Oxygen-Vacancy-Induced Enhancement of BiVO4 Bifunctional Photoelectrochemical Activity for Overall Water Splitting.

Hydrogen generation via photoelectrochemical (PEC) overall water splitting is an attractive means of renewable energy production so developing and designing the cost-effective and high-activity bifunctional PEC catalysts both for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) has been focused on. Based on first-principles calculations, we propose a feasible strategy to enhance either HER or OER performance in the monoclinic exposed BiVO4 (110) facet by the introduction of oxygen vacancies (Ovacs). Our results show that oxygen vacancies induce charge rearrangements, which enhances charge transfer between active sites and adatoms. Furthermore, the incorporation of oxygen vacancies reduces the work function of the system, which makes charge transfer from the inner to the surface more easily; thus, the charges possess stronger redox capacity. As a result, the Ovac reduces both the hydrogen adsorption-free energy (ΔGH*) for the HER and the overpotential for the OER, facilitating the PEC activity of overall water splitting. The findings provide not only a method to develop bifunctional PEC catalysts based on BiVO4 but also insight into the mechanism of enhanced catalytic performance.

A hydrogen sulfide photoelectrochemical sensor based on BiVO4/Fe2O3 heterojunction.

A BiVO4/Fe2O3 heterojunction for non-enzymatic photoelectrochemical (PEC) determination of hydrogen sulfide (H2S) is reported. The BiVO4/Fe2O3 heterojunction promoted the separation of photo-generated carriers, reduced electron-hole recombination, and thus improved electron collection and photocurrent. The proposed BiVO4/Fe2O3/FTO sensor exhibited a linear range of 1-500 µM and a detection limit of 0.51 nM H2S. In addition, high selectivity, good reproducibility, and stability were obtained for H2S sensing. The detection of H2S in water and serum samples demonstrated its feasibility. This work provides a new strategy to detect and understand the bio-function of H2S in the biological environment.

Promoting the Photoelectrochemical Properties of BiVO4 Photoanode via Dual Modification with CdS Nanoparticles and NiFe-LDH Nanosheets.

Bismuth vanadate (BiVO4) has long been considered a promising photoanode material for photoelectrochemical (PEC) water splitting. Despite its potential, significant challenges such as slow surface water evolution reaction (OER) kinetics, poor carrier mobility, and rapid charge recombination limit its application. To address these issues, a triadic photoanode has been fabricated by sequentially depositing CdS nanoparticles and NiFe-layered double hydroxide (NiFe-LDH) nanosheets onto BiVO4, creating a NiFe-LDH/CdS/BiVO4 composite. This newly engineered photoanode demonstrates a photocurrent density of 3.1 mA cm-2 at 1.23 V vs. RHE in 0.1 M KOH under AM 1.5 G illumination, outperforming the singular BiVO4 photoanode by a factor of 5.8 and the binary CdS/BiVO4 and NiFe-LDH/BiVO4 photoanodes by factors of 4.9 and 4.3, respectively. Furthermore, it exhibits significantly higher applied bias photon-to-current efficiency (ABPE) and incident photon-to-current efficiency (ICPE) compared to pristine BiVO4 and its binary counterparts. This enhancement in PEC performance is ascribed to the formation of a CdS/BiVO4 heterojunction and the presence of a NiFe-LDH OER co-catalyst, which synergistically facilitate charge separation and transfer efficiencies. The findings suggest that dual modification of BiVO4 with CdS and NiFe-LDH is a promising approach to enhance the efficiency of photoanodes for PEC water splitting.

Construction of dual Z-scheme Ag3VO4-BiVO4/InVO4 photocatalysts using vanadium source from spent catalysts for contaminated water treatment and bacterial inactivation.

