Ultrasonic Conditions Research Articles

Ultrasonic solidification mechanism and optimized application performances of ternary Mg71.5Zn26.1Y2.4 alloy

One dimensional (1D) and three dimensional (3D) ultrasound sources were applied to the solidification process of Mg71.5Zn26.1Y2.4 alloy. The acoustic spectra were in-situ measured, based on which the cavitation intensities and dynamic solidification mechanism were further investigated. With the increase of ultrasonic dimension and amplitude, the primary Mg3Zn6Y phase was significantly refined from petals to nearly pentagonal shape. The sound field measurements showed that the transient cavitation played a decisive role in generating a high local undercooling, which facilitated the formation of icosahedral clusters and promoted the nucleation of primary Mg3Zn6Y phase. The morphological transition of (α-Mg+Mg3Zn6Y) eutectic from lamellar to anomalous structure occurred under 3D ultrasonic condition. The stable cavitation took the main responsibility because the high pressure excited by nonlinearly oscillating bubbles induced the preferential nucleation of α-Mg phase rather than Mg3Zn6Y phase. As compared with its static values, the tensile strength and compression plasticity of this alloy were increased by the factors of 1.9 and 2.1, and its corrosion resistance was also improved with the corrosion current density decreased by one order of magnitude.

Acidic Ionic Liquids in Ultrasonic Irradiation Conditions Promote the Nucleophilic Addition to Chalcone Derivatives

Under solvent-free conditions and with the help of ultrasonic irradiation, the synthesis of pyrano[3,2-c]chromen and pyrano[3,2-c]quinolin derivatives was promoted by four different ionic liquids. All reaction was performed at 100 °C and had good to excellent yields. 1-butyl-1-methylpyrrolidin-1-ium acetate (A), 1-butyl-1-methylpiperidin-1-ium acetate (B), N,N,N-triethylbutan-1-aminium acetate (C), and tetrabutylammonium acetate (D) as perfect ionic liquids for this reaction show remarkable catalytic activity. The work was simply developed for the reaction of chalcones with 4-hydroxy-1-methylquinolin-2(1H)-one/4-hydroxycoumarin to perform pure products of pyran heterocycles.

Shape and diffusion instabilities of two non-spherical gas bubbles under ultrasonic conditions

Ultrasonic cavitation involves dynamic oscillation processes induced by small bubbles in a liquid under the influence of ultrasonic waves. This study focuses on the investigation of shape and diffusion instabilities of two bubbles formed during cavitation. The derived equations for two non-spherical gas bubbles, based on perturbation theory and the Bernoulli equation, enable the analysis of their shape instability. Numerical simulations, utilizing the modified Keller–Miksis equation, are performed to examine the shape and diffusion instabilities. Three types of shape instabilities, namely, Rayleigh–Taylor, Rebound, and parametric instabilities, are observed. The results highlight the influence of initial radius, distance, and perturbation parameter on the shape and diffusion instabilities, as evidenced by the R 0–P a phase diagram and the variation pattern of the equilibrium curve. This research contributes to the understanding of multiple bubble instability characteristics, which has important theoretical implications for future research in the field. Specifically, it underscores the significance of initial bubble parameters, driving pressure, and relative gas concentration in determining the shape and diffusive equilibrium instabilities of non-spherical bubbles.

Ultrasonic-pretreated hydrothermal synthesis of less dense zeolite CHA from the transformation of zeolite T

