Preparation of Bi-Based Ternary Oxide Photoanodes BiVO4, Bi2WO6, and Bi2Mo3O12 Using Dendritic Bi Metal Electrodes

Flexible and Dynamic Light-Guided Electrochemiluminescence for Spatiotemporal Imaging of Photoelectrochemical Processes on Hematite

Here, we report an electrochemiluminescence (ECL)-based approach for imaging of local photoelectrochemical processes on hematite in a spatially and temporally controlled manner. The local processes were guided by flexible and dynamic light illumination, not requiring any prepatterned conductive features or photomasks, with a digital micromirror device (DMD). The imaging approach was based on light-addressable electrochemical reactions on hematite, resulting in photoinduced ECL emission for spatiotemporally resolved imaging of photoelectrochemical processes selectively guided by light illumination. After clarifying the capability of hematite as a photosensitive electrode, we validated that the illuminated hematite exhibited stable light-guided ECL emission in correspondence with the illuminated area, with a spatial resolution of 0.8 μm and a temporal resolution of 1 μs, even over a long period of 6 h. More importantly, this study exemplified the simple yet effective ECL-based approach for electrochemical visualization of local photoelectrochemical processes guided by flexible and dynamic adjustment of light illumination in a spatiotemporally controlled way.

Peroxymonosulfate enhanced photoelectrocatalytic oxidation of organic contaminants and simultaneously cathodic recycling of silver

Degradation of organic contaminants with simultaneous recycling of Ag⁺ from silver-containing organic wastewater such as photographic effluents is desired. Although photoelectrocatalysis (PEC) technology is a good candidate for this type of wastewater, its reaction kinetics still needs to be improved. Herein, peroxymonosulfate (PMS) was employed to enhance the PEC kinetics for oxidation of phenol (PhOH) at the anode and reduction of Ag⁺ at the cathode. The degradation efficiency of phenol (PhOH, 0.1 mmol/L) was increased from 42.8% to 96.9% by adding 5 mmol/L PMS at a potential of 0.25 V. Meanwhile, the Ag (by wt%) deposited on the cathode was 28.1% (Ag₂O) in PEC process, while that of Ag (by wt%) was 69.7% (Ag⁰) by adding PMS. According to the electrochemistry analysis, PMS, as photoelectrons acceptor, enhances the separation efficiency of charges and the direct h⁺ oxidation of PhOH at the photoanode. Meantime, the increasing cathode potential avoided H₂ evolution and strongly alkaline at the surface of cathode, thus enabling the deposition of Ag⁺ in the form of metallic silver with the help of PMS. In addition, PMS combined with PEC process was effective in treating photographic effluents.

Laser-Reduced BiVO4 for Enhanced Photoelectrochemical Water Splitting

The present study proposes a laser irradiation method to superficially reduce BiVO4 photoelectrodes and boost their water oxidation reaction performance. The origin of this enhanced performance toward oxygen evolution reaction (OER) was studied using a combination of a suite of structural, chemical, and mechanistic advanced characterization techniques including X-ray photoelectron (XPS), X-ray absorption spectroscopy (XAS), electrochemical impedance spectroscopy (EIS), and transient absorption spectroscopy (TAS), among others. We found that the reduction of the material is localized at the surface of the sample and that this effect creates effective n-type doping and a shift to more favorable energy band positions toward water oxidation. This thermodynamic effect, together with the change in sample morphology to larger and denser domains, results in an extended lifetime of the photogenerated carriers and improved charge extraction. In addition, the stability of the reduced sample in water was also confirmed. All of these effects result in a two-fold increase in the photocurrent density of the laser-treated samples.

Preparing a dual-function BiVO4/NiFe-LDH composite photoanode for enhanced photoelectrocatalytic wastewater treatment and simultaneous hydrogen evolution

The proposed PEC degradation over the BiVO4/NiFe-LDH photoelectrode under visible light irradiation and simultaneous hydrogen evolution at the cathode.

