Electrostatic Method Research Articles

Unravelling the role of oxygen species in toluene oxidation over Co3O4-base catalysts: In situ DRIFTS coupled with quasi in situ XPS

The present work elucidated the role of oxygen species in toluene oxidation over Co3O4-base catalysts. Co3O4 nanoneedles, nanoflowers, nanocubes, and nanoplates (denoted as Co3O4-n, Co3O4-f, Co3O4-c, and Co3O4-p) were employed to anchor Pt nanoparticles by an electrostatic adsorption method. The catalytic activity of the Pt/Co3O4 catalyst for toluene oxidation was significantly enhanced compared to that of Co3O4. Among these catalysts, Pt/Co3O4-p exhibited outstanding catalytic activity with the temperature for 90 % toluene conversion (T90 = 167 °C) at 82 °C lower than Co3O4-p (T90 = 249 °C). The low-temperature reducibility was obviously enhanced by the Pt nanoparticles, which weakened the Co-O bond energy, and improved the capacity of oxygen mobility and the concentration of surface adsorbed oxygen. The results of in situ DRIFTS demonstrated benzoate was identified as the dominant intermediate in toluene oxidation toward Co3O4-based catalysts. Furthermore, combined with the results of quasi in situ XPS showed that oxidizing toluene largely into benzoate primarily by the active adsorbed oxygen species at low reaction temperature (50 °C), mainly following the Langmuir-Hinshelwood mechanism, while oxidizing toluene into CO2 mostly by the lattice oxygen species at high reaction temperature (180–250 °C), largely following the Mars-van Krevelen mechanism.

Covalent modification of surfaces with porous metal–organic materials

Enhancing MOF and PCC tunability: surface attachment explored via click chemistry, alkylation, and electrostatic methods.

The local entropy rate of production in unsteady-state conditions at presence of a gradient of temperature

Problems of a linear mode of thermodynamics with the purpose of studying the change of local entropy rate of production in a non-stationary thermal mode at presence of a gradient of temperature in bodies of the simple form are considered. Article is development of earlier work of authors in which on the basis of experimental thermogram by the electrostatic levitation method received and fixing process of spontaneous cooling of the spherical sample of the molybdenum which is being a solid phase, change of local entropy rate of production from time has been calculated. It has been shown, that in absence of a gradient of temperature on radius of sphere change of local entropy rate of production from time corresponds to a principle of an extremum. In the given work change of local entropy rate of production from time for a case when the non-stationary thermal mode is combined with presence of a gradient of temperature is defined. The task is solved on the basis of known analytical decisions of one-dimensional problems of heating of bodies of the simple form (a unlimited plate, sphere and the unlimited cylinder), under boundary conditions of the second sort which have been received in approach of constant properties. The general meaning of local entropy rate of production is calculated as the sum of the task with gradient of temperature by a making constant in time and the non-stationary task counted in absence of a gradient of temperature. The estimation of the contribution of temperature drop on thickness of a plate in a general meaning of local entropy rate of production is executed, as product of force and a heat flux corresponding force and is widespread to a case of sphere and the cylinder by virtue of equality of temperature drop for all three bodies. The size of a nonstationary component in a general meaning of local entropy rate of production pays off as function of the logarithm, which argument is the relation of two instant temperatures, and the function of the logarithm is divided on a difference the values of time. It is shown, that the non-stationary component in a general meaning of local entropy rate of production also corresponds to a principle of an extremum at increase of Fourier number. For the first time have made comparison a part of non-stationary local entropy rate of production for a plate, sphere and the cylinder which shows, that the principle of an extremum is most brightly shown for sphere.

A one step self-cleaning surface with robust superhydrophobic and photocatalytic properties: Electrostatic sprayed fluorinated ethylene propylene mixed with nano TiO2–SiO2 particles

In this research, a one-step and environmentally friendly method, free from the complexity of chemical techniques, was utilized to prepare a superhydrophobic surface that can be implemented on large scale. To this end, at first, silica nanoparticles were made hydrophobic through the silanization method, then got mixed with titanium dioxide nanoparticles and fluorinated ethylene propylene (FEP). Afterward, the combined materials were deposited on aluminum substrate using an electrostatic spraying method. In order to assess the fabricated surface, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and contact angle measurement are accomplished. In addition, the photocatalytic activity by the degradation of oleic acid and methylene blue (MB) upon UV exposure was studied. Results indicated formation of a superhydrophobic photocatalyst with contact angle over 150 ° . This superhydrophobic surface containing nano silica content 12 wt.% and TiO 2 20 wt.% exhibited excellent photocatalytic activities in the organic materials degradation. The obtained photocatalyst surfaces also revealed proper stability in acidic (pH = 5) and alkaline (pH = 11) media. Moreover, a suitable stability was observed in the fouling medium with duration 10 h while no change in the static contact angle occurred.