Vanadate-based photocatalysts have recently attracted substantial attention owing to their outstanding photocatalytic activity for degrading organic pollutants and generating energy via photocatalytic processes. However, the relatively high price of vanadium has hindered the development of vanadate-based photocatalysts for various applications. Spent catalysts obtained from oil refineries typically contain a significant quantity of vanadium, making them valuable for recovery and utilization as precursors for the production of high-value-added photocatalysts. In this study, we transformed the V present in spent catalysts produced by the petrochemical industry into ternary vanadate-based photocatalysts [BiVO4/InVO4/Ag3VO4 (BVO/IVO/AVO, respectively)] designed for water remediation. The ternary composites revealed an enhanced photocatalytic capability, which was 1.42 and 5.1 times higher than those of the binary BVO/IVO and pristine AVO due to the facilitated charge separation. The ternary photocatalysts not only effectively treated wastewater containing various organic dyes, such as methylene blue (MB), rhodamine 6G (R6G), and brilliant green (BG), but also exhibited remarkable photocatalytic performance in the degradation of antibiotics, reduction of Cr(VI), and bacterial inactivation. This paper proposes a feasible route for recycling industrial waste as a source of vanadium to produce highly efficient vanadate-based photocatalysts.

Biofunctional photoelectrochemical/electrochemical immunosensor based on BiVO4/BiOI-MWCNTs and Au@PdPt for alpha-fetoprotein detection.

A biofunctional immunosensor combining photoelectrochemical (PEC) and electrochemical (EC) was proposed for the quantitative detection of the liver cancer marker alpha-fetoprotein (AFP) in human blood. BiVO4/BiOI-MWCNTs photoactive materials were first prepared on conductive glass FTO, and the photoelectrode was functionalized by chitosan and glutaraldehyde. Then, the AFP capture antibody (Ab1) was successfully modified on the photoelectrode, and the label-free rapid detection of AFP antigen was achieved by PEC. In addition, Au@PdPt nanospheres were also used as a marker for binding to AFP detection antibody (Ab2). Due to the excellent catalytic properties of Au@PdPt in EC reaction, a signal increase in the EC response can be achieved when Ab2 binds to the AFP antigen, which ensures high sensitivity for the detection of AFP. The detection limits of PEC and EC are 0.050 pg/mL and 0.014 pg/mL, respectively. The sensor also possesses good specificity, stability and reproducibility, shows excellent performance in the detection of clinical samples and has good clinical applicability.

Dual Hole Transport Layers Heterojunction and Band Alignment Engineered Mo:BiVO4 Photoanodes for Efficient Water Splitting.

BiVO4-based photoanode is one of the most promising photoanodes for photoelectrocatalytic water splitting. However, the serious problem of interface charge recombination limits its further development. Here, a Mo:BiVO4/NiOx/CPF-TCzB/NiCoBi photoanode is constructed with double hole transport layer and an energy level gradient to achieve an effective photo-generated holes extraction and accumulation at the surface electrocatalyst. The conjugated polycarbazole framework CPF-TCzB is used as hole transport layer to eliminate the charge recombination center between Mo:BiVO4 and NiCoBi electrocatalyst and realize the extraction and storage of photo-generated hole; NiOx nanoparticles are further inserted between Mo:BiVO4 and CPF-TCzB to form a gradient energy level, eliminating the energy level barrier and optimizing band alignment. As a result, Mo:BiVO4/NiOx/CPF-TCzB/NiCoBi achieves a much higher photocurrent densities of 3.14 mA cm-2 than that of Mo:BiVO4 (0.42 mA cm-2) at 0.6 V versus RHE. This work provides an specific way to adjust the band structure of BiVO4-based photoanodes and realize efficient hole extraction and storage for PEC water splitting.

Simultaneous removal of tetracycline hydrochloride and hexavalent chromium by heterogeneous Fenton in a photocatalytic fuel cell system.