Morphological influence of BiVO4 nanostructures on peroxymonosulfate activation for highly efficient catalytic degradation of rhodamine B

Bismuth vanadate (BiVO₄) nanostructured films were prepared and successfully applied for peroxymonosulfate (PMS) activation for the degradation of rhodamine B (RhB) in aqueous solution. The BiVO₄ thin films were obtained by thermal reaction between electrodeposited bismuth (Bi) films and vanadium precursor. The as-prepared BiVO₄ porous, nanoflowers, and cluster nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and BET analysis. The catalytic performance of BiVO₄ nanostructures has been carefully evaluated in activating PMS for the degradation of RhB. The nanoflower-like BiVO₄ nanostructures exhibit the best catalytic activity. Under optimized conditions, the complete catalytic degradation of RhB using BiVO₄ nanoflowers/PMS system was achieved in 17 min at room temperature as revealed by high-performance liquid chromatography (HPLC) analysis. Quenching experiments suggested that sulfate radicals are the main active species in the degradation process. Additionally, BiVO₄ catalyst remained stable without any apparent activity loss after five cycling runs.

Manipulating the Fate of Charge Carriers with Tungsten Concentration: Enhancing Photoelectrochemical Water Oxidation of Bi2 WO6

Bismuth tungstate (Bi₂ WO₆ ) thin film photoanode has exhibited an excellent photoelectrochemical (PEC) performance when the tungsten (W) concentration is increased during the fabrication. Plate-like Bi₂ WO₆ thin film with distinct particle sizes and surface area of different exposed facets are successfully prepared via hydrothermal reaction. The smaller particle size in conjunction with higher exposure extent of electron-dominated {010} crystal facet leads to a shorter electron transport pathway to the bulk surface, assuring a lower charge transfer resistance and thus minimal energy loss. In addition, it is proposed based on the results from conductive atomic force microscopy that higher W concentration plays a crucial role in facilitating the charge transport of the thin film. The "self-doped" of W in Bi₂ WO₆ will lead to the higher carrier density and improved conductivity. Thus, the variation in the W concentration during a synthesis can be served as a promising strategy for future W based photoanode design to achieve high photoactivity in water splitting application.

Preparation of Nanoparticle Porous-Structured BiVO4 Photoanodes by a New Two-Step Electrochemical Deposition Method for Water Splitting

In the synthesis method of a BiVO4 photoanode via BiOI flakes, a BiOI film is formed by electrochemical deposition in Step 1, and a vanadium (V) source solution is placed by drop-casting on the BiOI film in Step 2. Following this, BiVO4 particles are converted from the BiOI–(V species) precursors by annealing. However, it is challenging to evenly distribute vanadium species among the BiOI flakes. As a result, the conversion reaction to form BiVO4 does not proceed simultaneously and uniformly. To address this limitation, in Step 2, we developed a new electrochemical deposition method that allowed the even distribution of V2O5 among Bi–O–I flakes to enhance the conversion reaction uniformly. Furthermore, when lactic acid was added to the electrodeposition bath solution, BiVO4 crystals with an increased (040) peak intensity of the X-ray diffractometer (XRD) pattern were obtained. The photocurrent of the BiVO4 photoanode was 2.2 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) under solar simulated light of 100 mW/cm2 illumination. The Faradaic efficiency of oxygen evolution was close to 100%. In addition, overall water splitting was performed using a Ru/SrTiO3:Rh–BiVO4 photocatalyst sheet prepared by the BiVO4 synthesis method. The corresponding hydrogen and oxygen were produced in a 2:1 stoichiometric ratio under visible light irradiation.

An electrochemical sensing of phenolic derivative 4-Cyanophenol in environmental water using a facile-constructed Aurivillius-structured Bi2MoO6

Harmful chemicals are always found in the environment and it is necessary to construct a viable sensor to detect those chemicals. In order to construct an electrochemical sensing platform, designing an electrode using bismuth mixed oxides are more important and which grabbed more attention due to its high electrocatalytic ability and conductivity. In this literature, we report a facile synthesis of thorn apple like structured pure bismuth molybdate (Bi₂MoO₆) using a simple hydrothermal assisted one-step calcination method and we report a facile method to sense 4-cyanophenol by electrochemical technique. Bi₂MoO₆ modified (Glassy Carbon electrode) GCE possess two linear ranges 0.1-39.1 µM and 46.6-110.1 µM with excellent detection limit 0.008297 µM and 0.01097 µM. Also, this novel sensor is steady with good stability, repeatability, and reproducibility. Successfully, the environmental water sample is analyzed as a real sample with a feasible and quantification results which were compared with HPLC analysis.

