Chemical State Analysis Research Articles

Plasma assisted single-step synthesis of carbon-coated SrFe2O4 electrodes for enhancing supercapacitor and oxygen evolution reaction

Developing highly efficient, conductive, and porous electrode materials for superior electrochemical bifunctional applications presents a formidable challenge, particularly when considering impurity-free large-scale production. This investigation focuses on synthesizing a composite material of highly conductive amorphous carbon-coated SrFe2O4 nanoparticles to enhance supercapacitor and oxygen evolution performance. The C@SrFe2O4 nanoparticles were synthesized through a thermal plasma process utilizing argon, methane, and carbon dioxide gas environments. The prepared samples' phase, crystal structure, morphology, elemental composition, and chemical state analysis were thoroughly examined. The electrochemical performance of the prepared samples, including Fe3O4, SrO, and C@SrFe2O4 electrodes, was evaluated for their suitability in electrochemical capacitor applications. Remarkably, C@SrFe2O4 nanoparticles exhibited notable electrochemical pseudocapacitive behavior, demonstrating a significantly higher specific capacitance of 588.7 F/g at a current density of 1 A/g. Moreover, at a current density of 10 A/g, the C@SrFe2O4 electrode exhibited outstanding cycling stability, maintaining 91 % of its initial capacitance over 5000 charge-discharge cycles. Furthermore, it showcased exceptional and uniform electrocatalytic activity for the OER, requiring only 186 mV in overpotentials to achieve a current density of 10 mA/ cm2. These findings underscore the potential of mesoporous C@SrFe2O4 nanoparticles as promising materials for supercapacitors and OER applications.

Biochar: Preserving the Long-Term Catalytic Activity of Biosynthesized PdNPs/AuNPs in Cr(VI) Reduction

Palladium nanoparticles (PdNPs) and gold nanoparticles (AuNPs) synthesized within yeast biomass can be effectively preserved in yeast biochar while maintaining their catalytic activity. Herein, we observe well-preserved PdNPs/AuNPs within yeast biochars, alongside the retention of cell morphology. Notably, the crystal structures of AuNPs within biochars exhibit similarity to that of uncarbonized samples, suggesting minimal influence of carbonization on nanoparticle structure. XPS analysis reveals the transformation of organic bacterial cells into heterocyclic aromatic-carbon material during pyrolytic carbonization. Chemical states analysis indicates the prevalence of metallic Pd(0)/Au(0) with limited PdOx/AuOx content in yeast biochars. FTIR analysis highlights increased aromaticity of biochars with typical bands for aromatic ring, and new bands appeared in Pd/Au-loaded biochars possibly attribute to PdOx/AuOx. Moreover, yeast biochars exhibit significantly improved Cr(VI) removal capacities compared to yeast biomass. Specifically, we detect complete removal within 18h for CYPd and CYPdG biochars, contrasting with less than 65% removal efficiency in yeast biomass. These findings underscore the potential of carbonization in enhancing the long-term catalytic activity of biosynthesized PdNPs/AuNPs for efficient Cr(VI) reduction, offering promising avenues for environmental remediation strategies.

Thermochromic properties and surface chemical states of reactive magnetron sputtered vanadium oxide thin films at various deposition pressures

Vanadium oxide thin films were prepared using reactive magnetron sputtering method, varying the deposition pressures from 4 to 10 mTorr while maintaining the other sputtering parameters constant. Our investigations revealed sensitive dependence of deposition pressure, chemical states of the V and O atoms, crystal phases, and thermochromic (TC) optical modulation. Specifically, the film deposited at 8 mTorr displayed distinct TC characteristics with a prevalent monoclinic m-VO2 phase according to X-ray diffraction (XRD), supported by X-ray photoelectron spectroscopy (XPS). Optical transmittance modulation and electrical property measurements revealed a metal–insulator transition (MIT), confirming the intimate connection between TC characteristics and presence of the m-VO2 phase. Films deposited at pressures lower or higher than 8 mTorr exhibited typical semiconductor behavior without TC characteristics, further supported by in situ XRD, where (110) plane shifted to lower angle upon heating above τC. Chemical state analysis by XPS revealed a clear correlation between V−O peaks and the presence of a VO2 phase, with the film deposited at 8 mTorr displaying relatively large peak fitted area indicative of the VO2 phase. These findings highlight the critical and sensitive dependence of the deposition conditions in tailoring the properties of vanadium oxide thin films and provide valuable insights for potential applications in chromogenic films.

