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• A method for assessing inorganic semiconductor electronic properties is suggested. • The ER-EIS analysis allowed the estimation of the valence and conduction band edges. • CB (-3.94 eV) and VB (-6.48 eV) results of the BiVO 4 are agreement with the reported values. • The band gap from ER-EIS is in correspondence with optical measurements and reported values. Bismuth vanadate (BiVO 4) is a promising photoelectrochemical water-splitting semiconductor. This study focuses on elucidating the electronic structure of BiVO 4 by analyzing energy-resolved electrochemical impedance spectroscopy (ER-EIS) data. The primary objective is to demonstrate the effectiveness of the ER-EIS, which is typically applied to organic semiconductors, in estimating the band edge positions of BiVO 4 films deposited on FTO substrates. The impedance spectra analysis as a function of an applied overpotential permits an estimation of the density of states, where the limits correspond to the valence (VB) and conduction band (CB) edge positions that determine the redox reactions the semiconductor can promote. The energy difference between the CB and VB corresponds to the material's band gap (E g). The calculated E g using ER-EIS closely matches the reported optical properties of the material, and the energy positions of the VB and CB align with the reported values for BiVO 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • Morphology effect of bismuth vanadate (BiVO 4) based on nanostructures. • Efficient gas sensor of BiVO 4 nanostructures for environmental monitoring applications. • The present review focuses on morphology control for modifying surface atomic active sites and improving gas sensing properties. • This review aims to explore the impact of morphology on the gas-sensing sensitivity of BiVO 4 nanostructures with various morphologies. Industrial pollution and its associated activities have significantly increased air pollution levels, thereby posing a major threat to human health and the environment. The respiratory system is particularly affected due to air pollution, with harmful gases causing respiratory illnesses and even sudden death. Numerous regrettable events throughout history have occured due to the release of hazardous gases into the surrounding air. The need of installing effective gas sensors to sense the range of ignitable, toxic, and hazardous gases present in the atmosphere has been highlighted by the numerous gas tragedies that occur globally, including leaks from gas, chemicals, and smoke due to external sources. This review focuses on morphology control, for tailoring the surface properties of gas-sensing materials and to enhance their performance. Bismuth vanadate (BiVO 4) has been emerging as a particularly attractive material for gas sensing due to its unique properties, including narrow band gap energy, tunable morphology, and excellent electrical conductivity by controlling the morphology of BiVO 4 nanomaterials. Different synthesis methods used to prepare BiVO 4 nanostructures with diverse morphologies, such as nanorods, nanoparticles, hierarchical structures, bulky, fusiform, clavate, and flower-patterned were used to examine the morphological effects for gas sensing characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile BiVO 4 /CNTs nanocomposite is synthesized via Sono chemical strategy and employed comprehensively for OER capabilities. • It provides practical alternatives for constructing and tweaking a cost-effective electrocatalyst. • Results demonstrate that at 10 mA cm−2 current density, BiVO 4 /CNTs has lesser overpotential and Tafel slope value 237 mV and 81 mV dec−1 correspondingly. • The integrated composite BiVO 4 /CNTs exhibits remarkable stability and durability for 100 hours without any decrease in current density. The increasing demand of maintainable energy boosts researchers to develop reliable electrocatalysts for enhanced water splitting mechanisms. All the synthesized materials, including CNTs, BiVO 4 , and BiVO 4 /CNTs, were characterized utilizing a variety of methodologies to assist the structural, configurational, morphological, and topographical investigations. This work aims to create unique BiVO 4 /CNTs nanocomposite, which may have higher electrocatalytic activity then previous materials (81 mV dec−1 tafel slope and overpotential of 237 mV at 10 mAcm−2). The composite exhibits notable qualities, including extended stability lasting up to 100 h, a substantial electrochemically active surface area (ECSA) of 586.5 cm2, minimal charge transfer resistance (Rct) of 1.3 Ω, a low onset potential, a reasonably reduced overpotential, and a relatively modest Tafel slope. The synergistic interaction between CNTs and BiVO 4 is responsible for electrocatalyst's exceptional catalytic efficiency and unique stability for 100-hour retaining both morphological and structural features, showcasing structural integrity of BiVO4/CNTs nano-composite. The objective of this research is to split water into its component molecules using a nano-composite made, and may also useful for future applications. [ABSTRACT FROM AUTHOR]

Considering its outstanding cost-to-efficiency ratio, N-type bismuth vanadate (BiVO 4) is an ideal photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the widespread application of BiVO 4 is being hindered commercially by innate challenges such as its poor carrier mobility, short hole diffusion length, and sluggish oxidation chemistry. Herein, we report the unique integration of surficial oxygen vacancies (O vac) in conjunction with two-dimensional (2D) nickel-iron (NiFe) layered double hydroxide (LDH) nanosheets onto pristine BiVO 4 photoanode to tweak the charge transfer kinetics during water splitting. The introduction of oxygen vacancies efficiently modulates band energetics, amplifies light absorption, and augments the carrier density. Concurrently, the 2D NiFe-LDH nanosheets play a dual role by facilitating interfacial hole transfer, thereby reducing excessive defect states, and serving as a protective layer against photocorrosion, ultimately resulting in a notable improvement in solar-driven water oxidation efficiency. The results of PEC water-splitting experiments demonstrate that the BiVO 4 photoanode enriched with surficial oxygen vacancies and NiFe-LDH (BiVO 4 :O vac /NiFe-LDH) achieved a photocurrent density of 2.92 mA cm−2 with ∼3-fold enhancement compared with a pristine BiVO 4 photoanode. The engineered BiVO 4 system yielded an impressive photoconversion efficiency of 1.29 %, charge separation efficiency (η sep) > 40 %, and charge transport efficiency (η trans) > 35 %, clearly evidencing a boost in the charge dynamics of pristine BiVO 4. Furthermore, during long-term stability testing, BiVO 4 :O vac /NiFe-LDH retained 91 % of its initial photocurrent density for ∼20 h without any significant deterioration. This work sheds light on the role of integrating surface and interface engineering tactics for enhancing photo-induced charge transport in BiVO 4 , thereby providing efficient and stable PEC water splitting. [Display omitted] • Surface and interface-engineered BiVO 4 fabricated via economic routes. • Controlled oxygen vacancies enhanced carrier density in pristine BiVO 4. • The 2D-NiFe LDH facilitated hole transfer and protects BiVO 4 from photocorrosion. • The BiVO 4 :O vac /NiFe-LDH sample showed the highest photocurrent with ∼20 h stability. • Integration of multiple strategies synergistically boosted the PEC activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • BiVO 4 has emerged as a potential material for photoelectrochemical (PEC) water-splitting. • Key challenges for modification of BiVO 4 were reviewed. • Recent advances in transition metal-based materials doped onto BiVO 4 for PEC water-splittings were reviewed. • Transition metal-based materials doped onto BiVO 4 exhibited higher PEC water-splitting performance than the commercial BiVO 4. • Modification of BiVO 4 effectively reduced the energy barrier, negatively shifted the onset potential, and suppressed the carrier recombination. To address the significant depletion of fossil fuel reserves, hydrogen (H 2) fuel has emerged as a promising alternative energy source due to its eco-friendly nature and impressive efficiency. Over the years, research efforts have led to the development of various methods for producing H 2 , with a particular focus on photoelectrochemical (PEC) water-splitting. Impressively, the interest in bismuth vanadate (BiVO 4) photoanode has been a research focus lately ascribed to its photosensitive characteristic and high electron mobility. Moreover, doping of metals, defects engineering, morphology modification, and synthesis of heterojunction material strategies have been exercised to further improve its PEC water-splitting activity. Consequently, several reviews have been published on the PEC performance of BiVO 4 modified with these strategies. However, to the best of our knowledge, there has been no comprehensive review specifically focusing on the impact of transition metal-based materials on the PEC performance of BiVO 4. In this context, we present a critical review of the recent developments involving the modification of BiVO 4 photoanode with transition metal-based materials for PEC water-splitting. Several transition metals such as nickel (Ni), cobalt (Co), iron (Fe), and tungsten (W) have been used in the recent development of BiVO 4 -based photoanodes. Surprisingly, all of the modified BiVO 4 exhibited a substantial improvement in PEC activity with the photocurrent density at 1.23 V RHE reaching as high as 10.3 mA/cm2 has been reported in a previous study. Ultimately, this review highlights the promising potential of modified BiVO 4 for the PEC water-splitting application. [ABSTRACT FROM AUTHOR]

