Photoelectrocatalytic Process Research Articles

Construction of 3D leaf-like Bi2O3-Bi2S3 nanosheets on Fe2O3 nanofilms and its photoelectrocatalytic performance

A novel 3D leaf-like Fe2O3-Bi2O3-Bi2S3 photoelectrocatalyst was constructed through electrodeposition and hydrothermal reaction and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and UV–Vis absorbance spectra. Results indicated the successful construction of 3D leaf-like Bi2O3-Bi2S3 nanosheets covered Fe2O3 nanoparticles, which could favor light refraction, improve light absorption, reduce charge transfer resistance, and facilitate the separation of photogenerated electron-hole pairs. The photocurrent density of Fe2O3-Bi2O3-Bi2S3 was ca. 8 and 7 times higher than that of bare Fe2O3 at 0.45 V vs Ag/AgCl under visible and UV–vis light irradiation, respectively. The Fe2O3-Bi2O3-Bi2S3 film exhibited higher photoelectrocatalytic (PEC) performance on the degradation of refractory pollutants than Fe2O3 and Fe2O3-Bi2O3 films under visible irradiation. Effects of applied potential and trapping agents were studied. The main active species in PEC process was the h+, HO• and O2•-. A proposed mechanism of charge transfer in Fe2O3-Bi2O3-Bi2S3 was discussed. This work provided a potential candidate material for PEC application in environmental remediation.

Visible light photoelectrocatalysis for wastewater treatment using bifacial N-TiO2/Graphene/Ho2O3/Titanium nanocomposite: Artificial neural network modeling and evaluation of ozone addition

In this paper, N-TiO2/Graphene/Ho2O3/Titanium bifacial nanocomposite electrode was prepared. First, the effect of Ho2O3 to N-TiO2 wt.% in the nanocomposite preparation matrix was investigated through studying visible light photoelectrocatalysis process in industrial wastewater decolorization. Characterizations of optimum catalyst were performed using DRS, XRD, SEM and EDX analyses. Then, the effect of operating variables i.e. catalyst dosage (electrode number(s)), wastewater pH, applied bias potential, visible light power and contact time on the extent of wastewater decolorization was investigated by the visible light photoelectrocatalysis process. It was observed that almost 80% wastewater decolorization was achieved using the photoelectrocatalysis at the optimum conditions by N-TiO2/Graphene/(10%) Ho2O3. Artificial neural network was used for model the photoelectrocatalysis process and determine the relative importance of investigated operating variables. It was also established that combination of photoelectrocatalysis with ozonation yielded 100% decolorization in 90 min and 96% COD removal in 270 min under the optimized conditions. Moreover, the catalyst sheet was enough stable to be used in all wastewater treatment experiments.

Effect of Structural Properties on the Photoelectrochemical Performance of Transition Metal Dichalcogenides

