Bismuth Precursor Research Articles

Halide precursor reduction strategy to modulate bismuthene with high selectivity and wide potential window for electrochemical CO2 reduction

AbstractDeveloping high‐performance electrocatalysts for CO2 reduction reaction (CO2RR) is vital in achieving a carbon‐neutral society by converting CO2 into valuable chemicals. CO2RR electrocatalyst with lower overpotential, higher selectivity and wider working potential range is urgently desired, but it is still challenging to realize these factors simultaneously. Here, high‐performance bismuthene‐based electrocatalysts were synthesized by reducing bismuth precursors like BiCl3, BiBr3, and BiI3 in liquid phases. Especially, bismuthene‐I derived from BiI3 showed a nanosheet morphology (around four‐layer) with significantly enhanced (110) surfaces. It enabled an ultrawide potential window (0.7 V) for high formate selectivity (>90%) in a H‐type cell and achieved an ultralow potential (−0.46 V vs. reversible hydrogen electrode) to attain a current density of 200 mA cm−2 in a gas‐diffusion flow cell. The prominent long‐term operational capability of bismuthene‐I was demonstrated in both H‐type and gas‐diffusion cells. Density functional theory calculations revealed that bismuthene‐I possessed abundant topological Bi(110) surfaces states that can reduce the CO2RR overpotential, suppress the competitive hydrogen evolution reaction, and facilitate electron donation during CO2 electrocatalysis. The bismuthene‐I realized low overpotential, high selectivity and wide working potential range simultaneously for electrochemical CO2RR. This work unfolds the broader plausibility of facilely reducing precursors for the scalable fabrication of high‐performing CO2RR electrocatalysts.

Facile synthesis of bismuth and iron co-doped hydroxyapatite nanomaterials for high-performance fluoride ions adsorption

Fluoride is essential, but excessive intake of it in drinking water can have adverse effects. Thus, it must be removed using routine techniques and novel nanomaterials that are environmentally friendly. In this study, we present a facile synthesis of bismuth and iron co-doped hydroxyapatite nanomaterials for high-performance fluoride ions adsorption. The crystal size and degree of crystallinity of the nanomaterials were controlled by the ratios of iron and bismuth precursors. The morphology analysis confirmed the presence of rod-like structures of variable sizes. Calcium, phosphorous, oxygen, bismuth, and iron were detected with the expected elemental state in the co-doped hydroxyapatite material. Batch adsorption experiments showed excellent fluoride ion adsorption performance for bismuth and iron co-doped hydroxyapatite nanomaterials. Pseudo-second order and Langmuir models better describe the experimental findings. This denotes that fluoride uptake through the synthesized material is a chemical process that forms a monolayer, and the surface is homogenous. Thermodynamic data showed that the defluoridation process absorbs heat energy but is spontaneous. Furthermore, in the regeneration and reuse analysis, 74.3% of 10 mg/L fluoride ions were removed even in the fifth cycle, which ensured the nanomaterial’s reusability. The proposed defluoridation mechanisms were electrostatic interaction and ion exchange. Insertions of bismuth and iron ions into hydroxyapatite structure provided a potent sorbent for fluoride removal. Fluoride adsorption performance and the ease of synthesis make this bismuth and iron co-doped hydroxyapatite nanomaterials attractive for water treatment and environmental remediation applications.

Synthesis of new water treatment photocatalytic coatings with controllable functional properties based on the SrO-Bi2O3-SiO2 system that use the energy of solar radiation

This work is devoted to the study of water purification from organic pollutants using new environmentally safe photocatalysts capable of using solar insolation to oxidize organic pollutants. Most methods of creating photocatalysts allow obtaining them only in powder form, which limits their application in water treatment plants. In this regard, photocatalysts formed as coatings on the carrier surface may be more promising. This work contributes to solving the problem of developing a technologically concise and economical method of creating bismuth photocatalytic coatings with biological indifference and high light absorption efficiency (LAE) of solar irradiation. The developed cleaning material is a structurally organized system consisting of a ceramic carrier on which a photocatalytic coating is formed. The coating was formed by soaking the silicate carrier in a bismuth precursor solution (BPS) followed by drying and oxidative pyrolysis. The highest catalytic activity and LAE (58.3–60.3%) were observed for the materials obtained at 10–15% wt. bismuth in BPS. The highest hydrolytic stability was observed at 25% wt. bismuth in BPS. Strontium bismuthate SrBi7.65O13 was the dominant phase in the coating composition for the samples with the highest activity and LAE. Increasing the content of another photocatalytically active phase Bi4Si3O12 resulted in the LAE decreasing to 51.9%, providing greater hydrolytic stability of the material. The proposed method allows for flexibly controlling the properties of the obtained photocatalytic coatings, thus making possible to directionally create different types of materials to be applied in the field of wastewater treatment.