[Display omitted] • BiVO 4 nanostructures were prepared with an environmentally responsible methodology. • Green procedures were used to decorate with nitrogen-doped graphene and silver NPs. • Novel N-G/Ag/BiVO 4 exhibited the best photoinactivation of pathogenic microorganisms. • Novel N-G/Ag/BiVO 4 NS exhibited the highest performance in the CV degradation. • Photocatalytic activity achieved was using inexpensive and low-power blue LEDs. Bismuth vanadate (BiVO 4) is an attractive compound because of its visible light photocatalytic activity with a narrow energy gap of less than 2.4 eV. In addition, it has favorable band edge positions and is stable in an aqueous environment. Its photocatalytic activity can be translated for potential use for degradation of organic matter. To assess this activity, BiVO 4 combined with graphene (N-G/BiVO 4), silver (Ag/BiVO 4), or both of them (N-G/Ag/BiVO 4) were synthesized. These nanostructures (NSs) were characterized using physicochemical analyses. The NSs were tested for their capabilities to photodegrade crystal violet and inactivate bacteria. Results showed that N-G/Ag/BV exhibited the highest activity for degrading crystal violet, reaching 100 % of photodegradation within 60 min of light exposure, while N-G/BiVO 4 , BiVO 4 and Ag/BiVO 4 achieved 81, 89 and 95 % within 180 min, respectively. In the case of bacterial inactivation, the Ag/BiVO 4 NS completely photoinactivated E. coli within 60 min. The main oxidative species acting in the E. coli photoinactivation and CV photodegradation over the Ag/BiVO 4 and N-G/AgBiVO 4 NSs were identified as •O 2 – and h+. Also, the chemical stability and effective re-use of the photocatalysts were evaluated. In conclusion, the Ag/BV and N-G/Ag/BV catalysts possess high stability, making them potential candidates for wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Towards more sustainable synthesis of BiVO 4 /carbon materials. • BiVO 4 /carbon as visible-light activated photocatalyst for tetracycline degradation. • Recovery and reuse of BiVO 4 /carbon photocatalysts. Bismuth vanadate (BiVO 4) has gained attention for several applications, including photocatalysis applied to water purification technologies. This applies to the most stable BiVO 4 polymorph (monoclinic scheelite), exhibiting photocatalytic activity under visible-light irradiation. However, this semiconductor presents some limitations, namely the cost and low adsorption capacity for organic pollutants. Finding green chemical strategies aiming at a more sustainable use of this semiconductor is the subject of the present research. By the hydrothermal carbonization of κ-carrageenan, a biopolymer extracted from red seaweeds, we describe the preparation of monoclinic BiVO 4 supported on carbon spheres. These hybrid materials show visible-light photocatalytic activity to remove tetracycline (TC) in water through a hydroxyl radical mechanism. The hybrid photocatalysts feature adequate wavelength range for photon harvesting, good adsorption capacity, durability, and the ability to reuse in subsequent catalytic steps, thus making them less costly and more sustainable. [ABSTRACT FROM AUTHOR]

Photo-excited charge carriers play a vital role in photocatalysts and photovoltaics, and their dynamic processes must be understood to improve their efficiencies by controlling them. The photo-excited charge carriers in photocatalytic materials are usually trapped to the defect states in the picosecond time range and are subject to recombination to the nanosecond to microsecond order. When photo-excited charge carrier dynamics are observed via refractive index changes, especially in particulate photocatalytic materials, another response between the trapping and recombination phases is often observed. This response has always provided the gradual increase of the refractive index changes in the nanosecond order, and we propose that the shallowly trapped charge carriers could still diffuse and be trapped to other states during this process. We examined various photocatalytic materials such as TiO2, SrTiO3, hematite, BiVO4, and methylammonium lead iodide for similar rising responses. Based on our assumption of surface trapping with diffusion, the responses were fit with the theoretical model with sufficient accuracy. We propose that these slow charge trapping processes must be included to fully understand the charge carrier dynamics of particulate photocatalytic materials.

Nanostructures exhibit numerous merits to improve the efficiency in solar-to-energy conversion. These include shortened carrier collection pathways, an increased volume ratio between depletion layer and bulk, enhanced light capture due to multiple light scattering in nanostructures, and a high surface area for photochemical conversion reactions. In this study, we describe the synthesis of morphology-controlled W-doped BiVO4 by simply tuning the solvent ratio in precursor solutions. Planar and porous W-doped BiVO4 thin films were prepared and compared. The porous film, which exhibits increased surface area and enhanced light absorption, has displayed enhanced charge separation and interfacial charge injection. Our quantitative analysis showed an enhancement of about 50% of the photoelectrochemical performance for the porous structure compared to the planar structure. This enhancement is attributed to improved light absorption (13% increase), charge separation (14% increase), and interfacial charge injection (20% increase).

High-efficient photoelectrocatalytic direct ammonia oxidation reaction (AOR) conducted on semiconductor photoanodes remains a substantial challenge. Herein, we develop a strategy of simply introducing ppm levels of Cu ions (0.5-10 mg/L) into NH 3 solutions to significantly improve the AOR photocurrent of bare BiVO 4 photoanodes from 3.4 to 6.3 mA cm -2 at 1.23 V RHE , being close to the theoretical maximum photocurrent of BiVO 4 (7.5 mA cm -2 ). The surface charge-separation efficiency has reached 90 % under a low bias of 0.8 V RHE . This AOR exhibits a high Faradaic efficiency (FE) of 93.8 % with the water oxidation reaction (WOR) being greatly suppressed. N 2 is the main AOR product with FEs of 71.1 % in aqueous solutions and FEs of 100 % in non-aqueous solutions. Through mechanistic studies, we find that the formation of Cu-NH 3 complexes possesses preferential adsorption on BiVO 4 surfaces and efficiently competes with WOR. Meanwhile, the cooperation of BiVO 4 surface effect and Cu-induced coordination effect activates N-H bonds and accelerates the first rate-limiting proton-coupled electron transfer for AOR. This simple strategy is further extended to other photoanodes and electrocatalysts., (© 2023 Wiley-VCH GmbH.)

