BiVO4 Layer Research Articles

Optimization of photogenerated charge transport using type-II heterojunction structure of CoP/BiVO4:WO3 for high efficient solar-driver water splitting

Bismuth vanadate oxide (BiVO4) is one of the most efficient light-absorber metal oxides for the photoelectrochemical (PEC) water splitting; however, the fast charge recombination and poor kinetics for water oxidation have hindered full utilization of their theoretical performance. The optimization of the band alignment to facilitate charge transport and injection is of paramount importance to achieve the ideal water splitting performance of the photoelectrode. In this study, a type-II heterojunction CoP/BiVO4:WO3 structure has been fabricated for highly efficient PEC water splitting. The WO3 layer in the junction readily collects the photoelectrons harvested from the BiVO4 layer owing to its highly conducting nature, enabling efficient bulk charge transport from the BiVO4:WO3 junction to the fluorine-doped tin oxide (FTO) substrate. In addition, the cobalt phosphide (CoP) nanoparticles (NPs) play the role of the hole conducting layer from the light-absorber layer to the water as well as a catalyst to enhance surface charge injection efficiency at the photoelectrode surface. As a result, the CoP/BiVO4:WO3 photoanode reveals a remarkable photocurrent density of 2.81 mA cm−2 at 1.23 V (vs. RHE) with a negative shift of the onset potential (610 mV) compare to that of bare BiVO4. Moreover, the CoP/BiVO4:WO3 electrode shows a highly stable photocurrent density for at least 5 h.

Role of sputtered WO3 underlayer and NiFeCr-LDH co-catalyst in WO3–BiVO4 heterojunction for enhanced photoelectrochemical water oxidation

WO3–BiVO4 (WO-60s/BVO) heterojunction was synthesized by radio-frequency sputtered WO3 onto FTO substrate, followed by spin-coating of BiVO4 layer. Furthermore, Cr incorporated NiFe-LDH (NiFeCr-LDH) oxygen evolution reaction (OER) co-catalyst was electrodeposited onto WO-60s/BVO. The sputtered WO3 underlayer in the WO-60s/BVO facilitated enhanced electron-hole separation and less transient time for the electron to arrive at back contact than conventional spin-coated WO3 layers. Incorporating Cr into NiFe-LDH increased the electrical conductivity of LDH, which resulted in an enhanced transfer of photogenerated charge-carrier and significant promotion of the OER kinetics. The heterojunction with sputtered WO3 underlayer and NiFeCr-LDH co-catalyst attained photocurrent density of 4.9 mA cm−2 at 1.23 V vs. RHE with an IPCE value greater than 56% in the 350–470 nm wavelength range. Moreover, the WO-60s/BVO-NiFeCr photoanode showed only 7% decay in photocurrent after 6 h with H2, and O2 evolution of 98 and 47 μmol cm−2 h, respectively, suggesting high stability for OER.

Intermediate Evaporation Controlled SnO2/Mo Doped BiVO4 photoanode for Enhanced Photoelectrochemical Performance

The design of multilayer oxide films heterojuctions for photoanodes enables the control of charge transport/transfer and optical properties, and thus leads to efficient photoelectrochemical performance. In this research, a SnO2/Mo-doped BiVO4/ based photoanode was fabricated by sequential spin coating method on an FTO substrate followed by thermal treatment. First, bottom SnO2 layers were deposited, and subsequently Mo doped BiVO4 layers were loaded. When Mo doped BiVO4 layers were coated, intermediate evaporation was controlled by varying temperature condition for a formation of uniform crystalline film, allowing an improved charge separation. The synthesized photoanodes were examined by SEM, TEM, XRD, UV-vis as well as electrochemical measurements.