Because of containing the same double 6-ring (D6R) building unit, the pure zeolite CHA with lower framework density (FDSi = 15.1 T/1000 Å3) has been transformed from zeolite T with higher framework density (FDSi = 16.1 T/1000 Å3) through ultrasonic-pretreated hydrothermal synthesis in MOH (KOH and NaOH) solution without adding organic template or seed crystals. Ultrasonic pretreatment facilitates the transformation rate and generates high-quality zeolite CHA. The ultrasound condition should be precisely controlled because that CHA phase is metastable, which is inclined to transform to other more stable phase. The ultrasonic conditions at 313 K and 333 K have been investigated in detail. In KOH solution, the ultrasonic treatment at 313 K can effectively restrain the generation of MER phase, however, it is hard to avoid the existence of MER phase when ultrasound temperature is 333 K. In NaOH solution, the samples with ultrasonic treatment of 313 K show the small particles size of about 1 μm, and the GIS framework topology starts to grow with the ultrasonic treatment of 333 K. The products prepared with the appropriate ultrasonic pretreatment represents smaller particles size, larger mesopore volume and higher CO2 adsorption capacity than the sample without the ultrasonic pretreatment. The structural evolution of interzeolite transformation has been explored by XRD, FT-IR and SEM observations. With the assistance of ultrasound, the parent zeolite T can quickly decompose into intermediate phase and then regenerate into CHA phase.

Electrochemical oxidation and sensing of para benzoquinone using a novel SPE based disposable sensor

Para-benzoquinone (PBQ) is an emerging micro-contaminant owing to its chronic toxicity to plants and animals as well as its potential to induce cytotoxicity in primary rat hepatocytes and kidney cell injury. Hence, it is of utmost importance to monitor this contaminant in industrial wastewater and groundwater. In this article, we devised a unique disposable sensor that is based on a screen-printed electrode using MnO2@Co–Ni MOFs/fMWCNTs nanocomposite and is able to detect PBQ. The as-produced nanocomposite was prepared via ultrasonic assisted reflux condition and thoroughly examined by several physicochemical characterisation methods such as SEM, EDX, TEM, Raman, AFM, UV–visible, and FT-IR. Moreover, electrochemical methods like CV, DPV, EIS, and chronoamperometry were used for detecting PBQ on MnO2@Co–Ni MOFs/fMWCNTs/SPCE. Sensor performance has been investigated thoroughly and optimized to enhance the analytical potential of the fabricated sensor. DPV analysis was done on MnO2@Co–Ni MOFs/fMWCNTs that exhibit high selectivity, low peak potential, a broader linear detection range (0.005 mM–30 mM), and a LOD of 0.0027 ± 0.0005 mM. The designed electrode has shown remarkable reproducibility and excellent repeatability, with relative standard deviations of 0.12%, and 0.17%, respectively. Additionally, MnO2@Co–Ni MOFs/fMWCNTs/SPCE have been used to analyse PBQ in industrial wastewater samples, and the results have shown a significant level of recovery between 96.91 and 105.67%. Moreover, the PBQ sensor displays high applicability and was verified via the use of HPLC techniques. This disposable sensor is quick, easy, and cost-effective, so it can be useful in the future for analysing other phenolic contaminants present in environmental samples.

Cu(II) supported on Chitosan/LDH/Fe3O4 magnetic nanocomposite as an effective heterogeneous nanocatalyst for synthesizing bis(indolyl) methanes under ultrasonic conditions

Chitosan is a natural, nontoxic biopolymer with amine and hydroxyl functional groups which make it easy for chitosan molecules to form intermolecular and intramolecular hydrogen bonds. In that context, the present study reports Cu(II) supported on Chitosan@MgCuAl-LDH@Fe3O4 magnetic nanocomposite (Fe3O4@MgCuAl-LDH@CS/Cu(II)) as an effective and a novel heterogeneous catalyst to perform electrophilic substitution reaction between indoles and aromatic aldehydes to yield bis(indolyl)methane derivatives (BIMs) in shorter reaction time under ultrasonic conditions. Copper ions were mainly adsorbed onto the core–shell magnetic nanocomposite (Fe3O4@MgCuAl-LDH) modified with chitosan by the chelating capacity of chitosan and LDH. The catalyst's physicochemical properties and morphological structure were characterized using advanced analytical techniques, including XRD, FT-IR, FESEM, HRTEM, TGA, VSM, ICP-OES and EDX. Overall, the results show that Sonication significantly enhanced the catalytic performances compared to conventional heating. Also, the prepared catalyst could be easily separated from the solution using an external magnetic field and reused up to nine times without considerable leaching or loss in its catalytic activity.

