Photoelectrocatalytic Research Articles

Metal−organic framework‐derived NiO/ZnO composites for photoelectro catalytic reduction of Cr(VI)

Metal−organic framework‐derived NiO/ZnO composites for photoelectro catalytic reduction of Cr(VI)

Facile Synthesis of a Micro–Nano-Structured FeOOH/BiVO4/WO3 Photoanode with Enhanced Photoelectrochemical Performance

In the realm of photoelectrocatalytic (PEC) water splitting, the BiVO4/WO3 photoanode exhibits high electron–hole pair separation and transport capacity, rendering it a promising avenue for development. However, the charge transport and reaction kinetics at the heterojunction interface are suboptimal. This study uses the hydrothermal–electrodeposition–dip coating–calcination method to prepare a microcrystalline WO3 photoanode thin film as the substrate material and combines it with nanocrystalline BiVO4 to form a micro–nano-structured heterojunction photoanode to enhance the intrinsic and surface/interface charge transport properties of the photoanode. Under the condition of 1.23 V vs. RHE, the photoelectric current density reaches 1.09 mA cm−2, which is twice that of WO3. Furthermore, by using a simple impregnation–mineralization method to load the amorphous FeOOH catalyst, a noncrystalline–crystalline composite structure is formed to increase the number of active sites on the surface and reduce the overpotential of water oxidation, lowering the onset potential from 0.8 V to 0.6 V (vs. RHE). The photoelectric current density is further increased to 2.04 mA cm−2 (at 1.23 V vs. RHE). The micro–nano-structure and noncrystalline–crystalline composite structure proposed in this study will provide valuable insights for the design and synthesis of high-efficiency photoelectrocatalysts.

Threefold Impact on Reaction Coordinate Mapping of Zirconium Based Tri‐Chalcogenide Pseudo‐Monolayers as Emerging Ultrathin Catalysts for Water Splitting

AbstractThe continuous quest of finding optimum catalysts for photo‐electrocatalytic (PEC) water splitting has been revolving around 2D ultrathin materials because of the fact of exploiting both the surface area. In this work, a threefold impact is envisaged route to enhance the activity both in terms of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the emerging Zirconium Tri‐sulfides (ZrS3) based pseudo‐monolayers. Due to the unique and distinct electronic properties of the tri‐chalcogenide systems as compared to the di‐chalcogenide counterpart of Zirconium, one could afford to explore the implications of not only single‐atom functionalization and vacancy defect, but also the external strain to expedite the bifunctional catalytic activity in this promising material. Rigorous electronic structure calculations have been performed for the mentioned threefold effect on not only the band‐edge alignment, but going beyond to it by further constructing the reaction coordinate mapping corresponding to HER and OER mechanism. The repercussion of external strain in addition to the single atom functionalization and vacancy defect on the adsorption free energies of the prime intermediates of HER and OER reaction has been further correlated with the work function variation in this pseudo‐monolayer system.

Disinfection of synthetic human urine by mixed metal oxide anode through photo/electrochemical oxidation

This study investigates the electrooxidation treatment of synthetic urine (SU) using quaternary mixed metal oxide (d-MMO) anodes in both batch and continuous modes. We combine photocatalysis (PC) and electrooxidation (EO) to enhance pollutant degradation. The impact of treatment time, pH, Na/Cl ratio, and current density on COD removal and the specific energy consumption is examined. Optimized parameters for batch EO treatment yield a desirability value (D) of 0.941, with COD removal of 90.55 % and energy consumption of 20.851 kWh/kg of COD removed. Treatment time is reduced from 10.05 h to 6.5 h with PEC (Photoelectrocatalysis) incorporation. The stability and durability of anodes are confirmed through XRD and FE-SEM/EDS analysis, even after 500 recycling cycles. This research stands out for utilizing innovative d-MMO anodes for EO and PEC, capturing molecular hydrogen gas during scale-up trials for SU. Through this study, we are proposing for the first time, the novel composition of d-MMO (Ti/IrO2/Ta2O5/SnO2/Sb2O5) for the treatment of SU on a pilot-scale in continuous mode with solar panels, thus making the process cost effective with less energy consumption.