Efficient dye removal using manganese oxide-modified nanocellulosic films from sugarcane bagasse

Removing toxic dyes from industrial wastewater is crucial for environmental protection. This research introduced novel composite films of manganese oxide (MnO2)-modified nanocellulose (MCel) and unmodified nanocellulose (Cel) derived from sugarcane bagasse for dye removal. Nanocellulose was extracted from sugarcane bagasse and subsequently transformed into MCel through in-situ MnO2 synthesis. The MCel/Cel composites, with various MCel to Cel ratios, were fabricated into films and evaluated for their efficiency in removing methylene blue (MB). The films were characterized using Fourier transform infrared spectroscopy for functional group analysis, X-ray diffraction for crystallinity, X-ray photoelectron spectroscopy for chemical state analysis, field emission scanning electron microscopy-energy dispersive spectroscopy for morphology and elemental composition, and Thermogravimetric Analysis for thermal behaviors. Adsorption results showed that all MCel/Cel composite films achieved over 97 % removal of MB (initial concentration 100 mg L−1) within 24 h, with convenient adsorbent retrieval after adsorption. The adsorption process followed a pseudo-second order kinetic model and Langmuir adsorption isotherm. The optimal 95:5 MCel/Cel film exhibited a rate constant of 6.16 × 10−4 g mg−1 min−1 and the calculated adsorption capacity of 181.85 mg g−1. These results demonstrate significant potential for wastewater treatment and sustainable waste valorization by converting sugarcane bagasse cellulose into environmentally friendly adsorbents for contaminant removal.

A composite electrocatalytic poly(3,4-ethylenedioxythiophene) film incorporated with silver nanowires for bifacial dye-sensitized solar cells

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a superior electrocatalyst for dye-sensitized solar cells (DSSCs). The porous PEDOT film, however, lacks directional conduction paths, resulting in slower electron transfer and lower cell efficiency. In this study, silver nanowires (Ag NWs) are incorporated into a PEDOT film to construct a PEDOT-coated Ag NW composite film, wherein the Ag NWs serve as highways for charge transport. The composite film is constructed by spreading Ag NWs on tin-doped indium oxide (ITO) glass via a three-step process (dip coating, brush painting, and thermal compression), followed by coating a PEDOT film via electropolymerization. The DSSC catalyzed by the PEDOT-coated Ag NW exhibited an efficiency of 9.22 % under one-sun illumination, outperforming platinum (9.09 % efficiency) and PEDOT (8.33 % efficiency) by increasing the short-circuit current density. Chemical state analyses were performed to determine the interactions between the Ag NWs and PEDOT. Impedance measurements and quantum chemical calculations were conducted to rationalize the functionality of the PEDOT-coated Ag NWs. Owing to its high transparency, the resulting DSSC achieves an efficiency of 6.74 % under rear illumination, demonstrating its high feasibility as a bifacial DSSC. The DSSC also exhibited high efficiencies ranging from 14.05 % to 19.69 % under front-side illumination at low intensities of 300–1000 lux.

