Peroxydisulphate activated FTO-WO3 nanorods based photoelectrocatalytic degradation of tetracycline: Intermediate products, degradation pathway and ecotoxicity studies.

This work reports sulphate radical assisted photoelectrocatalytic (SR-PEC) degradation of tetracycline using a visible light active fluorine-doped tin oxide - tungsten trioxide nanorods (FTO-WO3 NRs) photoanode. The WO3 NRs were synthesised via the hydrothermal method and then conducted on the FTO glass to form a photoanode. When the photoanode was applied without sulphate radicals for PEC degradation, 10 % of the tetracycline was degraded. Conversely, when 3 mM persulphate was added, the extent of tetracycline degraded was 88 % using the UV-vis spectrophotometer and 99 % using the ultra-performance liquid chromatography mass spectrometer (UPLC-MS) within 90 min at 1.5 V. The mechanism of tetracycline degradation was proposed based on the intermediate products identified using UPLC-MS and the extent of toxicity was evaluated using quantitative structure activity relationship (QSAR) analysis. Trapping experiment revealed that the photogenerated holes, sulphate radicals, and hydroxyl radicals were the oxidants that significantly took part in the degradation of tetracycline. Overall, the electrode was stable and reusable, therefore suggesting the suitability of FTO-WO3 NRs photoanode in the presence of sulphate radicals towards the decontamination of water laden with pharmaceutical pollutants.

Dendrimer-Gold Nanocomposite-Based Electrochemical Aptasensor for the Detection of Dopamine.

Dopamine is an important neurotransmitter and biomarker that plays a vital role in our neurological system and body. Thus, it is important to monitor the concentration levels of dopamine in our bodies. We report an aptamer-based sensor fabricated through an electro-co-deposition of a generation 3 poly(propylene imine) (PPI) dendrimer and gold nanoparticles (AuNPs) on a glassy carbon (GC) electrode by cyclic voltammetry. Through self-assembly, a single-stranded thiolated dopamine aptamer was immobilized on the GC/PPI/AuNPs electrode to prepare an aptasensor. Voltammetry and electrochemical impedance spectroscopy (EIS) were used to characterize the modified electrodes. The readout for the biorecognition event between the aptamer and various dopamine concentrations was attained from square wave voltammetry and EIS. The aptasensor detected dopamine from the range of 10-200 nM, with a limit of detection of 0.26 and 0.011 nM from SWV and EIS, respectively. The aptasensor was selective toward dopamine when different amounts of epinephrine and ascorbic acid were present. The aptasensor was applicable in a more complex matrix of human serum.

Sulfate Radical in (Photo)electrochemical Advanced Oxidation Processes for Water Treatment: A Versatile Approach.

The search for a simple and clean approach toward the production of sulfate radicals for water treatment gave rise to electrochemical and photoelectrochemical activation techniques. The photoelectrochemical activation method does not just distinguish itself as a promising activation method, it is also used as an efficient water treatment method with the ability to treat a myriad of pollutants due to the complementary effects of highly reactive oxidizing species. This perspective highlights some merits that distinguish sulfate monoanion radicals from hydroxyl radicals. It highlights the electrochemical, photoelectrochemical, and in situ photoelectrochemical routes of generating sulfate radicals for advanced oxidation process approach to water treatment. We provide a detailed account of the few known applications of sulfate radical enhanced photoelectrochemical treatments of water laden with organics. Finally, we placed this area of research in perspective by providing outlooks and conclusive remarks.

Heterogenous electro-Fenton degradation of sulfamethoxazole on a polyethylene glycol-coated magnetite nanoparticles catalyst.