Synthesis of isolated ZnO nanorods on introducing g-C3N4 for improved photoelectrocatalytic methanol production by CO2 reduction

The photoelectrocatalytic (PEC) CO2 reduction into fuels has been developed as a prospective approach to resolve the environmental and energy concerns. Herein, a composite catalyst comprising ZnO nanorods dispersed on the g-C3N4 surface (g-C3N4/ZnO) was successfully obtained by simple ZnO seed layer formation and then hydrothermal processes. The synthesized and characterized g-C3N4/ZnO catalytic composite showed 2.8 times enhanced photocurrent density at −1 V applied potential than the bare g-C3N4. The g-C3N4/ZnO catalyst exhibited 2.86 times enhanced the PEC CO2 reduction to methanol than the prepared bare ZnO catalyst. The catalyst’s enhanced PEC CO2 reduction performance was ascribed to the high surface area, and higher generation and lower recombination of e−/h+ pairs. For the first time, this study showed the enhanced methanol production by the PEC reduction of CO2 over the prepared g-C3N4/ZnO catalytic composite.

Building organic-inorganic heterojunction NiCo2O4/h-BN toward artificial photosynthesis—Boron as hole

To convert CO2 and water into organic chemicals via photoelectrocatalytic (PEC) reduction of CO2 under mild conditions is considered to be one of promising methods to address a series of problems like climate change and energy crisis caused by over-emission of CO2. Herein, the organic-inorganic heterojunctions were designed and fabricated by using organic h-BN and inorganic NiCo2O4 as precursors. The optimal NiCo2O4@h-BN-6 heterojunction exhibited impressive performance in CO2 reduction, yielding C2+ chemicals with 100 % selectivity in a rate of 28.5 μM cm−2 h−1. This phenomenon is attributed to the structural feature of three active sites of nitrogen in a unique hexacycle like benzene, which benefit the carbon-carbon coupling among the intermediates. The first observed *N-H species suggest that the N sites can adsorb protons and electrons and convert them into highly active hydrogen atoms. The verification experiments demonstrate that the material will oxidize intermediates to acetic acid where boron atoms are presented as holes in semiconductor. The isotopic labeling experiments of 13CO2 and H218O verified that the products were derived from CO2 and water. The key active intermediates such as *CHO, *=CO, and *COCHO in the synthetic process of C2+ products had been confirmed by operando FTIR spectra and DFT calculations.

Interface and Defect Engineering in 3D Co3O4‐Ov/TiO2 to Boost Simultaneous Removal of BPA and Cr(VI) upon Photoelectrocatalytic/Peroxymonosulfate (PEC/PMS) System

AbstractThe combination of photoelectrocatalytic (PEC) and peroxymonosulfate (PMS) is an innovative strategy for environmental treatment. And fabricating a highly efficient photoelectrode is the most pivotal factor in PEC reactions. This study designs an advanced Co3O4‐Ov/TiO2 photoelectrode by a dual‐modification strategy encompassing interface engineering and defect engineering. The photoelectric characterization validates the synergy of oxygen vacancies and dual heterojunctions. Simulated electron density distribution and Kelvin probe force microscopy (KPFM) elucidate the charge transfer pathway between Co3O4‐Ov and TiO2. 1O2 and SO4 .− are confirmed to be primarily responsible for the BPA oxidation in PEC/PMS system by radical scavenger experiments and the EPR technique. And the attack sites of BPA are precisely identified based on the Fukui index. Furthermore, density functional theory (DFT) calculations testify that Co3O4‐Ov can improve the adsorption capacity of PMS and reduce the energy barrier of the reaction process, while XPS analysis showed Co3+/Co2+ redox couple can accelerate PMS activation. Enhanced anode oxidation can effectively promote cathode reduction and consequently Co3O4‐Ov/TiO2‐PMS/PEC system presents a superior removal of both pollutants within only 15 min with fast kinetics (0.15 min−1 for BPA, 0.29 min−1 for Cr(VI)). This work provides unique insight into designing a highly efficient PMS/PEC system for simultaneous pollutant treatment.