Layered transition metal dichalcogenides (TMDCs) have become promising candidates for photoelectrochemical (PEC) studies from the 80’s. Both n- and p-type MoSe2, and WSe2 materials were studied in photoelectrocatalytic reactions using model redox couples and hydrogen evolution reaction. (1-2) Exfoliation of the bulk, layered crystals to single- and few-layered two-dimensional (2D) nanosheets leads to new physical phenomena, different from their bulk counterparts. (3) The electrochemical properties of 2D nanoflakes −which define the performance of these materials in energy-related applications− depends on their structural properties. These structural features include the number of layers, the basal/edge planes, and the defect density. (4-5) Therefore, to employ 2D nanosheets for energy conversion and storage we need to understand their fundamental PEC properties, using an approach with spatial resolution. In our study, TMDCs samples, MoSe2, WSe2, and MoWSe2 nanosheets were mechanically exfoliated to get bulk, few-layered, and monolayer specimens. The number of layers, and defect density in the separated nanosheets were characterised by Raman spectroscopy and atomic force microscopy. Our recently developed custom-designed microdroplet cell-based photoelectrochemical approach was applied to identify the structural parts and to measure the PEC activity of the flakes (10-50 μm droplets in diameter). PEC measurements, including photovoltammetry, photocurrent transient analysis, and quantum efficiency were carried out to reveal the role of structural properties on the light harvesting, charge transport, and recombination properties of TMDCs. We have determined the band diagrams of these materials using bandgap values from PEC studies and work functions achieved from ambient pressure photoemission spectroscopy (APS) and surface photovoltage spectroscopy (SPS) measurements. Our photoelectrochemical microscopy technique also allowed to probe the PEC reactivity of novel member of 2D family, such as MoWSe2 mixed transition metal dichalcogenide. Finally, I demonstrate the use of model reversible redox species (K4[Fe(CN)6], (NH4)2[IrCl6]) to mimic photoelectrocatalytic processes. (1) F. R. F. Fan, H. S. White, B. L. Wheeler, A. J. Bard; J. Am. Chem. Soc. 1980, 102, 5142-5148 (2) W. Kautek, H. Gerischer; Ber. Bunsenges. Phys. Chem. 1980, 84, 645-653 (3) K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, A. K. Geim; PNAS, 2005, 102, 10451-10453 (4) P. S. Toth, A. T. Valota, M. Velický, I. A. Kinloch, K. S. Novoselov, E. W. Hill, R. A. W. Dryfe; Chem. Sci., 2014, 5, 582-589 (5) M. Velický, M. A. Bissett, C. R. Woods, P. S. Toth, T. Georgiou, I. A. Kinloch, K. S. Novoselov, R. A. W. Dryfe; Nano Lett., 2016, 16, 2023-2032

Photo-electrocatalytic oxidation of atrazine using sputtured deposited TiO2: WN photoanodes under UV/visible light

Abstract Herein were report on the UV/visible light driven photo-electrocatalytic (PEC) degradation of Atrazine (ATZ) and its major degradation by-products (DEA, DIA, DEDIA and ATZ-OH) in synthetic and real agricultural surface waters. For this purpose, sub-stoichiometric TiO2-x, and tungsten-nitrogen codoped TiO2:WN photoanodes were prepared by means of a radio frequency magnetron sputtering (RF-MS) deposition process. The codoping’s objective was to shift the material’s optical absorption from the UV towards the visible light, while minimizing defect formation. This was achieved, and directly demonstrated via UV–vis transmittance spectra analysis. Tauc plot extrapolation was used to determine the values of the band gaps of the films. We found that the band gap of TiO2-x is 3.0 eV and narrows to reach 2.3 eV for TiO2:WN. TiO2-x photoanodes crystallised in a predominantly rutile phase, whereas codoped TiO2:WN photoanodes crystallised in a predominantly anatase phase. Prior to PEC oxidation, agricultural surface water (ASW) containing ATZ was first treated by coagulation using metal salts (FeCl3 and Al2(SO4)3, respectively) as to reduce turbidity and colloidal particles. Optimal jar tests conditions allowed 52.9% and 39.7% DOC removal with FeCl3 and Al2(SO4)3, respectively. Subsequently, our TiO2:WN driven PEC process was investigated for the removal of ATZ (100 μg L−1) from ASW. Degradation of ATZ was performed in a homebuilt 5 L reactor with degradation times reaching 300 min. The scavengers of oxidants (e.g. S O 4 2 - , H C O 3 - and C l - ) reacted with oxidants generated during PEC process (e.g. H O • , H O 2 • , and O 2 • - ), so that the efficiency of PEC in removing ATZ from ASW was reduced.

Removal of 5-fluorouracil by solar-driven photoelectrocatalytic oxidation using Ti/TiO2(NT) photoelectrodes

