Synthesis, characterization and photocatalytic performance of transition metal tungstates

Harmful effects of the semiconductor copper tungstate (CuWO4) on multiple photosynthetic parameters of the green microalga Raphidocelis subcapitata

The semiconductor copper tungstate (CuWO4) may end up in aquatic ecosystems since it has the potential for water decontamination. The toxic effects of CuWO4 are totally unknown for eukaryotic organisms. In view of this, we aimed to evaluate the toxicity of CuWO4 particles (size of 161.5 nm) on the cosmopolitan green microalga Raphidocelis subcapitata (a standardized test-organism for ecotoxicological assays), analyzing the growth and multiple photosynthetic parameters obtained by pulse amplitude modulated (PAM) fluorometry. At 1.2 mg l-1, the growth was affected, and there was an increase in reactive oxygen species (ROS) after 72 h The effective efficiency (ɸM') of photosystem II (PSII) was affected at 13.1 mg l-1, while the efficiency of the oxygen-evolving complex (OEC), responsible for the water-splitting process, decayed at 5.6 mg l-1. According to quenching parameters, energy allocated to photosynthetic processes (qP) decreased, indicating a malfunctioning of the PSII. We also observed a 50 % increase in the non-regulated energy dissipation by heat and fluorescence (Y(NO)), and a 50 % decrease in the regulated energy dissipation (NPQ), suggesting difficulties for algae to cope with light. Rapid light curves (RLC) were the second most sensitive parameter, as we observed a decay of the relative maximum electron transport rate (rETRmax) at 2.8 mg l-1. Therefore, since the microalga R. subcapitata was affected by concentrations up to 1.2 mg l-1 (0.01 mg l-1 dissolved Cu), it is important to evaluate carefully the use of CuWO4 to decontaminate natural waters, considering the protection of the aquatic biota.

The effects of nickel tungstate nanoparticles (NiWO4 NPs) on freshwater microalga Raphidocelis subcapitata (Chlorophyceae)

Among the vast array of functional nanoparticles (NPs) under development, nickel tungstate (NiWO4) has gained prominence due to its potential applications as a catalyst, sensor, and in the development of supercapacitors. Consequently, new studies on the environmental impact of this material must be conducted to establish a regulatory framework for its management. This work aims to assess the effects of NiWO4 (NPs) on multiple endpoints (e.g., growth, photosynthetic activity, and morphological and biochemical levels) of the freshwater microalga Raphidocelis subcapitata (Chlorophyceae). Quantification data revealed that the fraction of dissolved Ni and free Ni2+ increased proportionally with NiWO4 NP concentrations, although these levels remained relatively low. Biological results indicated that NiWO4 NPs did not inhibit the growth of algal cells, except at 7.9 mg L-1, resulting in a 9% decrease. Morphological changes were observed in cell size and complexity, accompanied by physiological alterations, such as a reduction in chlorophyll a fluorescence (FL3-H) and signs of impaired photosynthetic activity, indicated by the effective quantum yield, quenchings, and chlorophyll a (Chl a) content. Furthermore, the rapid light curves showed that the NPs in high concentrations affected microalga ability to tolerate high light intensities, as corroborated by the significant decrease in the relative electron transport rate (rETRmax) and saturation irradiance (Ek). Based on the present study results, we emphasize the importance of applying integrative approaches in ecotoxicological studies, since each endpoint evaluated showed different sensitivity.

Preparation and application of high thermal conductivity phase change microcapsules with fluorescence characteristics based on a ZnWO4 shell

Phase change microcapsules (NePCMs) with high latent heat values, thermal conductivity and stability were synthesized by coating stearic acid (SA) phase change materials (PCMs) with zinc tungstate (ZnWO4) as the shell material. The prepared ZnWO4 and microcapsule samples are characterized through various techniques, and their thermophysical properties under different core-shell ratios and emulsifiers are compared. The highest value that the phase transition enthalpy reaches is 83.63 J g-1 when the core-shell ratio is 1 : 1 and sodium dodecylbenzenesulfonate (SDBS) is adopted as the emulsifier. Based on SEM and TEM results, the regular spherical shape and the complete core-shell structure of the microcapsule can be found, and the particle size ranges between 100 and 300 nm. The thermal conductivity of SA increased by 141.18%-238.43% after using ZnWO4 as the shell material. Moreover, thermogravimetric and leak-proof performance tests demonstrated that microcapsule samples possess high thermal stability. There was no leakage from the six microcapsule samples after heating, proving their potential application in thermal energy storage (TES) under long-term high-temperature conditions. In addition, the cost of ZnWO4 prepared by this method can be reduced by about 40%. According to UV absorption and fluorescence spectrum evaluation, ZnWO4 and microcapsule samples exhibit good photoluminescence and UV absorption properties, indicating that the sample can be widely employed in fluorescent construction, coatings and textile industries at a lower cost.

