Oxygen Hole Research Articles

Alkali ionic state behavior in γ-Irradiated borate glasses for medical ultrasonic transducer fabrication

Lenses could be added to ultrasonic transducers used in medical applications to improve them. They may solve some limiting factors, like the acoustic impedance mismatch between the transducer and the tissues, the wave collimation difficulty, the wave scattering, etc. Novel ultrasonic transducers were developed that contained lenses made from new glass systems. Al2O3, MgO, and Li2O alkali-borate glass systems were prepared via the melt-quenching technique. Structural, electrical, and ultrasonic measurements were done with regard to the effect of gamma radiation. The XRD pattern showed the glassy, amorphous nature of the lenses. FTIR absorption spectra revealed the large stability of the main structural units of borate. Electron spin resonance (ESR) spectra clarified the low distortions caused by irradiation with g-values ∼ 2.025–2.026 and recognized the formation of oxygen hole centers (OHC) caused by breaking B–O connectivity. Al ions produced the most compact glass network, resulting in the highest ultrasonic velocity and wave passage. The characteristics of transducers with and without the lens were measured. The transducers with Al2O3 lenses demonstrated the lowest signal-to-noise ratio, the greatest beam diameter, and the highest sensitivity. The results ensured the effectiveness of the prepared glass as a lens in high-frequency ultrasonic transducers that are mainly used in medical applications.

Photo-Activating Biomimetic Polyoxomolybdate for Boosting Oxygen Evolution in Neutral Electrolytes.

Inspired by the metal-oxo cluster structural feature and charge separation behaviour of the oxygen evolving center (OEC) in photosystem II (PS-II) under photoirradiation, a new crystalline photochromic polyoxomolybdate, MV2 [β-Mo8 O26 ] (1, MV=methyl viologen cation), is designed as a biomimetic oxygen evolution reaction (OER) catalyst in neutral electrolytes. After photoinduced electron transfer (PIET) with colour change from colourless to grey, it remains in an ultra-stable charge-separated state over a year under ambient conditions. The observed overpotential at 10 mA ⋅ cm-2 and Tafel slope decrease by 49 mV and 62.8 mV ⋅ dec-1 after coloration, respectively. The outstanding OER performance of the coloured state in neutral electrolytes even outperforms the commercial RuO2 benchmark. Experimental and theoretical studies show that oxygen holes within polyanions after irradiation serve as sites for enhancing direct O-O coupling, thus effectively promoting OER. This is the first successful application of electron-transfer photochromism to realize OER activity gain.

Photo‐Activating Biomimetic Polyoxomolybdate for Boosting Oxygen Evolution in Neutral Electrolytes

AbstractInspired by the metal‐oxo cluster structural feature and charge separation behaviour of the oxygen evolving center (OEC) in photosystem II (PS‐II) under photoirradiation, a new crystalline photochromic polyoxomolybdate, MV2[β‐Mo8O26] (1, MV=methyl viologen cation), is designed as a biomimetic oxygen evolution reaction (OER) catalyst in neutral electrolytes. After photoinduced electron transfer (PIET) with colour change from colourless to grey, it remains in an ultra‐stable charge‐separated state over a year under ambient conditions. The observed overpotential at 10 mA ⋅ cm−2 and Tafel slope decrease by 49 mV and 62.8 mV ⋅ dec−1 after coloration, respectively. The outstanding OER performance of the coloured state in neutral electrolytes even outperforms the commercial RuO2 benchmark. Experimental and theoretical studies show that oxygen holes within polyanions after irradiation serve as sites for enhancing direct O−O coupling, thus effectively promoting OER. This is the first successful application of electron‐transfer photochromism to realize OER activity gain.