The efficient and safe degradation of drugs present in wastewater requires the design of a new material possessing high activity for that process. In addition to other methods, photoelectrocatalysis (PEC) merges the strengths of both photocatalytic and electrochemical methods, and the efficiency could be enhanced by the type of photoelectrode material. To address this challenge, three Ti/TiO2 nanotube-based photoelectrodes, differing in their tube morphology, were prepared by anodic oxidation and employed for the degradation of the 5-fluorouracil (5-FU) drug by the PEC process. The highest efficiency for 5-fluorouracil (5-FU) degradation by PEC was observed for the photoelectrode with a 1.7 μm length, 65 nm diameter and 8 nm wall thickness of TiO2 nanotubes, which were prepared by Ti foil anodization at 30 V. The effects of applied potential, irradiation intensity, initial pH and 5-FU concentration on PEC were investigated. Furthermore, our findings showed that the mechanism of photoelectrocatalysis in the presence of TiO2 nanotubes is based on ∙OH and h+ activity. To determine the 5-FU degradation pathway, the organic byproducts were identified by LC-MS analysis. Furthermore, the ecotoxicity evaluated during PEC dropped with decreasing 5-FU concentration.

Synthesis of N doped titania nanotube arrays photoanode using urea as nitrogen precursor for photoelectrocatalytic application

Addition of urea as nitrogen precursor during synthesis of TiO2 nanotube arrays photocatalyst has been investigated. This study aimed to increase the visible light photo response of TiO2 by applying nitrogen doped titania nanotube arrays (N-TNTAs) for photoanode preparation in the photoelectrocatalytic process. Nitrogen doped titania nanotube arrays (N-TNTAs) was synthesized by a one-step electrochemical anodization method at 50 V for 2 hour, in the electrolyte solution containing water, ammonium fluoride, glycerol and specified amounts of urea as nitrogen precursor followed by annealing at 500°C for 3 h to induce crystallization. Amount of urea (0.1, 0.2 and 0.4 wt%) in electrolyte solution and annealing atmosphere (air and N2) were varied to enhance visible light photo response. SEM analysis showed that TNTAs and N-TNTAs were successfully synthesized with diameters of 64–320 nm but the morphologies did not show a significant difference. The XRD results showed an identical pattern dominated by the anatase phase. The size of N-TNTAs crystallite is larger than the undoped TNTAs. UV-DRS analysis showed that N-TNTAs have smaller bandgap energy. The smallest bandgap energy was obtained 2.84 eV from N-TNTAs using 0.2% urea with N2 gas annealing (N-TNTAs 0.2% U-N2). Measurement of photocurrent density showed better activity under visible light with smaller bandgap energy.

Visible light driven photoelectrocatalysis on a FTO/BiVO4/BiOI anode for water treatment involving emerging pharmaceutical pollutants

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 BiVO4/BiOI photoanode under visible irradiation via photoelectrocatalytic process. The BiVO4/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 BiVO4/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 BiVO4/BiOI was higher than those of pristine BiVO4 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/BiVO4/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.

Fabricating I doped TiO2 photoelectrode for the degradation of diclofenac: Performance and mechanism study

The presence of diclofenac (DCF) in water has developed into a severe environmental problem due to its pernicious effects on animals and human being. Herein, a photoelectrocatalytic (PEC) method using I doped TiO2 (I-TiO2) photoelectrode has been developed, which exhibited excellent visible activity in the degradation of DCF as well as pharmaceutical wastewater. The Langmuir Hinshelwood kinetic model, active species trapping experiments and analysis of intermediate products were employed to analyze the PEC degradation mechanism of DCF. The results revealed that the decomposition of DCF was primarily performed on the photoelectrode (I-TiO2) surface, and the degradation process was accompanied by the dechlorination reaction. The degradation of DCF was caused mainly by holes (66.6%) and hydroxyl radicals (27.6%) when Na2SO4 acted as electrolyte. The degradation rate of DCF could be significantly enhanced under the condition of high Cl− concentration (NaCl acted as electrolyte), which was caused by the participation of chloride radicals (Cl) in the PEC process. The Cl was the major factor contributing to the decomposition of DCF, and the holes and hydroxyl radicals played a less important role than Cl under this condition.