Ultrasound and defect engineering-enhanced nanozyme with high laccase-like activity for oxidation and detection of phenolic compounds and adrenaline

Perusing metal-based redox nanozyme offers new opportunity for pollutant removal and biosensor, but ultrasound (US)-driven laccase-like nanozyme remains a significant challenge, especially in combination with defect engineering strategy. Herein, the Cu2Ov@Ce-TCPP was synthesized by doping Ce3+ on the surface of Cu2O nanocube and then coating with the porphyrin sonosensitizer. The Ce-doped porphyrin metal-structure in nanozyme was demonstrated to generate oxygen vacancy defects, which could obviously promote the laccase-like activity of Cu2Ov@Ce-TCPP nanozyme under US. XPS characterization and density functional theory (DFT) theoretical calculation revealed that the ultrasonic stimulation is beneficial to accelerate the electron transfer rate and O2 adsorption to improve catalytic activity, and Cu2Ov@Ce-TCPP nanozyme exhibits low adsorption energy and activation energy due to the presence of oxygen defect site, resulting in high laccase-like activity. The interaction between Ce atom and porphyrin structure also improved the sonocatalytic ability of the nanozyme. Meanwhile, Cu2Ov@Ce-TCPP nanozyme has been used for detecting and degrading a series of phenolic compounds. The detection adrenaline method has a linear range of 3.3-1000 μM and a detection limit as low as 0.96 μM with good reproducibility. The developed US-enhancing and recyclable laccase-like nanozyme system provides a promising strategy for the oxidation and detection of phenolic compounds.

Not Just Another Methanation Catalyst: Depleted Uranium Meets Nickel for a High-Performing Process Under Autothermal Regime

Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfully been employed as highly efficient, selective, and durable systems for CO₂ hydrogenation to substituted natural gas (SNG; CH₄ ) under an autothermal regime. The thermo-physical properties of DU and the unique electronic structure of f-block metal-oxides combined with a nickel active phase, generated an ideal catalytic assembly for turning waste energy back into useful energy for catalysis. In particular, Ni/UO_x stood out for the capacity of DU matrix to control the extra heat (hot-spots) generated at its surface by the highly exothermic methanation process. At odds with the benchmark Ni/γ-Al₂ O₃ catalyst, the double action played by DU as a "thermal mass" and "dopant" for the nickel active phase unveiled the unique performance of Ni/UO_x composites as CO₂ methanation catalysts. The ability of the weakly radioactive ceramic (UO_x ) to harvest waste heat for more useful purposes was demonstrated in practice within a rare example of a highly effective and long-term methanation operated under autothermal regime (i. e., without any external heating source). This finding is an unprecedented example that allows a real step-forward in the intensification of "low-temperature" methanation with an effective reduction of energy wastes. At the same time, the proposed catalytic technology can be regarded as an original approach to recycle and bring to a second life a less-severe nuclear by-product (DU), providing a valuable alternative to its more costly long-term storage or controlled disposal.

Preparation of Ag3PO4/CoWO4 S-scheme heterojunction and study on sonocatalytic degradation of tetracycline

In this study, 0.6Ag3PO4/CoWO4 composites were synthesized by hydrothermal method. The prepared materials were systematically characterized by techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption, and UV-vis diffuse reflectance spectrum (DRS). Furthermore, the sonocatalytic degradation performance of 0.6Ag3PO4/CoWO4 composites towards tetracycline (TC) was investigated under ultrasonic radiation. The results showed that, combined with potassium persulfate (K2S2O8), the 0.6Ag3PO4/CoWO4 composites achieved a high sonocatalytic degradation efficiency of 97.89 % within 10 min, which was much better than bare Ag3PO4 or CoWO4. By measuring the electrochemical properties, it was proposed that the degradation mechanism of 0.6Ag3PO4/CoWO4 is the formation of S-scheme heterojunction, which increases the separation efficiency of electron-hole pairs (e--h+) and generates more electrons and holes, thereby enhancing the degradation activity. The scavenger experiments confirmed that hole (h+) was the primary active substance in degrading TC, and free radicals (OH) and superoxide anion radical (O2-) were auxiliary active substances. The results indicated that 0.6Ag3PO4/CoWO4 nanocomposites could be used as an efficient and reliable sonocatalyst for wastewater treatment.

