Photoreduction synthesis of silver on Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> nanocomposites and their catalytic activity for the degradation of methyl orange

This paper demonstrates the preparation of pure TiO₂, 40% of Bi₂O₃ in TiO₂ and Ag loaded Bi₂O₃/TiO₂ nanocomposites by the hydrothermal method followed by the photoreduction process. The crystal structure, morphology and composition of the samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy respectively. The dispersion of Ag nanoparticles on the surface of Bi₂O₃/TiO₂ nanocomposites are found to bring the conduction band near to the valence band, resulting in the narrow band gap compared to pure TiO₂ and Bi₂O₃/TiO₂ nanocomposites. The XRD analysis demonstrated that silver nanoparticles were dispersed finely on the surface of Bi₂O₃/TiO₂ nanocomposites. All the characterization results revealed that the Ag/Bi₂O₃/TiO₂ nanocomposites were smaller crystallite size, stronger absorbance in the visible region and greater surface area than pure TiO₂ and Bi₂O₃/TiO₂ nanocomposites. The photoluminescence intensity decreases with an increase in the UV-illumination time of Ag loaded Bi₂O₃/TiO₂ revealing a decrease in the recombination rate of electron–hole pairs. In order to test them as a photocatalyst, methyl orange was used as a standard. The photocatalytic degradation of methyl orange shows that the ABT5 sample exhibits the maximum degradation efficiency of 99% within 180 min of irradiation.     

Exceptional photocatalytic activity for g-C3N4 activated by H2O2 and integrated with Bi2S3 and Fe3O4 nanoparticles for removal of organic and inorganic pollutants

Herein, hydrogen peroxide activated graphitic carbon nitride (agCN) was combined with Fe₃O₄ and Bi₂S₃ to fabricate agCN/Fe₃O₄/Bi₂S₃ nanocomposites via facile refluxing method, as visible-light-induced photocatalysts for photodegradations of anionic and cationic dyes such as MO, RhB, MB, and photoreduction of Cr(VI). The fabricated samples were explored by XRD, EDX, XPS, TGA, SEM, TEM, HRTEM, VSM, PL, FT-IR, BET, and UV-vis DRS. Photocatalytic activity of the nanocomposite with 20% of Bi₂S₃ was 16.6, 40.4, 19.5, and 12.5 times more than that of the pristine gCN in removal of RhB, MB, MO, and Cr(VI), respectively. A plausible photocatalytic mechanism on the agCN/Fe₃O₄/Bi₂S₃ nanocomposites was proposed by construction of n-n heterojunction between gCN and Bi₂S₃. Also, stability of the magnetic hybrid was characterized through cyclic photocatalytic tests.     

Facile integration of brown TiO2−x with Bi4V2O11 and BiVO4: Double S-scheme mechanism for exceptional visible-light photocatalytic performance in degradation of pollutants

Heterogeneous photocatalysis has been denoted as a promising approach to dealing with environmental and energy crises. Herein, quantum dots (QDs) of TiO_2?x/Bi₄V₂O₁₁/BiVO₄ (T_OVBBV) heterojunction photocatalysts were successfully synthesized through a facile one-pot hydrothermal process with varying amounts of integrated Bi₄V₂O₁₁ and BiVO₄ semiconductors. The resultant photocatalysts were characterized by XPS, FT-IR, EDX, XRD, PL, EIS, SEM, TEM, HRTEM, BET, and UV–vis DRS techniques, and their photocatalytic efficiencies were examined via removing tetracycline (TC), azithromycin (AZi), and rhodamine B (RhB) under visible-light illumination. The results showed exceptionally promoted photocatalytic degradation efficiencies of the studied pollutants using the ternary T_OVBBV-2 nanocomposite. The T_OVBBV-2 nanocomposite was 45.4, 11.6, and 19.8-times more effective than TiO₂, 7.24, 5.85 and 2.34-folds better than TiO_2?x, and 9.81, 9.23, and 1.61-times more effective than Bi₄V₂O₁₁/BiVO₄ for photooxidation of TC, AZi, and RhB, respectively. The significant enhancement in the photocatalytic efficacy of the T_OVBBV-2 nanocomposite originated from the defective oxygen sites in the titanium dioxide structure, which subsequently facilitated the transfer of photo-induced charge carriers through the formed tandem n-n heterojunctions amongst TiO_2?x, Bi₄V₂O₁₁, and BiVO₄ components. In addition to high photocatalytic activities, the T_OVBBV-2 photocatalyst demonstrated good photostability and durability after concurrent applications. This work recommends the T_OVBBV photocatalyst for facile photocatalytic treatment of pollutants owing to its simple preparation route, high degradation outcomes, and robust structure for practical applications.     