Photoelectrochemical (PEC) water splitting represents an attractive strategy to realize the conversion from solar energy to hydrogen energy, but severe charge recombination in photoanodes significantly limits the conversion efficiency. Herein, a unique BiVO 4 (BVO) nanobowl (NB) heterojunction photoanode, which consists of [001]-oriented BiOCl underlayer and BVO nanobowls containing embedded BiOCl nanocrystals, is fabricated by nanosphere lithography followed by in situ transformation. Experimental characterizations and theoretical simulation prove that nanobowl morphology can effectively enhance light absorption while reducing carrier diffusion path. Density functional theory (DFT) calculations show the tendency of electron transfer from BVO to BiOCl. The [001]-oriented BiOCl underlayer forms a compact type II heterojunction with the BVO, favoring electron transfer from BVO through BiOCl to the substrate. Furthermore, the embedded BiOCl nanoparticles form a bulk heterojunction to facilitate bulk electron transfer. Consequently, the dual heterojunctions engineered BVO/BiOCl NB photoanode exhibits attractive PEC performance toward water oxidation with an excellent bulk charge separation efficiency of 95.5%, and a remarkable photocurrent density of 3.38 mA cm -2 at 1.23 V versus reversible hydrogen electrode, a fourfold enhancement compared to the flat BVO counterpart. This work highlights the great potential of integrating dual heterojunctions engineering and morphology engineering in fabricating high-performance photoelectrodes toward efficient solar conversion., (© 2023 Wiley-VCH GmbH.)

The BiVO4 photoelectrochemical (PEC) electrode in tandem with a photovoltaic (PV) cell has shown great potential to become a compact and cost‐efficient device for solar hydrogen generation. However, the PEC part is still facing problems such as the poor charge transport efficiency owing to the drag of oxygen vacancy bound polarons. In the present work, to effectively suppress oxygen vacancy formation, a new route has been developed to synthesize BiVO4 photoanodes by using a highly oxidative two‐dimensional (2D) precursor, bismuth oxyiodate (BiOIO3), as an internal oxidant. With the reduced defects, namely the oxygen vacancies, the bound polarons were released, enabling a fast charge transport inside BiVO4 and doubling the performance in tandem devices based on the oxygen vacancy eliminated BiVO4. This work is a new avenue for elaborately designing the precursor and breaking the limitation of charge transport for highly efficient PEC‐PV solar fuel devices. [ABSTRACT FROM AUTHOR]

We present airbrush spray‐coating as a reproducible method for the preparation of Mo‐doped BiVO4 (Mo : BiVO4) as photoabsorber with different layer thicknesses and Mo content. Optimisation of layer thickness is aiming on diminishing limitations by the electronic conductivity within the photoabsorber, thus increasing the incident photon to current efficiency (IPCE) of the samples. Furthermore, the Mo to V ratio leading to the highest photocurrent density was determined, and the optimised Mo : BiVO4 samples were decorated with a variety of oxygen evolution reaction (OER) electrocatalysts such as cobalt phosphate and layered double hydroxides. A mass loading gradient of Ni−Fe LDH was sprayed on top of the Mo : BiVO4 photoanode for optimisation of the OER catalyst loading. The photocurrent density was enhanced by up to 5.8 times at 0.8 V vs. RHE in comparison with the pristine Mo : BiVO4 sample in absence of any OER electrocatalyst. [ABSTRACT FROM AUTHOR]

Biosynthesis of bismuth vanadate (BiVO4) nanorods was performed using dried fruit extracts of Hyphaene thebaica as a cost effective reducing and stabilizing agent. XRD, DRS, FTIR, zeta potential, Raman, HR-SEM, HR-TEM, EDS and SAED were used to study the main physical properties while the biological properties were established by performing diverse assays. The zeta potential is reported as − 5.21 mV. FTIR indicated Bi–O and V–O vibrations at 640 cm−1 and 700 cm−1/1120 cm−1. Characteristic Raman modes were observed at 166 cm−1, 325 cm−1 and 787 cm−1. High resolution scanning and transmission electron micrographs revealed a rod like morphology of the BiVO4. Bacillus subtilis, Klebsiella pneumonia, Fusarium solani indicated highest susceptibility to the different doses of BiVO4 nanorods. Significant protein kinase inhibition is reported for BiVO4 nanorods which suggests their potential anticancer properties. The nanorods revealed good DPPH free radical scavenging potential (48%) at 400 µg/mL while total antioxidant capacity of 59.8 µg AAE/mg was revealed at 400 µg/mL. No antiviral activity is reported on sabin like polio virus. Overall excellent biological properties are reported. We have shown that green synthesis can replace well established processes for synthesizing BiVO4 nanorods. [ABSTRACT FROM AUTHOR]

V2O5/BiVO4 cake-like microstructures with uniform diameter were successfully fabricated with excess NaVO3 in the reaction solution under hydrothermal conditions. As-fabricated V2O5/BiVO4 microstructures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, and Brunauer-Emmett-Teller (BET) surface area measurements. The possible formation mechanism of the cake-like V2O5/BiVO4 microstructure was proposed based on the morphological evolution versus the reaction time. The photocatalytic performance of the V2O5/BiVO4 composites was measured by studying the visible-light decomposition of rhodamine B (RhB) molecules in solution. The V2O5/BiVO4 composites exhibit an obviously enhanced photocatalytic activity compared to the pure BiVO4, as a result of the strengthened absorption ability in the visible-light region and the formation of heterojunction structure between V2O5 and BiVO4. This work presents a new way to develop BiVO4-based efficient photocatalysts in the application of wastewater treatment. [ABSTRACT FROM AUTHOR]

Monoclinic bismuth vanadate has been widely used as a promising n-type semiconductor for photoelectrochemical (PEC) water decomposition due to its high reserves, good stability in neutral solutions, and relatively narrow band gap. Here, we developed a simple method to prepare a thin NiOOH layer on the surface of BiVO 4 nanorod arrays. The heterostructured photoanode shows great enhancement for the photocurrent density of 2.7 mA cm−2 at 1.23 V vs. RHE, which is ~2.3 times higher than that of pristine BiVO 4 electrode, due to NiOOH as an efficient oxygen-releasing catalyst with abundant oxygen vacancies. The NiOOH/BiVO 4 photoanodes are systematically studied with X-ray diffraction, Raman, X-ray photoelectron spectra, scanning electron microscopy, transmission electron microscopy, and UV–vis diffuse-reflectance spectrum. The heterostructured photoanode shows excellent PEC activity, which can provide a promising and easy strategy to prepare such photoanode with high-efficient oxygen evolution co-catalysts. • An ultra-thin NiOOH layer on the surface of BiVO 4 was prepared. • The current density of NiOOH/BiVO 4 was 2.3 times higher than BiVO 4. • The NiOOH/BiVO 4 showed the ABPE of 0.68% at 0.8 V vs. RHE. • The NiOOH/BiVO 4 had super-duper PEC stability. [ABSTRACT FROM AUTHOR]

Visible light-active BiVO4 photocatalyst was successfully synthesized through a cyclic microwave irradiation method without further calcination process. The synthesized powder was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The BiVO4 powder revealed an excellent photocatalytic degradation of methylene blue under visible light irradiation. The degraded methylene blue was monitored by both UV-Vis spectrophotometer and absorbance in RGB channels. Similar decolorization percentage as well as pseudo first-order rate constant were achieved with high accuracy and sensitivity. The light absorption in RGB channels is an alternative simple and cartable way requiring lower amount of sample for detecting the dye degradation photocatalytic activity. [ABSTRACT FROM AUTHOR]

Nowadays, environment highly encounters various pollutants including toxic gases, organic volatiles and water pollutant. Many scientists have taken the effort to reduce or eliminate pollutant using photocatalytic materials. Due to good ferroelectric property in ferroelastic crystal as a result of the reduction in symmetry between the paraelastic and ferroelastic phases, it makes bismuth vanadate (BiVO4) one of attractive ferroelectric materials. In addition, BiVO4 with low optical band gap could be activated by visible light illumination so that it would be a potential candidate as a visible light driven photocatalyst. This work was carried out to synthesize BiVO4 nanoparticles by simple but effective method via sonochemical process through chemical route assisted by ultrasonic irradiation. The crystalline structure and surface morphologies of the synthesized products were observed by X-ray diffraction technique and Scanning Electron Microscope, respectively. Raman spectroscopy and Fourier Transform Infrared spectroscopy were used to approve the BiVO4 chemical bonding and relevant crystalline formation. Photocatalytic activity was studied by mean of the degradation of organic dye assigned as organic compound under visible light irradiation. [ABSTRACT FROM AUTHOR]