Hybrid Density Functional Theory Study of Native Defects and Nonmetal (C, N, S, and P) Doping in a Bi2WO6 Photocatalyst

Native defects and nonmetal doping have been shown to be an effective way to optimize the photocatalytic properties of Bi2WO6. However, a detailed understanding of defect physics in Bi2WO6 has been lacking. Here, using the Heyd-Scuseria-Ernzerhof hybrid functional defect calculations, we study the formation energies, electronic structures, and optical properties of native defects and nonmetal element (C, N, S, and P) doping into Bi2WO6. We find that the Bi vacancy (Bivac), O vacancy (Ovac), S doping on the O site (SO), and N doping on the O site (NO) defects in the Bi2WO6 can be stable depending on the Fermi level and chemical potentials. By contrast, the substitution of an O atom by a C or P atom (CO, PO) has high formation energy and is unlikely to form. The calculated electronic structures of the Bivac, Ovac, SO, and NO defects indicate that the band-gap reduction of Ovac 2+, Bivac 3-, and SO defects is mainly due to forming shallow impurity levels within the band gap. The calculated absorption coefficients of Ovac 2+, Bivac 3-, and SO show strong absorption in the visible light region, which is in good agreement with the experimental results. Hence, Ovac 2+, Bivac 3-, and SO defects can improve the adsorption capacity of Bi2WO6, which helps enhance its photocatalytic performance. Our results provide insights into how to enhance the photocatalytic activity of Bi2WO6 for energy and environmental applications through the rational design of defect-controlled synthesis conditions.

Enhanced photoelectrocatalytic degradation of bisphenol a by BiVO4 photoanode coupling with peroxymonosulfate

Peroxymonosulfate (PMS) was introduced into a photoelectrocatalytic (PEC) system with a bismuth vanadate (BiVO₄) photoanode to enhance the PEC oxidation of bisphenol A (BPA). With the addition of 5 mM PMS, the degradation efficiency of 10 mg/L BPA was significantly improved from 24.2% to 100.0% within 120 min and the side reaction of O₂ evolution was avoided at a potential as low as 0.25 V. The electron spin resonance and radicals quenching results suggested that photogenerated holes instead of SO₄^•- and OH were primarily responsible for the BPA degradation. To further explore the role of PMS, a photocatalytic fuel cell with the structure of BiVO₄ (photoanode)|10 mg/L BPA|proton exchange membrane (separator)|5 mM PMS|Pt (cathode) was constructed and demonstrated that PMS played a key role as electrons acceptor instead of the precursor of SO₄^•-. The PEC tests including open-circuit potential, linear sweep voltammetry and electrochemical impedance spectroscopy indicated that a more efficient separation of photogenerated charges was achieved in the PEC process with the help of PMS, thus generating more photogenerated holes for enhanced BPA degradation. This work may provide a novel way to enhance the separation of photogenerated charges at the photoanode.

Current progress in developing metal oxide nanoarrays-based photoanodes for photoelectrochemical water splitting

Solar energy driven photoelectrochemical (PEC) water splitting is a clean and powerful approach for renewable hydrogen production. The design and construction of metal oxide based nanoarray photoanodes is one of the promising strategies to make the continuous breakthroughs in solar to hydrogen conversion efficiency of PEC cells owing to their owned several advantages including enhanced reactive surface at the electrode/electrolyte interface, improved light absorption capability, increased charge separation efficiency and direct electron transport pathways. In this Review, we first introduce the structure, work principle and their relevant efficiency calculations of a PEC cell. We then give a summary of the state-of the-art research in the preparation strategies and growth mechanism for the metal oxide based nanoarrays, and some details about the performances of metal oxide based nanoarray photoanodes for PEC water splitting. Finally, we discuss key aspects which should be addressed in continued work on realizing high-efficiency metal oxide based nanoarray photoanodes for PEC solar water splitting systems.