Silver decoration of Cr2O3 nanoparticles: Facile preparation of Cr2O3 nanoparticles and Ag–Cr2O3 nanocomposites and characterization of their antibacterial activity and ability to photocatalytically degrade organic wastes under visible light

An eco-friendly, single-step process was adopted for the preparation of Cr2O3 nanoparticles (CR-NPs), and different concentrations of Ag were doped into the CR-NPs through liquid impregnation to synthesize a series of Ag-CRNPs composites. In order to prevent agglomeration, chemical transformation, and weak adhesion of Ag to CR-NPs, a mechanical process of circular-motion grinding and high-temperature treatment in a sealed condition were used. Well-defined heterojunctions were successfully formed between Ag and CR-NPs. In comparison to the CR-NPs, the Ag-doped CR-NP composites exhibited excellent performance in photocatalytic and antibacterial applications. Under visible light (VL), the best-performing composite (2 %-Ag decorated CR-NPs) showed 96 %, 79 %, and 57 % decomposition of methylene blue, Congo red, and tetracycline, respectively, in 100 min, which was attributed to a synergetic effect in the composites. The rate constant of the photocatalytic reaction is 14 times higher than that of the reaction without a photocatalyst. The enhanced efficiency was attributed to a reduced bandgap, prolonged retention of photogenerated electron–hole pairs, an increased amount of active spots, and increased absorption of VL. Similarly, the best-performing composite exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus with zones of inhibition of 15.4 and 15.1 mm, respectively. The 2 %-Ag decorated CR-NPs were the most efficient and exhibited robust recyclability until the fifth cycle (≥90 %). The photocatalytic activity was primarily driven by reactive oxygen species, holes and hydroxyl radicals.

SPECTRAL-LUMINESCENT AND ELECTROPHYSICAL STUDY OF RADIATION OXIDATION OF BERYLLIUM IN WATER

The radiation oxidation of Be in water at room temperature in the absorbed dose range Dγ = 0.5…180 kGy was studied by radiothermoluminescence (RTL), infrared reflection-adsorption spectroscopy (IRRAS), and electrical conductivity. The participation and role of surface relaxing intermediate-active particles in the dynamics of changes in the oxidation process are considered. Using the RTL method, the role of surface oxygen hole centers generated by γ-irradiation and chemisorbed oxygen in the formation of nanooxide films was experimentally established. The formation of nanooxide films on the surface of Be in water was traced in the IR reflection spectra. The kinetics of radiation oxidation of beryllium has been studied and its radiation passivation has been established. According to the logarithmic dose dependence of the surface resistivity Be, two stages of the oxidation process were revealed. It is shown that the formation of nano oxide films leads to a decrease in the surface electrical conductivity of beryllium by 2 orders of magnitude and an increase in the thickness of oxide films by 1.6 times.

Conductivities and grain interior transport properties of CaHf0.9In0.1O2.95

A perovskite-structured proton conductor, CaHf0.9In0.1O2.95, was synthesized via solid-state reaction, and proton conductivity and transport number of its grain interior were determined by using the defect equilibria model. The results reveal that the total conductivity of grain interior and the entire sample (grains and grain boundaries) of CaHf0.9In0.1O2.95, respectively, reaches 7.26 × 10−4 S∙cm−1 and 3.03 × 10−4 S∙cm−1 in a humid atmosphere at 800 °C. Moreover, it was observed that the conductivities of the grain interior exhibited higher values than those of the entire sample within the temperature range of 400–800 °C. The activation energy of the entire sample was higher than that of the grain interior; and for the charge carriers of CaHf0.9In0.1O2.95, the activation energy of oxygen vacancies and holes was higher than that of the proton. At 400–800 °C, transport properties of CaHf0.9In0.1O2.95 were dominated by proton conduction under the atmosphere containing oxygen and water vapor, where the transport numbers of proton in the grain interior and the entire sample were estimated to be 0.541 and 0.497, respectively, at a temperature of 800 °C. Thus, the proton transport number of grain interior was found to be higher than that of the entire sample. Therefore, the grain interior of CaHf0.9In0.1O2.95 can provide better proton conduction than grain boundary. In summary, these results exhibit that CaHf0.9In0.1O2.95 possesses certain application prospects in electrochemical sensors.