Structural, morphological, and chemical composition of ternary ZrHfN thin films deposited by reactive co-magnetron sputtering

This study focuses on a deposited ternary zirconium hafnium nitride (ZrHfN) thin film prepared using the reactive co-magnetron sputtering technique. The effect of the nitrogen (N2) flow rate on the films' structural, morphological, and chemical composition was investigated. The gracing-incidence X-ray diffraction (GIXRD) showed that all ZrHfN thin films exhibited a crystalline face-centered cubic structure with a strong (111) orientation. With increasing the N2 flow rate, the film's crystallography changed based on thermodynamic theory. The films demonstrated uniformity and homogeneity in their ternary nitride composition, as confirmed by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) mapping and electron probe microanalyzer (EPMA). Chemical state analysis using X-ray photoelectron spectroscopy (XPS) indicated the presence of both nitride and oxynitride species in all samples. Notably, the atomic concentration of the main elements (Zr, Hf, and N) remained relatively stable over the controlled N2 flow rate range. However, the N2 flow rate played a crucial role in forming hafnium nitride and oxynitride chemical states, whereas it did not significantly influence the Zr phases, dominated by Zr oxides. Additionally, the hardness of the ternary ZrHfN thin films exhibited enhancement comparable to typical ternary nitrides.

Green synthesis of g-C3N4 decorated with SnO2 nanocomposites using a novel Ananas comosus crown extract for boosted performance of asymmetric supercapacitors

The recent development of green chemistry, when preparing nanoparticles using plants and their various parts has received a lot of attention in today's world. Metal and metal oxide nanoparticles have gained recognition for their recent advances in green synthesis. In this work, the green synthesis of a 2D g-C3N4 nanosheet decorated with SnO2 nanocomposite was prepared by Ananas comosus crown extract for electrochemical storage applications. The novel Ananas comosus crown extract acts as a reducing or capping agent for a green approach. The prepared g-C3N4/SnO2 nanocomposites were studied with structural, functional group, morphological, elemental composition, chemical state, and surface area analysis of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET). SnO2 and various concentrations of g-C3N4 (25, 50, 75 & 100 mg) nanocomposite were investigated for electrochemical performance. At a current density of 1 Ag−1, the green synthesized (SnO2/g-C3N4 (50 mg)) SCN-50 nanocomposite displays a high specific capacitance of 302.7 Fg−1, as well as the composite demonstrates excellent capacitance retention of 94 % after 10,000 loops. Moreover, the asymmetric supercapacitor device of SnO2/g-C3N4//Activated carbon performed good reversible and cyclic stability with high energy and power density. The green synthesis of SnO2/g-C3N4 nanocomposite has promising electrode materials for future energy storage devices.

Step-by-step enhancing oxygen evolution ability of CoFe2O4 by hybrid structure engineering and fluorine doping

CoFe2O4 is a very promising platform to catalyze oxygen evolution reaction (OER). Herein, the largely enhanced intrinsic performance of CoFe2O4 derived from the ZIF-67 for OER was demonstrated by step-by-step hybrid structure engineering and fluorine doping (F-Co/CoFe2O4@NC). This electrode showed high surface area, rapid charge transfer ability, and catalytic kinetics compared to the CoFe2O4@NC and Co/CoFe2O4@NC catalysts. Specifically, an overpotential of 280 mV was required to drive a kinetic current density of 10 mA cm−2 (loading on glassy carbon electrode, no iR-correction), with a Tafel slope of 49.7 mV dec-1 and remarkable catalytic stability throughout a 50-hour test. Theoretical analysis revealed a charge redistribution among Co, and Fe atoms was triggered by fluorine doping, and a more rapid active phase of CoOOH was generated on the surface during catalysis as confirmed by in-situ Raman spectroscopy and the post-surface chemical state analysis. The stable F atoms were more likely to be doped into CoFe2O4, and the active layer of CoOOH formed over the F-CoFe2O4 surface was more active than other states. Moreover, the electronic interaction induced by F-doping is more conducive to improving the adsorption energy of *OOH species, thereby improving the reaction kinetics and catalytic activity of OER. The current work showed an effective step-by-step approach to boosting the intrinsic activity of traditional catalysts for energy-relevant catalysis reactions.