Preparation of rGO/AgCl QDs and its enhanced photoelectrocatalytic performance for the degradation of Tetracycline

AbstractA novel rGO/AgCl QDs composites have been obtained by an ultrasonic‐assisted method for the first time. Photoelectrocatalytic (PEC) performances of the obtained samples were studied by the degradation of 20 mg/L Tetracycline (TC) under visible light irradiation with an applied bias potential of 1.5 V (vs Ag/AgCl). Degradation of TC by different processes including Photocatalysis (PC), Electrocatalysis (EC), and PEC was compared, and the effect of different bias potential on the PEC degradation of TC was discussed. Results showed that rGO/AgCl QDs composites had displayed superior PEC activity than that of pristine AgCl QDs with degrading 85.2% of TC during 120 minutes, which was about 1.5 times higher than that of AgCl QDs (33%). Besides, compared to PC and EC removal of TC, PEC process showed the highest degradation efficiency of TC (85.2%) by rGO/AgCl QDs, which was about three times and one time higher than that of PC (39.18%) and EC (20.73%) system, respectively. Moreover, the reusibility and stability of the samples were tested by five times cycling tests, and results demonstrated that the stability of bare AgCl QDs was improved after the introduction of rGO. The enhanced PEC activity and stability of the samples could be attributed to the intimate contact between rGO and AgCl QDs and external electric field, which had benefitted the formation of more active sites and accelerated electron‐hole separation.

Photoelectrocatalytic oxidation of methane into methanol and formic acid over ZnO/graphene/polyaniline catalyst**Project supported by the National Natural Science Foundation of China (Grant Nos. 51602021 and 51474017) and the Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-15-107A1).

ZnO/graphene/polyaniline (PANI) composite is synthesized and used for photoelectrocatalytic oxidation of methane under simulated sun light illumination with ambient conditions. The photoelectrochemical (PEC) performance of pure ZnO, ZnO/graphene, ZnO/PANI, and ZnO/graphene/PANI photoanodes is investigated by cyclic voltammetry (CV), chronoamerometry (J–t) and electrochemical impedance spectroscopy (EIS). The yields of methane oxidation products, mainly methanol (CH3OH) and formic acid (HCOOH), catalysed by the synthesized ZnO/graphene/PANI composite are 2.76 and 3.20 times those of pure ZnO, respectively. The mechanism of the photoelectrocatalytic process converting methane into methanol and formic acid is proposed on the basis of the experimental results. The enhanced photoelectrocatalytic activity of the ZnO/graphene/PANI composite can be attributed to the fact that graphene can efficiently transfer photo-generated electrons from the inner region to the surface reaction to form free radicals due to its superior electrical conductivity as an inter-media layer. Meanwhile, the introduction of PANI promotes solar energy harvesting by extending the visible light absorption and enhances charge separation efficiency due to its conducting polymer characteristics. In addition, the PANI can create a favorable π-conjunction structure together with graphene layers, which can achieve a more effective charge separation. This research demonstrates that the fabricated ZnO/graphene/PANI composite promises to implement the visible-light photoelectrocatalytic methane oxidation.

Dual Quantum Dot-Decorated Bismuth Vanadate Photoanodes for Highly Efficient Solar Water Oxidation.

Photo-induced charge separation and photon absorption play important roles in determining the performance of the photoelectrocatalytic water splitting process. In this work, we utilize dual quantum dots (QDs), consisting of BiVO4 and carbon, to fabricate a hybrid homojunction-based BiVO4 photoanode for efficient and stable solar water oxidation. Formation of homojunctions, by decorating as-prepared BiVO4 substrate with BiVO4 QDs, enhances the charge separation efficiency by 1.3 times. This enhancement originates from lattice match, which benefits charge transfer across the interface. Furthermore, the use of carbon QDs as a stable photosensitizer effectively extends the photon absorption limit from 520 nm to over 700 nm, yielding an incident photon-to-electron conversion efficiency of 6.0 %, even at 600 nm at 1.23 V versus RHE. Finally, a remarkable photocurrent density of 6.1 mA cm-2 at 1.23 V was recorded after depositing FeOOH/NiOOH as cocatalysts, thereby, reaching 82 % of the theoretical efficiency for BiVO4 .