Fe3O4@Zeolite‐Y Functionalized with N‐Methylimidazolium Ionic Liquid: Design and Performance as a New Recyclable and Magnetically Nanocatalyst in the Three‐Component Synthesis of N‐Heterocyclic‐1,3‐thiazolidinones

AbstractIn this research, first, nanoporous zeolite‐NaY was functionalized with 3‐chloropropyltriethoxysilane (organic linker) and then N‐methylimidazole group. Then magnetic nanoparticles (Fe3O4) under ultrasonic energy conditions on the surface and internal pores of zeolite‐Y (1‐MeIm IL@ZY‐Fe3O4) were formed. The identification, confirmation of the structure and morphology of the prepared magnetic nanohybrid was done by using FTIR, FESEM, TEM, EDX, TGA, XRD, VSM and BET instrumental techniques. Next, its catalytic performance in the synthesis of a number of 3‐benzimidazolyl (or benzothiazolyl)‐1,3‐thiazolidin‐4‐one derivatives was investigated through the three‐component condensation reaction of various aromatic aldehydes, 2‐aminobenzimidazole or 2‐aminobenzothiazole, and thioglycolic acid in EtOH at room temperature. The results of the experiments show that the presence of magnetic nanoparticles (Fe3O4) inside the pores of zeolite functionalized with ionic liquid not only causes easy and quick separation of the nanocatalyst by an external magnetic field but also can be effective in catalyzing the reaction as a Lewis acid.

Removal of pesticides from fresh-cut Chinese cabbage (Brassica rapa var. chinensis L.) by sequential multi-frequency ultrasound cleaning treatments

Pesticides may remain on the surface of fresh produce due to inappropriate and inadequate cleaning. In view of the public health significance of pesticide residues in fresh produce and the long-term effects of low dose exposure of these pesticides, decontamination procedures are needed for ready-to-eat foods, especially vegetables. Ultrasound cleaning is considered to be an effective environmentally-friendly decontamination process which is unique in its ability to remove pesticides compared to other conventional methods. The reduction of dimethoate and diazinon residues from fresh Chinese cabbage by sequential multi-frequency ultrasound cleaning treatments was investigated in this study to ascertain the levels of reduction after cleaning. The ultrasonic treatment has higher efficiency on the removal of these organophosphorus pesticides compared to ordinary water cleaning. The removal rates of ultrasonic cleaning treatments for dimethoate and diazinon residues were in the range of 20.10–72.42% and 29.60–77.37% compared to the ordinary water cleaning with 13.24–19.89% and 17.32–24.16% respectively. In addition, quality parameters for the leaves treated were also assessed. The physical impairment and vitamin C loss increased with the increase in ultrasonic frequency combination and cleaning time. Application of triple frequency ultrasound and extended washing time resulted in high dimethoate (>70%) and diazinon reduction (>75%) alongside slight perceptible darkening in colour of the leaves. The use of multi-frequency ultrasound in sequential mode is an effective technique for the removal of pesticide residues from leafy vegetables. However, ultrasonic operating conditions should be considered to maintain product quality.

Internal curing mechanism of zeolite pretreated with NaCl under microwave and ultrasonic conditions

Natural zeolite has been used for internal curing to reduce shrinkage of cement-based materials, but the internal curing performance of zeolite needs to be improved. In this study, natural zeolite particles were modified by NaCl solution under conditions of microwave and ultrasonic to improve their internal curing performance. Firstly, the pore structure, chemical bond characteristics, pozzolanic activity, water absorption and water release performance of the modified zeolite were tested. Then, cement paste specimens internally cured with modified zeolite were prepared, the shrinkage, hydration products, and pore structure were tested, and the internal curing mechanism of modified zeolite was discussed. The results show that: (1) Pozzolanic activity of zeolite decreases after NaCl-microwave modification, but increases after NaCl-ultrasonic modification. (2) NaCl modification increases the pore volume and water adsorption of natural zeolite particles. (3) NaCl modified zeolite promotes the formation of ettringite in cement paste, especially for NaCl-microwave modified zeolite. (4) NaCl-microwave modified zeolite has better shrinkage reducing effect and strength improving effect than natural zeolite and NaCl-ultrasonic modified zeolite.