Synthesis, Characterization, Photocatalysis, and Antibacterial Study of WO3, MXene and WO3/MXene Nanocomposite

Tungsten oxide (WO₃), MXene, and an WO₃/MXene nanocomposite were synthesized to study their photocatalytic and biological applications. Tungsten oxide was synthesized by an easy and cost-effective hydrothermal method, and its composite with MXene was prepared through the sonication method. The synthesized tungsten oxide, MXene, and its composite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), energy-dispersive X-ray analysis (EDX), and Brunauer–Emmett–Teller (BET) for their structural, morphological, spectral, elemental and surface area analysis, respectively. The crystallite size of WO₃ calculated from XRD was ~10 nm, the particle size of WO₃ was 130 nm, and the average thickness of MXene layers was 175 nm, which was calculated from FESEM. The photocatalytic activity of as-synthesized samples was carried out for the degradation of methylene blue under solar radiation, MXene, the WO₃/MXene composite, and WO₃ exhibited 54%, 89%, and 99% photocatalytic degradation, respectively. WO₃ showed maximal degradation ability; by adding WO₃ to MXene, the degradation ability of MXene was enhanced. Studies on antibacterial activity demonstrated that these samples are good antibacterial agents against positive strains, and their antibacterial activity against negative strains depends upon their concentration. Against positive strains, the WO₃/MXene composite’s inhibition zone was at 7 mm, while it became 9 mm upon increasing the concentration. This study proves that WO₃, MXene, and the WO₃/MXene nanocomposite could be used in biological and environmental applications.

Dual-strategy biosensing of glucose based on multifunctional CuWO4 nanoparticles

The multifunctional CuWO4 NPs were prepared and exhibit large specific surface area, good conductivity and excellent peroxidase-like activity, which was exploited for electrochemical and colorimetric dual-strategy biosensing of glucose.

Synthesis, Characterization and Enhanced Visible Light Photocatalytic Performance of ZnWO4-NPs@rGO Nanocomposites

ZnWO4 nanoparticles on reduced graphene oxide (ZnWO4-NPs@rGO) nanocomposites were synthesized using the hydrothermal method. Structural, morphological, optical, and photocatalytic studies of the ZnWO4-NPs@rGO nanocomposites were successfully investigated. Photo-catalytic performances of the ZnWO4-NPs@rGO nanocomposites were examined for the degradation of hazardous methylene blue dye (HMBD) in a neutral medium. ZnWO4-NPs@rGO nanocomposites show superior photo-catalytic performances over pure ZnWO4 nanoparticles. ZnWO4-NPs@rGO nanocomposites degrade ~98% dye while pure ZnWO4 nanoparticles degrade ~53% dye in 120 min. The prepared nanocomposites also show excellent recycled photo-catalytic efficiencies over multiple cycles.

Hydrothermal Synthesis, Characterization and Exploration of Photocatalytic Activities of Polyoxometalate: Ni-CoWO4 Nanoparticles

This study demonstrated the hydrothermal synthesis of bimetallic nickel-cobalt tungstate nanostructures, Ni-CoWO4 (NCW-NPs), and their phase structure, morphology, porosity, and optical properties were examined using X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS), high resolution Transmission electron microscopy (HR-TEM), Brunauer-Emmett-Teller (BET) and Raman instruments. It was found that as-calcined NCW-NPs have a monoclinic phase with crystal size ~50–60 nm and is mesoporous. It possessed smooth, spherical, and cubic shape microstructures with defined fringe distance (~0.342 nm). The photocatalytic degradation of methylene blue (MB) and rose bengal (RB) dye in the presence of NCW-NPs was evaluated, and about 49.85% of MB in 150 min and 92.28% of RB in 90 min degraded under visible light. In addition, based on the scavenger’s study, the mechanism for photocatalytic reactions is proposed.