Gravity and electrostatic separation of unburned coal from a selected fly ash

Unburned coal grains make it difficult to use fly ash economically, which causes energy losses in the fuel. The article presents the possibilities of separating unburned coal from selected fly ash. In order to assess the possibility of separation of unburned carbon, the analysis of grain density and ash composition was used. Unburned coal was separated by four methods – one wet gravity and three dry methods. It has been found that despite very fine ash grains, the quality and quantity of separation products are significantly dependent on the separation method used and the separated grains’ qualitative characteristics. The analysis of the coal grains under an electron microscope has revealed that they contain mineral inclusions. Their presence enables selective separation of carbon without first grinding the middling grains. The most advantageous results of the separation of unburned coal were obtained by the electrostatic separation method. Separated coal can be used in high-value carbon applications.

3D nanorod-like Mn0.2Cd0.8S modified by amorphous NiCo2S4 was used for high efficiency photocatalytic hydrogen evolution

The Mn0.2Cd0.8S/NiCo2S4 was prepared using an electrostatic self-assembly method.

CuO nanoleaf and β-cyclodextrin functionalized reduced graphene oxide: a highly selective and sensitive electrochemical sensor for the simultaneous detection of 2-chlorophenol and 2, 4-dichlorophenol.

Chlorophenols are considered priority pollutants and are harmful to humans and the environment; consequently, sensitive, and selective detection of chlorophenols is very significant. In the present article, a glassy carbon electrode was modified by copper oxide nanoleaves, β-cyclodextrin, and reduced graphene oxide through an electrostatic self-assembly method (CuO NLs-β-CD-rGO-GCE) and successfully utilized for the selective and sensitive detection of 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP). The modified electrodes were characterized by using SEM, EDX, ATR-FTIR, CV, and EIS. The electrochemical behaviour of 2-CP and 2,4 DCP on different modified electrodes was investigated by cyclic voltammetry whereas differential pulse voltammetry was used for the quantitative determination of chlorophenols. Under the optimized conditions, the anodic peak current displayed a good linear relationship to concentration in the range of 5 to 50 μM for 2-CP and 5 to 30 μM for 2,4-DCP, with detection limits of 0.22 nM and 0.52 nM, respectively. Moreover the proposed sensor exhibited good reproducibility, high sensitivity, and long term stability. To further study the practical applicability of the newly developed sensor, the modified electrode was successfully used to determine 2-CP and 2,4-DCP in a water sample with good recovery.

The influence of activated binders (cement) on the process of their hardening

Introduction. The paper studies hardening activation with regard to binding systems (cements) and justifies the possibility of its implementation in construction engineering to prepare construction mixes when erecting buildings and structures out of cast-in-situ concrete and reinforced concrete. During hardening of binding systems (cements), hydrated cement phases are formed and the substance becomes solid, affecting the formation of cement stone and its strength. Purpose of the study. We aimed to study the mechanism of phenomena that occur during activation and hardening in binding systems as well as explore the possibility of their implementation and boosting in order to improve the physical and mechanical, processing, and performance properties of construction mixes. Methods. The properties and stability of binding (cement) systems, which are lyophilic systems, qualitatively characterize the interaction between a solid body and a fluid. The lyophilic behavior implies good wetting, low interfacial tension, and resistance of the surfaces to mutual adhesion. Results. A holistic approach to studying the mechanism of hardening activation in binding systems at the level of colloidal chemical phenomena as well as the energy of interaction between the binder and water in construction mix preparation will make it possible to determine the main directions of boosting the processes in binding systems through various types of energy impacts: mechanical, chemical, non-reagent, ultrasonic, electrostatic, and other methods.

The Effect of Electrostatic Precipitator Operating Methods on Energy Consumption Efficiency

The Effect of Electrostatic Precipitator Operating Methods on Energy Consumption Efficiency

Deterministic domain wall rotation in a strain mediated FeGaB/PMN-PT asymmetrical ring structure for manipulating trapped magnetic nanoparticles in a fluidic environment.