In this work, a novel double-chamber system (PFC-Fenton), combined photocatalytic fuel cell (PFC) with Fenton, was constructed for tetracycline hydrochloride (TCH) and hexavalent chromium (Cr(VI)) removal and electricity production. Therein, Zn5(OH)6(CO3)2/Fe2O3/BiVO4/fluorine-doped SnO2 (ZIO/BiVO4/FTO) and carboxylated carbon nanotubes/polypyrrole/graphite felt (CCNTs/Ppy/GF) were served as photoanode and cathode, respectively. Under light irradiation, the removal efficiencies of TCH and Cr(VI) with the addition of H2O2 (2 mL) could reach 93.1% and 80.4%, respectively. Moreover, the first-order kinetic constants (7.37 × 10-3 min-1 of TCH and 3.94 × 10-3 min-1 of Cr(VI)) were 5.26 and 5.57 times as much as the absence of H2O2. Simultaneously, the maximum power density could be obtained 0.022 mW/cm2 at a current density of 0.353 mA/cm2. Therein, the main contribution of TCH degradation was ·OH and holes in anode chamber. The synergistic effect of photoelectrons, generated ·O2-, and H2O2 played a crucial role in the reduction of Cr(VI) in cathode chamber. The high-performance liquid chromatography-mass spectrometry indicated that TCH could be partially mineralized into CO2 and H2O. X-ray photoelectron spectroscope and X-ray absorption near-edge structure spectra showed that Cr(VI) could be reduced to Cr(III). After 5 times of cycling, the removal efficiencies of TCH and Cr(VI) were still greater than 70%, indicating the remarkable stability of the PFC-Fenton system. Overall, this system could remove TCH/Cr(VI) and generate power simultaneously without iron sludge formation, demonstrating a promising method to further develop PFC-Fenton technology.

pH­responsive nanozyme cascade catalysis: A strategy of BiVO4 application for modulation of pathological wound microenvironment.

Persistent inflammation and bacterial infection commonly occur during the wound healing process, necessitating urgent development of effective strategies for treating drug-resistant bacterial infections. In this study, bismuth vanadate (BiVO4) was successfully synthesized as an antibacterial agent that promotes wound healing. Through In vitro antibacterial experiments, it was observed that the prepared BiVO4 exhibited excellent performance in catalyzing H2O2 to produce hydroxyl radicals (OH) at a lower concentration (0.2 mg mL-1), resulting in significant antibacterial effects against Gram-negative Extended-Spectrum ß-Lactamases-Producing Escherichia coli (ESBL-E. coli) strains. Furthermore, biosafety tests, cell scratch experiments, and ESBL-E. coli infected wound rat model experiments demonstrated high biocompatibility of BiVO4 with a cell survival rate exceeding 85 %. Additionally, BiVO4 promoted the production of vascular endothelial growth factors and fibroblasts migration while contributing to collagen production, effectively facilitating immune reconstruction at the wound site. By integrating peroxidase (POD)-like under acidic conditions (pH 4) and catalase (CAT)-like catalytic activities at under neutral conditions (pH 7), BiVO4 exhibited the ability to activate free radical sterilization and accelerate wound healing by activating O2. Therefore, our findings provide evidence for a dual enzyme regulatory mechanism involving antibacterial properties and promotion of wound tissue reconstruction for potential application in both antibacterial treatment and wound healing.

Construction of Ultrathin BiVO4-Au-Cu2O Nanosheets with Multiple Charge Transfer Paths for Effective Visible-Light-Driven Photocatalytic Degradation of Tetracycline.

In this study, unique BiVO4-Au-Cu2O nanosheets (NSs) are well designed and multiple charge transfer paths are consequently constructed. The X-ray photoelectron spectroscopy measurement during a light off-on-off cycle and redox capability tests of the photo-generated charge carriers confirmed the formation of Z-scheme heterojunction, which can facilitate the charge carrier separation and transfer and maintain the original strong redox potentials of the respective component in the heterojunction. The ultrathin 2D structure of the BiVO4 NSs provided sufficient surface area for the photocatalytic reaction. The local surface plasmon resonance (LSPR) effect of the electron mediator, Au NPs, enhanced the light absorption and promoted the excitation of hot electrons. The multiple charge transfer paths effectively promoted the separation and transfer of the charge carrier. The synergism of the abovementioned properties endowed the BiVO4-Au-Cu2O NSs with satisfactory photocatalytic activity in the degradation of tetracycline (Tc) with a removal rate of ≈80% within 30 min under visible light irradiation. The degradation products during the photocatalysis are confirmed by using ultra-high performance liquid chromatography-mass spectrometry and the plausible degradation pathways of Tc are consequently proposed. This work paves a strategy for developing highly efficient visible-light-driven photocatalysts with multiple charge transfer paths for removing organic contaminants in water.