Microwave Hydrothermal Synthesis of In2O3-ZnO Nanocomposites and Their Enhanced Photoelectrochemical Properties

Indium oxide (In2O3) doped zinc oxide (ZnO) nanocomposites were successfully synthesized through a facile microwave hydrothermal method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption isotherms (BET) and UV-Vis diffuse reflectance spectroscopy. The morphology of In2O3-ZnO composites was observed to be like flowers, and the diameter of particles constituting the porous petal was about 30 nm. The photoelectrocatalytic test results showed that the photoelectrocatalytic methylene blue (MB) degradation efficiency using In2O3-ZnO nanocomposites as photocatalysts under visible light irradiation and a certain voltage could reached above 95.3% after 60 min, much higher than that of In2O3 particles and ZnO particles. The enhanced photoelectrocatalytic activity was attributed to the doping of In2O3 and applied voltage, which beneficially reduced the recombination of electrons and holes in the photoelectrocatalytic process, therefore, it promoted the production of active species (•OH and •O−2).

A dual-cathode photoelectrocatalysis-electroenzymatic catalysis system by coupling BiVO4 photoanode with hemin/Cu and carbon cloth cathodes for degradation of tetracycline

When photoelectrocatalysis (PEC) couples with electroenzymatic catalysis (EEC), effective utilization of electrons from PEC process for yield of H2O2 plays an important role in the enzymatic catalysis. In the present work, we designed a novel dual-cathode PEC-EEC system for pollutant removal. In this system, BiVO4 photoanode was prepared by electrodeposition for visible light-driven PEC process while carbon cloth was used as the first cathode for electrogeneration of H2O2 and hemin/Cu prepared by electrophoretic deposition acted as the second cathode for enzymatic catalysis. The performances of the constructed dual-cathode PEC-EEC system were evaluated by decoloring Rhodamine B (RhB), which showed high decoloration percentage with acceptable stability and reusability. Further, the system was applied to degradation of tetracycline (TC), indicating that about 93.6% of TC was removed after 2-h treatment. A pathway for TC degradation in such a dual-cathode PEC-EEC system was proposed based on the intermediates determined by liquid chromatography coupled to mass spectrometry in tandem (LC-ESI-MS/MS).

A facile synthesis of Cs loaded TiO2 nanotube photoelectrode for the removal of 4-chloroguaiacol

In this study, novel Cesium (Cs) doped TiO2 nanotubes photoelectrode (Cs/TiO2NTs) were synthesized by simple electrochemical anodization method and characterized by several physicochemical techniques. In particular, the photocatalytic (PC), electrocatalytic (EC) and photoelectrocatalytic (PEC) activity of newly synthesized Cs/TiO2NTs electrodes was investigated using 4-Chloroguaiacol (4-CG). The effect of operating parameters like Cs concentration, electrolyte concentration, external current and pH on degradation efficacy was examined. PEC oxidation using Cs/TiO2NTs lead to 92% degradation of 4-CG in 6 h of solar light irradiation under optimized conditions (2.5 mM Cs, 160 mg L−1 Na2SO4, 0.03 A current and pH 3). A comparative assessment between PEC, PC and EC process manifested that PEC process was most efficient than the other two processes and Cs/TiO2NTs exhibited higher PEC activity than bare-TiO2 electrodes in terms of degradation and mineralization of organic pollutant. The generation of OH radicals was found to be highest in PEC when compared to EC and PC process. Possible intermediates/byproducts were identified by GC-MS technique and a corresponding tentative degradation pathway has been proposed. Cytotoxicity study showed that PEC has potential to detoxify 4-CG. Hence, combination of TiO2 electrodes decorated with Cs metal can act as a highly efficient photoelectrode for the degradation of hazardous pollutants.