Unveiling the surface of carbon black via scanning probe microscopy and chemical state analysis

Carbon black (CB) has wide range of industrial applications, including in the manufacturing of automobile tires, rubber products, inks, and plastics. To improve the properties of the target products and establish recycling systems, it must be fully characterized. However, characterization of CB is challenging owing to its structural complexity and the limitation of conventionally used experimental techniques, especially for surface structures at the nanoscale. In this study, we characterized the surface structures of two commercial CB via atomic force and scanning tunneling microscopy. Analysis of well-dispersed aggregates on atomically flat solid surfaces revealed primary particles of diverse sizes. The particle surfaces lacked edges, grooves, and steps that should be observed between stacked graphene sheets, which contradicts the widely accepted crystallite model. Observed images suggest that the graphene sheets exhibit a size distribution, inferring that multiple non-uniformly sized small graphene sheets are stacked turbostratically, with each sheet displaying a localized curvature rather than the ideal planar form. Varying size of sheets and curvature indicate the presence of a decent number of edges terminated with hydrogen and oxygen-containing functional groups. This interpretation was corroborated by conventional spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and infrared absorption spectroscopy.

A new device for high-resolution Li K X-ray spectroscopy using an electron microprobe

Lithium is one of the key elements in today's materials and battery industry, and the interest in non-destructive characterization techniques at a micron scale for materials containing lithium is steadily increasing. The electron microprobe is a reliable and accessible analysis tool widely used for this purpose, but performing X-ray emission spectroscopy in the low-energy range is still challenging.In this work, we demonstrate that spectroscopy in the Li K energy range is feasible by integrating a new detection system composed of a multilayer and ultra-thin separation windows into a commercial wavelength dispersive spectrometer of a microprobe. The detection system is described in detail, and the results, in form of spectra showing the Li K emission in LiF and in a ternary quasicrystalline sample, are presented and analyzed. In LiF the emission band is centered at 54.5 eV and has varying intensities for different beam exposure times. The spectra obtained in the ternary quasicrystal clearly demonstrate that the detection system has sufficient energy resolution to separate the Li emission band and the Al L2,3 and Cu M2,3 emission bands, enabling chemical state analysis by comparing the shapes of the emissions. To our knowledge, this is the first time such a detection system, implemented in a WDS spectrometer and enabling the acquisition of different Li K spectra in various compounds has been described in detail. This kind of system can be used for Li quantification using a common procedure in electron probe microanalysis.

Tribological properties of atmospheric plasma sprayed Cr3C2–NiCr/20% nickel-coated graphite self-lubricating coatings

Using atmospheric plasma spraying technology, Cr3C2–NiCr (CN)and Cr3C2–NiCr/20 % Nickel-coated graphite (CG) composite coatings were successfully deposited on 304 stainless steel substrates, with three different spraying distance parameters designed to optimize the experiment. The study investigated the influence of nickel-coated graphite on the structure, hardness, porosity, and friction-wear performance of the composite coatings. Wear mechanisms were investigated based on analyses of morphologies and chemical states of the worn surfaces of the CG composite coatings. Our results demonstrate that the CG coating exhibits lower friction coefficients, ranging from 0.24 to 0.28, than that of the CN coating. The incorporation of nickel-coated graphite leads to formation of a solid-lubricating film at friction interface, lowering friction and wear. What's more, presence of nickel-coated graphite mitigates brittleness of the CN coating, as is deemed important for improving abrasion resistance of the coatings.