Bismuth trichloride as a molecular precursor for silicon doping

Dopant impurity species can be incorporated into the silicon (001) surface via the adsorption and dissociation of simple precursor molecules. Examples include phosphine (PH3), arsine (AsH3), and diborane (B2H6) for the incorporation of phosphorus, arsenic, and boron, respectively. Through exploitation of precursor surface chemistry, the spatial locations of these incorporated dopants can be controlled at the atomic scale via the patterning of a hydrogen lithographic resist layer using scanning tunneling microscopy (STM). There is strong interest in the spatial control of bismuth atoms incorporated into silicon for quantum technological applications; however, there is currently no known precursor for the incorporation of bismuth that is compatible with this STM-based lithographic method. Here, we explore the precursor chemistry (adsorption, diffusion, and dissociation) of bismuth trichloride (BiCl3) on Si(001). We show atomic-resolution STM images of BiCl3 exposed Si(001) surfaces at low coverage and combine this with density functional theory calculations to produce a model of the surface processes and the observed features. Our results show that, at room temperature, BiCl3 completely dissociates to produce bismuth ad-atoms, ad-dimers, and surface-bound chlorine, and we explain how BiCl3 is a strong candidate for a bismuth precursor compound compatible with lithographic patterning at the sub-nanometer scale.

Bismuth Coordination Polymers with Fluorinated Linkers: Aqueous Stability, Bivolatility, and Adsorptive Behavior.

Bismuth metal-organic frameworks and coordination polymers (CP) are challenging to synthesize, given the poor solubility of bismuth precursors and asymmetric and labile ligation of Bi3+ due to its intrinsic lone pair. Here, we synthesize and structurally characterize three Bi3+-CPs, exploiting a tetrafluoroterephtalate (F4BDC) linker to determine the effect of high acidity on these synthesis and coordination challenges. Single-crystal X-ray diffraction characterization showed that pi-pi stacking of linkers directs framework arrangement and generally deters open porosity in the three structures, respectively featuring Bi chains (Bi chain -F 4 BDC), Bi dimers (Bi 2 -F 4 BDC) linked into chains, and Bi tetramers (Bi 4 -F 4 BDC). Powder X-ray diffraction and microscopic imaging show the high purity and stability of these compounds in water. Naphthalenedisulfonate (NDS) was used as a mineralizer in the synthesis of (Bi chain -F 4 BDC) and (Bi 4 -F 4 BDC), and studies of its role in assembly pathways yielded two additional structures featuring mixed NDS and F4BDC, respectively, linking monomer and octamer Bi nodes, and confirmed that F4BDC is the preferred (less labile) linker. Methylene blue (MB) adsorption studies show differing efficacies of the three Bi-F4BDC phases, attributed to surface characteristics of the preferential growth facets, while generally most effective adsorption is attributed to the hydrophobicity of fluorinated ligands. Finally, thermogravimetric analysis of all three Bi-F4BDC phases indicates simultaneous ligand degradation and in situ formation of volatile Bi compounds, which could be exploited in the chemical vapor deposition of Bi-containing thin films.

Bridging 1D Inorganic and Organic Synthesis to Fabricate Ultrathin Bismuth-Based Nanotubes with Controllable Size as Anode Materials for Secondary Li Batteries.

The growth of ultrathin 1D inorganic nanomaterials with controlled diameters remains challenging by current synthetic approaches. A polymer chain templated method is developed to synthesize ultrathin Bi2 O2 CO3 nanotubes. This formation of nanotubes is a consequence of registry between the electrostatic absorption of functional groups on polymer template and the growth habit of Bi2 O2 CO3 . The bulk bismuth precursor is broken into nanoparticles and anchored onto the polymer chain periodically. These nanoparticles react with the functional groups and gradually evolve into Bi2 O2 CO3 nanotubes along the chain. 5.0 and 3.0nm tubes with narrow diameter deviation are synthesized by using branched polyethyleneimine and polyvinylpyrrolidone as the templates, respectively. Such Bi2 O2 CO3 nanotubes show a decent lithium-ion storage capacity of around 600mA h g-1 at 0.1 A g-1 after 500 cycles, higher than other reported bismuth oxide anode materials. More interestingly, the Bi materials developed herein still show decent capacity at very low temperatures, that is, around 330mA h g-1 (-22 °C) and 170mA h g-1 (-35 °C) after 75 cycles at 0.1 A g-1 , demonstrating their promising potential for practical application in extreme conditions.