Enhanced visible-light-induced photocatalytic disinfection of Escherichia coli by ternary Bi2WO6/TiO2/reduced graphene oxide composite materials: Insight into the underlying mechanism

Composites coupling different semiconductors have attracted increasing attention for photocatalytic application owing to low visible-light absorption capability and weak photocatalytic activity of the single-component system. In this study, Bi₂WO₆/TiO₂/rGO ternary composites, successfully synthesized by a facile hydrothermal method, were manifested as an outstanding visible-light-response photocatalyst for the disinfection towards E. coli. X-ray diffraction, Fourier-transform infrared, and X-ray photoelectron spectroscopy demonstrated that GO coupled in the composites was efficiently reduced to rGO during the hydrothermal process, which was greatly beneficial for enhancing light harvest, promoting charge separation, and improving photocatalytic disinfection activity. UV–vis diffuse reflectance spectra, photoluminescence and time-resolved photoluminescence, photocurrent measurements, and ultraviolet photoelectron spectroscopy clearly showed that Bi₂WO₆/TiO₂/rGO composites had narrower band gap energy and much better suppression capability of photoinduced electron-hole recombination in comparison to the pure Bi₂WO₆ and TiO₂, and Bi₂WO₆/TiO₂. The radical trapping results revealed that the photogenerated holes (h⁺) were the leading active species responsible for the effective inactivation of E. coli under visible-light irradiation. Hence, the underlying mechanism for the enhanced photocatalytic disinfection performance of Bi₂WO₆/TiO₂/rGO composites was proposed. This study provides new insight into the design and development of composite materials with enhanced photocatalytic activity, which can be an inspiring alternative for environmental application.     

Fabrication of Bi2WO6/In2O3 photocatalysts with efficient photocatalytic performance for the degradation of organic pollutants: Insight into the role of oxygen vacancy and heterojunction

Photocatalysis is an attractive and green strategy for organic pollutant removal. The development of alternative and effective photocatalysts has attracted great attention. Herein, we rationally engineer an alternative rich-oxygen vacancies (OVs) Bi₂WO₆/In₂O₃ composite photocatalyst via integrating the calcination and hydrothermal method for removing organic dyes (rhodamine B). Thanks to the synergistic effect of OVs and heterojunction structure, the 80 wt% Bi₂WO₆/In₂O₃ (BiIn80) displays enhanced photocatalytic degradation effect. The degradation rate of BiIn80 is up to 97.3% under light irradiation within 120 min and the reaction rate constant k value (0.03221 min⁻¹) is about 15-fold and 4.17-fold as high as those of In₂O₃ (0.00203 min⁻¹) and Bi₂WO₆ (0.00772 min⁻¹), respectively. The heterostructure of Bi₂WO₆/In₂O₃ can extend the lifespan of the photogenerated charge carriers. Moreover, the density functional theory (DFT) calculations reveal that the OVs in Bi₂WO₆/In₂O₃ can boost visible light absorbability by decreasing band gap value and serve as the extra electron transfer channels to enhance the separation efficiency of photogenerated electron-hole pairs. This study not only provides an alternative route for fabricating highly efficient heterojunction photocatalysts, but also obtains better understanding of the synergistic effect of OVs and heterojunction on enhancing the photocatalytic performance.     