Studying Surface Chemistry of Mixed Conducting Perovskite Oxide Electrodes with Synchrotron-Based Soft X-rays.

A fundamental understanding of the electrochemical reactions and surface chemistry at the solid-gas interface in situ and operando is critical for electrode materials applied in electrochemical and catalytic applications. Here, the surface reactions and surface composition of a model of mixed ionic and electronic conducting (MIEC) perovskite oxide, (La0.8Sr0.2)0.95Cr0.5Fe0.5O3-δ (LSCrF8255), were investigated in situ using synchrotron-based near-ambient pressure (AP) X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure spectroscopy (NEXAFS). The measurements were conducted with a surface temperature of 500 °C under 1 mbar of dry oxygen and water vapor, to reflect the implementation of the materials for oxygen reduction/evolution and H2O electrolysis in the applications such as solid oxide fuel cell (SOFC) and electrolyzers. Our direct experimental results demonstrate that, rather than the transition metal (TM) cations, the surface lattice oxygen is the significant redox active species under both dry oxygen and water vapor environments. It was proven that the electron holes formed in dry oxygen have a strong oxygen character. Meanwhile, a relatively higher concentration of surface oxygen vacancies was observed on the sample measured in water vapor. We further showed that in water vapor, the adsorption and dissociation of H2O onto the perovskite surface were through forming hydroxyl groups. In addition, the concentration of Sr surface species was found to increase over time in dry oxygen due to Sr surface segregation, with the presence of oxygen holes on the surface serving as an additional driving force. Comparatively, less Sr contents were observed on the sample in water vapor, which could be due to the volatility of Sr(OH)2. A secondary phase was also observed, which exhibited an enrichment in B-site cations, particularly in Fe and relatively in Cr, and a deficiency in A-site cation, notably in La and relatively in Sr. The findings and methodology of this study allow for the quantification of surface defect chemistry and surface composition evolution, providing crucial understanding and design guidelines in the electrocatalytic activity and durability of electrodes for efficient conversions of energy and fuels.

Ba0.5Sr0.5TiO3/BaFe12O19 magnetic separation photocatalysts: Structural, optical, microstructure, photocatalytic activity, degradation pathway and mechanism

The Ba0.5Sr0.5TiO3/BaFe12O19 (BST5/BFO) magnetic photocatalysts were constructed by a polyacrylamide gel route combined with low temperature heat treatment process. The effect of different BFO contents on the phase, surface microstructure, magnetic and optical properties, and photocatalytic efficiency of BST5/BFO magnetic photocatalysts was investigated. The BST5, BFO and BST5/BFO magnetic photocatalysts were evaluated for the degradation of tetracycline hydrochloride (TC) under simulated sunlight irradiation for 120 min, pH=5, catalyst content of 1 g/L, initial TC concentration of 50 mg/L and the photocatalytic efficiency trend followed the order: pristine BFO < pristine BST5 < BST5/20%BFO < BST5/15%BFO < BST5/5%BFO <BST5/10%BFO. The improvement of photocatalytic efficiency of BST5/BFO magnetic photocatalyst is mainly attributed to the synergistic effect of optical absorption coefficient, squareness ratio (SQR), interface charge transfer and separation efficiency due to the impurity defect and magnetic field induced the formation of oxygen vacancy, hole, hydroxyl radical and superoxide radical. The reasonable photocatalytic mechanism of BST5/BFO magnetic photocatalysts and possible intermediate products were elucidated in detail on the basis of the first principles calculation, capture experiment, radical verification experiment, magnetic data and liquid chromatography-mass spectrometry.