Molecular structure models of amorphous bismuth and cerium carboxylate catalyst precursors

As our societal need for materials and energy has grown, so has our need for catalyst processes in hydrogen production. A major function in these applications, for both homogenous and heterogeneous catalysis processes, is the synthesis of an active metal catalyst. It must first be soluble to control the physical properties of the metal being used. Recent work in metal precursors has begun to turn toward these metal carboxylate types of material. Structural models are proposed for bismuth 2-ethylhexanoate and 2,2-dimethyloctanoate and cerium 2-ethylhexanoate. The bismuth compounds have been characterized at different ratios of bismuth to carboxylate as solutions of the free acids. Their structures are most consistent with a Bi4(RCO2)12 motif where the Bi ions are arranged in a flattened tetrahedron with Bi – Bi distances of about 4.3 Å. There is evidence for Bi – O – Bi linkages at low free acid concentrations. The cerium compound is most consistent with a linear tetracerium molecule where the Ce – Ce distances repeat at about 4.3 Å out to 16.4 Å. The models were generated by analogy with known crystal structures and compared to high-energy x-ray scattering data. To further evaluate the models, DFT calculations were made, and the equilibrium geometries were compared. The vibrational spectra calculated from those geometries are presented and compared to the experimental results. Magnetization vs. temperature data was collected on the cerium compound, and its behavior was consistent with the proposed model. A geometrical approach to determining the dimensionality and relative positions of the metal ions in these structures is presented.

Synthesis of star-like BiVO4 photocatalysts by organic-aqueous hetero-phase reaction: Interaction between bismuth and amino group of oleylamine

The bismuth vanadate (BiVO4) photocatalyst was successfully synthesized by an organic-aqueous hetero-phase reaction method using organic additives (oleic acid, oleyl alcohol, and oleylamine) to investigate the reaction mechanism. The BiVO4 with a star-like morphology could be synthesized with oleylamine. Bismuth precursors formed by the interaction between bismuth and the amino group of oleylamine were nano-sized complex particles with amorphous phase, finally resulted in the formation of star-like morphology. Moreover, BiVO4 synthesized with oleylamine showed excellent photocatalytic activity on degradation of rhodamine B.

Simple Bottom-Up Synthesis of Bismuthene Nanostructures with a Suitable Morphology for Competitive Performance in the Electrocatalytic Nitrogen Reduction Reaction

Nitrogen reduction to ammonia under ambient conditions has received important attention, in which high-performing catalysts are sought. A new, facile, and seedless solvothermal method based on a high-temperature reduction route has been developed in this work for the production of bismuthene nanostructures with excellent performance in the electrocatalytic nitrogen reduction reaction (NRR). Different reaction conditions were tested, such as the type of solvent, surfactant, reducing agent, reaction temperature, and time, as well as bismuth precursor source, resulting in distinct particle morphologies. Two-dimensional sheet-like structures and small particles displayed very high electrocatalytic activity, attributed to the abundance of tips, edges, and high surface area. NRR experiments resulted in an ammonia yield of 571 ± 0.1 μg h-1 cm-2 with a respective Faradaic efficiency of 7.94 ± 0.2% vs Ag/AgCl. The easy implementation of the synthetic reaction to produce Bi nanostructures facilitates its potential scale up to larger production yields.

High-performance vertically aligned Bi2O3 nanosheet arrays for water splitting applications by controlling the chemical bath deposition method parameters (precursor concentration and pH)

In this work, vertically aligned β-Bi2O3 nanosheet arrays are deposited on FTO using a simple, cost-effective, low-temperature, and easy-tunable technique called chemical bath deposition. Coatings were deposited through selective correlation of varying bismuth ion concentrations at fixed pH and, also, a fixed bismuth ion concentration at different pH values to optimize their structure, morphology, and optical properties. With an increase in bismuth precursor concentration from 0.008 M to 0.5 M, a more crystallized and compact coating with finer nanosheets was formed. Low pH values tended to result in either no coating or a coating composed of discrete particles. As the pH increased to the optimal level, a thicker and more compact coating with a morphology made of thicker and wider nanosheets was formed. Further increase in pH led to a non-uniform coating composed of small and large nanosheets that could not cover the entire surface of the substrate. The optimized photoelectrode exhibited a maximum photocurrent density of 470 μA/cm2 at 1.23 VRHE under 100 mW/cm2 simulated sunlight, which is among the top recorded values of Bi2O3 photoelectrodes.