We report the preparation and application of poly (ethylene) glycol (PEG) coated magnetite nanoparticles (MNPs) catalyst for the heterogeneous electro-Fenton (HEF) degradation of sulfamethoxazole in real wastewater PEG-coated MNPs of four MNP:PEG ratios were synthesised using the co-precipitation method. The synthesised MNP were characterised using FTIR, XRD, EDX, TEM, and CHN elemental analysis. It was observed that the coating of MNP with PEG influences the nanoparticle size, agglomeration tendencies and catalytic efficiency of MNPs properties in the HEF degradation process. A 1:1 optimal MNP:PEG catalyst yielded 91% sulfamethoxazole degradation and 48% total organic carbon removal in 60 min, which is an improvement of 11% over degradation with the uncoated MNP. The PEG-coated MNP showed higher stability in 10 consecutive reaction cycles, reduced leaching, and improved performance at a lower dosage and broader pH range than the uncoated MNPs. These results show that coating MNP with PEG enhances HEF catalytic performance in the degradation of sulfamethoxazole in wastewater.

An electrochemical immunosensor for an alpha-fetoprotein cancer biomarker on a carbon black/palladium hybrid nanoparticles platform.

The early detection of cancer is a key step in cancer survival. Thus, there is a need to develop low-cost technologies, such as electrochemical immunosensor technologies, for timely screening and diagnostics. The discovery of alpha-feto protein (AFP) as a tumour-associated antigen lends AFP as a biomarker for cancer detection and monitoring. Thus, immunosensors can be developed to target AFP in cancer diagnostics. Hence, we report the application of a hybrid nanocomposite of carbon black nanoparticles (CBNPs) and palladium nanoparticles (PdNPs) as a platform for the electrochemical immunosensing of cancer biomarkers. The hybrid carbon-metal nanomaterials were immobilised by using the drop-drying and electrodeposition technique on a glassy carbon electrode, followed by the immobilisation of the anti-AFP to fabricate an immunosensor. The nanoparticles were characterised with electron microscopy, voltammetry, and electrochemical impedance spectroscopy (EIS). Square wave voltammetry (SWV) and EIS were used to study the immunosensor signal toward the bio-recognition of the AFP cancer biomarker. The hybrid nanoparticles enhanced the immunosensor performance. A linear detection range from 0.005 to 1000 ng mL-1 with low detection limits of 0.0039 ng mL-1 and 0.0131 ng mL-1 were calculated for SWV and EIS, respectively. The immunosensor demonstrated good stability, reproducibility, and selectivity. Its real-life application potential was tested with detection in human serum matrix.

B-doping mediated formation of oxygen vacancies in Bi2Sn2O7 quantum dots with a unique electronic structure for efficient and stable photoelectrocatalytic sulfamethazine degradation.

This study devised a straightforward one-step approach that enabled simultaneous boron (B) doping and oxygen vacancies (OVs) production on Bi2Sn2O7 (BSO) (B-BSO-OV) quantum dots (QDs), optimizing the electrical structure of the photoelectrodes. Under light-emitting diode (LED) illumination and a low potential of 1.15 V, B-BSO-OV demonstrated effective and stable photoelectrocatalytic (PEC) degradation of sulfamethazine (SMT), achieving the first-order kinetic rate constant of 0.158 min-1. The surface electronic structure, the different factors influencing the PEC degradation of SMT, and the degradation mechanism were studied. Experimental studies have shown that B-BSO-OV exhibits strong visible light trapping ability, high electron transport ability, and superior PEC performance. DFT calculations show that the presence of OVs on BSO successfully reduces the band gap, controls the electrical structure, and accelerates charge transfer. This work sheds light on the synergistic effects of the electronic structure of B-doping and OVs in heterobimetallic oxide BSO under the PEC process and offers a promising approach for the design of photoelectrodes.

Photoelectrocatalytic Degradation of Methylene Blue on Electrodeposited Bismuth Ferrite Perovskite Films.