The manipulation of domain walls (DWs) in strain-mediated magnetoelectric (ME) heterostructures has attracted much attention recently, with potential applications in precise and location-specific manipulation of magnetic nanoparticles (MNPs). However, the manipulation ability in these structures is restricted to magnetostrictive circular ring structures only, where the required onion state is metastable, less thermally stable, and cannot be obtained easily. This work investigates the highly shape anisotropic FeGaB magnetostrictive elliptical ring structures of different aspect ratios and trackwidths on the PMN-PT piezoelectric substrate to manipulate fluid-borne MNPs using active control of DWs. The proposed model utilizes the attribute that the required onion state in a magnetostrictive elliptical ring is thermally stable and easily obtained compared to magnetostrictive circular ring structures. By varying the trackwidth of elliptical rings, nucleated DWs are rotated at different angles to capture and transport fluid-borne MNPs. Up to a critical trackwidth, DW rotation is predicted by dominant stress anisotropy energy that leads the rotation of DWs and attached MNPs toward the dominant tensile strain direction of PMN-PT with reversibility. Increasing the trackwidth beyond the critical trackwidth caused a complete 90° rotation of DWs and attached MNPs without reversibility and is given by dominant shape anisotropy energy. The fundamental relationship of capture probability with the size and velocity of injected MNPs is also demonstrated. The nucleation and rotation of DWs are predicated using the coupled elastodynamic and electrostatic Finite Difference Method (FDM) micromagnetic model. Dynamics of MNP capture and rotation are envisaged using an analytical model.

Condition monitoring of pitting evolution using multiple sensing

Pitting on surfaces is a type of rolling contact fatigue (RCF) occurs in rolling-sliding contacts operating under mixed or boundary lubrication conditions. The early detection of pitting is of great importance due to its potential detrimental effects on the performance and reliability of machinery components, such as rolling element bearings and gears. This research aims to investigate the responses of multiple sensors to the progression of pitting and achieve early detection of pitting initiation. Experiments were conducted on a TE74 twin-disc tribometer to investigate the behaviour of bearing steel discs. Mild wear and pitting fatigue were obtained with specimens of different roughness combinations. During testing, vibration, acoustic emission (AE) and electrostatic (ES) data were recorded, and post-test signal analysis was conducted in both the time domain and frequency domain. After testing, the worn surfaces were examined to determine the mechanisms responsible for specific features seen in the sensor data. The presence of pitting in the near-surface region was observed, and its development was effectively monitored using the employed sensing techniques. The stages of running-in, pitting initiation, and pitting formation were identified through the analysis of time-domain parameters and frequency spectrums. Vibration signal analysis exhibited a more prominent indication of pitting formation, whereas AE and ES methods demonstrated an ability to detect the onset of pitting at an earlier stage.

A direct Z-scheme Bi2WO6/La2Ti2O7 photocatalyst for selective reduction of CO2 to CO

Simulating photosynthesis to convert CO2 into valuable chemicals is an effective strategy to achieve sustainable carbon recycles, and the high conversion efficiency and selectivity of photocatalytic conversion CO2 to specific chemicals are the key challenges. Herein, a direct Z-scheme Bi2WO6/La2Ti2O7 photocatalyst is successfully synthesized by electrostatic self-assembly method. The selectivity of CO2 reduction to CO is improved from 74% of La2Ti2O7 to nearly 100%, and the CO yield is 7.5 times that of individual La2Ti2O7. The improvement of the photocatalytic performance is attributed to the formation of Z-scheme heterojunction between Bi2WO6 and La2Ti2O7, which facilitates the separation and transfer of photogenerated carriers. This work provides a new insight for the construction of efficient photocatalyst for selective reduction of CO2 to CO.

Self-Assembled MXene-Au Multifunctional Nanomaterials with Various Shapes for Label-free SERS Detection of Pathogenic Bacteria and Photothermal Sterilization.

Early diagnosis of pathogenic bacteria and treatment are essential to prevent further infection. Photothermal therapy (PTT) is a promising sterilization method with advantages of minimal invasiveness and high efficiency. The effect of PTT depends on the performance of photothermal materials. Herein, Ti3C2-Au nanomaterials were prepared by the electrostatic self-assembly method, and the absorption characteristics were modulated by changing the morphology of Ti3C2-Au to achieve high photothermal conversion efficiency and sensitive label-free SERS bacterial detection. The results showed that the prepared Ti3C2-Au had better SERS performance than Au and achieved direct and sensitive detection of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Under 808 nm laser irradiation, the photothermal conversion efficiency of Ti3C2-Au nanobipyramids (NBPs) was increased to 50.41% compared with the other two composites. The bactericidal rates of Ti3C2-Au NBPs against E. coli and S. aureus were 95.11 and 99.80% in 8 min, respectively, and the killing rates of nine other bacteria were all above 95%, showing broad-spectrum antibacterial properties. Cell viability studies showed that the Ti3C2-Au NBP had significantly improved biocompatibility compared with the Au NBP and was suitable for biological applications. It can simultaneously realize sensitive bacterial detection and photothermal sterilization and is important for the detection and inhibition of pathogenic bacteria.

