Photoelectrocatalytic Degradation Efficiency Research Articles

Boron functionalized carbon-based metal-free catalyst for efficient photoelectrocatalytic degradation of pollutants

Boron functionalized carbon-based metal-free catalyst for efficient photoelectrocatalytic degradation of pollutants

Constructing core-shell structured Co3O4–MnWO4 composite photoelectrode with superior PEC water purification performance

Semiconductor photoelectrocatalytic (PEC) technology is one of the most effective methods for removing organic pollutants from wastewater in advanced oxidation processes(AOPs). The selection of suitable semiconductor materials as photoanodes is a crucial factor for achieving superior PEC performance. Here, a core-shell structured Co3O4–MnWO4 architecture is created by enveloping MnWO4 nanoparticles onto the surface of Co3O4 nanowires through a two-step hydrothermal process. The optimized Co3O4–MnWO4-5 photoelectrode showed superior PEC degradation efficiency for KN-R (∼91.2% in 2 h) and durable stability (the accelerated lifetime reached ∼9100 s at a current density of 50 mA cm−2). Three actual wastewaters were also collected to verify the practical applicability of the photoelectrode.The energy consumption was measured at 4.48 kWhm−3, with a COD removal efficiency of 83% and a decolorization rate of 98%. These results demonstrate the excellent performance and promising application of the photoelectrode. The enhancement of PEC performance for the core-shell structured Co3O4–MnWO4 architecture can be attributed to the suitable energy band structure of the Co3O4–MnWO4 composite, higher OEP, larger electrochemical active surface area, accelerated transport of interface carriers, and lower charge transfer resistance. The energy band structure of the Co3O4–MnWO4 composite showed a strong redox ability to induce electrons/holes (e−/h+), which enhances the generation of intermediate active species (hydroxyl radical ·OH and superoxide radicals ·O2-). Therefore, the rationally designed core-shell structured Co3O4–MnWO4 architecture exhibited excellent practical applicability in the degradation of organic pollutants.

Robust photoelectrocatalytic degradation of antibiotics by organic-inorganic PDISA/Bi2WO6 S-scheme heterojunction membrane

Ensuring the stability of the photoelectrode is paramount for optimal photoelectrocatalysis performance. In this investigation, a hybrid nanofiber film, incorporating the π-π conjugated self-assembly of perylene diimide monomers (PDISA) with Bi2WO6 (PDISA/Bi2WO6), was fabricated through the electrospinning process. Subsequently, this flexible electrospun film was pressed onto a Ni mesh to create a robust PDISA/Bi2WO6 electrode membrane. Results from photoelectrocatalytic studies reveal that the devised PDISA/Bi2WO6 photoanode significantly enhances the photoelectrocatalytic degradation efficiency of tetracycline (TC) and ciprofloxacin (CIP). Specifically, the apparent rate constants for the photoelectrocatalytic degradation of TC by 30%PDISA/Bi2WO6, compared to pristine PDISA and Bi2WO6, are elevated by 1.9 and 2.0 times, respectively. Moreover, the reaction rates of the photoelectrocatalytic (PEC) process surpass those of photocatalysis (PC) and electrocatalysis (EC) by 1.9 times and 8.0 times, respectively. Impressively, even after five cycles of PEC degradation of TC, the photoelectrode maintains 98.4% of its initial degradation rate, indicating its exceptional stability. These improvements in degradation efficiency and stability are attributed to the creation of the PDISA/Bi2WO6 S-scheme heterojunction membrane photoanode and the synergistic effects of photoelectrocatalysis.

Fabrication of WO3 nanorod arrays modified by BiOBr and their enhanced photoelectrocatalytic activity