Electrodeposited bismuth ferrite (BiFeO3) thin films on fluorine-doped tin oxide (FTO) substrate were employed as photoanodes in the photoelectrocatalytic degradation of methylene blue. The BiFeO3 thin films electrodeposited for 300 s, 600 s, 1200 s, 1800 s and 3600 s were characterised with XRD, field emission scanning electron microscopy (FESEM) and UV-vis diffuse reflectance spectroscopy. SEM images displayed different morphology at different electrodeposition times which affects the photoelectrocatalytic (PEC) performances. The FESEM cross-sectional area was used to measure the thickness of the film. The optical properties showed that the band gaps of the photoanodes were increasing as the electrodeposition time increased. The photocurrent response obtained showed that all thin film photoanodes responded to visible light and lower charge transfer resistance (from electrochemical impedance spectroscopy studies) was observed with photoanodes electrodeposited at a shorter time compared to those at a longer time. The PEC application of the photoanode for the removal of methylene blue (MB) dye in water showed that the percentage degradation decreased with an increase in electrodeposition time with removal rates of 97.6% and 70% observed in 300 s and 3600 s electrodeposition time, respectively. The extent of mineralisation was measured by total organic carbon and reusability studies were carried out. Control experiments such as adsorption, photolysis, photocatalysis and electrocatalysis processes were also investigated in comparison with PEC. The electrodeposition approach with citric acid exhibited improved electrode stability while mitigating the problem of catalyst leaching or peeling off during the PEC process.

Sonoelectrochemical oxidation of sulfamethoxazole in simulated and actual wastewater on a piezo-polarizable FTO/BaZr x Ti(1-x)O3 electrode: reaction kinetics, mechanism and reaction pathway studies.

The sonoelectrochemical (SEC) oxidation of sulfamethoxazole (SMX) in simulated and actual wastewater on FTO/BaZr(0.1)Ti(0.9)O3, FTO/BaZr(0.05)Ti(0.95)O3 and FTO/BaTiO3 electrodes is hereby presented. Electrodes from piezo-polarizable BaZr(0.1)Ti(0.9)O3, BaZr(0.05)Ti(0.95)O3, and BaTiO3 materials were prepared by immobilizing these materials on fluorine-doped tin dioxide (FTO) glass. Electrochemical characterization performed on the electrodes using chronoamperometry and electrochemical impedance spectroscopy techniques revealed that the FTO/BaZr(0.1)Ti(0.9)O3 anode displayed the highest sonocurrent density response of 2.33 mA cm-2 and the lowest charge transfer resistance of 57 Ω. Compared to other electrodes, these responses signaled a superior mass transfer on the FTO/BaZr(0.1)Ti(0.9)O3 anode occasioned by an acoustic streaming effect. Moreover, a degradation efficiency of 86.16% (in simulated wastewater), and total organic carbon (TOC) removal efficiency of 63.16% (in simulated wastewater) and 41.47% (in actual wastewater) were obtained upon applying the FTO/BaZr(0.1)Ti(0.9)O3 electrode for SEC oxidation of SMX. The piezo-polarizable impact of the FTO/BaZr(0.1)Ti(0.9)O3 electrode was further established by the higher rate constant obtained for the FTO/BaZr(0.1)Ti(0.9)O3 electrode as compared to the other electrodes during SEC oxidation of SMX under optimum operational conditions. The piezo-potential effect displayed by the FTO/BaZr(0.1)Ti(0.9)O3 electrode can be said to have impacted the generation of reactive species, with hydroxyl radicals playing a predominant role in the degradation of SMX in the SEC system. Additionally, a positive synergistic index obtained for the electrode revealed that the piezo-polarization effect of the FTO/BaZr(0.1)Ti(0.9)O3 electrode activated during sonocatalysis combined with the electrochemical oxidation process during SEC oxidation can be advantageous for the decomposition of pharmaceuticals and other organic pollutants in water.

Enhanced Visible Light-Driven Photoelectrocatalytic Degradation of Paracetamol at a Ternary z-Scheme Heterojunction of Bi2WO6 with Carbon Nanoparticles and TiO2 Nanotube Arrays Electrode.