Efficient CO2 reduction to C2 products in a Ce-TiO2 photoanode-driven photoelectrocatalysis system using a Bnanometer Cu2O cathode

Excessive emission of CO2 into the atmosphere has caused significant environmental issues. Photoelectrocatalytic (PEC) reduction of CO2 is an effective method that combines the benefits of both photo- and electrocatalysis. This process effectively minimizes CO2 emissions, enhances the efficiency of CO2 reduction, and diminishes energy consumption during the reduction process. In this work, we have successfully developed a photoelectrochemical (PEC) system, integrating a Ce-doped TiO2 film as the photoanode and Cu2O as the dark cathode, in which the 4 % Ce-TiO2 film photoanode demonstrated the best performance. Electrochemical performance data revealed that the Cu2O catalysts, characterized by their octahedral geometry that optimally presents active sites for CO2 reduction, displayed superior activity in converting CO2. Through a straightforward hydrothermal synthesis, we crafted three-dimensional, flower-like TiO2 thin films. The strategic incorporation of cerium into the TiO2 matrix not only enhanced the material's crystallinity but also resulted in a uniform and compact morphology. This modification significantly narrowed the band gap of TiO2, thereby boosting its photocatalytic capabilities. In the system where a 4 % Ce-TiO2 thin film photoanode was used to drive the PEC reduction of CO2, the octahedral Cu2O catalyst demonstrated the highest selectivity for C2 products. This occurred at a reaction voltage of −1.4 V vs. RHE, resulting in a total Faraday efficiency of 67.33 %. Notably, this Faraday efficiency is double the one produced from the electrocatalytic (EC) system. This work demonstrates that the use of a 4 % Ce-TiO2 film as a photoanode is able to solve the photocorrosion problem of the Cu2O catalyst while employing a photovoltaic combination to enhance the selectivity to C2 products.

Photoelectrolysis of glucose and fructose containing solution in PGM-free cells for hydrogen and valuable chemicals production

This study investigates the reforming of glucose and fructose by photoelectrolyis, employing TiO2 NTs photoanodes for the selective oxidation of the carbohydrates and Ni foam as cathode. TiO2 NTs with different structural features were grown on Ti felt via anodizing and annealing to promote their crystallization.These electrodes were tested in aqueous solutions at three different pH values (i.e., 2, 7, and 12) both without and with the addition of biomass. When biomass was present, the hydrogen production rate increased, reaching faradic efficiencies (FEs) ∼ 100% in spite of the use of undivided cell, allowing the simultaneous production of valuable partial oxidation compounds, such as gluconic acid (GA) and formic acid (FA), with FEs of 24% and 55% respectively, and overall quantum yields of 5.67% and 4.36% respectively. The photoanodes used demonstrated high mechanical and chemical stability under all the tested conditions, with electrode performance remaining consistent over time, allowing the reuse of the same electrode for a not limited number of runs after a mild cleaning step.The results demonstrated that this photoelectrocatalytic (PEC) process is promising for both biomass valorization and H2 production.

Photoelectrocatalytic allylic C–H oxidation to allylic alcohols coupled with hydrogen evolution

Allylic C–H bond oxidation of cycloolefins to allylic alcohols has attracted tremendous attention owing to its widespread application in pharmaceuticals production and natural synthesis. However, the production of allylic alcohols still suffers from the challenges of unsatisfactory selectivity and harsh conditions. Herein, we report the sustainable photoelectrocatalytic (PEC) allylic C–H oxidation to allylic alcohols, achieving the oxidation of cyclohexene to 2-cyclohexenol with a selectivity of 97.2 %. We reveal the reaction pathway wherein photogenerated holes and OH– synergistically activate cyclohexene to carbocation intermediates, and these intermediates combine with OH– to produce 2-cyclohexenol. Additionally, the mechanism by enriching OH– in local area of photoanode surface to enhance PEC performance is uncovered. Furthermore, we designed a self-powered PEC reaction system, attaining a 2-cyclohexenol productivity of 11.95 μmol h–1 (selectivity > 97 %) coupled with a H2 productivity of 1.44 mL h–1, demonstrating the application potential of this new strategy.