Integration of aminosilicate functionalized-fullerene (C60) QDs on bismuth vanadate (BiVO4) nanolayers for the photocatalytic degradation of pharmaceutical pollutant

A composite system consisting of aminosilicate (APS) functionalized-fullerene quantum dots (C60 QDs) and bismuth vanadate (BiVO4-APS-C60) has been developed via a facile one-step hydrothermal process. The structural analysis by XRD revealed that the integrated QDs have not affected the crystal structure of the host BiVO4, while the XPS studies showed that these QDs have been integrated via the Bi-V-O-Si-C network. The optical studies indicated that both the C60 and APS-C60 QDs have hardly influenced the optical absorption properties of the composite system. On the other hand, the dispersion of aminosilicate functionalized-QDs considerably reduced the aggregation in the layers and yielded a few nanometer thick BiVO4 layers due to their inter-layer occupancy as seen from their high-resolution TEM images. The photoluminescence, photocurrent and electrochemical impedance studies showed that the integration of APS-C60 QDs greatly improved the photoactive properties of the composite by effectively enhancing the charge recombination resistance, charge separation and transfer process between the integrated materials and surroundings. As a result, BiVO4-APS-C60 composites showed the enhanced photocatalytic efficiency towards degradation of ciprofloxacin (CIP) molecules under solar light irradiation as compared to that of bare-BiVO4 and BiVO4-C60.

WO3/BiVO4 Photoanodes: Facets Matching at the Heterojunction and BiVO4 Layer Thickness Effects

Photoelectrochemical solar energy conversion offers a way to directly store light into energy-rich chemicals. Photoanodes based on the WO3/BiVO4 heterojunction are most effective mainly thanks to the efficient separation of photogenerated charges. The WO3/BiVO4 interfacial space region in the heterojunction is investigated here with the increasing thickness of the BiVO4 layer over a WO3 scaffold. On the basis of X-ray diffraction analysis results, density functional theory simulations show a BiVO4 growth over the WO3 layer along the BiVO4 {010} face, driven by the formation of a stable interface with new covalent bonds, with a favorable band alignment and band bending between the two oxides. This crystal facet phase matching allows a smooth transition between the electronic states of the two oxides and may be a key factor ensuring the high efficiency attained with this heterojunction. The photoelectrochemical activity of the WO3/BiVO4 photoanodes depends on both the irradiation wavelength and the thickness of the visible-light-absorbing BiVO4 layer, a 75 nm thick BiVO4 layer on WO3 being best performing.

Co-catalytic effects of Bi-based metal-organic framework on BiVO4 photoanodes for photoelectrochemical water oxidation

Metal-organic frameworks (MOFs) are promising co-catalysts for increasingenhancing the performance of photoelectrochemical (PEC) water splitting. In this work, we successfully fabricated an efficient BiVO4 photoanode for PEC water oxidation by decorating its surface with Bi-based MOF as a co-catalyst via an unconventional immersion process at an ambient temperature. Bi-MOF exhibits a large surface area and promotes bulk charge separation and surface charge transfer in the water oxidation reaction, resulting in an enhancement in the photocurrent density, which is approximately two times larger than that of the bare BiVO4 photoanode. In addition, the operation stability of our Bi-MOF/BiVO4 photoanode was dramatically improved, and more than 95% of its initial photocurrent density was retained even after 24 h, indicating that the improved charge transfer by the Bi-MOF layer prohibits the dissolution of the BiVO4 layer into the solution during the water oxidation reaction.

Electrodeposition of BiVO4 with needle-like flower architecture for high performance photoelectrochemical splitting of water