In this study, a ternary z-scheme heterojunction of Bi2WO6 with carbon nanoparticles and TiO2 nanotube arrays was used to remove paracetamol from water by photoelectrocatalysis. The materials and z-scheme electrode were characterised using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), EDS mapping, ultraviolet diffuse reflection spectroscopy (UV-DRS), photocurrent measurement, electrochemical impedance spectroscopy (EIS), uv-vis spectroscopy and total organic carbon measurement (TOC). The effect of parameters such as current density and pH were studied. At optimal conditions, the electrode was applied for photoelectrocatalytic degradation of paracetamol, which gave a degradation efficiency of 84% within 180 min. The total organic carbon removal percentage obtained when using this electrode was 72%. Scavenger studies revealed that the holes played a crucial role during the photoelectrocatalytic degradation of paracetamol. The electrode showed high stability and reusability therefore suggesting that the z-scheme Bi2WO6-CNP-TiO2 nanotube arrays electrode is an efficient photoanode for the degradation of pharmaceuticals in wastewater.

Improved Magnetite Nanoparticle Immobilization on a Carbon Felt Cathode in the Heterogeneous Electro-Fenton Degradation of Aspirin in Wastewater.

Toward the improvement of the application of heterogeneous electro-Fenton in water treatment, we report a new strategy of enhancing the immobilization of a magnetite nanoparticle catalyst on a carbon felt cathode. Exploiting the intrinsic ferrimagnetic properties of magnetite nanoparticles, magnet bars were used to attach the magnetite into the void spaces of the porous carbon felt (CF) cathode. The magnetite nanoparticles were prepared by coprecipitation with variations in the molar ratios of Fe2+/Fe3+. The magnetite was characterized, attached onto the CF electrode with magnetic bars, and used in the heterogeneous electro-Fenton (EF) degradation of aspirin. The effects of the following on the degradation were studied: Fe2+/Fe3+, pH, catalyst loading concentration, and voltage. The heterogeneous EF degradation of aspirin in wastewater improved by 23% when magnetic bars were used to enhance the immobilization of the magnetite catalysts. The 1:4 Fe2+/Fe3+ ratio resulted in the highest hetero-EF catalytic degradation of aspirin with complete degradation (100%) achieved after 140 min. For a mixture of pharmaceuticals, degradation percentages of 94.3% (aspirin), 88% (ciprofloxacin), and 80% (paracetamol) in 3 h were obtained. The magnetized magnetite on the cathode was reusable for 10 cycles. Thus, the use of magnets shows a promising strategy to avoid the leaching of ferrimagnetic nanoparticle catalysts embedded in the cathode for heterogeneous EF processes.

Electrochemical detection of nicotine at a carbon Nanofiber-Poly(amidoamine) dendrimer modified glassy carbon electrode.

Development of electrochemical sensors for important drugs such nicotine (an addictive drug) is important for the society. This study reports the electrochemical detection of nicotine at a carbon nanofiber/poly (amidoamine) dendrimer modified glassy carbon electrode. The carbon nanofiber (CNF) modified GCE was prepared by drop-coating followed by the electrodeposition of generation 4 poly (amidoamine) succinamic acid dendrimer (PAMAM) to form the sensor - CNF-PAMAM GCE. Characterization of prepared materials and modified electrodes was carried out using Fourier transmission infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The CNF-PAMAM composite was confirmed by microscopy. A marked reduction in charge transfer resistance and increase in current of the CNF-PAMAM GCE in comparison to the bare electrode showed a synergic improvement electrochemical response because of the CNF-PAMAM nanocomposite. The CNF-PAMAM demonstrated an enhanced performance in the oxidation of nicotine in comparison to the bare GCE by shifting the anodic potential Epa of nicotine from 0.9 V to 0.8 V. The electrochemical sensor achieved a detection limit (LOD) of 0.02637 µM in the concentration range of 0.4815-15.41 µM of nicotine in 0.1 M PBS at pH 7.5. The sensor ability to determine nicotine in real samples was assessed in cigarettes obtaining recovery percentages of 88.00 and 97.42%. The sensor demonstrated selectivity toward nicotine in the presence of interferences. Finally, the method was validated by ultraviolet-visible spectroscopy analysis.