Piezoelectricity ameliorates high-valent iron oxo species production in peroxymonosulfate activation for refractory atrazine remediation

Over the past few years, high-valent iron oxo species (Fe(IV)) have shown considerable promise. However, an improved solution is needed for the bottleneck of unsatisfactory electron transfer efficiency in Fe-based catalyst/PMS systems. In this study, Enteromorpha-derived biochar was pyrolyzed with iron and barium titanate (FeBCBa). Under ultrasonic treatment, it removes 94.5% of atrazine (10 mg/L) within 60 min, and is environmentally friendly. BaTiO3′s piezoelectricity enhances Fe(IV) production in FeBCBa, resulting in superior performance. In the ultrasonic condition, the apparent reaction rate was 1.42 times higher than in the non-ultrasonic condition. Using density functional theory calculations, it can be shown that due to the Fe dopant, electrons in ATZ’s LUMO are more easily transferred to the catalyst’s HOMO, which is beneficial for ATZ removal. The results of this study provide new guidance for constructing stable and efficient catalysts for environmental remediation.

Enzymatic Interesterification of Crude Palm Oil with Methyl acetate: Effect of Pre-treatment, Enzyme’s Dosage and Stability

In the present study, biodiesel was produced via the enzymatic interesterification of Crude Palm Oil (CPO) and methyl acetate within ultrasonic condition. In contrast to alcohol, methyl acetate as an acyl acceptor does not inhibit lipase activity and can create triacetin as a useful byproduct. In this work, Immobilized lipase from Candida Antartica A (CaLA) was utilized as biocatalyst and the effect of using non-pretreated CPO and pre-treated CPO as feedstock were explored. The pre-treatment of CPO involves degumming with acid, washing with water, and bleaching. The enzymatic interesterification was conducted in three-neck flasks using an ultrasonic water bath at 45o C. Few parameter effects on biodiesel production were also investigated, including the effect of molar ratio of CPO to methyl acetate, the effect amount of lipase, and the reusability of immobilized lipase (CaLA) in the interesterification reaction. The highest average Biodiesel yield of 80.6% was obtained from pretreated CPO at a molar ratio of 1:9 with 100 mg (1% w/v) of Immobilized CaLA, after three hours of reaction. Further research on the reusability of immobilized CaLA revealed that the yield of biodiesel reduced significantly after the second run. The results of the present study also demonstrated that Immobilized CaLA performed well at low concentrations but had low stability, with productivity decreasing to 92% upon reuse after the initial run. In order to make Immobilized lipase economically viable, further research must be conducted to overcome its low stability in the reaction.

Sonochemical reactor characterization in the presence of cylindrical and conical reflectors

Ultrasonic systems must be able to produce an acoustic field with the highest possible energy concentration in sonochemical reactors to accomplish maximum efficacy in the sonolytic degradation of water contaminants. In the present study, the impact of cylindrical and conical stainless-steel reflectors placed on the liquid surface on the sonochemical oxidation activity of ultrasonication reactors was investigated. The amount of effective acoustic power transferred to the ultrasonicated medium without and with reflectors was measured by calorimetric characterization of the sono-reactors at diverse ultrasonication frequencies in the interval of 300–800 kHz and different electrical powers in the range of 40–120 W. Iodide dosimetry without and with reflectors at diverse ultrasonication conditions (300–800 kHz and 40–120 W) and various aqueous solution volumes in the range of 300–500 mL was used to assess the sonochemical oxidation activity, i.e., the generation of oxidative species (mainly hydroxyl radicals). Sonochemiluminescence (SCL) imaging was used to study the active acoustic cavitation bubbles distribution in the sono-reactors without and with reflectors. Significant impacts of the position and shape of the reflectors on the active acoustic cavitation bubble distribution and the sonochemical oxidation activity were observed due to remarkable modifications of the ultrasonic field by directing and focusing of the ultrasonic waves. A significant augmentation in the triiodide formation rate was obtained in the presence of the conical reflector, especially at 630 kHz and 120 W (60.5% improvement), while iodide oxidation was quenched in the presence of the cylindrical reflector at all ultrasonication frequencies and powers. The SCL images show a noteworthy modification in the ultrasonic field and the acoustic cavitation bubble population when reflectors were used. The sonochemical oxidation activity was improved by the conical reflector when placed in the Fresnel zone (near field region).