BiOBr/WO3 nanorod array (NRA) composite photoelectrodes were successfully prepared using a solvothermal method. The instrumental characterisation of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, incident photoelectric conversion efficiency and ultraviolet diffuse reflectance indicates that the obtained BiOBr/WO3 NRAs exhibit good crystallinity and purity, and they can utilise light with wavelengths less than approximately 440 nm. On the surface of the WO3 nanorods, BiOBr thin nanosheets grow uniformly with strong adhesion and a 3D structure. The composite photoelectrode loaded with an appropriate amount of BiOBr (labelled BW-1 NRA) exhibits the best photoelectrocatalytic (PEC) activity. The PEC degradation efficiency of 10 mg/L of bisphenol A reached 95.7 % after 3 h at 1.0 V bias voltage. This value is 2.8 times that of individual photocatalytic degradation. After four times of recycling, the decrease in catalytic activity is insignificant, indicating the good stability of the catalyst. By analysing the results of the photoelectrochemical properties, band structures and types of free radicals, a conclusion is drawn that the excellent catalytic performance of BW-1 NRA is ascribed to the following aspects. (1) The formation of the p–n heterojunction by BiOBr and WO3 can effectively separate photogenerated electrons and holes. (2) Bias drives the migration of photogenerated electrons to the external circuit, further preventing the recombination of photogenerated electrons and holes. (3) The 3D structure of the photoelectrode has a large specific surface area and multiple active sites, improving light absorption and utilisation efficiency.

Unlocking a Type-II CoO@BiVO4 Heterostructure for Wastewater Purification.

Developing a semiconductor-based heterostructure photoanode is crucial in improving the photoelectrocatalytic (PEC) efficiency for degrading refractory organic pollutants. Nevertheless, the PEC performance of the photoanodes is usually restricted by electron/hole pair recombination, oxygen evolution, and slow electron transfer. Herein, a novel CoO@BiVO4 nanowire array film (Ti/CoO@BiVO4) with n-type semiconductor characteristics was prepared via a straightforward hydrothermal method. The optimized Ti/CoO@BiVO4 electrode exhibited excellent PEC decolorization efficiency of active brilliant blue KN-R (∼92.8%) and long-term stability, outperforming recent reports. The insight reason for enhancing the PEC degradation efficiency of the Ti/CoO@BiVO4 electrodes can be attributed to the large electrochemical active area, low charge transfer resistance, and negative flat band potential. The formation of a type-II heterostructure was investigated between CoO and BiVO4 further to promote the generation and separation efficiency of electron/hole pairs, indicating that the optimized Ti/CoO@BiVO4 electrode has the potential for the water PEC degradation ability and superior service life.

The improvement of photocatalytic activity of BiVO4 modified with Co(OH)2 nanoflake arrays for photocatalytic and photo-electrocatalytic desulfurization

Various and economical pure BiVO4 and Co(OH)2 nanoflake deposited BiVO4 photocatalysts have been prepared using the electrodeposition technique. Improved photocurrent density of 64 µA/cm2 at 1.0 V vs. Ag/AgCl was shown by Co(OH)2-BiVO4-150 photoanode (BiVO4 after 150 s of cobalt electrodeposition), which is about 8 times higher compared with BiVO4 photoanode. The catalysts prepared have also been used in the photocatalytic oxidation of dibenzothiophene (DBT), which is applied to stimulate fluid catalytic cracking for gasoline production in n-heptane solution. The corresponding parameters in the optimization of oxidative desulfurization of DBT were reaction time, temperature, solvent, DBT concentration and electrical bias voltage. The highest DBT desulfurization efficiency was shown by Co(OH)2-BiVO4-150. Based on the mechanism of photocatalytic oxidation, the superoxide and hydroxyl radicals played major parts in DBT degradation. Co(OH)2-BiVO4-150 photoanode showed better photo-electrocatalytic degradation efficiency, reaching a high 78.3% DBT removal even during the reaction time, in comparison with photocatalysis and electrocatalysis. The photocatalytic degradation system containing Co(OH)2-BiVO4-150 may be recycled six times without any important reduction of photocatalytic activity. This procedure introduces a simple and sustainable approach for the modification of BiVO4 to improve its photoelectrochemical and photocatalytic activity.