Photoelectrochemical (PEC) water splitting is a green and sustainable approach capable of driving mass hydrogen production in the future. To realize this vision, development of a well-performing photoelectrode is highly demanded. In this comprehensive study, electrodeposition technique was applied for fabricating BiVO4 films by regulating the deposition time from 1 min until 9 min. Interestingly, the morphology, crystallinity, chemical structure, and optical properties of BiVO4 films depend strongly on the deposition time. It is found that BiVO4 layer deposited for 7 min with a cross-section thickness of around 321.1–326.5 nm showed the optimum performance, whereby the photocurrent reached up to ~0.32 mA/cm−2 at 1.23 V vs. RHE. The deposited BiVO4 represents tiny and long petals, similar to “needle” nanostructures, which is embedded closely into compact agglomerates. Such morphology enables the BiVO4 films to perform efficiently as photoanode in PEC cells. Besides, high crystallinity is detected from the sharp peaks of XRD and Raman analysis, as well as good light absorption capability that are the main contributors to the enhancement of PEC performance. In addition to the facile fabrication offered by electrodeposition method, the non-toxic attributes and the impressive PEC performance of the optimum BiVO4 layer could serve as an interesting option for other applications such as gas sensors, solar cells, degradation of pollutants and photocatalytic water splitting.

Acid-Resistant BiVO4 Photoanodes: Insolubility Control by Solvents and Weak W Diffusion in the Lattice.

We have revealed for the first time that BiVO4 photoanodes can be used even in strong acid media by mixing organic solvents into the electrolyte and depositing multilayers with a WO3 bottom layer. In general, the BiVO4 photoanodes are photocorrosive, especially in acid solutions. However, this shortcoming has been overcome using a combination of the two aforementioned modifications. We deduced that the contribution of each mixing organic solvent for the anti-photocorrosion of BiVO4 in sulfuric acid solutions can be evaluated on the basis of a new empirical indicator that incorporates molecular density, the Hansen solubility parameter, and molecular polarizability. Acetone and tert-butyl alcohol were especially promising solvents for stabilizing BiVO4 in acid media. We confirmed that the mixed organic solvents stabilized surface-emergent Bi oxide species as a passivation layer, which was generated via multilayering with a WO3 bottom layer. During heat treatment in the fabrication process, W weakly diffused into the BiVO4 layer and a Bi oxide layer was formed on the outermost surface because of the Bi segregation that arose from the charge compensation between W6+ and V5+ in the BiVO4 lattice. The surface Bi oxide layer, which was protected by the mixed organic solvents, steadily served as a passivation layer for anti-photocorrosion of the underlying BiVO4 layer. We have confirmed that the BiVO4/WO3 photoanodes in acetone-mixed aqueous sulfuric acid solution reliably functioned for a photoelectrochemical reaction under simulated sunlight illumination, and photoelectrochemical production of S2O82- ions was confirmed under light irradiation at λ > 480 nm. These results suggest that the BiVO4-based photoanodes have significant potential for use in acid media in conjunction with very straightforward modifications.

In Situ Induced Crystalline-Amorphous Heterophase Junction by K+ to Improve Photoelectrochemical Water Oxidation of BiVO4.

Solar water splitting is one of the most efficient technologies to produce H2, which is a clean and renewable energy carrier. Photoanodes for water oxidation play the determining roles in solar water splitting, while its photoelectrochemical (PEC) performance is severely limited by the hole injection efficiency at the interface of semiconductor/electrolyte. To address this problem, in this research, by employing BiVO4 as the model semiconductor for photoanodes, we develop a novel, facile, and efficient method, which simply applies K cations in the preparation process of BiVO4 photoanodes, to in situ induce a crystalline-amorphous heterophase junction by the formation of an amorphous BiVO4 layer (a-BiVO4) on the surface of the crystalline BiVO4 (c-BiVO4) film for PEC water oxidation. The K cation is the key to stimulate the formation of the heterophase, but not incorporated in the final photoelectrodes. Without sacrificing the light absorption, the in situ formed a-BiVO4 layer accelerates the kinetics of the hole transfer at the photoanode/electrolyte interface, leading to the significantly increased efficiency of the surface hole injection to water molecules. Consequently, the BiVO4 photoanode with the crystalline-amorphous heterophase junction (a-BiVO4/c-BiVO4) exhibits almost twice the photocurrent density at 1.23 V (vs reversible hydrogen electrode) for water oxidation than the bare c-BiVO4 ones. Such advantages from the crystalline-amorphous heterophase junction are still effective even when the a-BiVO4/c-BiVO4 is coated by the cocatalyst of FeOOH, reflecting its broad applications in PEC devices. We believe this study can supply an efficient and simple protocol to enhance the PEC water oxidation performance of photoanodes, and provide a new strategy for the potential large-scale application of the solar energy-conversion related devices.