Er-Doped BiVO4/BiFeO3 Nanocomposites Synthesized via Sonochemical Process and Their Piezo-Photocatalytic Application.

In this work, Er-doped BiVO4/BiFeO3 composites are prepared using the sonochemical process with a difference of rare earth loading compositions. The crystallinity and chemical and morphological structure of as-synthesized samples were investigated via X-ray diffraction, Raman scattering, and electron microscopy, respectively. The diffuse reflectance technique was used to extract the optical property and calculate the optical band gap of the composite sample. The piezo-photocatalytic performance was evaluated according to the decomposition of a Rhodamine B organic compound. The decomposition of the organic compound was achieved under ultrasonic bath irradiation combined with light exposure. The Er-doped BiVO4/BiFeO3 composite heterojunction material exhibited significant enhancement of the piezo-photocatalytic activity under both ultrasonic and light irradiation due to the improvement in charge generation and separation. The result indicates that Er dopant strongly affects the phase transformation, change in morphology, and alternation in optical band gap of the BiVO4 matrix. The incorporation of BiFeO3 in the composite form with BiVO4 doped with 1%Er can improve the photocatalytic performance of BiVO4 via piezo-induced charge separation and charge recombination retardment.

Advancing BiVO4 Photoanode Activity for Ethylene Glycol Oxidation via Strategic pH Control.

The photoelectrochemical (PEC) conversion of organic small molecules offers a dual benefit of synthesizing value-added chemicals and concurrently producing hydrogen (H2). Ethylene glycol, with its dual hydroxyl groups, stands out as a versatile organic substrate capable of yielding various C1 and C2 chemicals. In this study, we demonstrate that pH modulation markedly enhances the photocurrent of BiVO4 photoanodes, thus facilitating the efficient oxidation of ethylene glycol while simultaneously generating H2. Our findings reveal that in a pH = 1 ethylene glycol solution, the photocurrent density at 1.23 V vs. RHE can attain an impressive 7.1 mA cm-2, significantly surpassing the outputs in neutral and highly alkaline environments. The increase in photocurrent is attributed to the augmented adsorption of ethylene glycol on BiVO4 under acidic conditions, which in turn elevates the activity of the oxidation reaction, culminating in the maximal production of formic acid. This investigation sheds light on the pivotal role of electrolyte pH in the PEC oxidation process and underscores the potential of the PEC strategy for biomass valorization into value-added products alongside H2 fuel generation.

Mo-BiVO4 Photocatalytically Modified Ceramic Ultrafiltration Membranes for Enhanced Water Treatment Efficiency.

This study highlights the effectiveness of photocatalytically modified ceramic ultrafiltration (UF) membranes in alleviating two major drawbacks of membrane filtration technologies. These are the generation of a highly concentrated retentate effluent as a waste stream and the gradual degradation of the water flux through the membrane due to the accumulation of organic pollutants on its surface. The development of two types of novel tubular membranes, featuring photocatalytic Mo-BiVO4 inverse opal coatings, demonstrated a negligible impact on water permeance, ensuring consistent filtration and photocatalytic efficiency and suggesting the potential for maintaining membrane integrity and avoiding the formation of highly concentrated retentate effluents. Morphological analysis revealed well-defined coatings with ordered domains and interconnected macropores, confirming successful synthesis of Mo-BiVO4. Raman spectroscopy and optical studies further elucidated the composition and light absorption properties of the coatings, particularly within the visible region, which is vital for photocatalysis driven by vis-light. Evaluation of the tetracycline removal efficiency presented efficient adsorption onto membrane surfaces with enhanced photocatalytic activity observed under both UV and vis-light. Additionally, vis-light irradiation facilitated significant degradation, showcasing the versatility of the membranes. Total Organic Carbon (TOC) analysis corroborated complete solute elimination or photocatalytic degradation without the production of intermediates, highlighting the potential for complete pollutant removal. Overall, these findings emphasize the promising applications of Mo-BiVO4 photocatalytic membranes in sustainable water treatment and wastewater remediation processes, laying the groundwork for further optimization and scalability in practical water treatment systems.