Iron and Manganese Codoped Cobalt Tungstates Co1-(x+y)Fe x Mn y WO4 as Efficient Photoelectrocatalysts for Oxygen Evolution Reaction

Photoelectrocatalysts are robust materials for the production of energy through different ways such as water splitting. Narrow optical band gaps and high overpotentials are limiting the development of photoelectrocatalysts. In this study, a series of Co_1-(x+y)Fe _x Mn _y WO₄ solid solutions of cobalt tungstate codoped with iron and manganese have been synthesized hydrothermally. The synthesized solid solutions have been characterized by powder XRD, UV-visible spectra, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). They all crystallize in a wolframite-type monoclinic crystal system with space group P2/c. Doping of iron and manganese leads to narrowing of the optical band gap of Co_1-(x+y)Fe _x Mn _y WO₄ from 2.60 to 2.04 eV. The electrocatalytic activity toward oxygen evolution reaction of all of the samples has been evaluated through LSV measurements. It is found that the sample named C5, which is codoped with manganese and iron, has the lowest onset potential and needs the lowest overpotential to attain the targeted 5 mA cm^-2 and standard 10 mA cm^-2 current densities as compared with all other synthesized samples. This study shows that the synthesized tungstates can be good candidates for the photoelectrocatalytic oxygen evolution reaction.

Co/Ni-polyoxotungstate photocatalysts as precursor materials for electrocatalytic water oxidation

An open-core cobalt polyoxometalate (POM) [(A-α-SiW9O34)Co4(OH)3(CH3COO)3]8-Co(1) and its isostructural Co/Ni-analogue [(A-α-SiW9O34)Co1.5Ni2.5(OH)3(CH3COO)3]8-CoNi(2) were synthesized and investigated for their photocatalytic and electrocatalytic performance. Co(1) shows high photocatalytic O2 yields, which are competitive with leading POM water oxidation catalysts (WOCs). Furthermore, Co(1) and CoNi(2) were employed as well-defined precursors for heterogeneous WOCs. Annealing at various temperatures afforded amorphous and crystalline CoWO4- and Co1.5Ni2.5WO4-related nanoparticles. CoWO4-related particles formed at 300 °C showed substantial electrocatalytic improvements and were superior to reference materials obtained from co-precipitation/annealing routes. Interestingly, no synergistic interactions between cobalt and nickel centers were observed for the mixed-metal POM precursor and the resulting tungstate catalysts. This stands in sharp contrast to a wide range of studies on various heterogeneous catalyst types which were notably improved through Co/Ni substitution. The results clearly demonstrate that readily accessible POMs are promising precursors for the convenient and low-temperature synthesis of amorphous heterogeneous water oxidation catalysts with enhanced performance compared to conventional approaches. This paves the way to tailoring polyoxometalates as molecular precursors with tuneable transition metal cores for high performance heterogeneous electrocatalysts. Our results furthermore illustrate the key influence of the synthetic history on the performance of oxide catalysts and highlight the dependence of synergistic metal interactions on the structural environment.

Superior UV-light photocatalysts of nano-crystalline (Ni or Co) FeWO4: structure, optical characterization and synthesis by a microemulsion method

A new NiFeWO₄ photocatalyst showing super photocatalytic activity for MB degradation under UV after 60 min due to photoexcited electrons.

Sonochemical synthesis of samarium tungstate nanoparticles for the electrochemical detection of nilutamide

This study reports the sonochemical synthesis of samarium tungstate nanoparticles (SWNPs) for applications in electrochemical sensors. The synthesis process is based on a precipitation reaction, which was investigated by ultrasound and compared with the effect of stirring. A bath sonicator operated at a frequency and power of 37/100 kHz and ~60 W, respectively, was employed to prepare the material. The shock waves efficiently irradiated the reaction conditions as much as possible, resulting in the good crystallinity of the monoclinic phase of the SWNPs, which was confirmed by XRD analysis. The surface morphology and structural composition was further evaluated by HRTEM, EDS and XPS. The good crystallinity and uniform distribution of elements in the nanoparticles were confirmed. The performance of the SWNPs to electrochemically sense nilutamide (NLT) was studied, which revealed a good electrochemical signal. As a result, the SWNPs were applied to an electrode material for the detection of NLT. This study revealed the excellent activity of the SWNPs for NLT detection, resulting in a low detection limit (0.0026 µM) and good linear range (0.05-318 µM). Furthermore, the results show appreciable analytical performances, which could be applied to electrochemical anti-androgen drug nilutamide sensors.