Interfacial internal-electric field on nanoneedle CoOOH/WO3 photoelectrode realized efficient photoelectrocatalytic degradation of 4-fluorophenol via facilitated H2O oxidation and physical contact

Development of photoelectrodes capable of efficiently degrading fluorinated pollutants with C-F bonds remains a significant challenge in the photoelectrocatalytic (PEC) system. Herein, a nanoneedle CoOOH-loaded nanoplate WO3 photoelectrode (CoOOH/WO3) was successfully fabricated, which exhibited a high rate of 3.92 × 10−2 min−1 in the PEC degradation of 4-fluorophenol, much higher than that of pristine WO3. The ∙OH generation rate by CoOOH/WO3 was 1.5 times that by WO3. Photoelectric features demonstrated that an interfacial internal-electric field provided a driving force for efficient charge separation in the CoOOH/WO3; Density functional theory calculations demonstrated that constructing CoOOH onto WO3 reduced thermodynamic barriers for H2O oxidation and for *OH formation, thereby promoting the ∙OH generation; Computational fluid dynamic simulations confirmed the facilitated surface reactions and intensified contact between pollutants and ∙OH. This study provided viable insights into simultaneously improving the charge separation efficiency, surface H2O oxidation kinetic and physical contact in PEC wastewater treatment.

Fabrication of rGO/BiOI photocathode and its catalytic performance in the degradation of 4-Fluoroaniline

Organic fluorine compounds are acute carcinogenic and mutagenic to humans. Photoelectrocatalysis (PEC) treatment is an innovative technology in the field of the removal of fluorine compounds, and thus current research focused on improving stability and catalytic ability of photoanode. In this study, it has been synthesized a rGO/BiOI photocathode for the efficient degradation of 4-Fluoroaniline (4-FA). The physical characterization and photoelectrochemical properties of the photocathode was determined. The results indicate that the PEC treatment with the rGO/BiOI photocathode was more efficient compared with individual processes. During the optimization experiments, the PEC treatment achieved 99.58 % and 72.12 % of 4-FA degradation and defluorination within 1 h. Cyclic stability experiments show that rGO/BiOI photocathode was efficient and stable, which reached 96.91 % and 67.64 % of 4-FA degradation and defluorination after five cycles. Mechanism analysis indicates that the PEC process was based on an electrochemical reaction and photo-induced processes. The degradation product of 4-FA was mainly 2,4-di-t-butylphenol, and trapping experiments indicates that h+ is the primary oxidizing species. Therefore, PEC treatment with rGO/BiOI photocathode is a competitive green approach to remove fluorine compounds pollutants and brings new insights into development of PEC treatment.

Assessment of Ti, Ir, Ta and Ru influence on mixed metal oxide electrodes for photoelectrochemical generation of persulfate: Impact on sulfamethoxazole degradation