G-C3N4 photoanode for photoelectrocatalytic synergistic pollutant degradation and hydrogen evolution

Photoelectrocatalytic (PEC) technique for hydrogen evolution from water splitting and pollutant degradation is one of the most sustainable and environmental approaches for wastewater treatment and energy regeneration. Herein, a porous graphitic carbon nitride (g-C3N4)/reduction graphene oxide (rGO) structure (CNG) is constructed via a solvothermal approach. By using a facile electrophoretic deposition method, CNG is deposited on nickel (Ni) foam with the formation of highly active CNG-Ni foam photoanode. rGO were utilized to load g-C3N4, and also acts as the bridge for accelerating the rate of electron transfer from g-C3N4 to Ni foam. The resulted photoanode exhibits an excellent photoelectrochemical performance for synergistic pollutant degradation and H2 evolution under visible light irradiation (λ > 420 nm). Such excellent PEC activity is attributed to the strong visible-light absorption and fast electron transmission of the as-obtained photoanode. The visible light-driven photocurrent value of the optimal photoanode can be well maintained up to 24 h, indicating its high stability during the PEC process. This work also shows significance for paving a facile route to fabricating highly active photoelectrodes for environmental and energy applications.

Degradation of diazinon by new hybrid nanocomposites N-TiO2/Graphene/Au and N-TiO2/Graphene/Ag using visible light photo-electro catalysis and photo-electro catalytic ozonation: Optimization and comparative study by Taguchi method

A series of nitrogen doped TiO2/Graphene/Au (N-TiO2/G/Au) and nitrogen doped TiO2/Graphene/Ag (N-TiO2/G/Au) modified nanocomposite electrodes were prepared by a simple electrophoretic deposition method to assess their visible light photo-electro catalytic and photo-electro catalytic ozonation activities against diazinon. The structural and morphological analyses of the synthesized composites were made by XRD, SEM and EDX while the optical properties were studied by DRS technique. The effect of Au and Ag ratio to N-TiO2, Na2SO4 concentration, voltage and initial pH of the solution was optimized by Taguchi method on the degradation of diazinon using photo-electro catalytic process. High degradation 76.7% for N-TiO2/G/Au and 81.1% for N-TiO2/G/Ag was observed when Au and Ag ratio to N-TiO2 was 0.2 wt%, Na2SO4 concentration = 56 mM, voltage = 900 mV and pH = 6 after 60 min visible light irradiation. The main intermediates of diazinon degradation were identified using GC-MS spectrometry. Finally, the visible light photo-electro catalytic ozonation of diazinon using optimized nanocomposites were studied. The results demonstrate that the photo-electro catalytic ozonation highly enhanced the degradation rate of diazinon (nearly 100%) compared to photo-electro catalytic and ozonation processes, solely. Also, nanocomposites showed good catalytic activities even after seven successive degradation cycles.

H2O2-assisted photoelectrocatalytic degradation of Mitoxantrone using CuO nanostructured films: Identification of by-products and toxicity

CuO nanostructured thin films supported on silicon with 6.5 cm2 area (geometric area greater than the studies reported in the literature) were synthesized by a chemical bath deposition technique. The electrodes were characterized by MEV, XRD, XPS, contact angle, cyclic voltammetry and electrochemical impedance spectroscopy analyses. To evaluate the photoelectrochemical properties of the CuO films, photocurrent–voltage measurements were performed using linear voltammetry. The catalytic activities of CuO nanostructures were evaluated by monitoring photodegradation of Mitoxantrone (MTX) under UV-A light irradiation. The method of photoelectrocatalysis (PEC), applying a voltage of 1.5 V and assisted by adding H2O2, was undertaken. To the best of our knowledge, no studies on the degradation of anticancer agents using PEC process have been found in the literature. For comparison purposes, experiments were performed under the same conditions by assisted photocatalysis (PC) with H2O2 and direct photolysis. CuO deposits consist of a needle-like morphology. The presence of CuO in the tenorite phase was evidenced by XRD and the XPS spectra showed the presence of copper(II) oxide. The increase in current under illumination shows that CuO exhibits photoactivity. The PEC system showed a 75% level of MTX degradation, while the level achieved using PC was 50%. Under UV-A light alone only 3% removal was obtained after 180 min. Up to 10 by-products were identified by chromatography-mass spectrometry (LC-MS) with m/z values ranging between 521 and 285 and a plausible degradation route has been proposed. It is worth mentioning that 9 by-products identified in this work, were not found in the literature in other studies of degradation or products generated as metabolites. The toxicity tests of MTX before and after PEC treatment with Artemia Salina and Allium cepa showed a decrease in the acute toxicity of the medium as the antineoplastic was degraded.