Pollution and the scarcity of water resources are considered major issues of concern in recent years. Treatment technology is important for reuse of water and wastewater, especially industrial wastewater. The photocatalytic process using semiconductors has emerged as a promising method in removing aqueous pollutants. Among the semiconductor photocatalysts, bismuth vanadate (BiVO4) is an effective visible light driven photocatalyst with various excellent properties such as narrow bandgap, resistance to corrosion, and low toxicity. In the past, much research was focused on synthesizing BiVO4 and enhancing its photocatalytic activity. A comprehensive discussion on synthesis and characterization (including morphology and structure) are presented in this review. Furthermore, the application of BiVO4 photocatalytic activity in water treatment is also discussed; the degradation of dye molecules and actual organic pollutants in the photocatalytic system under visible light irradiation is explained. This review is beneficial for further related research such as material development and pollution prevention. [ABSTRACT FROM AUTHOR]

• MWCNT/BiVO 4 photocatalysts were prepared by electro-spinning technology. • Calcination temperature affected degradation performance of MWCNT/BiVO 4 remarkably. • OH, O 2 − and carbon radical signals were detected after the light irradiation by EPR. • Six reaction pathways of OTC were proposed based on the results of UPLC–MS/MS. To enhance the photocatalytic performance of bismuth vanadate (BiVO 4) and reveal its catalytic mechanism, a multi-walled carbon nanotube photocatalyst (MWCNT/BiVO 4) was prepared by sol-gel preparation and an electro-spinning process. Oxytetracycline was used as the target trace persistent pollutant to research its potential degradation pathways catalyzed by MWCNT/BiVO 4. X-ray powder diffraction spectroscopy (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM) and field emission transmission electron microscopy (FE-TEM) were used to observe the crystalline phase, morphological structure of MWCNT/BiVO 4. The modification by MWCNTs caused changes of functional groups on the surface and a binding energy shift of Bi4f and V2p, as determined from X-ray photoelectron spectroscopy (XPS). Ultraviolet–visible diffuse reflectometry (UV–Vis DRS) revealed that the band gap became narrower and photoluminescence spectra suggested the recombination of photogenerated electron–hole pairs were inhibited after MWCNT modification. All of the characterizations showed enhancement of catalytic performance of MWCNT/BiVO 4. The results from the high-performance liquid chromatography (HPLC) indicated that the degradation rate of oxytetracycline had increased by 42.2% and reached 88.7% within 60 min. Electron paramagnetic resonance (EPR) signals of ·OH and ·O 2 − were detected and potential photocatalytic mechanisms of the photocatalysts were put forward. Six reaction pathways were proposed based on ultra-performance liquid chromatography triple-quadrupole tandem mass spectrometry (UPLC–MS/MS) results: demethylation (−14 Da), secondary alcohol oxidation (−2 Da), dehydration (−18 Da), hydroxylation (+16 Da), decarbonylation (−28 Da) and deamination (−15 Da). The present study provides a reference for the application of photocatalytic degradation by MWCNT/BiVO 4 on hard degradable substances in aquatic environment. [ABSTRACT FROM AUTHOR]

• The effect of photocharging treatment on the PEC performance of Mo-BVO is investigated. • Photocharged Mo-BVO shows a 0.25 V cathodic shift in onset potential. • Photocurrent density is improved 2.2-fold after photocharging treatment for 2% Mo-BVO. • Photocharging mainly passivates the surface of Mo-BVO rather than improving the poor charge transport. The two main drawbacks of monoclinic bismuth vanadate (BiVO 4 : BVO) as a photoanode, i.e., poor charge transport property and fast electron-hole recombination, were improved by simultaneous Mo doping and photocharged surface passivation methods. First, molybdenum-doped BiVO 4 (BiVO 4 : Mo) was prepared to control the donor concentration without producing any secondary phase. Subsequently, photocharging treatment of the Mo-BVO photoanode induced a cathodic shift in onset potential, ~0.15 V (0.75–0.6 V vs RHE) and improved the photocurrent density (~2.2-fold). Moreover, the photocharged 2% Mo-BVO photoanode exhibited an enhanced incident photon current efficiency (IPCE) of about 50% compared to only around 30% (440 nm > λ > 330 nm range) for the non-photocharged photoanode. Mott-Schottky analysis revealed that 2% Mo doping greatly increased the donor concentration (~1000-fold), whereas the photocharging technique only slightly increased the donor concentration (~1.5-fold). [ABSTRACT FROM AUTHOR]

• TACo is an effective cocatalyst to improve PEC water oxidation of BiVO 4. • TACo enhances the thermodynamic process of BiVO 4. • TACo effectively accelerates the kinetic process of BiVO 4. • The maximum ABPE value of BiVO 4 /TACo reaches up to 0.96 % at 0.74 V (vs. RHE). Bismuth vanadate (BiVO 4) has been regarded as a promising photoanode material for photoelectrochemical (PEC) water splitting owing to its low cost, and small band gap energy (∼2.4 eV). However, the achieved current density of the BiVO 4 photoanode remains far below its theoretical value (∼7.5 mA cm−2) because of its severe surface charge recombination. Herein, a simple process is developed for preparing a new type of low-cost metal-organic coordination composed of tannic acid coordinated with Co ions (TACo) as an efficient cocatalyst to suppress the charge-carrier recombination on BiVO 4 photoanodes. For the BiVO 4 /TACo photoanode, a high photocurrent density of 4.8 mA cm−2 was achieved at 1.23 V (vs. reversible hydrogen electrode (RHE), AM 1.5 G), which approximately 3-fold higher than that of bare BiVO 4. Systematic studies reveal that the enhanced water oxidation performance of BiVO 4 /TACo photoanode can be ascribed to the synergistic effect of following factors: (i) For the thermodynamic process, the photogenerated holes are directly transferred to TACo layer; (ii) For the kinetic process, the transferred holes can directly oxidied Co2+ to generate Co3+ active sites, which could directly oxidize H 2 O to molecular O 2. This work provides a new tool-kit for designing efficient water oxidation PECs. [ABSTRACT FROM AUTHOR]

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Rational assembly of cocatalysts on crystal‐based photocatalysts with anisotropic facets, namely the reduction cocatalyst on the reduction facets and oxidation cocatalyst on the oxidation facets, can enhance the photocatalytic activity remarkably. However, this strategy of selective loading of cocatalysts on crystal‐facet engineered photoelectrodes is rarely discussed in photoelectrocatalysis (PEC). Herein, we fabricated BiVO4 microcrystal photoanodes with simultaneous exposure of oxidation {110} and reduction {010} facets to study the effect of facet‐selective assembly of cocatalysts on the activity of PEC water oxidation. By elaborative photodeposition, identical cocatalysts of MnOx were selectively loaded on the reduction, the oxidation and all the facets of BiVO4 photoanodes (respectively designated as R‐BVO, O‐BVO and O/R‐BVO). We found that MnOx facilitates the charge separation in BiVO4 more significantly on the oxidation facets than on the reduction ones, contributing to the net increase in photocurrent of O‐BVO being as 5.2 and 2.2 times that of R‐BVO and O/R‐BVO, respectively. Surface photovoltage analysis reveals that the interaction between the inherent built‐in electric field in BiVO4 crystals and the additive electric filed induced by the MnOx was account for the difference. Our work emphasizes the effect of facet‐selective assembly of cocatalyst in PEC systems, which may guide the rational design of highly efficient photoelectrodes for solar energy conversion. [ABSTRACT FROM AUTHOR]