The presence of persulfate (S2O82−) in decontamination processes favors the oxidation of organic pollutants due to its strong oxidation power. In this research we study the photoelectrochemical generation of persulfate using five mixed metal oxides electrodes (MMO) with different compositions and its effect on the degradation of sulfamethoxazole antibiotic (SMX) by photoelectrocatalysis (PEC) and electro-oxidation (EO).By PEC, all anodes generated a higher concentration of S2O82− than those not exposed to light. The high S2O82−concentration obtained by PEC was 0.150 mM using MMO[Ti/Ir/Ta] in a solution with Na2SO4 100 mM applying a current density of 2 mA/cm2. On the other hand, the maximum concentration obtained was 0.250 mM at 30 min of electrolysis for MMO[Ti/Ir/Ta] using Na2SO4 50 mM and applying current density of 5 mA/cm2. S2O82−production by EO was between 0.005 and 0.089 mM. It is observed that MMO based in Ta2O5 showed the best S2O82− production.The effect of S2O82− electro-generation (using the anode with the highest and the anode with the lowest S2O82− production) on the degradation of sulfamethoxazole by PEC and EO was studied using the experimental conditions with the best production of this oxidant. MMO[Ti/Ir/Ta] and MMO[Ti/Ru] were used as anodes, and it was observed that by PEC, 100% of SMX was degraded after 30 min of electrolysis using MMO[Ti/Ir/Ta] and 60 min using MMO[Ti/Ru]. By EO, the degradation of SMX was partial, demonstrating that the electrophotocatalytic effect favors the generation of S2O82−, enhancing the degradation of SMX at short electrolysis times.

Developing Z-scheme Bi2MoO6@α-MnO2 beaded core-shell heterostructure in photoelectrocatalytic treatment of organic wastewater

Photoelectrocatalysis (PEC) oxidation technology with the combination of electrocatalysis and photocatalysis is an ideal candidate for treatment of dyeing wastewater containing multifarious intractable organic compounds with high chroma. Constructing high-quality heterojunction photoelectrodes can effectively suppress the recombination of photo-generated carriers, thereby achieving efficient removal of pollution. Herein, a beaded Bi2MoO6@α-MnO2 core-shell architecture with tunable hetero-interface was prepared by simple hydrothermal-solvothermal process. The as-synthesized Bi2MoO6@α-MnO2 had larger electrochemically active surface area, smaller charge transfer resistance and negative flat band potential, and higher separation efficiency of e−/h+ pairs than pure α-MnO2 or Bi2MoO6. It is noteworthy that the as-synthesized Bi2MoO6@α-MnO2 showed Z-scheme heterostructure as demonstrated by the free radical quenching experiments. The optimized Bi2MoO6@α-MnO2-2.5 exhibited the highest degradation rate of 88.64% in 120 min for reactive brilliant blue (KN-R) and accelerated stability with long-term(∼10000s) at the current density of 50 mA cm−2 in 1.0 mol L−1 H2SO4 solution. This study provides valuable insights into the straightforward preparation of heterogeneous electrodes, offering a promising approach for the treatment of wastewater in various industrial applications.

Charge Redistribution in Nise2/Mos2 n–n Heterojunction Towards the Photoelectrocatalytic Degradation of Ciprofloxacin

AbstractThis study reports the photoelectrocatalytic (PEC) activity of a n–n heterojunction comprising MoS2 and NiSe2. The synthesis of the composite was achieved through a facile solvothermal method, yielding an exfoliated MoS2 layered sheet loaded with NiSe2 nanoparticles. Under visible light radiation and an external electric field, the obtained composite NiSe2/MoS2 exhibited enhanced catalytic activity for ciprofloxacin (CIP) degradation. The NiSe2/MoS2 heterojunction achieved about 78 % degradation efficiency with a first‐order kinetic rate of 0.0111 min−1, compared to 38 % efficiency and a first‐order kinetic rate of 0.0044 min−1 observed for MoS2. The NiSe2/MoS2 heterojunction was more advantageous due to the synergy of charge carrier induction by visible light radiation and improved charge carrier separation induced by the external electric field. The formation of n–n heterojunction at the interface of the two materials resulted in charge redistribution in the materials, with a simultaneous realignment of the band structure to achieve Fermi energy equilibration. The primary reactive species responsible for CIP degradation was identified as the photo‐induced h+. Furthermore, the catalyst exhibited high stability and reusability, with no significant reduction in activity observed after five experimental cycles. This study reveals the potential of exploring the synergy between the photocatalytic and electrocatalytic processes in removing harmful pharmaceutical compounds from water.