Enhanced antibacterial activity and mechanism studies of Ag/Bi2O3 nanocomposites

In this work, sphere-like Ag/Bi₂O₃ nanocomposites with the average size of ca. 170?nm were successfully synthesized by simple deposition-precipitation method. The antibacterial activities of as-prepared Ag/Bi₂O₃ nanocomposites were evaluated by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and colony counting methods. It was found that Ag/Bi₂O₃ nanocomposites displayed greatly improved antibacterial ability against common pathogenic Gram-positive and Gram-negative bacteria in comparison with single-component Bi₂O₃ nanospheres. More importantly, Ag/Bi₂O₃ nanocomposites exhibited remarkably outstanding antibacterial activities against clinical drug-resistant bacteria. The antibacterial activity of Ag/Bi₂O₃ nanocomposite increased with the increase of Ag content and 15?wt% Ag/Bi₂O₃ nanocomposites showed the highest antibacterial activity. Furthermore, a plausible antibacterial mechanism of Ag/Bi₂O₃ nanocomposite was proposed. It was believed that the enhanced generation of H₂O₂ could lead to the membrane leakage of cytosol and the inactivation of respiratory chain dehydrogenaes, which was possibly responsible for the enhanced antibacterial activities of nanocomposites.     

Preparation of Bi2Ti2O7/TiO2 nanocomposites and their photocatalytic performance under visible light irradiation

To improve visible-light-driven photocatalytic activity of TiO₂, the octahedral Bi₂Ti₂O₇ nanoparticles have been successfully supported on TiO₂ nanotubes (Bi₂Ti₂O₇/TiO₂) for the first time by a simple hydrothermal method. The structure and electro-optical property of the Bi₂Ti₂O₇/TiO₂ were characterized in detail. The obtained Bi₂Ti₂O₇/TiO₂ exhibited a markedly enhanced photocatalytic activity and good stability for degradation of organic pollutants under visible light. The study presents a new way to synthesize Bi₂Ti₂O₇/TiO₂ using TiO₂ nanotubes as both supporter and reactant.     

Anchoring Bi4O5I2 and AgI nanoparticles over g-C3N4 nanosheets: Impressive visible-light-induced photocatalysts in elimination of hazardous contaminates by a cascade mechanism

In this research, Bi₄O₅I₂ and AgI nanoparticles were anchored over g-C₃N₄ nanosheets (denoted as NGCN/Bi₄O₅I₂/AgI) to preparation highly impressive visible-light-driven samples. The synthesized nanocomposites were investigated by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), UV–vis diffuse reflectance spectroscopy (DRS), energy dispersive analysis of X-rays (EDX), electrochemical impedance spectroscopy (EIS), photocurrent density, Brunauer-Emmett-Teller (BET), and photoluminescence (PL) analyses. Among the ternary photocatalysts, the NGCN/Bi₄O₅I₂/AgI (20%) photocatalyst illustrated the highest photoactivity in degradation of rhodamine B (RhB), which was approximately 58.4, 15.2, and 12.8 times higher than the GCN, NGCN, and NGCN/Bi₄O₅I₂ (20%) samples, respectively. Furthermore, the O₂⁻ was discovered as the main species in the respective system by the quenching tests. Also, by studying the electrochemical properties, a cascade photocatalytic mechanism was suggested based on the energy bands to describe the enhanced charge carriers migration and separation, which caused impressive photocatalytic performances in degradations of four hazardous contaminants. This study highlights the rational anchoring of Bi₄O₅I₂ and AgI nanoparticles over NGCN to prepare highly efficient photocatalysts for wastewater remediation.     

Heterostructured Fe3O4/Bi2O2CO3 photocatalyst: Synthesis,characterization and application in recyclable photodegradation of organic dyes under visible light irradiation

Heterostructured Fe₃O₄/Bi₂O₂CO₃ photocatalyst was synthesized by a two-step method. First, Fe₃O₄ nanoparticles with the size of ca. 10 nm were synthesized by chemical method at room temperature and then heterostructured Fe₃O₄/Bi₂O₂CO₃ photocatalyst was synthesized by hydrothermal method at 180 °C for 24 h with the addition of 10 wt% Fe₃O₄ nanoparticles into the precursor suspension of Bi₂O₂CO₃. The pH value of synthesis suspension was adjusted to 4 and 6 with the addition of 2 M NaOH aqueous solution. By controlling the pH of synthesis suspension at 4 and 6, sphere- and flower-like Fe₃O₄/Bi₂O₂CO₃ photocatalysts were obtained, respectively. Both photocatalysts demonstrate superparamagnetic behavior at room temperature. The UV–vis diffuse reflectance spectra of the photocatalysts confirm that all the heterostructured photocatalysts are responsive to visible light. The photocatalytic activity of the heterostructured photocatalysts was evaluated for the degradation of methylene blue (MB) and methyl orange (MO) in aqueous solution over the photocatalysts under visible light irradiation. The heterostructured photocatalysts prepared in this study exhibit highly efficient visible-light-driven photocatalytic activity for the degradation of MB and MO, and they can be easily recovered by applying an external magnetic field.     