Enhanced H2S gas sensing utilizing UV-assisted In2O3@ZnO nanosheets

In the realm of environmental protection, there is a growing demand for efficient and environmentally friendly gas sensors. In this study, we employed a simple hydrothermal method to synthesize nanosheets composed of zinc oxide (ZnO)-doped indium oxide (In2O3), utilizing zeolitic imidazolate framework-8 (ZIF-8) as a precursor. These nanosheets demonstrated exceptional sensitivity and selectivity in detecting hydrogen sulfide (H2S) gas. A comprehensive analysis of crystal structure, chemical states, elemental composition, surface area, and morphology was conducted. Brunauer–Emmett–Teller (BET) surface area measurements to assess the materials' textural properties revealed that the nanosheets labeled In2O3/0.1ZnO possessed a high specific surface area of 49.02 m2/g, greater than the 45.65 m2/g of pure In2O3 nanosheets, a crucial factor contributing to the observed exceptional sensitivity and selectivity in detecting H2S gas. Particularly noteworthy is the substantial improvement in gas detection response from 109.9 to 146.2 (approximately 24.7 %) observed in the In2O3/0.1ZnO material under UV irradiation at the optimal temperature of 250 °C. This enhancement emphasizes the material's potential for superior gas detection. The incorporation of ZIF-8-derived ZnO nanostructures played a crucial role in creating additional active sites, further enhancing the gas-sensing capabilities. Importantly, this innovative synthesis technique ensures the production of clean, non-toxic materials, aligning with environmental conservation objectives, and holds promise for achieving heightened sensitivity and selectivity in the detection of environmentally harmful gases.

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

We report a new thermal atomic layer deposition (thermal-ALD) process including an air exposure as a third precursor to deposit crystalline TiO2 anatase thin films from tetrakis(dimethylamido)titanium(IV) (TDMAT) and water at deposition temperatures as low as 180 °C and film thicknesses as low as 10 nm. This ALD process enables TiO2-antase crystal growth during the deposition at low temperatures (< 220 °C). This additional oxidant pulse is used to fully oxidize the Ti to a 4+ state in the amorphous film, lowering the barrier to crystalline anatase formation. This new approach is informed by preliminary studies of post-deposition annealing (PDA) of thermal ALD films in both nitrogen and air atmospheres, which demonstrate the importance of having an oxidizing atmosphere to achieve the nucleation of the crystalline anatase phase. This oxidizing atmosphere is subsequently introduced into the ALD cycle as a third precursor and is shown to be more effective and efficient in promoting the crystalline transformation than even by post-deposition annealing. The crystalline anatase phase is verified by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The mechanism for crystallization during the TDMAT/H2O/air ALD cycle is probed by chemical state analysis via X-ray photoelectron spectroscopy (XPS). We propose that sub-oxidation in TiO2 thin films deposited by the thermal-ALD process inhibits crystallization during ALD from TDMAT/H2O chemistry. Scanning electron microscopy (SEM) is used to investigate the microstructure of these TiO2 thin films as a function of thickness (5 nm to 50 nm) and deposition temperature (180 °C to 220 °C). The reported layer-by-layer air anneal process is found to crystallize entire films in shorter total process times than thermal-ALD with ex situ post deposition annealing at identical temperatures, presumably due to the improved surface diffusion kinetics accessed during the deposition process.

Cation Modulation in AgSbTe2 Realizes Carrier Optimization, Defect Engineering, and a 7% Single-Leg Thermoelectric Efficiency.

AgSbTe2 plays a pivotal role in mid-temperature thermoelectric generators (TEGs). Leveraging the seminal advances in cation manipulation within AgSbTe2, this study demonstrates an enhanced TE power factor (PF=S2σ) of 1.5mWm-1K-2 and a peak zT of 1.5 at 583K in an off-stoichiometric Ag1.04Sb0.96Te2 crystal. The introduction of Ge in place of Ag leads to an increased nH as evidenced by the detection of trace Ge4+ through XPS analysis. Further chemical state analysis reveals the simultaneous presence of Ag+, Sb3+, and Ge4+, elucidating the effect of cation modulations. TEM characterizations validate the presence of superlattice structure, and the linear defects discerned within the AgSbTe2 matrix. Consequently, the lattice thermal conductivity κL is substantially reduced in the Ag1.02Ge0.02Sb0.96Te2 crystal, yielding a peak zT of 1.77 at 623K. This notable advancement is attributed to the counterbalance achieved between the enhanced PF and the reduced κL, facilitated by cation modulation. Additionally, a single-leg TE device incorporating Ag1.02Ge0.02Sb0.96Te2 demonstrates a conversion efficiency of 7% across a temperature gradient (ΔT) of 350K. This study corroborates the efficacy of cation modulation through thermodynamic approaches and establishes a relationship between transport properties and the presence of defects.