Charge carrier separation and enhanced PEC properties of BiVO4 based heterojunctions having ultrathin overlayers

The photoelectrochemical performance of a BiVO4 photoanode is limited by its poor charge transport properties, despite other useful optical absorption properties. Modifying the surface charge transport properties by forming heterojunction of BiVO4 with other metal oxides layers having ultralow thickness is a promising route, as it may facilitate charge separation/transport without affecting other properties of BiVO4. In this study, the structural, optical and PEC properties of heterojunction of BiVO4 having ultrathin overlayers of Fe2O3, MoO3 and ZnO has been investigated. The electrochemical impedance (via electrochemical impedance spectra in PEC cell) and surface photovoltage (using KPFM) measurements indicates improved charge transport owing to staggered band alignment and favourable band bending in case of BiVO4/MoO3 heterojunction as compared to pristine BiVO4, BiVO4/Fe2O3 and BiVO4/ZnO heterojunctions. Enhanced photocurrent density in BiVO4/MoO3 of ~0.22 mA/cm2 at 1.23 VRHE which is 6 times as compared to pristine BiVO4 layers has been observed. The results of the present study show that by forming heterojunction with a suitable semiconductor material can be used to enhance the PEC response by modifying the surface charge transfer characteristics and there is a large possibility of using other semiconductor materials for further investigations and improvement.

Atomic Layer Deposition Seeded Growth of Rutile SnO2 Nanowires on Versatile Conducting Substrates.

Extended and oriented rutile nanowires (NWs) hold great promise for numerous applications because of their various tunable physicochemical properties in air and/or solution media, but their direct synthesis on a wide range of conducting substrates remains a significant challenge. Their device performance is governed by relevant NW geometries that cannot be fully controlled to date by varying bulk synthetic conditions. Herein, orientation engineering of rutile SnO2 NWs on a variety of conducting substrates by atomic layer deposition (ALD) seeding has been investigated. The seeded growth controls the nucleation event of the NW, and thicknesses and crystallographic properties of seed layers are the key parameters toward tuning the NW characteristics. The seed layers on carbon cloth produce NWs with highly enhanced electrochemically active surface area, which would show efficient electrochemical CO2 reduction. In addition, the hierarchical architecture resulted from the seeded growth of NWs on SnO2 nanosheets allows thin layers of BiVO4, forming a heterojunction photoanode, which shows a record charge separation efficiency of 96.6% and a charge-transfer efficiency of 90.2% at 1.23 V versus the reversible hydrogen electrode among, to date, the reported BiVO4-based photoanodes for water oxidation. Our study illustrates that such a versatile interfacial engineering effort by the ALD technique would be promising for further wide range of practical applications.

Photoelectrodeposition of BiVO4 layer on FTO/WO3 photoanodes for highly efficient photoelectrocatalytic chemical oxygen demand sensor applications