Ultrathin layer TAFC on BiVO4 with ligand-to-metal charge transfer enhances built-in electric field for boosting photoelectrochemical water oxidation.

To reveal the mechanism of charge transfer between interfaces of BiVO4-based heterogeneous materials in photoelectrochemical water splitting system, the cocatalyst was grown in situ using tannic acid (TA) as a ligand and Fe and Co ions as metal centers (TAFC), and then uniformly and ultra-thinly coated on BiVO4 to form photoanodes. The results show that the BiVO4/TAFC achieves a superior photocurrent density (4.97 mA cm-2 at 1.23 VRHE). The charge separation and charge injection efficiencies were also significantly higher, 82.0 % and 78.9 %, respectively. From XPS, UPS, KPFM, and density functional theory calculations, Ligand-to-metal charge transfer (LMCT) acts as an electron transport highway in TAFC ultrathin layer to promote the concentration of electrons towards metal center, leading to an increase in the work function, which enhances the built-in electric field and further improves the charge transport. This study demonstrated that the LMCT pathway on TA-metal complexes enhances the built-in electric field in BiVO4/TAFC to promote charge transport and thus enhance water oxidation, providing a new understanding of the performance improvement mechanism for the surface-modified composite photoanodes.

BiVO4 Photoanode with NiV2O6 Back Contact Interfacial Layer for Improved Hole-Diffusion Length and Photoelectrochemical Water Oxidation Activity.

The short hole diffusion length (HDL) and high interfacial recombination are among the main drawbacks of semiconductor-based solar energy systems. Surface passivation and introducing an interfacial layer are recognized for enhancing HDL and charge carrier separation. Herein, we introduced a facile recipe to design a pinholes-free BiVO4 photoanode with a NiV2O6 back contact interfacial (BCI) layer, marking a significant advancement in the HDL and photoelectrochemical activity. The fabricated BiVO4 photoanode with NiV2O6 BCI layer exhibits a 2-fold increase in the HDL compared to pristine BiVO4. Despite this improvement, we found that the front surface recombination still hinders the water oxidation process, as revealed by photoelectrochemical (PEC) studies employing Na2SO3 electron donors and by intensity-modulated photocurrent spectroscopy measurements. To address this limitation, the surface of the NiV2O6/BiVO4 photoanode was passivated with a cobalt phosphate electrocatalyst, resulting in a dramatic enhancement in the PEC performance. The optimized photoanode achieved a stable photocurrent density of 4.8 mA cm-2 at 1.23 VRHE, which is 12-fold higher than that of the pristine BiVO4 photoanode. Density Functional Theory (DFT) simulations revealed an abrupt electrostatic potential transition at the NiV2O6/BiVO4 interface with BiVO4 being more negative than NiV2O6. A strong built-in electric field is thus generated at the interface and drifts photogenerated electrons toward the NiV2O6 BCI layer and photogenerated holes toward the BiVO4 top layer. As a result, the back-surface recombination is minimized, and ultimately, the HDL is extended in agreement with the experimental findings.

A Core/Shell Bi2S3/BiVO4 Nanoarchitecture for Efficient Photoelectrochemical Water Oxidation.