Constructing metal-free heterophotocatalyst using two-dimensional carbon nitride sheets and violet phosphorene for highly efficient visible-light photocatalysis

Two-dimensional (2D) carbon nitride sheets (CNs) with nanoscale thickness have great potential in solar energy conversion owing to their intrinsic bandgap. However, their photocatalytic efficiency falls far below the practical requirements because the generated electron-hole pairs rapidly recombine. We construct a metal-free 2D p–n junction heterophotocatalyst from CNs and violet phosphorene (VP) using a simple electrostatic self-assembly method. The experimental results and density functional theory calculations show that the built-in electric field of the p–n junction promotes photogenerated carrier transport at the heterojunction interface, thereby promoting the separation of photogenerated electron-hole pairs. Under visible-light illumination, the visible-light photocatalytic hydrogen and CO production rates of the CNs/VP heterojunction were increased by 5.85 and 1.51 times, respectively, when compared to that of CNs. This study provides new insights into the design of metal-free heterogeneous photocatalysts with high catalytic activity.

Fabrication of highly efficient Au and layered double hydroxide modified g-C3N4 ternary composites for degradation of pharmaceutical drug: Pathways and mechanism

Graphitic carbon nitride (CN), a conjugated polymer widely recognized as a chemically stable and low toxic catalyst for the degradation of organic molecules. But it acquires certain limitations like a limited visible light response, high recombination rate of charge carriers, and lower charge density. To overcome such drawbacks, we synthesized a series of Ni-Al layer double hydroxide (LDH)/CN composites by loading 5–15 wt% of Ni-Al LDH onto CN by electrostatic self-assembly method. Further, Au nanoparticles were deposited photochemically on LDH/CN nanocomposites. The Au/LDH/CN nanocomposites exhibited enhanced photocatalytic degradation of tetracycline (TCH) under visible light. Particularly, the Au/LDH/CN nanocomposite with LDH and Au contents of 10 and 1 wt%, sequentially, displayed the highest degradation, which was much better than that for pure CN. The face-to-face interface between LDH and CN and the electron-accepting capability of Au nanoparticles in Au@LDH/CN boosts the separation and transfer efficiencies of photogenerated charge carriers. The intermediate products formed after the degradation of TCH were detected by LCMS and possible degradation pathways were shown. Based on photoluminescence, scavenging experiments, and LC-MS analysis, a possible mechanism for degradation of TCH on Au@LDH/CN nanocomposite was proposed.

Crystallinity Tuning of Na3 V2 (PO4 )3 : Unlocking Sodium Storage Capacity and Inducing Pseudocapacitance Behavior.

As a promising cathode material of sodium-ion batteries, Na3 V2 (PO4 )3 (NVP) has attracted extensive attention in recent years due to its high stability and fast Na+ ion diffusion. However, the reversible capacity based on the two-electron reaction mechanism is not satisfactory limited by the inactive M1 lattice sites during the insertion/extraction process. Herein, self-supporting 3D porous NVP materials with different crystallinity are fabricated on carbon foam substrates by a facile electrostatic spray deposition method. The V5+ /V4+ redox couple is effectively activated and the three-electron reactions are realized in NVP for sodium storage by a proper crystallinity tuning. In a disordered NVP sample, an ultra-high specific capacity of 179.6 mAh g-1 at 0.2 C is achieved due to the coexistence of redox reactions of the V4+ /V3+ and V5+ /V4+ couples. Moreover, a pseudocapacitive charge storage mechanism induced by the disordered structure is first observed in the NVP electrode. An innovative model is given to understand the disorder-induced-pseudocapacitance phenomenon in this polyanion cathode material.

Shuttle-inhibited 3D sandwich MXene/SnO2QDs sulfur host for high-performance lithium-sulfur batteries

Herein, sandwich-like Ti3C2Tx MXene/SnO2 quantum dots composites were synthesized as sulfur host, aiming to alleviate the shuttle effect of polysulfides present in lithium-sulfur batteries. SnO2 quantum dots (SnO2QDs) were introduced into the interlayer of MXene through a simple electrostatic self-assembly method, and the mass fraction of SnO2QDs was controlled to construct sandwich MXene/SnO2QDs. While SnO2QDs effectively alleviating the stacking tendency of MXene, Ti and Sn co-chemisorb polysulfides and the interlayer structure physically confines polysulfides. Significantly, the synergistic effect between MXene with SnO2QDs effectively alleviates the shuttle effect of polysulfides and buffers the volume expansion. Meanwhile, with the help of the catalysis of SnO2QDs, the liquid-solid reaction kinetics of lithium polysulfides converting to Li2S2/Li2S is accelerated. Electrochemical test results showed that the MXene/SnO2QDs/S cathode has a high initial discharge specific capacity (1147.6 mAh g−1 at 0.1 C, while MXene/S is only 615.4 mAh g−1), as well as excellent rate performance and cycling stability in Li-S batteries.