Enhanced photoelectrocatalytic degradation of diclofenac sodium using a system of Ag-BiVO4/BiOI anode and Ag-BiOI cathode.

We report the photoelectrocatalysis of diclofenac sodium using a reactor consisting of Ag-BiVO4/BiOI anode and Ag-BiOI cathode. The electrodes were prepared through electrodeposition on FTO glass and modified with Ag nanoparticles through photodeposition. The structural and morphological studies were carried out using XRD, SEM, and EDS which confirmed the successful preparation of the materials. The optical properties as observed with UV-DRS revealed that the electrodes were visible light active and incorporation of metallic Ag particles on the surface increased the absorption in the visible light region. Presence of p-n heterojunction in the anode led to decrease in the spontaneous recombination of photoexcited electron-hole pairs as seen in the photocurrent response. The results from photoelectrocatalytic degradation experiments revealed that replacing platinum sheet with Ag-BiOI as counter electrode resulted in higher (92%) and faster removal of diclofenac sodium as evident in the values of apparent rate constants. The reaction mechanism further revealed that efficiently separated photogenerated holes played a major role in the degradation of the pharmaceutical. The prepared electrodes showed good stability and impressive reusability. The reports from this study revealed that the dual photoelectrodes system has a great potential in treating pharmaceutical polluted wastewater using visible light irradiation.

Perovskite Oxide-Based Materials for Photocatalytic and Photoelectrocatalytic Treatment of Water.

Meeting the global challenge of water availability necessitates diversification from traditional water treatment methods to other complementary methods, such as photocatalysis and photoelectrocatalysis (PEC), for a more robust solution. Materials play very important roles in the development of these newer methods. Thus, the quest and applications of a myriad of materials are ongoing areas of water research. Perovskite and perovskite-related materials, which have been largely explored in the energy sectors, are potential materials in water treatment technologies. In this review, attention is paid to the recent progress in the application of perovskite materials in photocatalytic and photoelectrocatalytic degradation of organic pollutants in water. Water treatment applications of lanthanum, ferrite, titanate, and tantalum (and others)-based perovskites are discussed. The chemical nature and different synthetic routes of perovskites or perovskite composites are presented as fundamental to applications.

A Silver-Loaded Exfoliated Graphite Nanocomposite Anti-Fouling Electrochemical Sensor for Bisphenol A in Thermal Paper Samples.

Silver nanoparticles (AgNPs) were synthesized separately and loaded onto the expanded layers of exfoliated graphite (EG) to form a silver nanoparticle-exfoliated graphite nanocomposite (AgNPs-EG). The AgNPs-EG was compressed into a pellet (0.6 cm in diameter) and used to prepare an electrochemical sensor for bisphenol A (BPA) in standard samples and in thermal paper. The synthesized materials were characterized by ultraviolet-visible spectrophotometry, X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive X-ray. The electrochemical behavior of BPA on the AgNPs-EG sensor was investigated by cyclic voltammetry and square wave voltammetry. Under optimized experimental conditions, the oxidation peak current was linearly proportional to bisphenol A concentrations in the range from 5.0 to100 µM, with a coefficient of determination (R2 ) of 0.9981. The obtained limit of detection of the method was 0.23 µM. The fabricated sensor was able to overcome electrode fouling with good reproducibility (RSD = 2.62%, n = 5) by mechanical polishing of the electrode on emery paper. The proposed method was successfully applied to determine bisphenol A in thermal paper samples and demonstrated good accuracy of 93.1 to 113% recovery.

The application of FTO-Cu2O/Ag3PO4 heterojunction in the photoelectrochemical degradation of emerging pharmaceutical pollutant under visible light irradiation.