• P-type tetragonal zircon BiVO 4 (P-BiVO 4) film was grown on FTO glass via hydrothermal method. • Interstitial oxygen is the main cause of p-type conductivity. • The P-BiVO 4 exhibit photocatalytic hydrogen production activity even its conduction band level is not negative enough. • The downward band-bending and the hot-electrons lead to the H 2 reduction. Tetragonal zircon BiVO 4 (P-BiVO 4) were grown on fluorine-doped tin oxide (FTO) glass via hydrothermal method. The cathodic photocurrent and Mott-Schottky analysis indicate that the tetragonal zircon BiVO 4 is a p-type semiconductor. Inductively coupled plasma (ICP) analysis and X-ray photoelectron spectrum showed that there are Bi vacancies and interstitial oxygen exist in the crystal, which are the origin of the p-type conductivity. The flat band potential of the P-BiVO 4 is about 1.33 V (vs Ag/AgCl) inferred from Mott-Schottky plots. Combining with diffuse reflection spectrum and valence band X-ray photoelectron spectrum, the calculated conduction band value of the P-BiVO 4 is about 0.06 V vs RHE, slightly higher than the reduction potential of hydrogen. However, the P-BiVO 4 exhibit hydrogen production activity under Xe light irradiation even though its conduction band level is not negative enough. This can be attributed to the hot carrier processes in p-type semiconductors. [ABSTRACT FROM AUTHOR]

• A non-enzymatic PEC glucose sensor based on BiVO 4 electrode was successfully prepared. • The adsorption of glucose on the surface of BiVO 4 agrees well with the classical Langmuir adsorption model. • The photogenerated holes of BiVO 4 can directly oxidize glucose molecules adsorbed on the electrode surface. • The resulting sensor showed an outstanding photocurrent response to glucose with favorable selectivity. A non-enzymatic photoelectrochemical (PEC) glucose sensor based on nanoporous bismuth vanadate (BiVO 4) electrode is fabricated on fluorine doped tin oxide by electrochemical deposition. The photogenerated holes of BiVO 4 show a strong oxidizing ability, with adsorption of glucose on the surface of BiVO 4 , agreeing well with the classical Langmuir adsorption model. Under visible light irradiation, the glucose molecules adsorbed on the BiVO 4 electrode surface can be oxidized by the photogenerated holes, which results in increased photocurrent. The fabricated BiVO 4 non-enzymatic photoelectrochemical sensor shows outstanding catalytic activity, favourable selectivity, good reproducibility, and long-term stability for glucose detection under optimized conditions. The linear range was 0–5 mM (correlation coefficient, R = 0.997) with a detection limit of 0.13 μmol L−1 (signal-to-noise = 3). In addition, the proposed PEC sensor was successfully applied to detect glucose in human serum samples. Our work provides a new strategy for the non-enzymatic detection of glucose. [ABSTRACT FROM AUTHOR]

Graphical abstract Pb(NO 3) 2 photooxidation or photoreduction reactions can be controlled in aqueous solution with and without adding NaIO 3 as a electron scavenger, leading to the selective deposition of PbO 2 or Pb on {110} or (010) surfaces of BiVO 4 , respectively. Highlights • Phase-pure, monoclinic BiVO 4 nanoislands grown on (001) yttria-stabilized zirconia. • BiVO 4 nanoislands with a truncated pyramid shape containing (010) and {110} facets. • A strong size-dependent photocatalytic activity for rhodamine B degradation. • Selective deposition of PbO 2 or Pb on {110} or (010) surfaces of BiVO 4. Abstract Photocatalytic studies performed on well-defined epitaxial thin films and heterostructures allow the direct investigation of crystallographic-dependent reactivity, and can provide fundamental insights into the reaction mechanisms. In this work, we show that phase-pure, monoclinic BiVO 4 nanoislands with a truncated pyramid shape with the (010) top surface and {110} sidewalls can be grown on (001)-oriented yttria-stabilized zirconia (YSZ) substrates with an epitaxial relationship of BiVO 4 (010)[001] // YSZ(001)[100]. The resulting nanostructures show a strong size-dependent mass-normalized photocatalytic activity, with highly dispersed nanoislands at low coverage being the most active. Pb(NO 3) 2 photooxidation or photoreduction reactions can be controlled in aqueous solution with and without adding NaIO 3 as a electron scavenger, leading to the selective deposition of PbO 2 or Pb on {110} or (010) surfaces of BiVO 4 , respectively. [ABSTRACT FROM AUTHOR]

BiVO4 crystals synthesized by an ultrasonic‐assisted method (Sono‐BiVO4) showed improved efficiency as a heterogeneous photocatalyst under visible‐light irradiation. Sono‐BiVO4 was successfully used for the C−C bond cleavage of alkenes to generate carbonyl compounds. Styrene derivatives were converted into carbonyl compounds in the presence of Sono‐BiVO4 under highly sustainable conditions requiring only natural sources, that is, molecular oxygen, visible light, and water at room temperature. Additionally, Sono‐BiVO4 could be easily separated from the reaction mixture and reused. [ABSTRACT FROM AUTHOR]

• The BiVO 4 /BiO x composite is prepared using hydrothermal synthesis and NaOH etching. • The BiVO 4 /BiO x composite achieves p-n heterojunction to improve the charge transfer. • Different concentrations of NaOH are used for making BiVO 4 /BIO X as photocatalysts. • BiVO 4 /BiO x electrode shows photocurrent density of 0.48 mA/cm2 at 1.23 V vs. RHE. • Long-term stability of a BiVO 4 /BiO x electrode is improved after depositing NiCOOH. BiVO 4 is a well-known photocatalyst for water oxidation due to small band gap and suitable band positions, but short diffusion length is necessary to solve for practical applications. This study adopts common alkaline etching process for fabricating BiVO 4 and BiO x composite as photocatalyst for water oxidation for the first time. The BiVO 4 /BiO x heterojunction is fabricated on conducting glasses using hydrothermal synthesis and NaOH etching process for establishing heterojunction. Different NaOH concentrations are used for fabricating BiVO 4 /BiO x electrodes with different BiO x amounts. Due to adequate amount of BiO x for achieving effective charge transfer and suitable amount of continuous aggregations on the surface for reducing charge recombination at nanoparticle boundaries, the BiVO 4 /BiO x electrode prepared using 0.15 M NaOH for etching shows the highest photocurrent density of 0.48 mA/cm2 at 1.23 V versus reversible hydrogen electrode under air mass 1.5 global illumination. The BiVO 4 electrode only shows the photocurrent density of 0.06 mA/cm2 measured at the same conditions. Long-term stability of the BiVO 4 /BiO x electrode is further improved by ten-fold after depositing NiOOH co-catalyst on the surface for reducing charge recombination. The result indicates the significance for the bismuth oxide amount in the BiVO 4 /BiO x composite on influencing the photoelectrochemical catalytic ability toward water oxidation. [ABSTRACT FROM AUTHOR]