Carbon dots sensitized 2D-2D heterojunction of BiVO4/Bi3TaO7 for visible light photocatalytic removal towards the broad-spectrum antibiotics

Focused on the removal of the complicated residual antibiotic in aqueous environment, in this work, a novel carbon dots (C-dots) sensitized 2D-2D heterojunction of BiVO₄/Bi₃TaO₇ were assembled through a simple hydrothermal process. The characteristic by TEM, SEM, and XPS confirmed C-dots evenly anchored on the surface of BiVO₄/Bi₃TaO₇ heterojunction. The as-prepared C-dots/BiVO₄/Bi₃TaO₇ showed superior performance for the degradation of the various antibiotics under visible light illumination. When the concentration of C-dots in the composite is 3 wt.%, the photodegraded rates are obtained to be 91.7%, 89.3%, 87.1%, for tetracycline (TC), amoxicillin (AMX) and ciprofloxacin (CIP), respectively, without significant deactivation during consecutive ten recycle experiments. Furthermore, by assessing the antibiotics mixture solution of TC, AMX and CIP, it is proposed that the prepared samples are potentially effective for the wastewater effluents. A probable mechanism was reasonably proposed. The improved photocatalytic activities could be attributed to the unique construction of the C-dots mediated heterojunction, which could expedite electron migration, improve light harvesting capacity and enhance charge separation efficiency. The present investigation may provide a new perspective to design C-dots mediated heterojunction which could be a potential visible-light-driven photocatalysts for the better practical applications in remediation of broad-spectrum antibiotic residues.

Elaborately Modified BiVO4 Photoanodes for Solar Water Splitting

Photoelectrochemical (PEC) cells for solar-energy conversion have received immense interest as a promising technology for renewable hydrogen production. Their similarity to natural photosynthesis, utilizing sunlight and water, has provoked intense research for over half a century. Among many potential photocatalysts, BiVO₄ , with a bandgap of 2.4-2.5 eV, has emerged as a highly promising photoanode material with a good chemical stability, environmental inertness, and low cost. Unfortunately, its charge transport properties are modest, at most a hole diffusion length (L_p ) of ≈70 nm. However, recent rapid developments in multiple modification strategies have elevated it to a position as the most promising metal oxide photoanode material. This review summarizes developments in BiVO₄ photoanodes in the past 10 years, in which time it has continuously broken its own performance records for PEC water oxidation. Effective modification techniques are discussed, including synthesis of nanostructures/nanopores, external/internal doping, heterojunction fabrication, surface passivation, and cocatalysts. Tandem systems for unassisted solar water splitting and PEC production of value-added chemicals are also discussed.

Facile synthesis of hierarchically nanostructured bismuth vanadate: An efficient photocatalyst for degradation and detection of hexavalent chromium

Heterostructured nanomaterials can paid more significant attention in environmental safety for the detection and degradation/removal of hazardous toxic chemicals over a decay. Here, we report the preparation of hierarchically nanostructured shuriken like bismuth vanadate (BiVO₄) as a bifunctional catalyst for photocatalytic degradation and electrochemical detection of highly toxic hexavalent chromium (Cr(VI)) using the green deep eutectic solvent reline, which allows morphology control in one of the less energy-intensive routes. The SEM results showed a good dispersion of BiVO₄ catalyst and the HR-TEM revealed an average particle size of ca. 5-10 nm. As a result, the BiVO₄ exhibited good photocatalytic activity under UV-light about 95% reduction of Cr(VI) to Cr(III) was observed in 160 min. The recyclability of BiVO₄ catalyst exhibited an appreciable reusability and stability of the catalyst towards the photocatalytic reduction of Cr(VI). Also, the BiVO₄-modified screen printed carbon electrode (BiVO₄/SPCE) displayed an excellent electrochemical performance towards the electrochemical detection of Cr(VI). Besides, the BiVO₄/SPCE demonstrated tremendous electrocatalytic activity, lower linear range (0.01-264.5 μM), detection limit (0.0035 μM) and good storage stability towards the detection of Cr(VI). Importantly, the BiVO₄ modified electrode was also found to be a good recovery in water samples for practical applications.

Oxygen-deficient bismuth tungstate and bismuth oxide composite photoanode with improved photostability

A homogeneous layer of Bi₂O₃-Bi₁₄WO₂₄ composite (BWO/Bi₂O₃) thin film was fabricated using a combination of electrodeposition and thermal treatment. The evenly distributed Bi₁₄WO₂₄ component within the Bi₂O₃ layer was found to be important in stabilising the photoelectrochemical performances of Bi₂O₃ photoanode by promoting the photoelectron transport. The unmodified Bi₂O₃ suffered from severe photocorrosion as proven by X-ray diffraction (XRD) and inductively coupled plasma (ICP) analyses while the composite thin film was active without noticeable activity decay for at least 3 h of illumination. This strategy might be applicable to other photocatalysts with stability issues.