We report the photoelectrochemical application of a visible light active FTO-Cu2O/Ag3PO4 photoanode for the abatement of sulfamethoxazole in water. The as-synthesised photoanodes were characterised using XRD, field emission SEM, EDX, diffuse reflectance UV-vis, impedance spectroscopy and chronoamperometry. The results obtained confirmed a successful formation of p-n heterojunction at the Cu2O/Ag3PO4 interface. The highest photocurrent response of 0.62 mAcm-2 was obtained for the composite photoanode which was four times higher than pure Cu2O and about three times higher than pristine Ag3PO4. The photoanode gave 67% removal efficiency within 2 h upon its photoelectrochemical application in the degradation of sulfamethoxazole with 1.5 V bias potential at pH 6.2. The FTO-Cu2O/Ag3PO4 electrode was also applied in the treatment of a cocktail of synthetic organics containing sulfamethoxazole and orange II dye. The photogenerated holes was found to be the major oxidant and the photoanodes was stable and reusable.

Towards visible light driven photoelectrocatalysis for water treatment: Application of a FTO/BiVO4/Ag2S heterojunction anode for the removal of emerging pharmaceutical pollutants.

Pharmaceuticals have been classified as emerging water pollutants which are recalcitrant in nature. In the quest to find a suitable technique in removing them from contaminated water, photoelectrocatalytic oxidation method has attracted much attention in recent years. This report examined the feasibility of degrading ciprofloxacin and sulfamethoxazole through photoelectrocatalytic oxidation using FTO-BiVO4/Ag2S with p-n heterojunction as anode. BiVO4/Ag2S was prepared through electrodeposition and successive ionic layer adsorption/reaction on FTO glass. Structural and morphological studies using XRD, SEM, EDS and diffusive reflectance UV-Vis confirmed the successful construction of p-n heterojunction of BiVO4/Ag2S. Electrochemical techniques were used to investigate enhanced charge separation in the binary electrode. The FTO-BiVO4/Ag2S electrode exhibited the highest photocurrent response (1.194 mA/cm-2) and longest electron lifetime (0.40 ms) than both pristine BiVO4 and Ag2S electrodes which confirmed the reduction in recombination of charge carriers in the electrode. Upon application of the prepared FTO-BiVO4/Ag2S in photoelectrocatalytic removal of ciprofloxacin and sulfamethoxazole, percentage removal of 80% and 86% were achieved respectively with a low bias potential of 1.2 V (vs Ag/AgCl) within 120 min. The electrode possesses good stability and reusability. The results obtained revealed BiVO4/Ag2S as a suitable photoanode for removing recalcitrant pharmaceutical molecules in water.

Solar-Light-Responsive Titanium-Sheet-Based Carbon Nanoparticles/B-BiVO4/WO3 Photoanode for the Photoelectrocatalytic Degradation of Orange II Dye Water Pollutant.

We report the preparation and application of a heterostructured photoelectrocatalyst comprising carbon nanoparticles (CNPs) and boron codoped BiVO4 and WO3 for the removal of an organic dye pollutant in water. The materials, synthesized by hydrothermal method, were characterized by X-ray diffraction, diffuse reflectance UV-visible spectroscopy, energy-dispersive X-ray spectroscopy, and electron microscopy. The catalysts were immobilized on treated titanium sheets by drop-casting. The fabricated electrodes were characterized by linear sweep voltammetry (LSV) and chronoamperometry. Diffuse reflectance spectroscopy of the catalysts reveals that the incorporation of CNPs and B into the structure of monoclinic BiVO4 enhanced its optical absorption in both UV and visible regions. The LSV measurements carried out in 0.1 M Na2SO4 showed that the BiVO4- and WO3-based photoelectrode demonstrated significant photoactivity. CNP/B-BiVO4 and CNP/B-BiVO4/WO3 photoanodes gave photocurrent densities of approximately 0.83 and 1.79 mA/cm2, respectively, at 1.2 V (vs 3 M Ag/AgCl). The performance of the electrodes toward degradation of orange II dye was in the order BiVO4 < B-BiVO4 < WO3 < CNP-BiVO4 < CNP/B-BiVO4 < CNP/B-BiVO4/WO3, and the apparent rate constants obtained by fitting the experimental data into the Langmuir Hinshelwood kinetic model are 0.0924, 0.1812, 0.254, and 0.845 h-1 for BiVO4, WO3, CNP/B-BiVO4, and CNP/B-BiVO4/WO3, respectively. The chemical oxygen demand abatement after 3 h of electrolysis at the best performing photoanode was 58%. The study showed that BiVO4 and WO3 are promising anodic materials for photoelectrocatalytic water treatment plant.