The research focus is on developing the photoelectrocatalytic (PEC) technique to obtain the simple, rapid, and nontoxic method for chemical oxygen demand (COD) sensor application. We have developed the heterojunction of a WO3/BiVO4 layer deposition on a fluorine-doped tin oxide (FTO) substrate using an electrodeposition method. The highlight of this development is the capability to immobilize a BiVO4 layer on the FTO/WO3 semiconductor electrode through our novel photoelectrodeposition method. A FTO/WO3/BiVO4 characteristics were studied to confirm the chemical composition, crystalline structure, morphology, optical properties, and charge transfer resistance. The results showed that the high efficiency of the BiVO4 layer deposited on the FTO/WO3 electrode improved the visible light absorption, surface morphology, and charge transfer rate and enhanced the PEC activities over the FTO/WO3 electrode by up to 2.5 times. The FTO/WO3/BiVO4 electrode was applied as a photoanode for COD determination using the designed PEC cell. The developed PEC cell exhibits relative standard deviation of 2.03% and percentage recovery of 98%, which indicate the method’s high precision and accuracy for COD determination. The proposed PEC cell for the COD sensor represents a simple, rapid, low-cost, environmentally friendly, and highly efficient method for COD monitoring in a wastewater treatment system.

Strengthened absorption of ultra-thin film bismuth vanadate using a motheye-structured triple-deck photoanode

Bismuth vanadate (BiVO4) is one of the most promising materials used in photoelectrochemical cells (PEC cells), which are significant generators of clean energy. As with many promising materials used as photoanodes, the main problem limiting the efficiency of BiVO4-based photoanodes is the trade-off between their large light penetration depth and small diffusion length. To reduce this gap, various methods have been investigated to improve the absorption efficiency of ultra-thin BiVO4 layers, including template-assisted nanostructuring. In this study, we have implemented a densely packed sub-wavelength-scale nanocone array inspired by the motheye morphology using a direct printing method. Subsequently, we fabricated a series of triple-deck hierarchical photoanodes using a motheye template via the successive deposition of Au, SnO2, and BiVO4. The fabricated motheye structures exhibit a gradual change in their refractive index, which is excellent for reducing the reflection of high refractive index materials. In addition, the synergy between the light trapping effects of the nanocone array and gap-plasmon structure (reflector/spacer/antenna) maximizes the absorption of incident solar light. Due to this enhancement, a current density of 1.48 mA/cm2 was obtained using a thin layer of BiVO4 (200 nm) at 1.23 V vs. RHE under a simulated solar light (AM 1.5G). Our results can be applied toward many promising candidate materials used for photoanode and optoelectronic devices, where poor electronic properties and high reflectivity limit the absorption and power generation efficiencies.

Bismuth vanadate thin films for efficient photoelectrochemical water splitting

Monoclinic bismuth vanadate has attracted much attention as one of the efficient photoanode materials that can harvest a wide range of visible light to split water efficiently. In this study, we report the preparation of nanoporous BiVO4 via wet chemical approach coupled with dip-coating technique. The monoclinic scheelite phase of BiVO4 is revealed by X-ray diffraction (XRD). Characterisation techniques like Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM) have been analysed and confirmed the formation of BiVO4 layers on FTO. Photoelectrochemical studies of BiVO4 thin films have been performed in a three-electrode potentiostat system, illuminated under visible light-emitting diode (LED) source of intensity 100 mW/cm2. The optimised 10 layered BiVO4 thin film with average thickness of ~ 300 nm shows an optimum photocurrent density of ~ 0.67 mA/cm2 at 1.23 V vs RHE and photoconversion efficiency of 0.4% at 1.23 V vs RHE as compared with different layered BVO photoanodes. The measurements of flat band potential and confirmation of n-type behaviour of BiVO4 semiconductors were carried out by Mott–Schottky analysis. Electrochemical impedance spectroscopy (EIS) study clearly indicate the less charge transfer resistance and high hole transfer mobility of optimised BiVO4 photoanode films.