Effects of heating rate and deposition cycle on the structural, optical, and photoelectrocatalytic properties of electrodeposited hematite films

In this research, electrodeposited hematite films were prepared at voltammetry deposition cycles of 60 and calcined at 550 °C in a furnace after ramping the temperature at the rates of 2 °C/min, 10 °C/min, 35 °C/min, and rapid heating of about 100 °C/min. Additional samples were fabricated at deposition cycles of 15, 30, and 80, and also calcined at 550⁰C at a heating rate of 10⁰C/min. The impact of heating rate and deposition cycle number variations on the structural, optical, and photoelectrocatalytic (PEC) properties of the hematite films were assessed. All the films' X-ray diffraction (XRD) measurements showed strong peaks at the lattice planes (104) and (110), verifying hematite's rhombohedral crystal structure. The films prepared at the heating rate of 10⁰C/min boosted the crystallization of the films by 47.2 % relative to the ones prepared at 2⁰C/min. An increase in the deposition cycle number resulted in increasing film thickness and the sample’s crystallization. An indirect bandgap of 1.94–2.1 eV was estimated for the samples, with the least value obtained for the films treated at the heating rate of 10⁰/min and deposition cycles of 60. The same samples also yielded the largest photocurrent density of 26.2 μA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), while the photoanodes fabricated at 2 °C/min exhibited the lowest photo-activity. The enhanced photocurrent observed for the films has been associated with high crystallinity, improved photon absorption, reduced flatband potential, and increased charge separation at the film’s surface. This research underscores the importance of optimizing both the heating rate and deposition cycle numbers in the fabrication of electrodeposited photoelectrodes for PEC applications.

Synthesis and evaluation of a self-standing CuBi2O4/CuO/Fe2O3 electrode for arsenic removal via photoelectrocatalysis

Water contamination by arsenic (As) poses a significant threat to millions of people worldwide. The development of an effective, affordable, and decentralized system for As removal remains a critical need, particularly to treat As at environmentally relevant concentrations. In this study, a self-standing electrode composed of an engineered interface of CuBi2O4/CuO/Fe2O3 was synthesized on fluorine-doped tin oxide (FTO) substrate using electrodeposition and dip-coating techniques. Each layer Bi2O3, CuBi2O4, CuO, and Fe2O3 was characterized photochemically and electrochemically to identify their light harvesting and electron transfer capacities. The efficacy of the CuBi2O4/CuO/Fe2O3 electrode for removing 0.5 mg L−1 As (III) was evaluated under various treatment conditions, including adsorption, photocatalysis (PC), electrocatalysis (EC), and photoelectrocatalysis (PEC). The PEC treatment at 1.0 V vs Ag/AgCl under visible light irradiation exhibited outstanding As removal efficiency of 96.8 %, surpassing PC (40.4 %) and EC (54.5 %). Fundamental evaluation of the removal mechanism revealed that CuBi2O4/CuO/Fe2O3 oxidizes As (III) to As (V) for enhanced adsorption onto iron oxide sites, as confirmed by X-ray photoelectron spectroscopy (XPS), which identified both As (III) and As (V) adsorbed on the surface. These findings underscore the importance of a rational design approach for photoanodes in As adsorption, highlighting the significant role of individual layers.

Recent Developments in Nickel-Based Layered Double Hydroxides for Photo(-/)electrocatalytic Water Oxidation.