Motivated by replacing the kinetically unfavorable oxygen evolution reaction (OER) and producing value‐added products in photoelectrochemical cells (PECs), we report that bismuth vanadate (BiVO4) photoelectrodes modified with a cobalt phosphate (CoPi) overlayer facilitate 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐mediated selective oxidation of 5‐hydroxymethylfurfural (HMF). CoPi layers with sufficient thickness were found to reduce the potential required for TEMPO oxidation by 0.5 V, as well as increase charge injection efficiency sevenfold compared to BiVO4 without CoPi. Furthermore, the undesired OER was completely suppressed when using the heterostructured photoanodes. Transient photocurrent measurements suggested that CoPi alleviates recombination losses resulting from the back reduction of oxidized TEMPO. The PECs with BiVO4/CoPi bilayer achieved 88 % yield to 2,5‐furandicarboxylic acid (FDCA) from HMF oxidation under mild conditions, whereas <1 % FDCA was generated with BiVO4. These findings suggest that suppression of the back reduction process substantially improves the efficiency of the oxidation, giving a potential route to more efficient solar fuel/chemical production. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is a rational and effective way that imitates natural photosynthesis for direct conversion of solar energy into clean hydrogen fuels. Developing highly efficient photoanodes to enhance the kinetics of the rate‐determining oxygen evolution reaction is generally regarded as the key to achieve artificial photosynthesis. Recently, bismuth vanadate (BiVO4) has emerged as a promising photoanode material for PEC applications. In this Review, recent progress in designing BiVO4‐based photoanodes is presented and summarized, including morphological control, heteroatom/defect doping, hetero‐/homo‐junction fabrication and co‐catalyst deposition. In addition, typical unbiased tandem devices of photoanode/photocathode and photovoltaic/photoanode systems using BiVO4 as the front‐absorber photoanodes are reviewed. Finally, a future outlook is provided to highlight the issues to be addressed for commercial applications of PEC devices for solar water splitting. [ABSTRACT FROM AUTHOR]

Monoclinic bismuth vanadate (m-BiVO4) yellow pigments were synthesized by non-hydrolytic sol-gel (NHSG) route without any surfactants. The presence of Bi–O–V band in the sol and xerogel, indicates that the excellent atomic scale homogeneity could be reached. It is beneficial to achieve high purity m-BiVO4 phase and submicron scale particles (738 nm) with homogenous distribution at low temperature (400 °C), resulting in a brilliant yellow hue (b* = 71.18, hab = 89.73). These pigments have better chromatic performance than previously reported and commercially available BiVO4 yellow pigments. Meanwhile, the cytotoxicity of the pigment was tested in Mus musculus skin melanoma cells, and showed nontoxic for human cells, indicating its potential application in the high quality paints for automotive and architectural finishes. Highlights: BiVO4 pigment was prepared via non-hydrolytic sol-gel method at 400 °C. It exhibited high purity and brilliant yellow hue (L* = 74.83, a* = −0.34, b* = 71.18). The pigment has low cytotoxicity for human cells. [ABSTRACT FROM AUTHOR]

This work investigates the removal of acid orange 7 dye from aqueous solution through photo electrochemical technique using a composite of exfoliated graphite and bismuth vanadate (EG-BiVO4) as photoanode. Monoclinic sheelite BiVO4 nanoparticles were synthesised through the hydrothermal route and subsequently added to prepared EG to form a composite. The EG-BiVO4 composite was fully characterised through XRD, SEM and FTIR. The cyclic voltammograms of the EG-BiVO4 electrodes were obtained in potassium ferricyanide and ferrocyanide redox probe. The XRD result revealed that the BiVO4 has a monoclinic sheelite crystal lattice with particle size of 74.17 nm. The EG-BiVO4 photoanode was applied for the photoelectrochemical degradation of acid orange 7 dye. Concentration decay of the dye was monitored using the UV-Vis spectrophotometer. The photo-assisted process gave improved degradation efficiency of 88% within 90 min. Kinetics study revealed that the process followed the pseudo first-order kinetics and fast with apparent rate constant of 1.60 × 10−2 min−1. The results of this investigation reveal the potential application of BiVO4 photoanode in the photoelectrochemical treatment of dye contaminated water. [ABSTRACT FROM AUTHOR]

• CoO x /BiVO 4 catalysts were prepared and tested for propyl paraben degradation. • Optimal results were obtained for the samples containing 0.5 wt.% Co. • Rate enhancement is attributed to the formation of p-n heterojunction. • Photogenerated holes (h+) have a predominant role in the degradation process. Cobalt-promoted bismuth vanadate photocatalysts of variable cobalt content (0–1.0 wt.%) were synthesized and characterized with various techniques including BET, XRD, DRS, XPS and TEM. BiVO 4 exists in the monoclinic scheelite structure, while cobalt addition improves the absorbance in the visible region although it does not affect the band gap energy of BiVO 4. Cobalt exists in the form of well-dispersed Co 3 O 4 nanocrystallites, which are in intimate contact with the much larger BiVO 4 nanoparticles. Photocatalytic activity was evaluated for the degradation of propyl paraben (PP) under simulated solar radiation. The activity of pristine BiVO 4 is significantly improved adding small amounts of cobalt and is maximized for the catalyst containing 0.5 wt.% Co. PP degradation in ultrapure pure water increases with increasing photocatalyst loading (100 mg/L to 1.5 g/L), and decreasing PP concentration (1600–200 μg/L). Experiments in bottled water, as well as in pure water spiked with bicarbonate and chloride ions showed little effect of non-target inorganics on degradation. Conversely, degradation is severely impeded in secondary treated wastewater. The enhancement of the photocatalytic activity of the synthesized catalysts is attributed to efficient electron-hole separation, achieved at the p-n junction formed between the p-type Co 3 O 4 and the n-type BiVO 4 semiconductors. [ABSTRACT FROM AUTHOR]

• Pt@BiVO 4 /g-C 3 N 4 photocatalyst shows a remarkable photodegradation performance. • The photocatalyst was evaluated using real industrial poultry wastewater. • The Pt@BiVO 4 /g-C 3 N 4 shows a good photostability over 3 cyclic activity. The discharge of a high concentration of contaminants from industrial poultry wastewater has caused a major catastrophic towards environmental remediation. Herein, different amounts of platinum nanoparticles were successfully incorporated into Pt@BiVO4/g-C 3 N 4 photocatalyst via wet-impregnation technique. The crystallographic, morphological and optical properties of the photocatalysts were comprehensively analysis via several characterization techniques. The photocatalytic degradation performance of Pt@BiVO 4 /g-C 3 N 4 photocatalyst was evaluated using real industrial poultry wastewater under solar light irradiation. The effects of the pH wastewater and the amount of platinum loading were systematically studied using response surface methodology (RSM). The Pt@BiVO 4 /g-C 3 N 4 photocatalyst prepared at 1.5 wt. % platinum with the pH of 8 exhibited superior photodegradation performance with 93.5% rate of COD removal within 3 h. The FESEM micrograph analysis suggested that the intimate contact between Pt, BiVO 4 , and g-C 3 N 4 in the as-developed photocatalyst allows a smooth migration and separation of photogenerated charge carriers. In addition, the XRD, EDX and XPS analysis further confirmed the successful formation of the as-prepared Pt@BiVO 4 /g-C 3 N 4 photocatalyst. Moreover, the as-prepared photocatalyst showed very good recyclability and photostability up to 3 cycles, indicating that the as-developed photocatalyst successfully inhibits the fast recombination rate between photogenerated charge carriers. This work serves as solid evidence of the photocatalyst technology readiness to be put in the real practical application in treating the industrial wastewater. [ABSTRACT FROM AUTHOR]