Frequency-influenced dielectric analysis of sol-gel assisted Mg2+ substituted ZnMn2O4 nanoparticles

This study deals with the effect of Mg2+ doping on the structural, optical, and dielectric properties of zinc manganite nanoparticles. A series of MgxZn1-xMn2O4 (x = 0–0.5) samples were prepared with an auto-combustion synthesis method. Rietveld refinement of XRD revealed a pure tetragonal inverse spinel phase, supported by FTIR spectral analysis. Morphological studies indicated the transformation of micro-spherical to rod-like shapes for doped samples. With increased dopant concentration, the three Raman active modes shift towards higher frequencies. The co-existence of Mn2+, Mn3+, and Mn4+ states was revealed by chemical state analysis. The MZMO-5 sample exhibited the smallest energy bandgap (∼1.64 eV). The refractive indices of these samples were estimated to be ∼ 0.4 which might be useful for switching and filter circuits. These nano-manganite samples exhibited high dielectric constants and low losses, indicating their potential use in communication devices.

Monolithic deformable mirror based on lithium niobate single crystal for high-resolution X-ray adaptive microscopy

X-ray microscopy is very promising not only for nondestructive and high-spatial-resolution observation of the internal structure of a sample but also for elemental distribution and chemical state analysis. However, the spatial resolution of microscopes remains unsatisfactory owing to the fabrication error in the objective lens. To realize an ultra-high-resolution, we propose and develop a monolithic deformable mirror based on a lithium niobite single crystal and a novel adaptive imaging system based on it. An X-ray interferometer confirmed that shape modification is possible with an accuracy of 0.67 nm in peak to valley under high stability (0.17 nm over 7 h) and hysteresis-free deformation control. Introducing this adaptive mirror into an X-ray microscope based on advanced Kirkpatrick-Baez mirror optics and correcting the wavefront aberration demonstrated that the X-ray image quality could be significantly improved.

In-air micro-PIXE chemical state analysis of phosphorus and sulfur using a new parallel-beam wavelength-dispersive X-ray emission spectrometer

The proton induced K X-ray emission spectra of several different phosphorus and sulfur compounds were recorded with the new parallel-beam wavelength dispersive X-ray emission spectrometer. The spectrometer was installed recently at the external proton microbeam at the J. Stefan Institute to perform high energy resolution in-air micro-PIXE analysis in the tender X-ray range. Reported measurements are used to probe the capabilities of the spectrometer to perform also chemical state analysis. For phosphorus measurements, where the energy resolution of the spectrometer is the highest, a clear correlation between measured energy position of the Kα emission line and the phosphorus formal oxidation state is obtained. Chemical contrast is increased further in the Kβ emission spectra reflecting the structure of occupied valence molecular orbitals defined by the first coordination shell around the central phosphorus atom. A reasonable chemical contrast is maintained also in the sulfur Kβ emission spectra, despite the fact that the energy resolution of the spectrometer declines with increasing X-ray energy. Finally, an example of phosphorus speciation in reference biological material is presented, demonstrating the feasibility of the new setup to extend the capabilities of in-air micro-PIXE analysis towards chemical speciation.

CuMoO4/Ti3C2Tx nanocomposite layers perform as an ultrasensitive electrochemical sensor for the detection of antioxidant rutin.