Evaluation of the sterilization effect on biphasic scaffold based on bioactive glass and polymer honeycomb membrane

AbstractThe sterilization is a core preoccupation when it comes to implantable biomaterials. The most common in industry is the gamma sterilization; however, the radiation used in this method can induce modifications in the material properties. This study investigates the impact of such radiations on the physicochemical properties and biological toxicity of a new biomaterial based on a poly‐l‐co‐d,l‐lactide polymer honeycomb membrane and bioactive glass (BG), combined, to form an assembly (membrane/BG assembly). The investigated BGs are the S53P4, which is FDA approved and clinically used, and 13‐93B20, a BG containing boron promising for bone regeneration. Infrared and photoluminescence measurements revealed that, upon irradiation, defects are created in the BGs molecular matrix. Defects were identified to be mainly non‐bridging oxygen hole center and occur in higher proportion in the 13‐93B20 making it more sensitive to irradiation compared to the S53P4. However, the irradiation does not significantly impact the structure of the BGs. On the membrane side, the molecular weight is divided by two resulting in a lower shear stress resistance. However, the membrane honeycomb topography does not seem to be impacted by the irradiation. In contact with cells, no toxicity effect was observed, and BGs keep their bioactive properties by releasing ions beneficial to the cell fate and with no influence on apatite precipitation speed. Overall, this study showed that, despite some impact on the physicochemical properties, the irradiation does not induce deleterious effect on the membrane/BG assemblies and is therefore a suitable method for the sterilization of this novel biomaterial.

Radiation effects of B depletion and the generation of point defects in ternary borosilicate glasses by gamma rays

Borosilicate glass is one of the base materials which can solidify high-level radioactive waste. Therefore, its resistance to radiation attracted extensive attention. The borosilicate glass samples with different compositions were irradiated with gamma rays at ambient temperature. The interaction between the gamma rays and the glass network was discussed. The radiation effects were analyzed with nano-indentation, photoluminescence, Raman, Infrared, Ultraviolet and visible absorption, and X-ray photoelectron spectroscopies. The results indicate point defects such as non-bridging oxygen hole center (NBOHC) and peroxy radical were produced in glasses after irradiation. The depletions of sodium and boron in the surface of glasses were identified, which led to a decrease in hardness. The Urbach energies increased with the absorbed dose. A new analyzing method, the noise of Raman spectrum, was deduced to analyze the glass disorder. The noise and Urbach energy depended on the concentration of NBOHC, which is led by gamma radiation.

Relationship between the Coloration Mechanism and Gemological Properties of Purple Scapolite

Purple scapolite is a precious gemstone. In this paper, we compared the crystal structure and spectral characteristics of purple scapolite before and after heat treatment with conventional gemological tests, EPMA, XRF, LA-ICP-MS, infrared spectroscopy, Raman spectroscopy, UV–vis spectrophotometer, EPR, and other tests. The XRD results showed that the structure of purple scapolite fits perfectly with that of marialite. Compositional analyses indicate that purple scapolite has an average Me value of 16.85 and belongs to the subspecies marialite, and thus its specific gravity and refractive index are low. The absorption peak at 1045 cm−1 in the infrared spectra has a direct relationship with the Me value, which is blue-shifted with increasing Me value. After heating at 400 °C for 2 h, the purple scapolite changed to colorless, and no phase transformation or significant structural changes occurred during this process. But this process is accompanied by the disappearance of the signal at g = 2.011 in the EPR spectra, which indicates the presence of oxygen hole centers, thus proving that the color of purple scapolite is caused by oxygen hole centers rather than Fe3+. The chlorine in the marialite structure occupies the structural center, which provides for the appearance of oxygen hole centers, and thus purple scapolite always has a high marialite content. This further leads to the refractive index and specific gravity always being lower. That is a new explanation for the relationship between scapolite coloration mechanism, specific gravity, and refractive index.