Layered double hydroxides (LDHs), especially those containing nickel (Ni), are increasingly recognized for their potential in photo(-/)electrocatalytic water oxidation due to the abundant availability of Ni, their corrosion resistance, and their minimal toxicity. This review provides a comprehensive examination of Ni-based LDHs in electrocatalytic (EC), photocatalytic (PC), and photoelectrocatalytic (PEC) water oxidation processes. The review delves into the operational principles, highlighting similarities and distinctions as well as the benefits and limitations associated with each method of water oxidation. It includes a detailed discussion on the synthesis of monolayer, ultrathin, and bulk Ni-based LDHs, focusing on the merits and drawbacks inherent to each synthesis approach. Regarding the EC oxygen evolution reaction (OER), strategies to improve catalytic performance and insights into the structural evolution of Ni-based LDHs during the electrocatalytic process are summarized. Furthermore, the review extensively covers the advancements in Ni-based LDHs for PEC OER, including an analysis of semiconductors paired with Ni-based LDHs to form photoanodes, with a focus on their enhanced activity, stability, and underlying mechanisms facilitated by LDHs. The review concludes by addressing the challenges and prospects in the development of innovative Ni-based LDH catalysts for practical applications. The comprehensive insights provided in this paper will not only stimulate further research but also engage the scientific community, thus driving the field of photo(-/)electrocatalytic water oxidation forward.

Stabilizing Layered BiOBr Photoelectrocatalyst by Van Der Waals Heterojunction Strategy

AbstractThe photoelectrocatalytic (PEC) hydrogen evolution reaction (HER) holds immense promise as a clean and sustainable method for hydrogen production. However, finding a suitable catalyst which is efficient, stable and scalable still remains an open challenge. BiOBr is a 2D layered material studied as photoelectrocatalyst because of its suitable band gap for light absorption and potential for up‐scalable production. However, its application in HER is not commonly reported, because of instability in a cathodic PEC environment, driven by a strong tendency to reduction to metallic bismuth. To solve this problem, 2D MoS2 is used to induce the formation of a van der Waals (vdW) layered heterojunction (HJ) to stabilize the lattice of BiOBr during HER. By performing PEC HER with the HJs containing different ratios of MoS2, it is found that the HJ with 1 % MoS2 can increase the stability of BiOBr, while the one with 50 % MoS2 can even accelerate the reduction of BiOBr to metallic bismuth. DFT calculations reveal that the interface between BiOBr and MoS2 in the HJ with 1 % MoS2 tends to push active electrons on the sulfur atoms, thus favoring HER. On the other hand, in the 50 % HJ, active electrons are prone to react with BiOBr to induce reduction. In situ wide‐angle X‐ray diffraction (WAXD) on the MoS2/BiOBr HJs with 1 % and 50 % of MoS2 allows to track the phase change and the phase transfer speed of BiOBr during PEC HER. Interestingly, when the HJ is illuminated with UV light, a lower amount of BiOBr is reduced to Bi under negative potential, due to the presence of photogenerated holes reacting with the extra electrons derived from the negative bias and preventing the BiOBr photon absorber to be further reduced.

BiVO4 photoanode modified with FeOOH cocatalyst for visible-light-driven photoelectrocatalytic degradation of organic pollutants

Photoelectrocatalytic (PEC) could effectively and gently treat wastewater. Nonetheless, catalysts face the pronounced tendency of sluggish photogenerated carrier transfer and carrier recombination. In this paper, we herein fabricate FeOOH/BiVO4 photoanode through the incorporation of a cocatalyst FeOOH onto the BiVO4 surface. This modified photoanode demonstrated improved performance when coupled with peroxomonosulfate (PMS) for the purpose of oxidizing tetracycline hydrochloride (TCH) within the PEC system. In the presence of 0.3 mM PMS, the degradation efficiency of TCH increased from 65 % to 88 % within 60 min. The effects of PMS concentration, applied voltage and TCH concentration on the decomposition were studied in detail. Through free radical scavenging experiments, it was found that SO4•-, h+ and ·OH played an important role in TCH degradation. In addition, the FeOOH/BiVO4 with PMS activation in the PEC system also could be capable of dealing with some more organic pollutants (antibiotics and dyes) and achieving good degradation effect. More importantly, TCH degradation rate by FeOOH/BiVO4 photoanode is still over 80 % after five cycles of reuse. This work provides a promising approach for the synthesis of novel photoanodes in the PEC systems with excellent PEC properties in removing environmental pollutants.