Co-Doping of Cerium and Bismuth into Lead-Free Double Perovskite Cs2AgInCl6 Nanocrystals Results in Improved Photoluminescence Efficiency.

Lead-free double cation metal halide perovskites have recently attracted considerable attention, with continuing research efforts focusing on the improvement of their stability and photoluminescence quantum yield (PL QY). In this study, Ce3+ has been co-doped together with Bi3+ into lead-free double perovskite Cs2AgInCl6 nanocrystals (NCs) in order to improve their crystallinity and PL QY. Both uncoordinated chloride ions and silver vacancies could be eliminated using this co-doping strategy, and the resulting Ce3+,Bi3+-co-doped Cs2AgInCl6 NCs showed adjustable PL emission peaks in the range of 589 to 577 nm by varying the doping amount of Ce3+ with a fixed feeding ratio of bismuth precursor set at 1%. Cs2AgInCl6 NCs doped with 1% Bi alone reached a PL QY of 10% for the PL peak centered at 591 nm, while those co-doped with 1% Bi and 2% Ce together achieved the highest PL QY of 26% for the PL peak centered at 580 nm. The use of Ce3+ as a dopant promoted the localization of self-trapped excitons to prevent PL quenching, although the ion's 5d excited state may potentially provide an energetically favorable indirect route for the radiative relaxation process. This also resulted in a blue shift of the PL maximum and increased the exciton binding energy, thus promoting the radiative recombination of self-trapped excitons.

A disposable and flexible electrochemical sensor for the sensitive detection of heavy metals based on a one-step laser-induced surface modification: A new strategy for the batch fabrication of sensors

In this study, we developed a disposable and flexible electrochemical sensor for the sensitive determination of heavy metal ions based on an efficient one-step laser-induced surface modification. A flexible polyimide film was used as the substrate of the sensor, which was sprayed with a corresponding bismuth precursor ink to form a sensitive coating, i.e., bismuth nanoparticle@laser-induced graphene (BiNP@LIG). Then, Nafion was pipetted on BiNP@LIG to form a cover layer. The BiNP@LIG nanocomposite was successfully synthesized by laser irradiation (470 nm), and the composition of the obtained material was further verified by X-ray diffraction, energy dispersive spectroscopy and Raman spectroscopy. Moreover, the morphology of the BiNP@LIG nanocomposite was investigated by scanning electron microscopy, which showed that BiNPs were uniformly distributed on LIG, and the average diameter of the BiNPs was approximately 38 nm. Finally, a possible sensing mechanism of the Nafion/BiNP@LIG electrochemical sensor was proposed. The results show that the proposed electrochemical sensor exhibited satisfactory sensitivity and stability for the detection of Pb(II) and Cd(II). In addition, the laser-induced surface modification method proposed in this study could be an attractive candidate for the batch fabrication of sensors based on the noncontact, computer-controlled and pattern-making characteristics of laser induction.

Facile preparation of bismuth vanadate-sheet/carbon nitride rod-like interface photocatalyst for efficient degradation of model organic pollutant under direct sunlight irradiation

The photocatalytic performance of a semiconducting catalytic system is strongly influenced by charge-carrier separation rate, charge transport properties, surface area, utilization of light energy, and interface bonding. Herein, a series of bismuth vanadate (BiVO4) samples were prepared via hydrothermal method by changing the volume ratios of ethelene glycol and ethanol as a solvent mixture for bismuth precursors. Further, the optimized BiVO4 sheets with hierarchical morphology were used to construct an interface with rod-like g-C3N4 materials, which was confirmed by HRSEM and HRTEM. Due to the formation of an effective interface bonding between BiVO4/g-C3N4, the photoinduced charge carrier's recombination rate was suppressed as confirmed by the PL analysis. The prepared BiVO4/g-C3N4 sample were used to assess the photodegradation efficiency of Rhodamine B (RhB) under direct sunlight irradiation and the photocatalysts degraded ~92.8% of RhB within 2 h. The TOC measurements revealed a 66.4% mineralization efficiency for RhB. In addition, the radical trapping experiments demonstrated that superoxide and hydroxyl radicals are the main reactive species for the degradation. Based on the experimental evidences, a plausible charge transfer mechanism has been proposed. The enhanced photocatalytic activity has been mainly attributed to the inhibition of the recombination rate, enhanced charge carrier transfer efficiency, and high rate of production of reactive species.