The Improved Photoelectrochemical Performance of WO3/BiVO4 Heterojunction Thin‐Film Photoanodes via Thermal Treatment

Improvement in the photoelectrochemical (PEC) performance of WO3/BiVO4 heterojunction photoanodes is achieved by thermal treatment. The heterostructure systems consist of WO3 and BiVO4 layers spin coated onto fluorine‐doped tin oxide (FTO)‐coated glass substrates. The morphology and optical properties are modified by varying annealing conditions and calcining time. The crystal structure, morphology, and optical properties are studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and UV–vis spectroscopy, respectively. The results show that the WO3/BiVO4 photoanodes obtain an interconnected structure which helps promote the PEC activity by increasing the active area for reaction and shortening the distance for carrier diffusion. Also, the preannealing treatment can improve film qualities, namely crystallinity, uniformity, and optical absorbance, leading to an enhancement of the PEC performance. The optimal thermal treatment is preannealing at 60 °C for 15 min, followed by calcining at 400 °C for 5 h. The photoanode with such an optimal treatment exhibits the highest photocurrent density under light‐emitting diode (LED) illumination, and the efficiency is increased by 3–4 times compared with the others. Herein, a simple method is offered to improve the PEC performance of a heterojunction photoelectrode.

Controlled nanostructured morphology of BiVO4 photoanodes for efficient on-demand catalysis in solar water-splitting and sustainable water-treatment

Improving the kinetic properties of Bismuth vanadate (BiVO4) by nanoparticles or controlling the morphology of decagonal particles with crystal facets is receiving strong interest. Accordingly, we report an effective water-splitting and -purification system based on the photocatalytic performance of BiVO4 using a combined nano-structured morphology and crystal facets. BiVO4 thin film spin-coated at different Bi/V concentrations (viz. 1, 2, and 3) revealed a drastic change from nanoparticle (multifacet) to combined nanostructured morphology i.e., nanoparticles and sheet-like (decagonal facet). Such a morphology with multi-crystal facet in which {0 1 0} and {1 1 0} planes are prevalently active surfaces for Bi/V = 3 sample was found to disrupt the laminar boundary layer effectively, as confirmed from the lower contact-angle. Moreover, improved intercalation of the electrolyte in the nanoporous BiVO4 layer resulted in excellent photoelectrochemical performance with a photocurrent density of 1.98 mA/cm2 (@1.23 VRHE) and on-set potential of 0.40 VRHE in hole-scavenger compared to simple morphology. Congo-red (CR) and methylene-blue (MB) dye remediation under solar-radiation indicated an excellent degradation efficiency of 86 % in 90 min and 96 % in 300 min, respectively. Interestingly, the dual nanostructured morphology maintained consistent performance in ~5 (CR) and 9 (MB) repeated batch runs, demonstrating their high photocatalytic activity under visible-light and good durability in repeated use. Our results suggest that changes in the Bi/V ratio help tailoring the crystal facet from the {0 1 0} to a combined {0 1 0} and {1 1 0} with the evolution of dual nanostructured morphology, which increases the charge-transfer efficiency and is beneficial for efficient water-splitting and water-treatment processes.

Facile loading of cobalt oxide on bismuth vanadate: Proved construction of p-n junction for efficient photoelectrochemical water oxidation

Cobalt oxide is an excellent water oxidation cocatalyst used in photoelectrochemical (PEC) water splitting field. Finding a facial way to load cobalt oxide on a semiconductor anode is important to effectively realize PEC water splitting on a large scale. In this work, a simple impregnation and calcination method is developed to fabricate CoOx/BiVO4 anode. The constructed CoOx/BiVO4 anode provides a photocurrent of 3.1 mA cm−2 at 1.23 V vs. RHE, about 2.8 times that of BiVO4 anode (1.1 mA cm−2). Furthermore, both the charge separation and injection efficiency are improved by loading CoOx nanoparticles onto the BiVO4 layer. Importantly, input voltage–output current characteristic curves are used for the first time to prove the formation of p-n junction between CoOx and BiVO4, which benefits to the separation of photogenerated holes and electrons. All results indicate that the impregnation and calcination method is efficacious for facile fabrication of CoOx/BiVO4 photoanode with high performance.