The construction of nanostructured heterostructure is a potent strategy for achieving high-performance photoelectrochemical (PEC) water splitting. Among these, constructing BiVO4-based heterostructure stands out as a promising method for optimizing light-harvesting efficiency and reducing severe charge recombination. Herein, we present a novel approach to fabricate a type II heterostructure of core/shell Bi2S3/BiVO4 using electrolytic deposition and successive ionic layer adsorption and reaction (SILAR) methods. We identify the type II heterostructure and the difference in fermi energy using UV-Vis spectroscopy, X-ray photoelectron spectroscopy, and PEC measurements. This redistribution of charges due to the fermi energy difference induces an interfacial built-in electric field from BiVO4 to Bi2S3, reinforcing the photogenerated hole transfer kinetics from BiVO4 to Bi2S3. The Bi2S3/BiVO4 heterostructure exhibits a superior photocurrent (6.0 mA cm-2), enhanced charge separation efficiency (85 %), and higher open-circuit photovoltage (350 mV). Additionally, the heterostructure displays a prolonged average lifetime of charge (1.63 ns), verifying this heterojunction could boost interfacial carriers' migration via an additional nonradiative quenching pathway. Furthermore, the lower photoluminescence (PL) intensity demonstrates the interfacial built-in electric field is beneficial for boosting charge migration.

Hierarchical Ti3C2/BiVO4 microcapsules for enhanced solar-driven water evaporation and photocatalytic H2 evolution.

Desalination processes frequently require a lot of energy to generate freshwater and energy, which depletes resources. Their reliance on each other creates tension between these two vital resources. Herein, hierarchical MXene nanosheets and bismuth vanadate (Ti3C2/BiVO4)-derived microcapsules were synthesized for a photothermal-induced photoredox reaction for twofold applications, namely, solar-driven water evaporation and hydrogen (H2) production. For this purpose, flexible aerogels were fabricated by introducing Ti3C2/BiVO4 microcapsules in the polymeric network of natural rubber latex (NRL-Ti3C2/BiVO4), and a high evaporation rate of 2.01 kg m-2 h-1 was achieved under 1-kW m-2 solar intensity. The excellent performance is attributed to the presence of Ti3C2/BiVO4 microcapsules in the polymeric network, which provides balanced hydrophilicity and broadband sun absorption (96 %) and is aimed at plasmonic heating with microscale thermal confinement tailored by heat transfer simulations. Notably, localized plasmonic heating at the catalyst active sites of the Ti3C2/BiVO4 heterostructure promotes enhanced photocatalytic H2 production evolved after 4 h of reaction is 9.39 µmol, which is highly efficient than pure BiVO4 and Ti3C2. This method turns the issue of water-fuel crisis into a collaborative connection, presenting avenues to collectively address the anticipated demand rather than fostering competition.

BiVO4-Based Heterojunction Photocathode for High-Performance Photoelectrochemical Hydrogen Peroxide Production.

Photoelectrochemical (PEC) cells provide a promising solution for the synthesis of hydrogen peroxide (H2O2). Herein, an integrated photocathode of p-type BiVO4 (p-BVO) array with tetragonal zircon structure coupled with different metal oxide (MOx, M = Sn, Ti, Ni, and Zn) heterostructure and NiNC cocatalyst (p-BVO/MOx/NiNC) was synthesized for the PEC oxygen reduction reaction (ORR) in production of H2O2. The p-BVO/SnO2/NiNC array achieves the production rate 65.46 µmol L-1 h-1 of H2O2 with a Faraday efficiency (FE) of 76.12%. Combined with the H2O2 generation of water oxidation from the n-type Mo-doped BiVO4 (n-Mo:BVO) photoanode, the unbiased photoelectrochemical cell composed of a p-BVO/SnO2/NiNC photocathode and n-Mo:BVO photoanode achieves a total FE of 97.67% for H2O2 generation. The large area BiVO4-based tandem cell of 3 × 3 cm2 can reach a total H2O2 production yield of 338.84 µmol L-1. This work paves the way for the rational design and fabrication of artificial photosynthetic cells for the production of liquid solar fuel.

2D TiO2 Nanosheets Decorated Via Sphere-Like BiVO4: A Promising Non-Toxic Material for Liquid Phase Photocatalysis and Bacterial Eradication.