The focus of this paper is laid on synthesizing layered compounds of CuMoO4 and Ti3C2Tx using a simple wet chemical etching method and sonochemical method to enable rapid detection of rutin using an electrochemical sensor. Following structural examinations using XRD, surface morphology analysis using SEM, and chemical composition state analysis using XPS, the obtained CuMoO4/Ti3C2Tx nanocomposite electrocatalyst was confirmed and characterized. By employing cyclic voltammetry and differential pulse voltammetry, the electrochemical properties of rutin on a CuMoO4/Ti3C2Tx modified electrode were examined, including its stability and response to variations in pH, loading, sweep rate, and interference. The CuMoO4/Ti3C2Tx modified electrode demonstrates rapid rutin sensing under optimal conditions and offers a linear range of 1 µΜ to 15 µΜ, thereby improving the minimal detection limit (LOD) to 42.9 nM. According to electrochemical analysis, the CuMoO4/Ti3C2Tx electrode also demonstrated cyclic stability and long-lasting anti-interference capabilities. The CuMoO4/Ti3C2Tx nanocomposite demonstrated acceptable recoveries when used to sense RT in apple and grape samples. In comparison to other interfering sample analytes encountered in the current study, the developed sensor demonstrated high selectivity and anti-interference performance. As a result, our research to design of high-performance electrochemical sensors in the biomedical and therapeutic fields.

Performance Degradation of a Double-Perovskite PrBaCo2O5+δ Cathode Operating under a CO2/H2O-Containing Atmosphere.

The electrochemical activity and stability of the PBCO electrode are investigated under the annealing processes in an atmosphere containing CO2/H2O for solid oxide fuel cells (SOFCs). The electrochemical impedance spectrum results unequivocally confirm the significant deterioration in PBCO cathode performance upon annealing under ambient air conditions, particularly when exposed to CO2/H2O atmospheres. Microstructure and surface chemical state analyses reveal the segregation of BaO on the PBCO surface, and the formation of insulating BaCO3 degraded the electrochemical performance. CO2 and H2O exhibit a significant induced effect on the segregation of Ba in PBCO to the surfaces, thereby causing a rapid decline in electrode performance. Additionally, the analysis of volume relaxation reveals that the presence of oxygen in the electrode environment can also influence the deposition process occurring on the surface of the electrode. However, this phenomenon is not observed in N2. This study emphasizes the impact of various gases present in the working atmosphere on surface-separated BaO, which consequently plays a pivotal role in the activity and long-term stability of PBCO electrodes.

Feasibility and mechanism of removing Microcystis aeruginosa and degrading microcystin-LR by dielectric barrier discharge plasma

Harmful cyanobacterial bloom is one of the serious environmental problems worldwide. Microcystis aeruginosa is a representative harmful alga in cyanobacteria bloom. It is of great significance to develop new technologies for the removal of Microcystis aeruginosa and microcystins. The feasibility and mechanism of removing microcystis aeruginosa and degrading microcystins by dielectric barrier discharge (DBD) plasma were studied. The suitable DBD parameters obtained in this study are DBD (41.5 W, 40 min) and DBD (41.5 W, 50 min), resulting in algae removal efficiency of 77.4% and 80.4%, respectively; scanning electron microscope and LIVE-DEATH analysis demonstrate that DBD treatment can disrupt cell structure and lead to cell death; analysis of elemental composition and chemical state indicated that there are traces of oxidation of organic nitrogen and organic carbon in microcystis aeruginosa; further intracellular ROS concentration and antioxidant enzyme activity analysis confirm that DBD damage microcystis aeruginosa through oxidation. Meanwhile, DBD can effectively degrade the microcystin-LR released after cell lysis, the extracellular microcystin-LR concentration in the DBD (41.5 W) group decreased by 88.7% at 60 min compared to the highest concentration at 20 min; further toxicity analysis of degradation intermediates indicated that DBD can reduce the toxicity of microcystin-LR. The contribution of active substances to the inactivation of microcystis aeruginosa is eaq− >•OH > H2O2 > O3 > 1O2 >•O2− >ONOO−, while on the degradation of microcystin-LR is eaq− >•OH > H2O2 > O3 >•O2− >1O2 > ONOO−. The application of DBD plasma technology in microcystis aeruginosa algae removal and detoxification has certain prospects for promotion and application.