Boosting interfacial S-scheme charge transfer and photocatalytic H2-production activity of 1D/2D WO3/g-C3N4 heterojunction by molecular benzene-rings integration

A novel benzene-ring engineered 1D/2D WO3/g-C3N4 S-scheme photocatalyst (BCNW) was rationally designed and successfully synthesized by the electrostatic self-assembly method. Experimental and Density Functional Theory results reveal that the integration of molecular benzene-ring in the framework of g-C3N4 can not only narrow its bandgap and accelerate charge separation by forming a mid-state at the top of its valence band but more importantly open up a new additional bridge for speeding up the interfacial S-scheme charge transfer in BCNW. Benefitting from those multiple positive effects of benzene-ring integration, as expected, BCNW S-scheme photocatalysts show superior photocatalytic H2-production activity and reach 2971 μmol h–1 g–1 under visible-light illumination, which is 3.35 times WO3/g-C3N4 S-scheme photocatalyst without benzene-ring integration. This work supplies an innovative strategy for the design of a high-efficiency S-scheme photocatalytic system by constructing a facile and additional molecular charge transfer channel at the interface.

Comparative Study of Physicochemical Properties of Alginate Composite Hydrogels Prepared by the Physical Blending and Electrostatic Assembly Methods.

Alginate hydrogel commonly suffers from defects, such as weak mechanical properties, the shortage of long-term stability in physiological medium and the lack of mammalian cell adhesivity due to its strong hydrophilicity in biomedical application. For this reason, the homogeneous alginate hydrogels (Alg Gel) were successfully prepared by the D-glucono-δ-lactone/hydroxyapatite (HAP/GDL) cross-linking system, and then, the physical blending and alternating electrostatic assembly technology were proposed to fabricate alginate composite hydrogels (Alg-GT, Alg-CS-GT and ALG/GT-CS). The feasibility of the design methods was verified through the comparative analysis of their physicochemical properties and biological activity. In particular, the effects of physical blending and alternating electrostatic assembly technology on the pore structure, mechanical properties, swelling, degradation, cell adhesion and proliferation of composite hydrogels were also investigated. Experimental results showed that the formation of polyelectrolyte complexes by electrostatic assembly between biological macromolecules and the covalent cross-linking of EDC/NHS to GT improved the vulnerability of ion cross-linking, enhanced the mechanical properties and swelling stability of the composite hydrogels, and regulated their pore structure and in vitro biodegradability properties. Furthermore, MC3T3-E1 cells could exhibit good cell adhesion, cell viability and cell proliferation on the alginate composite hydrogels. Among them, Alg-CS-GT showed the best cell proliferation ability and differentiation effect due to its good cell adhesion. In view of the excellent physicochemical properties and biological activity of Alg-CS-GT, it exhibited great potential in biomedical application for tissue engineering.

MXene-PANI/PES composite ultrafiltration membranes with conductive properties for anti-fouling and dye removal

The appearance of the composite membrane provides a new research direction for reducing membrane fouling. In this study, polyaniline (PANI) and Ti3C2Tx (MXene) were combined by the electrostatic assembly method where PANI was used to adjust the distance between MXene layers and construct the conductive network. The conducting mixed ultrafiltration membranes were prepared by the non-solvent induced phase separation method, in which MXene and PANI were mixed into a polyethersulfone (PES) matrix. The permeation flux of pure water of the MXene-PANI/PES membrane was increased by 200.9%, the retention rate of bovine serum albumin (BSA) was kept above 99%, and the retention rate of Congo Red and Methyl blue dyes was 99.1% and 98.4%, respectively, this goes well beyond the PES membrane. In addition, through a series of conductivity tests, it has been proved that the conductive properties of composite membranes were greatly improved, and the conductivity of the MXene-PANI/PES composite membrane can reach 0.5 S m−1. After applying a negative voltage to the membrane, the negative charge around the surface of the membrane repels the negatively charged contaminant under the action of an electrostatic repulsion force, thereby the enrichment of pollutants on the membrane surface can be effectively reduced, and the FRR reached 93.7%. On the basis of ensuring membrane conductivity, we improved the permeability, selective separation, and anti-fouling ability of the membrane. This research shows great potential for the efficient development of an anti-fouling conductive separation membrane based on MXene.