Visible light responsive Bi2S3-graphene/TiO2 nanocomposites: one pot-hydrothermal synthesize and improved photocatalytic properties

Abstract

Herein, we obtained chemically bonded Bi₂S₃-Graphene/TiO₂ composites using a facile one pot-hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide to graphene and loading of Bi₂S₃ and TiO₂ particles on graphene nanosheet were achieved. The resulting composites are characterized by X-Ray diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM). The optical properties are studied using UV–visible diffuse reflectance spectroscopy (DRS), which confirms that the spectral responses of the composite catalysts are extended to the visible light region. The dramatically enhanced activity of Bi₂S₃-Graphene/TiO₂ composite photocatalysts can be attributed to great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties, simultaneously. This work may provide new insights into the design of novel composite photocatalysts system with efficient visible light activity.     

Optical Properties and Photoconductivity of Bismuth Titanate

The optical absorption spectra and photoelectric properties of undoped and doped (CaF, CdO, ZnO, Ga₂O₃, Fe₂O₃, Bi₂₄FePO₄₀, and Bi₂₄AlPO₄₀) Bi₁₂TiO₂₀single crystals were studied before and after vacuum annealing. The optical absorption and photoconductivity in Bi₁₂TiO₂₀crystals were shown to be due to impurities. The band gap of Bi₁₂TiO₂₀was determined to be 3.21 ± 0.03 eV. Doping and vacuum annealing have a significant effect on the optical properties of Bi₁₂TiO₂₀via the formation of acceptor and donor levels in the band gap.     

Observation of surface plasmon resonance of silver particles and enhanced third-order optical nonlinearities in AgCl doped Bi2O3-B2O3-SiO2 ternary glasses

Bi₂O₃-B₂O₃-SiO₂ ternary glasses embedded with Ag nanoparticles were prepared by introducing AgCl into the bismuthate glasses using conventional melt quenching method and characterized by several experimental techniques. Scanning electron microscopic studies indicated the formation of Ag contained nanoclusters which crack and become regular with increase of AgCl content in these composites. Optical absorption spectra of the nanocomposites showed the presence of absorption band of surface plasmon resonance (SPR) due to Ag nanoparticles at ∼600 nm. Z-scan measurement with femtosecond laser was used to investigate third-order optical nonlinearities of the nanocomposites. The results show that the nonlinear refraction γ was dramatically increased up to 30 times by the appearance of Ag nanoparticles when excited within its SPR region, while nonlinear absorption due to two-photon absorption exhibited opposite tendency or even saturated behavior. The calculation of figure of merit suggests that the Ag particle embedded Bi₂O₃-B₂O₃-SiO₂ glass composites are promising candidates for optoelectronic devices.     

Photocatalytic performance of oxygen vacancy rich-TiO2 combined with Bi4O5Br2 nanoparticles on degradation of several water pollutants

Despite significant advancements in the improvement of heterogeneous photocatalysis towards water treatment, these processes still have some bottlenecks. In this research paper, oxygen vacancy rich-TiO₂ was combined with Bi₄O₅Br₂ nanoparticles (denoted as TiO₂-OVs/Bi₄O₅Br₂) by eco-friendly hydrothermal approach. The outcomes demonstrated that the photoactivity strongly depends on plenteous active sites, reinforced charge segregation, as well as striking visible-light absorption ability in TiO₂-OVs/Bi₄O₅Br₂ nanocomposite with n-n heterojunction. The photoactivity was found to follow the trend: TiO₂-OVs/Bi₄O₅Br₂ (30%) > TiO₂-OVs > TiO₂. Briefly, the removal efficiencies of RhB, MB, and fuchsine were 100%, 96.2%, and 84.7% using TiO₂-OVs/Bi₄O₅Br₂ (30%) in 120 min, while they were 25.1%, 20.0%, and 15.3% over the TiO₂, respectively. Further, the boosted rate constant was observed for the photoreduction of Cr (VI) on the TiO₂-OVs/Bi₄O₅Br₂ (30%) nanocomposite, which was 19.4 and 7.8-folds more than the TiO₂ and TiO₂-OVs photocatalysts, respectively. The radical scavenging tests with different quenchers demonstrated that holes and superoxide anion radicals take part in the degradation reaction. Finally, by investigating the electrochemical properties, a mechanism was offered to describe the improved e^–/h⁺ pairs separation and migration. This research displayed that the design of n-n heterojunction using TiO₂-OVs could be suitable for severely improving photocatalytic performance of TiO₂ under visible light.     