Efficient photoelectrocatalytic degradation of amoxicillin using nano-TiO2 photoanode thin films: A comparative study with photocatalytic and electrocatalytic methods

Excessive utilization of antibiotics in human, animal, and aquaculture poses a substantial threat to human health and the environment. Photoelectrochemical processes are increasingly applied for water remediation because they generate oxidizing species and mineralize organic pollutants, making even small water quantities more amenable for utilization. Thus, this study presents the fabrication of an efficient nano-TiO2 photoanode thin film (PATF) specifically designed for the photoelectrocatalytic (PEC) degradation of amoxicillin (AMX). The TiO2 PATFs were deposited on fluorine-doped tin oxide (FTO) substrate using an ultrasonic spray pyrolysis process with various titanium isopropoxide (TTIP) acetylacetone (AcacH) molar ratios (1:1 to 1:10). The PEC oxidation of AMX was investigated using various molar ratios of TTIP:AcacH TiO2 PATF/FTO by linear sweep voltammetry, and a 1:8 M ratio of PATF exhibited superior PEC oxidation activity than other TiO2 PATFs. Subsequently, the PEC degradation efficiency of AMX was compared with that of photocatalytic (PC) and electrocatalytic (EC) methods. The results demonstrated that the PEC process effectively eliminated 76.2% of AMX within 120 min at 0.8 V, outperforming the removal rates attained by the EC (32.3%) and PC (52.6%). Notably, increasing the voltage to 1.0 V accelerated the PEC degradation of AMX, attaining a removal efficiency of 91.2% within 90 min and exceeding 95% within 120 min.

Achieving High-Efficient Photoelectrocatalytic Degradation of 4-Chlorophenol via Functional Reformation of Titanium-Oxo Clusters

Rational design of crystalline catalysts with superior light absorption and charge transfer for efficient photoelectrocatalytic (PEC) reaction coupled with energy recovery remains a great challenge. In this work, we elaborately construct three stable titanium-oxo clusters (TOCs, Ti10Ac6, Ti10Fc8, and Ti12Fc2Ac4) modified with a monofunctionalized ligand (9-anthracenecarboxylic acid (Ac) or ferrocenecarboxylic acid (Fc)) and bifunctionalized ligands (Ac and Fc). They have tunable light-harvesting and charge transfer capacities and thus can serve as outstanding crystalline catalysts to achieve efficient PEC overall reaction, that is, the integration of anodic organic pollutant 4-chlorophenol (4-CP) degradation and cathodic wastewater-to-H2 conversion. These TOCs can all exhibit very high PEC activity and degradation efficiency of 4-CP. Especially, Ti12Fc2Ac4 decorated with bifunctionalized ligands exhibits better PEC degradation efficiency (over 99%) and H2 generation than Ti10Ac6 and Ti10Fc8 modified with a monofunctionalized ligand. The study of the 4-CP degradation pathway and mechanism revealed that such better PEC performance of Ti12Fc2Ac4 is probably due to its stronger interactions with the 4-CP molecule and better •OH radical production. This work not only presents the effective combination of organic pollutant degradation and simultaneously H2 evolution reaction using crystalline coordination clusters as both anodic and cathodic catalyst but also develops a new PEC application for crystalline coordination compounds.

Anodic pre-oxidation of BiOI/rGH for efficient photoelectrocatalytic degradation of pollutants

Bismuth oxyiodide/graphene hydrogel (BiOI/rGH) photoelectrode was successfully synthesized by three-step method. The BiOI/rGH photoelectrode was pre-oxidized at different bias voltages. The electronic structure and oxygen vacancy of BiOI/rGH were effectively regulated, resulting in a close interaction between rGH and BiOI. After conditional optimization, the degradation rate of phenol is up to 94.08 % within 70 min.

Construction of a type-II BiVO4/BiOI heterojunction for efficient photoelectrocatalytic degradation of β-naphthol and coal gasification wastewater under visible-light irradiation.

Herein, a novel type-II BiVO4/BiOI (BVOI) heterojunction electrode material was successfully fabricated by using a facile two-step electrodeposition approach. The experimental results revealed that BiOI nanosheets were deposited onto the surface of BiVO4 particles successfully, with the special morphology providing more active sites, which was beneficial to the improvement of PEC performance. According to the electrochemical performance tests, it could be observed that the construction of a heterojunction effectively promoted the separation of photoinduced electron-hole pairs and increased the transfer rate of surface charges. Under visible-light irradiation, the BVOI-300 photoanode possessed the highest PEC β-naphthol degradation rate at pH = 7, which approximately reached 82%, whose corresponding kinetic constant was 1.4 and 1.5 times higher than those of pure BiVO4 and BiOI. After five cycles, the degradation rate still remained at 64.61%. The band structure of the BVOI electrode was deduced, and the PEC mechanism of the BVOI electrode was investigated through the radical trapping quenching experiments and ESR test, which indicated that the ˙OH, h+ and ˙O2- radicals were crucial active species in the PEC β-naphthol degradation process. For the BVOI-300 working electrode, the TOC content of coal gasification wastewater (CGW) decreased from 94.44 to 54.4 mg L-1, and the removal rate reached 42.4%. GC-MS was used to identify the organic components of coal gasification wastewater, which was expected to provide reference for remedying actual gasification wastewater containing refractory organic pollutants and offer a new development direction for the treatment of actual coal chemical wastewater.