Biodegradation of phthalic acid esters (PAEs) by Bacillus sp. LUNF1 and characterization of a novel hydrolase capable of catalyzing PAEs

Phthalic acid esters (PAEs), the universal plasticizers, have widely entered the environment and cause serious contamination, potentially threatening human health. Furthermore, PAEs are highly resistant to degradation due to their hydrophobicity. In the present study, a PAE degrader, Bacillus sp. LUNF1, was isolated from sewage sludge. Strain LUNF1 completely removed dibutyl phthalate (DBP) from wastewater, demonstrating its great potential for PAE bioremediation. The genetic mechanism underlying PAE degradation by strain LUNF1 was elucidated by identification of the novel PAE hydrolase DphBL1 belonging to family VII. The hydrolase was overexpressed in E. coli BL21(DE3) and purified by affinity chromatography. It displayed high hydrolytic efficiency toward DBP at 10–50 °C and pH 5.0–9.0. Importantly, DphBL1 maintained its stability in the presence of β-mercaptoethanol (β-ME), phenylmethylsulphonyl fluoride (PMSF) and various metal ions, which did not significantly inhibit DphBL1. It was also found that the catalytic triad (Ser190-His395-Glu306), oxygen hole (Gly107-Ala108) and other residues (Phe310, Ile358, Phe359, Leu309 and Leu269) were involved in interacting DBP. DphBL1 mutants with significantly reduced activity confirmed the essential role of these active residues and revealed the catalytic mechanism of DphBL1. These results will support structural modification of PAE hydrolases to improve catalytic efficiency in bioremediation, and promote the development of efficient strategies for PAE remediation in the environment.

Defect generation mechanisms in silica under intense electronic excitation by ion beams below 100 K: Interplay between radiative emissions

Ion-beam effects on bulk silica at low temperature have been studied with the aim of understanding the routes and mechanisms leading from the initial generation of free carriers and self-trapped excitons (STEs) to the production of two stable defect structures in irradiated silica, non-bridging oxygen hole centers (NBOHCs) and oxygen deficient centers (ODCs). Ion beam induced luminescence (ionoluminescence, IL) spectra were obtained using 3 MeV H, 3.5 MeV He, 19 MeV Si, and 19 MeV Cl ions and a range of cryogenic irradiation temperatures from 30 to 100 K. The kinetic behavior of three emission bands centered at 1.9 eV (assigned to NBOHCs), 2.1 eV (assigned to the intrinsic decay of STEs), and 2.7 eV (assigned to ODCs) reveal the physical origin of these emissions under intense electronic excitation. The creation of NBOHCs is governed by a purely electronic mechanism. The kinetics curve of the NBOHC band shows two main contributions: an instantaneous (beam-on) contribution, followed by a slower fluence- and temperature-dependent process correlated with the concentration of STEs. The beam-on contribution is proportional to deposited ionization energy. The growth of the ODC band is linear in fluence up to around 2 × 1012 cm−2. The growth rate is independent of temperature but proportional to the number of radiation-induced oxygen vacancies per ion, showing, unambiguously, that the 2.7 eV emission can be associated with ODCs created in an excited state.

Theoretical studies on intrinsic electron traps in strained amorphous silica

Charge trapping in amorphous silica (a-SiO2) dielectric layer can degrade electrical performances of semiconductor devices. Earlier studies demonstrate that a SiO4 tetrahedra unit with a wide O-Si-O angle (≥132.0∘) can act as an electron trapping site in unstrained a-SiO2 cells. With first-principle calculations, in conjunction with molecular dynamic calculations, this work investigates the impacts of uniaxial tensile strain on one-electron trapping behaviors of a-SiO2, including atomic configurations and electronic properties. Stable states of strained a-SiO2 cells with an extra electron indicate that a SiO4 with a wide O-Si-O angle (≥132.0∘) and a long Si-O bond (≥1.660Å) making up the angle can act as a novel intrinsic electron tap. An electron trapping on this trap can generate a stable defect complex with two components: a negatively charged non-bridging oxygen hole center and a neutral oxygen vacancy with an unpaired electron.