Synthesis and photocatalytic properties of HTaWO6/(Pt,TiO2) and HTaWO6/(Pt,Fe2O3) nanocomposites

HTaWO₆/(Pt,TiO₂) and HTaWO₆/(Pt,Fe₂O₃) nanocomposites were synthesized by successive intercalation reactions of HTaWO₆ with [Pt(NH₃)₄]Cl₂ aqueous solution, n-C₃H₇NH₂/n-heptane mixed solution and acidic TiO₂ colloid solution or [Fe₃(CH₃CO₂)₇(OH)(H₂O)₂]NO₃ aqueous solution followed by UV light irradiation. The gallery heights of HTaWO₆/(Pt,TiO₂), HTaWO₆/TiO₂, HTaWO₆/(Pt,Fe₂O₃) and HTaWO₆/Fe₂O₃ was less than 0.51 nm. The host HTaWO₆ was white possessing band gap energy of 3.1 eV, whereas HTaWO₆/Pt, HTaWO₆/(Pt,TiO₂), HTaWO₆/Fe₂O₃ and HTaWO₆/(Pt,Fe₂O₃) were yellow and showed broad reflection over 400–600 nm together with that corresponding to the host layer. Photocatalytic activities of HTaWO₆/TiO₂ and HTaWO₆/Fe₂O₃ were superior to those of unsupported TiO₂ and Fe₂O₃ and were greatly enhanced by co-incorporation of Pt. HTaWO₆/Pt, HTaWO₆/(Pt,TiO₂), HTaWO₆/Fe₂O₃ and HTaWO₆/(Pt,Fe₂O₃) showed photocatalytic activity.     

Preparation and photocatalytic activity of novel efficient photocatalyst Sr2Bi2O5

A novel visible-light-driven photocatalyst of Sr₂Bi₂O₅ is prepared by solid-state reaction at 780 °C. The optical band gap of Sr₂Bi₂O₅ is determined to be 2.87 eV by UV-Vis diffuse reflectance spectroscopy. Under both UV and visible-light irradiation, the photocatalytic activity for degrading methyl orange (MO) over Sr₂Bi₂O₅ is higher than those over BiVO₄, and SrBi₂O₄. The relationships between the photocatalytic properties of Sr₂Bi₂O₅, SrBi₂O₄, and BiVO₄ and their crystal structures are discussed. Among Sr₂Bi₂O₅, SrBi₂O₄, and BiVO₄, the higher photocatalytic activity of Sr₂Bi₂O₅ is ascribed to its higher level of distortion of the metal-oxygen polyhedra, and the lower packing factor degree.     

Role of bismuth and titanium in Na2O-Bi2O3-TiO2-P2O5 glasses and a model of structural units

0.60Na₂O-0.40P₂O₅ and (0.55−z)Na₂O-0.05Bi₂O₃-zTiO₂-0.40P₂O₅ glasses (0≤z≤0.15) were prepared by melting at 1000°C mixtures of Na₂CO₃, Bi₂O₃, TiO₂ and (NH₄)₂HPO₄. Differential Scanning Calorimetry (DSC) measurements give the variation of glass transition temperature (T_g) from 269°C (for 0.60Na₂O-0.40P₂O₅) to 440°C (for z=0.15). The density measurements increases from 2.25 to 3.01 g/cm³. FTIR spectroscopy shows the evolution of the phosphate skeleton: (PO₃)_∞ chains for 0.60Na₂O-0.40P₂O₅ to P₂O₇⁴⁻ groups in the glasses containing Bi₂O₃ or both Bi₂O₃ and TiO₂. When bismuth oxide and titania are added to sodium phosphate glass, phosphate chains are depolymerized by the incorporation of distorted Bi(6) and Ti(6) units through POBi and POTi bonds. Bi₂O₃ and TiO₂ are assumed to be present as six co-ordinated octahedral [BiO_6/2]³⁻and [TiO_6/2]²⁻ units again with shared corners. This is accompanied by the simultaneous conversion of [POO_3/2] into [PO_4/2]⁺ units which achieves charge neutrality in the glasses.     