Self-supporting Cu9S5@nanoporous copper heterogenous photoanodes for efficient photoelectrocatalytic degradation

Self-supporting Cu9S5@nanoporous copper (Cu9S5@NPC) heterogenous photoelectrodes with controllable morphologies and hierarchical porous structures are synthesized through dealloying and anodization strategy. 3D Cu9S5 nanostructures (nanosheets or nanorods) grown in-situ on the surface of nanoporous copper (NPC) network are affected by the concentration ratio of Na2S and NaOH in the mixed aqueous solutions. It is found that lower Na2S concentration induces the formation of nanosheets. Attributing to the fertile porous channels, self-supporting structures as well as synergistic effect of Cu9S5 and NPC, the Cu9S5@NPC photoelectrodes possess outstanding photoelectrocatalytic (PEC) performance for the degradation of Methylene blue (MB) dye at the bias of 0.5 V under visible irradiation. Moreover, the possible PEC mechanism is further investigated.

Spray deposited yttrium incorporated TiO2 photoelectrode for efficient photoelectrocatalytic degradation of organic pollutants

This work presents result on yttrium-doped titanium dioxide (YTO) thin films using a cost-effective spray pyrolysis technique for the photoelectrocatalytic degradation of phthalic acid (PA) and benzoic acid (BA). The physicochemical properties of YTO thin films were studied using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, UV–vis spectroscopy, etc. The obtained results confirm the presence of yttrium in the host lattice. The band bending and flat band positions were studied using Mott–Schottky analysis. The film with 1% doping amount shows the highest degradation efficiency for both the model pollutants compared to TiO2. The stability of 1% YTO film confirms excellent performance analyzed by recycling tests using a UV–vis spectrophotometer. These results highlight the significance of rare earth metal doping in TiO2 for improved photoelectrocatalytic degradation efficiency.

Photoelectrocatalytic degradation of m-chloronitrobenzene through rGO/g-C3N4/TiO2 nanotube arrays photoelectrode under visible light: Performance, DFT calculation and mechanism

The photoelectrocatalytic (PEC) technology by combing photocatalysis and electrochemistry has attracted widespread concerns in the organic pollutant degradation due to its effective degradation performance. TiO2 nanotube arrays (TNAs) can be used not only as photocatalyst but also as electrode and is regarded as a popular photoelectrode in PEC system. However, the fast photogenerated carrier recombination and low visible light utilization of TNAs restrict practical application of PEC technology for organic pollutant degradation. In this work, the graphitic carbon nitride (g-C3N4) and reduced graphene oxide (rGO) were loaded on TNAs surface to prepare ternary photoelectrode (rGO/g-C3N4/TNAs) for PEC degradation of m-chloronitrobenzene (m-CNB) under visible light. The surface structure and composition analysis revealed that rGO and g-C3N4 were successfully deposited on TNAs surface. The good light absorption capacity of g-C3N4 and good conductivity of rGO inhibited the photogenerated carrier recombination of TNAs and g-C3N4. The rGO/g-C3N4/TNAs prepared with 60 mg/L graphene oxide (rGO/g-C3N4/TNAs-60) possessed wider visible-light absorption range, higher carrier density and photoconversion efficiency than other as-prepared photoelectrodes, which promoted PEC degradation efficiency of m-CNB. The cyclic degradation experiment indicated that rGO/g-C3N4/TNAs-60 photoelectrode had good reusability and stability. The radical scavenging experiments and electron paramagnetic resonance (EPR) spectra demonstrated that OH, O2– and h+ were major active species, and e− was auxiliary species for PEC degradation of m-CNB by rGO/g-C3N4/TNAs-60. The degradation pathways of m-CNB were proposed according to gas chromatography mass spectra and density functional theory calculation. The comprehensive toxicity of m-CNB was relieved after PEC degradation according to the toxicity prediction.