Abstract Contamination of water bodies by harmful and recalcitrant organic substances is a global challenge. A promising technique for removing these organics from water/wastewater is photoelectrocatalytic oxidation which combines electrolytic and photocatalytic processes. Herein, we report the degradation of emerging pharmaceutical pollutants – acetaminophen and ciprofloxacin – at a BiVO 4 /BiOI photoanode under visible irradiation via photoelectrocatalytic process. The BiVO 4 /BiOI was electrodeposited on a FTO glass and characterised with XRD, SEM, EDS and diffusive reflectance UV–Vis. The results confirmed the successful electrodeposition of BiVO 4 /BiOI on the glass substrate. Mott-Schotty plots confirmed the formation of p-n heterojunction between the two electrodeposited semiconductors. The calculated charge carrier density of BiVO 4 /BiOI was higher than those of pristine BiVO 4 and BiOI. The binary electrode also gave improved photocurrent response compared with unitary electrodes. Degradation efficiencies of 68% and 62% were achieved upon the application of the prepared photoanode (FTO/BiVO 4 /BiOI) in PEC degradation of acetaminophen and ciprofloxacin respectively using a bias potential of 1.5 V within 2 h. A synthetic pharmaceutical wastewater containing a mixture acetaminophen and ciprofloxacin was also treated with the photoanode. The photoanode was also effective in the degradation of dye. The findings of this study suggest the suitability of the prepared photoanode for the photoelectrocatalytic degradation of organic pharmaceutical pollutants in wastewater. Graphical abstract Image 1 Highlights • A solar active BiVO 4 /BIOI heterojunction photoanode is prepared for water treatment. • BiVO 4 /BIOI heterojunction was prepared in a two-step electrodeposition on FTO glass. • Mott-Schottky plot and photocurrent response study confirmed a p-n heterojunction. • Photoelectrocatalytic degradation of acetaminophen and ciprofloxacin was achieved. [ABSTRACT FROM AUTHOR]

The photocatalyst BiVO4/Bi2O3@SiO2 nanoparticle was synthesized in a high-pressured microwave method. The as-prepared photocatalytst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy. The visible-light-driven activity of the prepared photocatalyst was evaluated by degradation of Rhodamine B (RhB). The results show that the as-prepared sample appears in a core-shell structure with the heterojunction BiVO4/Bi2O3 as core and amorphous porous SiO2 as shell. BiVO4/Bi2O3@SiO2 has a large specific surface area (99.63 m2 g-1) and exhibits superior photocatalytic activity in the degradation of RhB under visible-light illumination. The degradation rate constant of RhB over BiVO4/Bi2O3@SiO2 are 9.8, 9.0, 8.4, and 5.6 times as high as that over Bi2O3, BiVO4, BiVO4/Bi2O3 and BiVO4/SiO2, respectively. The enhanced photocatalytic activity of BiVO4/Bi2O3@SiO2 is attributed to both high surface area and low recombination rate of photoinduced electron-hole pairs. The high surface area provides more active sites and superior adsorption properties, which promotes the photocatalytic activity. The low recombination rate of photoinduced electron-hole pairs is due to both the hetero-junction between BiVO4 and Bi2O3 and the presence of impurity level of SiO2. [ABSTRACT FROM AUTHOR]

As the performance of photoanodes for solar water splitting steadily improves, the extension of the absorption wavelength in the photoanodes is highly necessary to substantially improve the water splitting. We use a luminescent back reflector (LBR) capable of photon upconversion (UC) to improve the light harvesting capabilities of Mo:BiVO4 photoelectrodes. The LBR is prepared by dispersing the organic dye pair meso‐tetraphenyltetrabenzoporphine palladium and perylene capable of triplet–triplet annhilation‐based UC in a polymer film. The LBR converts the wavelengths of 600–650 nm corresponding to the sub‐band gap of Mo:BiVO4 and the wavelengths of 350–450 nm that are not sufficiently absorbed in Mo:BiVO4 to a wavelength that can be absorbed by a Mo:BiVO4 photoelectrode. The LBR improves the water splitting reaction of Mo:BiVO4 photoelectrodes by 17 %, and consequently, the Mo:BiVO4/LBR exhibits a photocurrent density of 5.25 mA cm−2 at 1.23 V versus the reversible hydrogen electrode. The Mo:BiVO4/LBR exhibits hydrogen/oxygen evolution corresponding to the increased photocurrent density and long‐term operational stability for the water splitting reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A Type II n-n staggered heterojunction photoanode of V 2 O 5 /BiVO 4 was synthesized. • A high photocurrent density of 1.53 mA/cm2 at 1.5 V vs Ag/AgCl was measured. • This was due to lower charge resistance and faster transit time showed by EIS/IMPS. • Photo-excitons transfer in V 2 O 5 /BiVO 4 was validated by theoretical band diagram. Abstract Conventional photoanode using a singular semiconductor material is not technically viable for photoelectrochemical (PEC) water oxidation owing to the properties relating to its wide band gap, sluggish charge mobility, as well as poor separation and rapid recombination of photogenerated charge carriers. The main aim of this study was to fabricate an n-n heterojunction photoanode of V 2 O 5 /BiVO 4 via a facile electrodeposition synthesis method in order to overcome the technical bottlenecks encountered in conventional singular photoanode structures. Additionally, the synergistic effect of band potentials matching and conductivity difference between BiVO 4 and V 2 O 5 were studied using LSV, IMPS, EIS, HR-TEM, XRD, XPS, Raman and ultraviolet-visible spectroscopies. This was followed by the performance evaluation of the light-induced water splitting using a standard three-electrode assembly PEC cell under 1.5 AM solar simulator. Results showed that the V 2 O 5 /BiVO 4 heterojunction photoanode achieved a significantly improved photocurrent density of 1.53 mA/cm2 at 1.5 V vs Ag/AgCl, which was a 6.9-fold and a 7.3-fold improvement over the individual pristine BiVO 4 (0.22 mA/cm2) and V 2 O 5 (0.21 mA/cm2), respectively. The improvement was attributed to the lower charge resistances at the FTO/semiconductor, semiconductor/FTO and semiconductor/electrolyte interfaces as well as the fast transit time (τ) of 6.4 ms for photo-injected electrons in the V 2 O 5 /BiVO 4 heterojunction photoanode. Finally, the experimental results were used to reconstruct a theoretical band diagram in validating the heterojunction alignment between V 2 O 5 and BiVO 4 as well as in elucidating the photogenerated charge carriers transfer mechanism in the V 2 O 5 /BiVO 4 heterojunction photoanode. [ABSTRACT FROM AUTHOR]