The facile co-precipitation synthesis of strontium tungstate anchored on a boron nitride (SrWO4/BN) composite as a promising electrocatalyst for pharmaceutical drug analysis

Strontium tungstate/boron nitride (SrWO₄/BN) composite considered efficient electrocatalysts in the area of electrochemical sensors.

Synergetic Effects of Pd0 Metal Nanoparticles and Pd2+ Ions on Enhanced Photocatalytic Activity of ZnWO4 Nanorods for Nitric Oxide Removal

Doping and novel metallic nanoparticles loading on the photocatalyst are two effective means to enhance its photocatalytic activity. In our study, Pd⁰/Pd²⁺-co-modified ZnWO₄ nanorods were fabricated by a two-step hydrothermal process and room-temperature reduction method. The performance of the as-prepared samples was evaluated through the photocatalytic nitric oxide (NO_x) removal under simulated solar and visible-light irradiation. Pd⁰/Pd²⁺-co-modified ZnWO₄ nanorods present a significantly enhanced photocatalytic activity for NO_x removal compared with Pd⁰-loaded or Pd²⁺-doped ZnWO₄ under simulated sunlight irradiation owing to a narrower band gap of Pd²⁺ doping compared with that of pure ZnWO₄. The role of Pd⁰ nanoparticles is to act as an electron reservoir to restrain the recombination of e^-/h⁺ pairs. According to the trapping measurements, the photoinduced holes and electrons play critical roles during the photocatalytic process. In addition, electron spin resonance (ESR) results further confirm that ^•O₂^- and ^•OH radicals are present and assist in the photocatalysis under simulated solar light irradiation. Stability test demonstrated that 1.5% Pd⁰/0.5% Pd²⁺-co-modified ZnWO₄ nanorods as photocatalyst have high photocatalytic stability in NO_x removal. This work proved that Pd⁰/Pd²⁺-co-modified ZnWO₄ nanorods can be considered as an efficient photocatalyst for NO_x removal.

Evidence of Wolframite-Type Structure in Ultrasmall Nanocrystals with a Targeted Composition MnWO4

Here, we report a study of white-ochre powders with targeted composition MnWO₄ prepared via a coprecipitation method. Through X-ray total scattering combined with pair distribution function analysis and Rietveld refinement of X-ray diffraction data, we find that their crystal structure is similar to that of bulk-MnWO₄, despite a mean crystallite size of 1.0-1.6 nm and a significant deviation of the average chemical composition from MnWO₄. The chemical formula derived from elemental and thermogravimetric analyses is Mn_0.8WO_3.6(OH)_0.4·3H₂O. X-ray absorption and magnetic susceptibility measurements show that Mn and W have the same oxidation states as in MnWO₄. No magnetic ordering or spin glass or superparamagnetic behavior is observed above 2 K, unlike in the case of MnWO₄ nanocrystals having a mean size higher than 10 nm.

ZnWO4 nanocrystals: synthesis, morphology, photoluminescence and photocatalytic properties

The best photocatalytic properties for monoclinic ZnWO₄ nanocrystals are related to the surface energy and the types of clusters formed on their surface.

NiO/NiWO4 Composite Yolk-Shell Spheres with Nanoscale NiO Outer Layer for Ultrasensitive and Selective Detection of Subppm-level p-Xylene

NiO/NiWO₄ composite yolk-shell spheres with a nanoscale NiO outer layer were prepared using one-pot ultrasonic spray pyrolysis and their gas sensing characteristics were studied. The NiO/NiWO₄ yolk-shell spheres exhibited an extremely high response to 5 ppm p-xylene (ratio of resistance to gas and air = 343.5) and negligible cross-responses to 5 ppm ethanol, ammonia, carbon monoxide, hydrogen, and benzene, whereas pure NiO yolk-shell spheres showed very low responses and selectivity to all the analyte gases. The detection limit for p-xylene was as low as 22.7 ppb. This ultrasensitive and selective detection of p-xylene is attributed to a synergistic catalytic effect between NiO and NiWO₄, high gas accessibility with large specific surface area, and increased chemiresistive variation due to the formation of a heterojunction. The NiO/NiWO₄ yolk-shell spheres with a thin NiO outer layer can be used to detect subppm-level p-xylene in a highly sensitive and selective manner for monitoring indoor air pollution.