Depolymerization of GeO2 and GeO2 · Sb2O3 glasses by Bi2O3

Glasses that contain at least 60 mol% GeO₂ were prepared in the Bi₂O₃ · GeO₂ and Bi₂O₃ · Sb₂O₃ · GeO₂ systems. Their densities, refractive indices, and infra-red spectra were recorded. Negative molar volume deviations and positive refraction deviations occur for all of the binary glasses. These create deviations for the 60 to 80 mol % GeO₂ ternary glasses that indicate non-ideal mixing when Sb³⁺ substitutes for Bi³⁺. Also, the main Ge-O stretching vibration shifts to as low as 695 cm^?1 for the Bi₂O₃-rich binary and ternary glasses. All of these findings show that Bi₂O₃ more effectively depolymerizes GeO₂ than does Sb₂O₃. The probable structural reasons for this behaviour are discussed.     

Some details of the ternary system Bi2O3-CaO-CuO

Before investigating the ternary system Bi₂O₃-CaO-CuO, a revision of the binary bounding system Bi₂O₃-CaO was first necessary. In the range between 20 and 70 mol % CaO the solid solutions and '₁ and the stoichiometric compounds Bi₂CaO₄, Bi₆Ca₄O₁₃, and Bi₂Ca₂O₅ were found to exist for 675 °CT780 °C. Above 780 °C a new high temperature compound with the formula Bi₆Ca₅O₁₄ has been identified. The X-ray powder diffraction data, unit cell dimensions, as well as the space group, have been reported. The ternary system contains no intermediate compounds and also no solubility was found for the binary bounding phases. Below 780 °C all the Bi-Ca oxides mentioned above are in equilibrium with CuO. At 820 °C, a wide liquidus field is dominating so that these quasibinary equilibria disappear. For 780 °C6Ca₅O₁₄ forms an equilibrium with Ca₂CuO₃ and CuO. Other equilibria are deduced. For a fixed ternary composition the reaction path of the sintering process was investigated as a function of time and temperature.     

Selective-syntheses, characterizations and photocatalytic activities of nanocrystalline ZnTa2O6 photocatalysts

Nanocrystalline ZnTa₂O₆ photocatalysts with different crystal structures were prepared via a simple and facile sol-gel method in a temperature range of 650-950 °C. The absorption edges and particle sizes of the samples were located at about 285 nm (corresponding a band gap of 4.35 eV) and ranged from 25 to 150 nm, respectively. The photocatalytic activities of the samples were tested by the degradation of methyl orange under UV light irradiation. The results indicated that the crystal structure of ZnTa₂O₆ was a main factor for the different photocatalytic activities of the ZnTa₂O₆ samples. Moreover, the effects of crystallinities and surface areas of the obtained samples on the catalytic activities were also discussed.     

Electronic structure and photocatalytic water splitting of lanthanum-doped Bi2AlNbO7

Bi_2−xLa_xAlNbO₇ (0 ≤ x ≤ 0.5) photocatalysts were synthesized by the solid-state reaction method and characterized by powder X-ray diffraction (XRD), infrared (IR) spectra and ultraviolet-visible (UV-vis) spectrophotometer. The band gaps of the photocatalysts were estimated from absorption edge of diffuse reflectance spectra, which were increased by the doping of lanthanum. It was found from the electronic band structure study that orbitals of La 5d, Bi 6p and Nb 4d formed a conduction band at a more positive level than Bi 6p and Nb 4d orbitals, which results in increasing the band gap. Photocatalytic activity for water splitting of Bi_1.8La_0.2AlNbO₇ was about 2 times higher than that of nondoped Bi₂AlNbO₇. The increased photocatalytic activity of La-doped Bi₂AlNbO₇ was discussed in relation to the band structure and the strong absorption of OH groups at the surface of the catalyst.