Novel two-step synthesis method of thin film heterojunction of BiOBr/Bi2WO6 with improved visible-light-driven photocatalytic activity

A novel two-step ionic liquid assisted procedure was applied for a controllable synthesis of BiOBr/Bi2WO6 heterojunction thin films. The preparation route involved an anodic oxidation of tungsten foil and hydrothermal transformation of as-anodized oxide in the presence of bismuth precursor and ionic liquid, N-butylpyridinium bromide [BPy][Br]. The BiOBr plates with irregular shapes adhered to the surface of flower-like Bi2WO6 and formed a heterojunction between BiOBr and Bi2WO6, as confirmed by the analysis of their structure and composition. The highest efficiency of phenol degradation was achieved when the highest amount of IL was used (the apparent quantum efficiency was almost 8 and 71.5 times higher compared to BiOBr and Bi2WO6, respectively). In addition, superoxide radicals (•O2–) were found as the main factor responsible for the photodegradation. A possible reaction mechanism was further investigated as a function of monochromatic irradiation to determine the exact range of the composite photoactivity.

Engineering 2D compressed layered g-C3N4 nanosheets by the intercalation of BiVO4-Bi2WO6 composites for boosting photocatalytic activities

The traditional bulk graphitic carbon nitride has disadvantages of weak visible light absorption ability and fast charge carrier recombination speed, which greatly limit its further industrial application. In this work, we successfully construct a new ternary heterojunction photocatalyst that 2D compressed layered g-C3N4 nanosheets (CNNs) are modified by the intercalation of BiVO4-Bi2WO6 composites (CVW-I) through one-step hydrothermal method, in which the bismuth precursors are introduced and confined in the interlayer of CNNs and hence the compressed adjacent layers are formed simultaneously in CNNs. Since the close contact of different components with compressed carbon nitride layers, the built-in electric field is relatively formed and the recombination rate between photogenerated electrons and holes is remarkably suppressed. Attributing to these improvements, the as-constructed CVW-I composite achieves more striking photocatalytic activity, and the rate constant of CVW-I reached the highest values for RhB and TC degradation (k = 0.058 min−1 and 0.048 min−1), which are 4.5 and 3.6 times higher than those of carbon nitride, respectively.

An Investigation of Photocatalytic Activity of Coatings Based on Strontium Bismuthate Deposited on a Ceramic Carrier

A study was carried out to obtain effective photocatalytic coatings on a ceramic silicate carrier. The analysis of the characteristics of silicate materials, such as: ceramic carrier "Biopur"; porous glass carrier "Siporax"; glass-ceramic carrier (sitall) "Biopur forte" produced by the company "SERA", Germany, was made. According to X-ray phase analysis data, it was shown that the “Biopur” ceramic support is formed by magnesium aluminosilicates of the composition MgAl2Si3O10 and MgAl2Si4O12. The porous material “Siporax” is X-ray amorphous. The silicate material “Biopur forte” does not have a pronounced amorphous component in its structure and can be assigned to the class of sitall with a high SiO2 content and a low content of alkali and alkaline earth metal cations in the structure. A method for impregnating a ceramic support with a solution of a bismuth photo-catalyst precursor, a specially developed composition of a complex of bismuth with sorbitol, is considered. An effective concentration of a solution of a complex of bismuth with sorbitol in ethanol equal to 10% was found. By low-temperature pyrolysis at , photo-catalytically active coatings of strontium bismuthates were obtained on each of the considered types of ceramic supports. The highest photocatalytic activity was detected in the coating deposited on a ceramic carrier with a glass structure – “Biopur forte”. A study of the photocatalytic activity of coatings, based on strontium bismuthate, depending on the multiplicity of coating on a “Biopur forte” ceramic carrier, was made. The effective number of layers of the photocatalytic coating on a “Biopur forte” ceramic carrier is determined, which corresponds to the highest rate of decrease in the optical density of a model organic pollutant upon irradiation with visible light in the spectrum.