• 3-D microspheres Z-scheme Ag 3 VO 4 /BiVO 4 heterojunction photocatalyst was first obtained. • The build-in electric field directed from Ag 3 VO 4 to BiVO 4 will assist charge transfer. • Photocatalytic reduction of Cr6+ and oxidation of BPS were enhanced. • Comparative Experimental and DFT study of Ag 3 VO 4 /BiVO 4 , Z-scheme heterojunction is performed. A novel three-dimensional microspheres mediator-free Z-scheme Ag 3 VO 4 /BiVO 4 heterojunction photocatalyst was successfully obtained for the first time. The photocatalytic performance of the as-prepared photocatalyst was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of Bisphenol S under visible-light irradiation. Among these samples, 0.24-Ag 3 VO 4 /BiVO 4 exhibits the highest photocatalytic performances, the photocatalytic reduction and oxidation efficiency of 74.9 and 94.8%, respectively, can be achieved. The enhanced photocatalytic performance is attributed to the build-in electric field assisted charge transfer between the Ag 3 VO 4 and BiVO 4 , and the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, it has been verified that the Ag 3 VO 4 /BiVO 4 heterostructures follow a typical Z-scheme charge transfer mechanism rather than conventional type-II heterojunction charge transfer mechanism. Furthermore, the theoretical understanding of the underlying mechanism was also supported, while the energy band structure, and Fermi level were systematically calculated using the density functional theory approach. The results show that a built-in electric field directed from Ag 3 VO 4 to BiVO 4 surface was established as an equalized Fermi level was reached, which benefits the separation of photogenerated charge carriers in the way of a Z-scheme charge transfer mechanism. The strategy to form the three-dimensional microspheres Z-scheme heterojunction photocatalyst may offer new insight into the Z-scheme charge transfer mechanism for applications in the field of solar energy conversion. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Mo-BVO electrodes were fabricated via a four dip-coating cycles method. • Photocurrent density increased 15-fold for 2% Mo-BVO compared with pure BVO. • Mott-Schottky results indicated 2% Mo-BVO has the maximum donor concentration. • The PEC measurement showed shifting of onset potential to lower voltage for Mo-BVO. • The Impedance data exhibited 2% Mo-BVO has the best PEC performance compared to other photoanodes. Abstract Molybdenum (Mo)-doped Monoclinic Bismuth Vanadate (Mo-BiVO 4 ; BVO) catalysts were fabricated via a simple dip coating method. We systematically studied the effect of Mo-doping with various concentration (1–5%) in BVO electrode through photoelectrochemical (PEC), Mott-Schottky and impedance measurement. Intermediate heat treatment and number of successive dip coating deposition were utilized to control the monoclinic crystallization and thickness of Mo-BVO photoanodes. Furthermore, the effect of Mo-doping in morphology, structure, chemical states and optical properties of the obtained electrodes were characterized by different physico-chemical and morphological methods BVO with 2% Mo doping (2% Mo-BVO) showed the best PEC performance, of about 15 times higher than that of the pure BVO. Improved charge carrier transport and optimized light absorption obtained upon Mo doping into the BVO crystal lattice while the monoclinic scheelite structure with small band-gap was retained. To understand the effect of Mo-doping, Mott Schottky and Impedance measurement carried out, in order to evaluate the donor concentration and conductivity of pure BVO and Mo-BVO. Interestingly, 2% Mo-BVO showed the maximum donor concentration (5.7E + 27) and minimum flat band potential (V fb = −0.45) compared to other prepared electrodes. Furthermore, we attempt to discuss the improved PEC performance of Mo-BVO using high donor concentration, up-shifting of Fermi level and consequently facilitating electrons transport in Mo-BVO compared to pure BVO. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) is promising for solar‐assisted water splitting. The performance of BiVO4 is limited by charge separation for >70 nm films or by light harvesting for <700 nm films. To resolve this mismatch, host–guest architectures use thin film coatings on 3D scaffolds. Recombination, however, is exacerbated at the extended host–guest interface. Underlayers are used to limit this recombination with a host‐underlayer‐guest series. Such underlayers consume precious pore volume where typical SnO2 underlayers are optimized with 65–80 nm. In this study, conformal and ultrathin SnO2 underlayers with low defect density are produced by atomic layer deposition (ALD). This shifts the optimized thickness to just 8 nm with significantly improved space efficiency. The materials chemistry thus determines the dimension optimization. Lastly, host–guest architectures are shown to have an applied bias photon‐to‐charge efficiency of 0.71 %, a new record for a photoanode absorber prepared by ALD. [ABSTRACT FROM AUTHOR]

Solar water oxidation is considered as a promising method for efficient utilization of solar energy and bismuth vanadate (BiVO4) is a potential photoanode. Catalyst loading on BiVO4 is often used to tackle the limitations of charge recombination and sluggish kinetics. In this study, amorphous nickel oxide (NiOx) is loaded onto Mo‐doped BiVO4 by photochemical metal–organic deposition method. The resulting NiOx/Mo:BiVO4 photoanodes demonstrate a two‐fold improvement in photocurrent density (2.44 mA cm−2) at 1.23 V versus reversible hydrogen electrode (RHE) compared with the uncatalyzed samples. After NiOx modification the charge‐separation and charge‐transfer efficiencies improve significantly across the entire potential range. It is further elucidated by open‐circuit photovoltage (OCP), time‐resolved‐microwave conductivity (TRMC), and rapid‐scan voltammetry (RSV) measurements that NiOx modification induces larger band bending and promotes efficient charge transfer on the surface of BiVO4. This work provides insight into designing BiVO4‐catalyst assemblies by using a simple surface‐modification route for efficient solar water oxidation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A highly conformal 10–15 nm layer of NiFe based Prussian blue co-catalyst is coated on BiVO 4 electrodes. • The coating boosted the photocurrent of BiVO 4 electrodes by 10-fold to 3.23 mA/cm2. • A low onset potential of 0.2 V and photo-corrosion inhibition for > 50 h are also achieved. Abstract BiVO 4 is one of the most promising semiconductors for photoelectrochemical water splitting. BiVO 4 is, however, limited by poor charge separation and slow oxygen evolution dynamics, for which surface modification with oxygen evolution catalysts (OECs) becomes indispensable. Among many OECs, Prussian blue type coordination polymers have lately attracted an escalating research interest attributable to their low cost, chemical robustness and easy synthesis using nontoxic earth-abundant elements. In this study, we report a simple method for efficient surface modification of Zr-doped BiVO 4 nanostructured electrodes with an amorphous Ni-Fe based Prussian blue (NiFePB) polymer. The method resulted in a remarkable 10-fold enhancement of photocurrent (3.23 mAcm−2 at 1.23 V versus the reversible hydrogen electrode RHE) and a low onset potential of 0.208 V versus RHE, which are both records for Prussian blue (PB) type materials. Our coating method results in a (Zr)BiVO 4 /NiFePB core-shell structure, in which a 10–15 nm NiFePB shell makes a superior conformal coating with complete coverage on the (Zr)BiVO 4 nanoparticles. The high conformity and amorphous nature of the coating are believed to be key features for the high photocatalytic activity and for a high photocorrosion resistance of the photoanodes during > 50 h of AM1.5 G solar illumination. Our method illustrates the large potential of Prussian blue type materials, when properly coated, as efficient and highly stable OECs. [ABSTRACT FROM AUTHOR]

In the present work, graphitic carbon nitride‐bismuth vanadate (g‐C3N4‐BiVO4) nanohybrid materials with different wt. % of g‐C3N4 were successfully synthesized by a simple hydrothermal method and characterized by UV‐Visible diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PLS), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Fourier‐transform infrared spectroscopy (FT‐IR), field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray (EDAX) absorption spectroscopy, high‐resolution transmission electron microscopy (HR‐TEM) and selected area electron diffraction (SAED) analysis. The photoelectrocatalytic performance of g‐C3N4‐BiVO4 nanohybrid materials were investigated by water splitting under AM 1.5G (100 mWcm−2) illumination. The g‐C3N4‐BiVO4 photoanode with 10 wt. % of g‐C3N4 exhibited higher photoelectrocatalytic activity towards water splitting, which was 1.6 and 2.8‐folds higher than that of the pure BiVO4 and g‐C3N4, respectively. The remarkably enhanced photoelectrocatalytic activity of the nanohybrid is due to the efficient photogenerated electron‐hole separation through Z‐scheme mechanism, enhanced interfacial charge transfer process and suppression in the charge recombination rate. Hence, the g‐C3N4‐BiVO4 nanohybrid materials can be potential candidates for light harvesting applications. [ABSTRACT FROM AUTHOR]