Combined photoelectrocatalytic microbial fuel cell (PEC-MFC) degradation of refractory organic pollutants and in-situ electricity utilization

A new photoelectrocatalytic (PEC) and microbial fuel cell (MFC) process was developed and applied to simultaneously remove refractory organic pollutants (i.e., phenol and aniline) from wastewater while recovering energy for in-situ utilization. The current generated by the MFC process was applied to drive the PEC reaction. Compared with single PEC or MFC processes, the PEC-MFC combined process showed higher pollutant and chemical oxygen demand (COD) removal capacities and electricity production. Over 95% of the phenol or aniline was removed by these process, even at high initial concentrations. The COD removal efficiencies for phenol and aniline were ca. 96% (from 700 to 29 mg L−1) and 70% (from 165 to 49 mg L−1), respectively. Although the PEC process showed a limited contribution to phenol and aniline removals (16.5% and 43%, respectively), the utilization of PEC-treated phenol or aniline streams resulted in a MFC with higher voltage output, higher coulombic efficiency, maximal volumetric power density, and lower internal resistance as compared to untreated water. High-performance liquid chromatography coupled with mass spectrometry measurements revealed quinones/hydroquinones and low molecular weight organic acids to be produced as intermediates after the PEC process, which could improve the production of electricity in the MFC.

Removal of atrazine by photoelectrocatalytic process under sunlight using WN-codoped TiO2 photoanode

The present study was focused on the degradation of Atrazine (ATZ) and major by-products (DEA, DIA, DEDIA and ATZ-OH) from water by photoelectrocatalytic (PEC) oxidation process under solar light. The undoped TiO2, sub-stoichiometric TiO2 (TiO2−x) and codoped TiO2 (TiO2:WN) photoanodes were prepared by means of a radio frequency magnetron sputtering (RF-MS) deposition process. The X-ray photoelectron spectra (XPS) analysis shows that the N and W atoms were incorporated into the O and Ti lattice sites of TiO2 respectively (case of TiO2:WN film), while the XPS measurements of the TiO2−x films composition was determined to be TiO1.9. The UV–Vis transmittance spectra shows that in the case of the TiO2:WN films, the presence of nitrogen and tungsten improve the optical response of TiO2 under visible range compare to the presence of oxygen vacancies in to the TiO2−x films. The experimental results under solar light with an initial concentration of ATZ (100 µg L−1) show that after 180 min of treatment, the degradation of ATZ were 34.98%, 68.57% and 94.33% using TiO2, TiO2−x and TiO2:WN photoanodes, respectively. These results of ATZ degradation proved that TiO2:WN photoanode was more photoactive under solar light. The evolution by-products of ATZ under sunlight show that the principal mechanism of ATZ degradation was the oxidation of alkyl side chain and dealkylation.

The use of chitosan as a bioactive polysaccharide in non-invasive detection of malondialdehyde biomarker in human exhaled breath condensate: A new platform towards diagnosis of some lung disease

Herein, a reusable and time-saving strategy for the electrochemical polymerization of dopamine (EPD) is reported. In this work, biocompatible polymer chitosan (CS) was electrodeposited on the surface of PDA modified glassy carbon electrode. Owing to the abundant catechol and amine groups in the PDA layer, uniform silver nanoparticles (Ag NPs) are deposited onto the POLY(DA-CS) and can effectively prevent the recombination of electron-hole pairs generated from photo-electrocatalysis and transfer the captured electrons to participate in the photo-electrocatalytic reaction process. Compared with pristine POLY(DA-CS), the as-prepared POLY(DA-CS)-AgNPs organic-inorganic hybrid exhibit electrochemical sensitivity for detecting MDA and display excellent durability. Furthermore, the mussel-inspired electropolymerization strategy and the fast EPD-Ag nanoparticle decorating process presented herein can be readily extended to various biomedical analysis and lung cancer detection. It is the adaptation of the established POLY(DA-CS)-Ag NPs organic-inorganic hybrid for a selective, robust, and generalizable sensing system that is the emphasis of this work.