Facile fabrication of SnO2/TiO2 nanotube arrays for efficient degradation of pollutants

Herein, an efficient Z-scheme SnO2/TiO2 nanotube arrays (NTAs) was synthesized through a facile solvothermal method. The investigation indicates that SnO2 can improve the photoelectrocatalytic (PEC) activity of TiO2 NTAs, the photocurrent density of 0.07-SnO2/TiO2 NTAs can reach 0.94 mA cm−2, which is 4.48 times higher than that of TiO2 NTAs. The PEC degradation efficiency of MB and RhB (5 mg·L−1) is 94.71% and 80.58% over 0.07-SnO2/TiO2 NTAs after 90 min under 300 W Xe lamp irradiation, and the film-shaped 0.07-SnO2/TiO2 NTAs maintains a stable PEC performance during four times of recycling without a complex separation process. Based on the energy band structures analysis and the radical trapping experiments, the boosted PEC activity is benefited from a Z-scheme charge transfer route between SnO2 and TiO2 NTAs, which can inhibit the charge recombination and maintain the strong redox capacity of electrons and holes. This work provides a simple way to construct film-shaped TiO2 based heterojunction in PEC technology for environmental pollution remediation.

Coexisting Chloride Ion for Boosting the Photoelectrocatalytic Degradation Efficiency of Organic Dyes

Coexisting Chloride Ion for Boosting the Photoelectrocatalytic Degradation Efficiency of Organic Dyes

Fabrication of Ag particles deposited BiVO4 photoanode for significantly efficient visible-light driven photoelectrocatalytic degradation of β-naphthol

Herein, we successfully fabricated the Ag deposited BiVO4 (ABVO) electrode via the combination of electrodeposition and photodeposition for efficient photoelectrocatalytic degradation of β-naphthol under visible-light illumination (λ > 420 nm). The photocurrent density of ABVO photoanode was around 1.6 times higher than that of BiVO4 (BVO) under visible-light irradiation at 1.5 V vs. Ag/AgCl, which was ascribed to the reduced recombination rate of photoinduced electron-hole pairs, as confirmed by electrochemical impedance spectroscopy (EIS) and Mott-Schottky plots. Additionally, the photoelectrocatalytic (PEC) degradation rate of β-naphthol (10 mg L−1, 300 mL) by ABVO could approximately reach 80%, whose corresponding kinetic constant was 1.56 times higher than BVO. Based on the radical quenching experiments and EPR results, the •OH and •O2- radicals played crucial roles in PEC degradation of β-naphthol. The enhanced PEC performance of ABVO can be ascribed to the synergy of photocatalysis, electrocatalysis and the localized surface plasmon resonance (LSPR) effect of deposited Ag particles, which can effectively suppress the recombination of photoinduced electron-hole pairs, thereby prolonging the photo-excited charges lifespans and promoting the PEC performance. Furthermore, the ABVO photoanode possesses excellent recyclability, outstanding stability and strong resistance to acid and alkali, which can be a promising candidate for PEC organic contaminants degradation.

NiO-Ni foam supported Ag3PO4 for efficient photoelectrocatalytic degradation of oil pollutant in water

The treatment of oily wastewater has received significant attention because of its negative influence on environments. Despite various methods on oil removal were developed, photoeletrocatalysis (PEC) technique is considered to be a promising method. In this study, Ag3PO4@NiO-Ni foam photoelectrode was synthesized through the “hydrothermal-impregnation-calcination” three-steps to realize the PEC degradation of oil pollutants in water. The introduction of NiO-Ni foam provides simultaneous advantages of functioning as an electrode material and the synergistic photodegradation with Ag3PO4. The resulting Ag3PO4@NiO-Ni foam photoelectrode are characterized and utilized for the degradation of diesel and crude oil under PEC condition. Within two hours, the photoelectric removal of 1000 mg/L diesel can reach 88.7%. The influence of virous environmental factors, such as pH, temperature, inorganic cation and humic acid, on PEC degradation have been investigated. After 10 cycles, the removal of more than 70% can still be maintained. Finally, the possible PEC degradation mechanism was analyzed. This provides effective theoretical support for the treatment of actual oily wastewater.