Characterization of Bi2Se3 prepared by electrodeposition

Bi2Se3 compound was deposited catholically under potential control, from a mixture solution composed from equimolar SeO2 and BiCl3. The concentration of selenium and bismuth precursors was about 5 ∙ 10−3 M. The electrodeposited films were grown on FTO substrates (Transparent Conductive Glass Fluorine-Doped Tin Oxide (FTO)–Coated Glass). Deposition potential was determined from cyclic voltammetry (CV) where the platinum mesh was taken as working electrode. The growth kinetics depends on the applied potential. It was found, using EDS technique, that suitable ratio of Se/Bi corresponding to Bi2Se3 was reached at − 250 mV vs. SCE (saturated calomel electrode). X-ray and grazing X-ray diffraction revealed that the obtained film at − 250 and − 200 mV/SCE consisted a rhombohedral Bi2Se3 structure. Raman shift was employed to corroborate the X-ray results with the possibility of formation of a rhombohedral Bi2Se3 when the applied potential was − 200 mV (vs. SCE). The Bi2Se3-obtained films were an n-type semiconductor with a carrier charge concentration which depends on the applied potential.

Stepwise Bi-Bi Bond Formation: From a Bi-centered Radical to Bi4 Butterfly and Bi8 Cuneane-Type Clusters.

In contrast to their lighter homologues (P, As, Sb), the synthesis of polybismuthane clusters is still restricted to classical solid-state approaches. We herein report on systematic reduction reactions of different bismuth precursors with Ga(I) and Mg(I) complexes. This study not only yielded the first metal-coordinated tetrabismuthane ([{L1(Cl)Ga}2-μ,η1:1-Bi4] 3, L1 = HC[C(Me)N(2,6-i-Pr2C6H3)]2) and realgar-type bismuth cluster ([(L2Mg)4(μ4,η2:2:2:2-Bi8)] 4, L2 = HC[C(Me)N(2,4,6-Me3C6H2)]2) in addition to the bismuth-centered radical [L1Ga(Cl)]2Bi• 1 and dibismuthene [L1(Cl)GaBi]2 2, but clearly demonstrates the crucial role of the substituents and the oxidation state of the bismuth precursor as well as the specific reduction potential of the main group metal reductants on the product formation. Compounds 3 and 4 were spectroscopically characterized (1H, 13C NMR, IR), and the structures of 1-4 were determined by single-crystal X-ray diffraction. Computational calculations gave deeper insights into the electronic structures of 1', 3', and 4'.

Employing Successive Ionic Layer Adsorption and Reaction (SILAR) Method on the Fabrication of Cu3BiS3-Semiconductor-Sensitized Solar Cells

Successive ionic layer adsorption and reaction (SILAR) method is a modified version of chemical bath deposition (CDB) that serves as a low-cost and convenient on the production of ternary metal chalcogenides. This research reported the utilization of SILAR method on the fabrication of Cu3BiS3 semiconductor-sensitized solar cells. The concentration of bismuth and copper precursor were varied, namely 0.03 M and 0.1 M, whereas the precursor of sulfide was varied in the concentration of 0.02 M and 0.05 M. The variation of SILAR cycles was employed to investigate the most appropriate cycle numbers in producing Cu3BiS3, in particular 3-9 cycles, 5-15 cycles, and 6-6 cycle with the immersing time of 20 s for each. The results show that there were only two suitable peaks appeared for 3-9 cycles and 6-6 cycles, while 5-15 cycles provide the more preferable XRD patterns with the power conversion efficiency of 0.02% (Jsc of 1.75 mA/cm2; Voc of 0.04 V; FF of 29.65%). It can be said that SILAR method with higher number of cycles can be employed to fabricate Cu3BiS3; however, smaller PCE came from inappropriate structure alignment between Cu3BiS3 and metal oxide layer.

Synthesis of (001) oriented BiOI thin films by a dual-port ultrasonic spray pyrolysis system

A dual-port ultrasonic spray pyrolysis (DP-USP) system was developed to obtain bismuth oxyiodide (BiOI) thin films. Independent bismuth and iodine precursor solutions were separately atomized and mixed in a chamber just above the heated substrate where reacted to form the film. This configuration allowed a complete reaction and uniform substrate coverage. Crystalline BiOI films were tetragonal with the typical layered structure; their band gap was around 1.6 eV and showed photocatalytic response under simulated sunlight. Photocatalytic activity, tested with indigo carmine (IC) dye molecule, was pH dependent, reaching the highest degradation at pH = 3. A careful evaluation of IC’s absorbance spectra indicated its decomposition into two degradation products. This was confirmed by comparison with theoretical calculations of the absorbance spectrum of IC and its degradation products.