Defect characteristic of oxygen-deficient Ge-doped preform using photoluminescence spectroscopy

Study has been made of the Photoluminescence properties of Ge-doped silica preforms fabricated using the MCVD process and subsequently subjected to γ-ray irradiation. The photoluminescence emissions pointed to the presence of defects related to oxygen vacancies. Two types of preform were fabricated, obtained using a different flow rate and deposition temperature for each case. Results from the absorption spectra of the samples named as P1 and P2, show a signature absorption peak at 5.1 eV and 6.8 eV, indicative of oxygen-deficient and oxygen-rich defects respectively. Photoluminescence investigation have been carried out before and after the irradiation process with both samples reveal two main peaks at 1.5 eV. The highest intensity at 1.5 eV is known as an interaction between the Non- Bridging Oxygen Hole Centre (NBHOC) with the presence of impurity in the glass matrix. Upon irradiation, weak peak can be observed at 1.8 eV, sample P1 and P2, the PL intensity increases by a factor of 20 × and 50 × , respectively. This peak is associated with the oxygen deficient state in the sample. The peak referring to defect known as Germanium Lone Pair Centre (GLPC) are observed in both samples, peak shown at 3.1 eV, regardless of the Germanium Oxygen Deficient Centre (GODC) content. In regard to this, it can be concluded that this defect is generated independently in all germanium samples and are not correlated with the GODC band observed in the absorption band.

Resolving the polar interface of infinite-layer nickelate thin films.

Nickel-based superconductors provide a long-awaited experimental platform to explore possible cuprate-like superconductivity. Despite similar crystal structure and d electron filling, however, superconductivity in nickelates has thus far only been stabilized in thin-film geometry, raising questions about the polar interface between substrate and thin film. Here we conduct a detailed experimental and theoretical study of the prototypical interface between Nd1-xSrxNiO2 and SrTiO3. Atomic-resolution electron energy loss spectroscopy in the scanning transmission electron microscope reveals the formation of a single intermediate Nd(Ti,Ni)O3 layer. Density functional theory calculations with a Hubbard U term show how the observed structure alleviates the polar discontinuity. We explore the effects of oxygen occupancy, hole doping and cation structure to disentangle the contributions of each for reducing interface charge density. Resolving the non-trivial interface structure will be instructive for future synthesis of nickelate films on other substrates and in vertical heterostructures.

Optical spectroscopy assessment of the impact of γ-ray irradiation on Gd3+-doped phosphate glass

The effects of γ-ray irradiation (10, 100 kGy) on Gd3+-doped phosphate glass were evaluated. Glass irradiated at 100 kGy was characterized alongside the pristine by differential scanning calorimetry, Fourier transform-infrared spectroscopy and Raman scattering, wherein a lack of alteration in thermal and structural properties was supported. Yet, absorption bands developed around 500 nm with γ-ray dose indicating phosphorus oxygen hole center defects. Optical band gap and Urbach energies exhibited decreasing and increasing trends, respectively, reflecting the influence of trapped electrons and increased disorder/defects. By exciting γ-irradiated samples at 265 nm, blue radio-photoluminescence was observed where intensity increased with dose. Decay curves measured monitoring 415 nm emission showed first-order kinetics suggested to arise from phosphorus electron centers. Emission from Gd3+ was quenched with gamma-ray dose while the 6P7/2 emitting state lifetimes decreased. Correlations between Gd3+ emission intensities and lifetimes with optical band gaps suggest electron center defects perform as ‘energy sinks’.

Gallosilicate glass and fiber for radiation detection

AbstractAs ionizing radiation can cause harmful effects to human and electronic devices, accurate dose monitoring plays an important role in fields such as radiotherapy, nuclear industry, and aerospace. Currently, it is still a challenge to fabricate a miniaturized dosimeter that can achieve real‐time monitoring. Here, a gallosilicate glass with potential application in visualization detection of ultraviolet and ionizing radiation, as well as cumulative dose measurement, is presented. Color centers are induced in the glass upon exposure to ultraviolet or ionizing radiation, resulting in a darkening effect. The color change of glass is related to the energy and intensity of incident photons and can be erased by subsequent heat treatment. Electron paramagnetic resonance measurement indicates that the formation of color centers is associated with non‐bridging oxygen hole centers related to gallium. The glass can be fabricated into fiber with perfect core‐cladding structure, which provides an alternative for preparing a new type of high‐sensitivity radiation dosimeter.