A Simple g-C3N4/TNTs Heterojunction for Improving the Photoelectrocatalytic Degradation of Methyl Orange

In this work, highly ordered titanium dioxide nanotube arrays (TNTs) were first prepared by anodic oxidation method. Then, g-C3N4/TNTs heterojunctions were prepared by ultrasonically loading graphitic carbon nitride (g-C3N4) onto the TNTs. The morphology and crystal structure of TNTs and g-C3N4/TNTs were characterized by SEM/TEM and XRD. The photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TNTs and g-C3N4/TNTs was studied in a PEC degradation system. The photocatalytic (PC), electrocatalytic (EC), and PEC degradation properties were compared, and the effect of pollutant concentration on the degradation performance of the catalysts was analyzed. According to the experimental results, the degradation rate of MO with TNTs only reaches 65.1% after 120 min, while the degradation rate of MO with g-C3N4/TNTs reaches 84.6% in the same time. Due to the synergistic effect of light and electricity, the PEC degradation efficiency of the two catalysts is greater than the sum of PC and EC degradation, proving that g-C3N4/TNTs heterojunctions provide excellent PEC performance for the degradation of MO.

Unraveling Electron-deficient Setaria-viridis-like Co3O4@MnO2 heterostructure with superior photoelectrocatalytic efficiency for water remediation

Photoelectrocatalytic (PEC) degradation efficiency of refractory organic pollutants depends strongly on the characteristics of photoanode semiconductors. Therefore, choosing a photoanode semiconductor material to enhance the PEC efficiency is a critical problem. Here, we assemble a unique Co3O4@(δ-)MnO2 setaria-viridis-like heterostructure employing a two-step hydrothermal method. To maximize PEC degradation efficiency, coupling Co3O4 with an appropriate amount of MnO2 achieves Co3O4@MnO2-0.05, resulting in high oxygen evolution potential, fast carrier transfer, low resistance, electron-deficient surface, and high photo-response current. Those properties endow Co3O4@MnO2-0.05 as a promising candidate for practice application of dye degradation, with a degradation rate of ∼ 94.8 % and long-term durability (∼12000 s) under 1.0 mol·L−1 H2SO4 condition at a current density of 250 mA·cm−2 for blue KN-R degradation. Remarkably, the superior PEC degradation efficiency of Co3O4@MnO2-0.05 outperformed that of Co3O4-based and MnO2-based catalysts due to the dominant role of •O2− and h+ radical during degradation experiments.

Efficient photoelectrocatalytic degradation of azo-dyes over polypyrrole/titanium oxide/reduced graphene oxide electrodes under visible light: Performance evaluation and mechanism insights

Herein, polypyrrole/titanium oxide/reduced graphene oxide (PTi/r-GO) electrodes were prepared and successfully applied for the photoelectrocatalytic (PEC) degradation of methyl orange (MO) under visible light. Polypyrrole-TiO2 composites rich in p-n heterojunctions were first prepared, then modified with r-GO to improve the electrical conductivity and facilitate charge separation under visible light irradiation. The obtained PTi/r-GO composites were then deposited onto a titanium mesh, which served as the working electrode in PEC experiments. A MO removal efficiency of 93% was achieved in 50 min using PTi/r-GO electrode under PEC conditions (Xe lamp, λ > 420 nm, bias of 0.6 V, 0.1 M Na2SO4 electrolyte), which was far higher than MO removal efficiencies under electrocatalytic oxidation (22%) or photocatalytic oxidation (47%) conditions. This confirmed that excellent activity of the PTi/r-GO electrode under PEC conditions was due to a combination of electrochemical and photocatalytic oxidation processes (involving •OH and •O2− generation). Further, PTi/r-GO was very stable under the applied PEC conditions, with the MO removal efficiency remaining >90% after five cycles. PEC degradation pathways for MO on PTi/r-GO were explored, with a number of key intermediates in the MO mineralization process identified. Results demonstrate that PEC electrodes combining p-type polypyrrole, n-type TiO2 and rGO are very effective in the treatment of hazardous organic compounds in wastewater.