Cobalt Hexacyanoferrate on BiVO4 Photoanodes for Robust Water Splitting

The efficient integration of photoactive and catalytic materials is key to promoting photoelectrochemical water splitting as a sustainable energy technology built on solar power. Here, we report highly stable water splitting photoanodes from BiVO₄ photoactive cores decorated with CoFe Prussian blue-type electrocatalysts (CoFe-PB). This combination decreases the onset potential of BiVO₄ by ∼0.8 V (down to 0.3 V vs reversible hydrogen electrode (RHE)) and increases the photovoltage by 0.45 V. The presence of the catalyst also leads to a remarkable 6-fold enhancement of the photocurrent at 1.23 V versus RHE, while keeping the light-harvesting ability of BiVO₄. Structural and mechanistic studies indicate that CoFe-PB effectively acts as a true catalyst on BiVO₄. This mechanism, stemming from the adequate alignment of the energy levels, as showed by density functional theory calculations, allows CoFe-PB to outperform all previous catalyst/BiVO₄ junctions and, in addition, leads to noteworthy long-term stability. A bare 10-15% decrease in photocurrent was observed after more than 50 h of operation under light irradiation.

Synthesis of α-Bi2Mo3O12/TiO2 Nanotube Arrays for Photoelectrochemical COD Detection Application

One-dimensional anodic TiO₂ nanotube arrays hold great potential as a photoelectrochemical sensor for the determination of chemical oxygen demand (COD). In this work, we report a warm synthesis of modified TiO₂ nanotube arrays with enhanced photoelectrochemical determination performance. Herein, a bismuth-based semiconductor (α-Bi₂Mo₃O₁₂) was introduced into TiO₂ nanotube arrays by sequential chemical bath deposition (CBD) at room temperature. Field-emission scanning electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy were used to investigate the morphologies, structures, and elemental analysis of the products. The photoelectrochemical properties of TiO₂ and α-Bi₂Mo₃O₁₂/TiO₂ NTAs were measured by amperometry and cyclic votammetry methods. The α-Bi₂Mo₃O₁₂/TiO₂ nanotube arrays decrease the background photocurrent and increase the current response to organics at the same time, both of which are beneficial to enhancing the photoelectrochemical detection performance. The optimized α-Bi₂Mo₃O₁₂/TiO₂ NTAs with enhanced photoelectrochemical detection performance can achieve a detection sensitivity of 2.05 μA·cm^-2/(mg·L^-1) and a COD detection range of 0.366-208.9 mg/L respectively. With the α-Bi₂Mo₃O₁₂ modification, the surface electrochemical reactions of TiO₂ NTAs were regulated, the mechanisms of which were also further studied.

Ultrafast fabrication of highly active BiVO4 photoanodes by hybrid microwave annealing for unbiased solar water splitting

Hybrid microwave annealing (HMA) with a silicon susceptor in a household microwave oven produces BiVO₄-based photoanodes of much improved performance in photoelectrochemical water oxidation in only 6 min relative to conventional thermal annealing in a traditional muffle furnace (FA) that needs a much longer time, 300 min. This technique can apply equally effectively to bare as well as modified BiVO₄ by Mo-doping, heterojunction formation with WO₃, and an oxygen evolution co-catalyst. Relative to FA, HMA forms BiVO₄ films of smaller feature sizes, higher porosity, and increased three dimensional roughness, which decrease the diffusion distance of holes to the surface and thereby increase mainly the bulk charge separation efficiency (η_bulk) of the photoanodes. Thus, the HMA-treated BiVO₄/WO₃ film achieves the state-of-the art η_bulk of ∼90% for water oxidation. Combination of a photoanode of NiOOH/FeOOH/BiVO₄/WO₃ (HMA, 6 min) with a 2p c-Si solar cell allows a solar to hydrogen conversion efficiency of ∼5.0% in unbiased overall water splitting, which is also comparable to the state-of-the-art for a similar material combination.