Electro-Fenton and photoelectro-Fenton degradation of sulfamethazine using an active gas diffusion electrode without aeration.

A novel superhydrophobic gas diffusion electrode based on carbon black (CB)- polytetrafluoroethylene (PTFE) modified graphite felt cathode was prepared to increase oxygen mass transfer efficiency and produce hydrogen peroxide at the gas-liquid-solid three-phase interface without aeration. The gas diffusion electrode system was further tested for the degradation of sulfamethazine (SMT) by electro-Fenton (EF) and photoelectro-Fenton (PEF). In the EF process, SMT was removed effectively, but the mineralization degree was not high due to the generation of organic acids which were difficult to be further degraded. While in the PEF process, organic contaminant can be destroyed by the combined action of Fe2+/H2O2, UV/H2O2 and UV radiation, and more efficient mineralization (>83.5%) at low current (50 mA) was attained, which might be attributed to the high H2O2 utilization (70-90%), rapid regeneration of Fe2+ and photolysis of intermediates. In addition, it was verified that the PEF system had a good adaptability to pH and pollutant concentration. Compared with aeration system, the use of this active gas diffusion cathode in electrochemical advanced oxidation processes significantly reduced energy consumption.

Cu2O as an emerging semiconductor in photocatalytic and photoelectrocatalytic treatment of water contaminated with organic substances: a review.

A wide range of semiconductor photocatalysts have been used over the years in water treatment to eliminate toxic organic substances from wastewater. The quest for visible or solar light driven photocatalysts with striking merits such as wide range of applications, ease of preparation, tailored architecture that gives rise to improved performance, ability of dual existence as both p type or n type semiconductor, among others, presents copper(i) oxide as a promising photocatalyst. This paper reviews the recent applications of Cu2O in photocatalytic and photoelectrocatalytic treatment of water laden with organic pollutants such as dyes and pharmaceuticals. It covers the various modes of synthesis, morphologies and composites or heterostructures of Cu2O as found in the literature. Concluding remarks and future perspectives on the application of Cu2O are presented.

Switching Anionic and Cationic Semipermeability in Partially Hydrolyzed Polyacrylonitrile: A pH-Tunable Ionic Rectifier.

Membrane materials with semipermeability for anions or for cations are of interest in electrochemical and nanofluidic separation and purification technologies. In this study, partially hydrolyzed polyacrylonitrile (phPAN) is investigated as a pH-switchable anion/cation conductor. When switching from anionic to cationic semipermeability, also the ionic current rectification effect switches for phPAN materials deposited asymmetrically onto a 5, 10, 20, or 40 µm diameter microhole in a 6 µm thick polyethylene-terephthalate (PET) film substrate. Therefore, ionic rectifier behavior can be tuned and used to monitor and characterize semipermeability. Effects of electrolyte type and concentration and pH (relative to the zeta potential at approximately 3.1) are investigated by voltammetry, chronoamperometry, and impedance spectroscopy. A computational model provides good qualitative agreement with the observed electrolyte concentration data. High rectification effects are observed for both cations (pH > 3.1) and anions (pH < 3.1) but only at relatively low ionic strengths.