Revealing the relationship between photoelectrochemical performance and interface hole trapping in CuBi2O4 heterojunction photoelectrodes.

p-Type CuBi2O4 is considered a promising metal oxide semiconductor for large-scale, economic solar water splitting due to the optimal band structure and low-cost fabrication. The main challenge in utilizing CuBi2O4 as a photoelectrode for water splitting, is that it must be protected from photo-corrosion in aqueous solutions, an inherent problem for Cu-based metal oxide photoelectrodes. In this work, several buffer layers (CdS, BiVO4, and Ga2O3) were tested between CuBi2O4 and conformal TiO2 as the protection layer. RuOx was used as the co-catalyst for hydrogen evolution. Factors that limit the photoelectrochemical performance of the CuBi2O4/TiO2/RuOx, CuBi2O4/CdS/TiO2/RuOx, CuBi2O4/BiVO4/TiO2/RuOx and CuBi2O4/Ga2O3/TiO2/RuOx heterojunction photoelectrodes were revealed by comparing photocurrents, band offsets, and directed charge transfer measured by modulated surface photovoltage spectroscopy. For CuBi2O4/Ga2O3/TiO2/RuOx photoelectrodes, barriers for charge transfer strongly limited the performance. In CuBi2O4/CdS/TiO2/RuOx, the absence of hole traps resulted in a relatively high photocurrent density and faradaic efficiency for hydrogen evolution despite the presence of pronounced deep defect states at the CuBi2O4/CdS interface. Hole trapping limited the performance moderately in CuBi2O4/BiVO4/TiO2/RuOx and strongly in CuBi2O4/TiO2/RuOx photoelectrodes. For the first time, our results show that hole trapping is a key factor that must be addressed to optimize the performance of CuBi2O4-based heterojunction photoelectrodes.

Artificial photosynthesis for alcohol and 3-C compound formation using BiVO4-lamelar catalyst

The high levels of atmospheric CO2 transformed this compound in a preoccupant pollutant. However, a wide range of semiconductors, including bismuth vanadate (BiVO4), can be applied for CO2 reduction aiming generation of fuels. This work reports the optimization of the BiVO4 layer synthesis by microwave system using factorial experimental design, where the variables time (5 to 15 min) and temperature (120 to 160 °C) were studied. For evaluation purposes, the materials synthetized were applied in photocatalytic reduction of CO2. All the BiVO4 materials analyzed promoted the formation of methanol. The best condition was obtained under the material synthesized at 160 °C with 15 min of reaction, where 1.5 mmol L−1 gcat−1 of methanol was produced after 120 min of photocatalysis. For the first time, acetone formation was observed in this kind of material. The best condition for acetone production was acquire with the material prepared at 140 °C with 10 min of synthesis, where 0.030 mmol L−1 gcat−1 was generated after 240 min of CO2 reduction. Differences in methanol concentration obtained among the samples were probably related to crystallographic patterns of the material, once the presence of Bi2O3 or other BiVO4 crystallographic species may affect the efficiency of the material. The results obtained in this work show that the use of BiVO4 layer semiconductor prepared by microwave system for CO2 reduction leads to the generation of high amounts of methanol under just UV–vis light incidence, aside from promoting the production of acetone.

Visible light illuminated high-performance WO3-TiO2-BiVO4 nanocomposite photoanodes capable of energy self-storage for photo-induced cathodic protection

In this work, WO3-TiO2-BiVO4 nanocomposite photoanodes are prepared, enabling photoelectrochemical cathodic protection (CP) under visible light illumination, while the energy self-storage capability makes the photo-induced CP functional in darkness. The outer BiVO4 layer causes an enhanced optical absorption of visible light for photoelectrochemical reaction. The inner WO3 layer is charged with photoelectrons and discharged in darkness. The nanocomposite photoanode can cathodically polarize 304 stainless steel by 300 mV compared to its corrosion potential under visible light. In darkness, the stainless steel can also be polarized by 130 mV cathodically in chloride solutions for effective corrosion protection.