Cooperative Catalytic Effect of ZrO2 and α-Fe2 O3 Nanoparticles on BiVO4 Photoanodes for Enhanced Photoelectrochemical Water Splitting

Photoelectrochemical water splitting with metal oxide semiconductors offers a cost-competitive alternative for the generation of solar fuels. Most of the materials studied so far suffer from poor charge-transfer kinetics at the semiconductor/liquid interface, making compulsory the use of catalytic layers to overcome the large overpotentials required for the water oxidation reaction. Herein, we report a very soft electrolytic synthesis deposition method, which allows remarkably enhanced water oxidation kinetics of BiVO₄ photoanodes by the sequential addition of Zr and Fe precursors. Upon a heat treatment cycle, these precursors are converted into monoclinic ZrO₂ and α-Fe₂ O₃ nanoparticles, which mainly act as catalysts, leading to a five-fold increase of the water oxidation photocurrent of BiVO₄ . This method provides a versatile platform that is easy to apply to different semiconductor materials, fully reproducible, and facile to scale-up on large area conductive substrates with attractive implications for technological deployment.

Highly Enhanced Photoelectrochemical Water Oxidation Efficiency Based on Triadic Quantum Dot/Layered Double Hydroxide/BiVO4 Photoanodes

The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is ∼1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.

TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment

Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host-guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm(2) at 1.23 V vs RHE.

Bandgap Tunability in Sb-Alloyed BiVO₄ Quaternary Oxides as Visible Light Absorbers for Solar Fuel Applications

The challenge of fine compositional tuning and microstructure control in complex oxides is overcome by developing a general two-step synthetic approach. Antimony-alloyed bismuth vanadate, which is identified as a novel light absorber for solar fuel applications, is prepared in a wide compositional range. The bandgap of this quaternary oxide linearly decreases with the Sb content, in agreement with first-principles calculations.

Enhanced photoelectrocatalytic decomposition of copper cyanide complexes and simultaneous recovery of copper with a Bi2MoO6 electrode under visible light by EDTA/K4P2O7

Simultaneous photoelectrocatalytic (PEC) oxidation of cyanides and recovery of copper in a PEC reactor with a Bi(2)MoO(6) photoanode was investigated at alkaline conditions under visible light irradiation. The surface variation of the Bi(2)MoO(6) photoanode and titanium cathode was characterized. The Cu mass distribution onto the anode, in the solution, and onto the cathode was fully investigated. In the individual PEC oxidation of copper cyanides, the formation of a black copper oxide on the anode occurred. By keeping the initial cyanide concentration at 0.01 mM, the effect of EDTA/K(4)P(2)O(7) was examined at different molar ratios of EDTA/K(4)P(2)O(7) to cyanide. It was indicated that the oxidation of cyanides increased and simultaneous copper electrodeposition with zero value onto the cathode was feasible at pH 11. Under the optimal conditions, the total cyanide concentration was lowered from 250 to 5.0 mg/L, and the Cu recovery efficiency deposited onto the cathode was higher than 90%. Cyanate was the only product. The role of the photogenerated hole in the oxidation of cyanide ions was confirmed.

Mo-doped BiVO4 photoanodes synthesized by reactive sputtering

We report a scalable and reproducible method for reactive co-sputtering of Mo-doped BiVO4 thin films with broad compositional control. Optimal photoanode performance is achieved at a Mo concentration of 3 at. %. Incorporation of Mo promotes growth of large grains and reduces majority carrier transport limitations, resulting in maximum AM1.5G photocurrent densities of 3.5 mA cm(-2) at 1.23 V vs. RHE in pH 6.8 buffer solution containing 0.1 M Na2 SO3 as a hole scavenger. Operation as a front-illuminated water oxidation photoanode is achieved by balancing the operational stability, catalytic activity, and parasitic optical absorption of a FeOOH oxygen evolution catalyst. FeOOH/Mo:BiVO4 thin film photoanodes enable water oxidation under the front-side illumination conditions used in integrated tandem water splitting devices.

Nanostructured hexahedron of bismuth ferrite clusters: delicate synthesis processes and an efficient multiplex catalyst for organic pollutant degradation

(1) Synthesis: an evolution mechanism of NSCC-Bi₂Fe₄O₉viaa delicate synthesis processes; (2) application: visible-light photo-Fenton oxidation for organic pollutant removal and (3) multiplex catalysis: its catalytic mechanism in light or dark conditions.