An in-depth investigation was conducted on a promising composite material (BiVO4/TiO2), focusing on its potential toxicity, photoinduced catalytic properties, as well as its antibiofilm and antimicrobial functionalities. The preparation process involved the synthesis of 2D TiO2 using the lyophilization method, which was subsequently functionalized with sphere-like BiVO4 through wet impregnation. Finally, we developed BiVO4/TiO2 S-scheme heterojunctions which can greatly promote the separation of electron-hole pairs to achieve high photocatalytic performance. The evaluation of concentration- and time-dependent viability inhibition was performed on human lung carcinoma epithelial A549 cells. This assessment included the estimation of glutathione levels and mitochondrial dehydrogenase activity. Significantly, the BiVO4/TiO2 composite demonstrated minimal toxicity towards A549 cells. Impressively, the BiVO4/TiO2 composite exhibited notable photocatalytic performance in the degradation of rhodamine B (k=0.135 min-1) and phenol (k=0.016 min-1). In terms of photoinduced antimicrobial performance, the composite effectively inactivated both gram-negative E. coli and gram-positive E. faecalis bacteria upon 60 minutes of UV-A light exposure, resulting in a significant log 6 (log 10 CFU/mL) reduction in bacterial count. In addition, a 49 % reduction of E. faecalis biofilm was observed. These promising results can be attributed to the unique 2D morphology of TiO2 modified by sphere-like BiVO4, leading to an increased generation of (intracellular) hydroxyl radicals, which plays a crucial role in the treatments of both organic pollutants and bacteria. This research has significant potential for various applications, particularly in addressing environmental contamination and microbial infections.

Visible-Light-Driven Z-Type Pg-C3N4/Nitrogen Doped Biochar/BiVO4 Photo-Catalysts for the Degradation of Norfloxacin.

Antibiotics cannot be effectively removed by traditional wastewater treatment processes, and have become widespread pollutants in various environments. In this study, a Z-type heterojunction photo-catalyst Pg-C3N4 (PCN)/Nitrogen doped biochar (N-Biochar)/BiVO4 (NCBN) for the degradation of norfloxacin (NOR) was prepared by the hydrothermal method. The specific surface area of the NCBN (42.88 m2/g) was further improved compared to BiVO4 (4.528 m2/g). The photo-catalytic performance of the catalyst was investigated, and the N-Biochar acted as a charge transfer channel to promote carrier separation and form Z-type heterojunctions. Moreover, the NCBN exhibited excellent performance (92.5%) in removing NOR, which maintained 70% degradation after four cycles. The main active substance of the NCBN was •O2-, and the possible degradation pathways are provided. This work will provide a theoretical basis for the construction of heterojunction photo-catalysts.

The CuSCN layer between BiVO4 and NiFeOx for facilitating photogenerated carrier transfer and water oxidation kinetics.

Modification of oxygen evolution co-catalyst (OEC) on the surface of bismuth vanadate (BiVO4) can effectively improve the kinetics of water oxidation, but it is still limited by the small hole extraction driving force at the BiVO4/OEC interface. Modulating the BiVO4/OEC interface with a hole transfer layer (HTL) is expected to facilitate hole transport from BiVO4 to the OEC surface. Herein, a copper(I) thiocyanate (CuSCN) HTL is inserted between BiVO4 and NiFeOx OEC to create BiVO4/CuSCN/NiFeOx photoanode, resulting in a significant enhancement of photoelectrochemical (PEC) water splitting performance. From electrochemical analyses and density functional theory (DFT) simulations, the markedly enhanced PEC performance is attributed to the insertion of CuSCN as an HTL, which promotes the extraction of holes from BiVO4 surface and boosts the water oxidation kinetics. The optimal photoanode achieves a photocurrent density of 5.6 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (vs. RHE) and an impressive charge separation efficiency of 96.2 %. This work offers valuable insights into the development of advanced photoanodes for solar energy conversion and emphasizes the importance of selecting an appropriate HTL to mitigate recombination at the BiVO4/OEC interface.