Enhancing the Photocatalytic Activity of TiO2 for the Degradation of Congo Red Dye by Adjusting the Ultrasonication Regime Applied in Its Synthesis Procedure

Recently, the ultrasound-assisted sol-gel synthesis procedure of mesoporous titania (TiO2) photocatalysts caught the researcher’s attention, due to the physicochemical properties enhancement of the resulting titania nanomaterials. Thus, by varying different synthesis parameters particular characteristics could be obtained. In the present study, the ultrasound pulse on/off ratio has been considered and the effect of the envisaged parameter on the textural, morphological, and optical features of titania nanomaterial has been investigated. Therefore, X-ray Diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), N2-sorption measurements, SEM imaging, and UV-Vis Diffuse Reflectance spectroscopy (UVDR) have been used. And further, the photocatalytic activity of the prepared TiO2 materials was evaluated by the features developed about the applied ultrasound pulse on/off ratio as 1/1, 2/1, 3/1, 4/1, 1/3 and 2/2. It was found that the ultrasound pulse on/off ratio considered in the synthesis procedure of titania leads to TiO2 materials with different textural (SBET = 98–156 m2/g), morphological, and optical (Eg = 3.1–3.2 eV) characteristics. For this reason, TiO2 nanomaterials prepared were found to exhibit suitable features for photocatalytic applications. Thus, the TiO2 4.1 sample prepared at 4/1 ultrasound pulse on/off ratio revealed the highest photodegradation efficiency of Congo Red dye (98.28%) as the results of photocatalytic tests show. More than that, a possible reaction mechanism of the CR photodegradation process through the contribution of reactive oxygen species (·HO, ·O2−), holes (h+), and electrons (e−) of developed titania photocatalyst was proposed.

Electrochemical-enhanced nanoscale oxygen-vacancy CuFe2O4 to activate persulfate (E/oxygen-vacancy CuFe2O4/PS) for separation of Ebselen from wastewater

ABSTRACT To enhance the catalytic activity of CuFe2O4 on PS, a nanoscale oxygen-vacancy CuFe2O4 was prepared by hydrogenation reduction technique to construct an advanced oxidation system of electrochemical-enhanced nanoscale oxygen-vacancy CuFe2O4-activated persulfate. Using Ebselen (EBS) as a model pollutant, the degradation efficiency, activation mechanism and degradation pathway were studied. The oxygen-vacancy CuFe2O4 was characterized and analysed by FESEM, EDS and XPS. The results show that under the optimal reaction conditions (PS = 0.8 g/L, oxygen-vacancy CuFe2O4 = 0.3 g/L, initial pH = 6.5), the removal rate of 20 mg/L EBS can reach 92% after reaction for 60 min, which proves that the formation of oxygen-vacancy changed the catalytic inertness of CuFe2O4 on PS. It is speculated that in the E/oxygen-vacancy CuFe2O4/PS system, the existence of oxygen holes enhances the electron transfer ability and reducibility of the catalyst, so the oxygen-vacancy CuFe2O4 can efficiently activate PS to degrade EBS. The quenching experiments show that both SO 4 ⋅ − and ⋅ OH are involved in the oxidation reaction as reactive radicals in the system, with SO 4 ⋅ − being the main reactive radical. In addition, both dissolved oxygen (DO) and anions in the solution inhibit the oxidative degradation of EBS by oxygen-vacancy CuFe2O4/PS system. Through GC-MS detection, a possible degradation pathway is proposed.