the monolayer covering of the nanocomposites is the main adsorption mechanism. Under visible-light irradiation, 150 mg/L of high concentration MB solution and 20 mg/L of 4-chlorophenol (4-CP) solution could be completely removed by adsorption and photocatalysis over ZnO/ML-Ti3C2 for 4 h. The electron spin resonance (ESR) trapping method and free radical scavenger experiments both show that hydroxyl radicals and superoxide free radicals are reactive species in the degradation process. The photoluminescence (PL) spectrum analysis shows that coupling TMO and MXene inhibits the recombination of photogenerated electron-hole pairs. The synergistic removal of pollutants by strong adsorption and visible photocatalysis of MXene-based nanocomposites provides a new idea for environmental pollution control.

Versatile superhydrophobic bismuth molybdate cotton fabric for oil/water separation and decompose dyestuff.

Water pollution caused by the discharged insolubility petroleum contaminants and organic compound dyes seriously threatens the natural self-purity capacity of the water body and the survival of aquatic species, so it is imperative to restraint the deterioration of the aquatic environment. In this paper, pathways are propounded for the simultaneous removal of insoluble spilling oil and organic dye contaminants. Particularly, hydrophobic ZnSnO3 after stearic acid modification and Bi2MoO6 photocatalysts are introduced into the cotton fabric substrate through solution dip-coating. The durability of the prepared fabric suffers from the acid-base corrosion, thermal treatment and mechanical wear, while still exhibiting remarkable water-repellent (WCA > 150°) property. Furthermore, the remarkable photocatalytic activity makes it possible for reusable degradation and the primary active species, namely the holes, to be verified by the radicals-capturing experiment. It is worth observing that as-prepared superhydrophobic fabric possesses admirable water-proof property and cycling durability of decomposing toxic water-soluble organic dye, thereby contributing to further realizing the ecological concept of clear waters.

Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries

Based on the same rocking-chair principle as rechargeable Li-ion batteries, Na-ion batteries are promising solutions for energy storage benefiting from low-cost materials comprised of abundant elements. However, despite the mechanistic similarities, Na-ion batteries require a different set of active materials than Li-ion batteries. Bismuth molybdate (Bi2MoO6) is a promising NIB anode material operating through a combined conversion/alloying mechanism. We report an operando x-ray diffraction (XRD) investigation of Bi2MoO6-based anodes over 34 (de)sodiation cycles revealing both basic operating mechanisms and potential pathways for capacity degradation. Irreversible conversion of Bi2MoO6 to Bi nanoparticles occurs through the first sodiation, allowing Bi to reversibly alloy with Na forming the cubic Na3Bi phase. Preliminary electrochemical evaluation in half-cells versus Na metal demonstrated specific capacities for Bi2MoO6 to be close to 300 mAh g−1 during the initial 10 cycles, followed by a rapid capacity decay. Operando XRD characterisation revealed that the increased irreversibility of the sodiation reactions and the formation of hexagonal Na3Bi are the main causes of the capacity loss. This is initiated by an increase in crystallite sizes of the Bi particles accompanied by structural changes in the electronically insulating Na–Mo–O matrix leading to poor conductivity in the electrode. The poor electronic conductivity of the matrix deactivates the Na x Bi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

Sunlight mediated enhanced photocatalytic degradation of antibiotics in aqueous medium using silicon doped carbon quantum dots decorated Bi2MoO6 nanoflakes

Residual antibiotics in water bodies, including drinking water has led to developing strategies for their removal. Here we report a very efficient method of photocatalytic degradation of tetracycline and ciprofloxacin in an aqueous medium using an optimized batch of silicon doped carbon quantum dot decorated on bismuth molybdate (1.0SiCQDs/Bi2MoO6) nanocomposite as a solar photocatalyst. The photocatalyst is synthesized by the hydrothermal route. Its structural, compositional, morphological, and optical properties are thoroughly characterized. About 97% of tetracycline (TC) and 95% of ciprofloxacin (CIP) are degraded in 90 min of sunlight exposure with a photocatalyst dose of 60 mg per 100 mL, which corresponded to a degradation rate of 0.023 min−1 and 0.025 min−1, respectively. The total organic carbon estimation in the reaction medium after photocatalytic degradation revealed 87.1% and 80.2% mineralization of TC and CIP, respectively. The photocatalytic degradation is attributed to the in-situ generation of reactive oxygen species (ROS), e.g., superoxide radicals, hydroxide radicals, and the role of ROS towards the degradation of tetracycline and ciprofloxacin is confirmed from ROS scavenging studies. The degradation mechanism has been discussed by analyzing the degradation products via ultra-performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UPLC-Q-Tof-MS). The photocatalytic degradation of tetracycline and ciprofloxacin by 1.0SiCQDs/Bi2MoO6 nanocomposites is significantly enhanced as compared to Bi2MoO6 photocatalyst, attributed to interfacial transfer of a photogenerated electron from Bi2MoO6 to SiCQDs, leading to effective charge separation of Bi2MoO6 and the charge carrier mobility.

PH dependent synthesis and characterization of bismuth molybdate nanostructure for photocatalysis degradation of organic pollutants.

Bismuth molybdate (Bi2MoO6) nanostructures has attracted many researches as an advanced photocalysts for the organic contaminants. In this paper, bismuth molybdate Bi2MoO6 nanoparticles were synthesized using a simple hydrothermal method at varied pH (2, 4, 6, 8, and 10) for 15h at 180°C. The results reveal the variation pH precursor solutions have a significant impact on the morphology, phase formations, and photocatalytic activity of samples. The synthesized samples at low pH level were characterized by FESEM analysis revealing Bi2MoO6 nanoplates have formed while gradually convert to Bi2MoO6 spherical nanoparticle at high PH level as shown in energy dispersive X-ray spectroscopy (DES) peaks. The X-ray diffraction patterns reveal characteristic peaks corresponding to mixed phases of Bi2MoO6 and cubic Bi4MoO9 at high pH value. The optical absorption study exhibit Bi2MoO6 nanoplates absorbed visible light with blue shift when compared to the cubic Bi4MoO9 structures. Moreover, the photocatalytic activity results revealed that nanoplates in pH = 4 sample has excellent photocatalytic activity for degradation of rhodamine (RhB), methylene orange (MO), and phenol under visible-light irradiation (λ > 400nm) as well as exhibit the photodegradation 90% of phenol within 300min.