Structural evolution, growth mechanism and photoluminescence properties of CuWO4 nanocrystals

Copper tungstate (CuWO₄) crystals were synthesized by the sonochemistry (SC) method, and then, heat treated in a conventional furnace at different temperatures for 1h. The structural evolution, growth mechanism and photoluminescence (PL) properties of these crystals were thoroughly investigated. X-ray diffraction patterns, micro-Raman spectra and Fourier transformed infrared spectra indicated that crystals heat treated and 100°C and 200°C have water molecules in their lattice (copper tungstate dihydrate (CuWO₄·2H₂O) with monoclinic structure), when the crystals are calcinated at 300°C have the presence of two phase (CuWO₄·2H₂O and CuWO₄), while the others heat treated at 400°C and 500°C have a single CuWO₄ triclinic structure. Field emission scanning electron microscopy revealed a change in the morphological features of these crystals with the increase of the heat treatment temperature. Transmission electron microscopy (TEM), high resolution-TEM images and selected area electron diffraction were employed to examine the shape, size and structure of these crystals. Ultraviolet-Visible spectra evidenced a decrease of band gap values with the increase of the temperature, which were correlated with the reduction of intermediary energy levels within the band gap. The intense photoluminescence (PL) emission was detected for the sample heat treat at 300°C for 1h, which have a mixture of CuWO₄·2H₂O and CuWO₄ phases. Therefore, there is a synergic effect between the intermediary energy levels arising from these two phases during the electronic transitions responsible for PL emissions.

Elucidation of CuWO4 Surface States During Photoelectrochemical Water Oxidation

Electrochemical, photoelectrochemical, and impedance spectroscopy measurements were performed to investigate the role of CuWO₄ surface states during water oxidation. We found that a capacitive feature related to a surface state is clearly observable under water oxidation conditions. The magnitude of the surface state capacitance is light intensity-dependent, with a peak potential that coincides with the water oxidation onset potential region. The surface state is not observed in the dark nor in contact with nonaqueous solvents. These results strongly support our assignment of this surface state as the buildup of water oxidation intermediate species at the surface of CuWO₄ photoanodes, not a permanent or intrinsic state as previously reported. We suggest this is a general feature that controls the behavior and efficiency of solar water splitting reactions.

Synthesis, characterization, and enhanced photocatalytic properties of NiWO4 nanobricks

NiWO₄ nanobricks were used as photocatalysts in the degradation of organic pollutants in neutral and basic media.

Synthesis of pearl necklace-like ZnO–ZnWO4 heterojunctions with enhanced photocatalytic degradation of Rhodamine B

Pearl necklace-like ZnO–ZnWO₄ heterojunctions with enhanced photocatalytic degradation of Rhodamine B were successfully synthesized by precipitation method followed by calcination.

Improved Charge Separation in WO₃/CuWO₄ Composite Photoanodes for Photoelectrochemical Water Oxidation

Porous tungsten oxide/copper tungstate (WO₃/CuWO₄) composite thin films were fabricated via a facile in situ conversion method, with a polymer templating strategy. Copper nitrate (Cu(NO₃)₂) solution with the copolymer surfactant Pluronic^®F-127 (Sigma-Aldrich, St. Louis, MO, USA, generic name, poloxamer 407) was loaded onto WO₃ substrates by programmed dip coating, followed by heat treatment in air at 550 °C. The Cu²⁺ reacted with the WO₃ substrate to form the CuWO₄ compound. The composite WO₃/CuWO₄ thin films demonstrated improved photoelectrochemical (PEC) performance over WO₃ and CuWO₄ single phase photoanodes. The factors of light absorption and charge separation efficiency of the composite and two single phase films were investigated to understand the reasons for the PEC enhancement of WO₃/CuWO₄ composite thin films. The photocurrent was generated from water splitting as confirmed by hydrogen and oxygen gas evolution, and Faradic efficiency was calculated based on the amount of H₂ produced. This work provides a low-cost and controllable method to prepare WO₃-metal tungstate composite thin films, and also helps to deepen the understanding of charge transfer in WO₃/CuWO₄ heterojunction.

g-C3N4/Bi4O5I2 2D–2D heterojunctional nanosheets with enhanced visible-light photocatalytic activity

The 2D–2D heterojunctional g-C₃N₄/Bi₄O₅I₂ nanosheets were successfully constructed based on band gap engineering design. It exhibits high visible-light-driven photocatalytic activity for degradation of RhB and NO removal.