Magnetic and ultrasonic integrated photocatalytic hydrogen evolution effects with Nanosize CoOCu2OZnO and TiO2 decorated on reduced graphene oxide

In this study, metal oxide composite (CoOCu2OZnO) and TiO2 on graphene oxide composite (CCZ−G−T) were synthesized to improve visible light-driven H2 evolution through the addition of a cation scavenger, ultrasonic effect, and magnetic field effect. The synthesized nanocomposites were characterized through structural, surface, and electrochemical analyses with band structure. The photocatalyst showed hydrogen production of 792 μmol·g−1 for 4 hours. Moreover, this CCZ−G−T photocatalyst exhibits relatively high photocatalytic activity at (530−810) μmol·g−1 when using a scavenger, 1,190 μmol·g−1 when using a magnetic field of 0.14 T, and 1,230 μmol·g−1 when using ultrasonic waves. The CCZ−G−T composite exhibited 630 μmol·g−1 under a magnetic field condition of 0.14 T for 1 hour, which was significantly higher than the hydrogen production rate of 510 μmol·g−1 under ultrasonic conditions. The current study provides new insights into the magnetic field effect on the hydrogen evolution reaction (HER) of graphene-based photocatalysts.

Effect of ultrasonic treatment on the quality of Mianning ham.

This paper investigates the optimal process for ultrasonic desalination of Mianning ham. The study analyzed various factors such as ultrasonic treatment time, temperature, and power to determine their impact on the rate of desalination of hams. A single factor test was conducted to study the rate of desalination. Further, A Box-Behnken experimental design was used to evaluate the effect of Mianning ham desalination. The design examined the impacts of ultrasound on the physicochemical properties, texture, and sensory of the ham. Response surface processing group underwent oral processing to determine the optimal ultrasonic treatment conditions with the highest acceptance level. The results show that the best conditions were: ultrasonic time 84.56 min, ultrasonic temperature 40.35°C, and ultrasonic power 150.85 W. The average desalination rate of the ham under the optimal conditions was 25.93% ± 0.69%, and the hardness was 4.48 N ± 0.62 N. Overall, this process significantly improved the desalination rate, texture, and sensory quality of Mianning ham, providing solid theoretical support for desalination processing at the back end of ham.

Effect of ultrasonic processing on the properties of polyphenol oxidase from potato (Solanum tuberosum L.)

In present work, the effects of ultrasound on activity and conformation of polyphenol oxidase (PPO) from potato were investigated under different ultrasonic gradient for ultrasonic power (240-600 W), time (15-120 min), temperature (20-50℃) and pH (5.4-8.2). The results indicated that potato PPO exhibited a decrease in activity treated by different ultrasonic treatment conditions. Furthermore, the ultrasound significantly down-regulated the expression of PPO gene. The CD analysis demonstrated that the secondary structures such as α-helix were destroyed compared with the pristine PPO. The PPO activity showed a corresponding decrease along with the changes in the secondary structure. This investigation revealed that ultrasound inactivate PPO activity by changing the conformation of enzyme protein and down-regulating gene expression.

Effect of ultrasonication conditions on polyethylene microplastics sourced from landfills: A precursor study to establish guidelines for their extraction from environmental matrices

Establishing concentration of microplastics (MPs), designated as CMP, in aqueous, semi-solid and solid samples originating from unscientifically created landfills/dumpsites (UCLDs) and engineered landfills (ELFs) is of utmost importance to assess their impact on the geoenvironment. However, the accuracy of CMP will be guided by the extraction efficiency of MPs from these samples. The extraction of MPs from semi-solid and solid samples of UCLDs/ELFs would be cumbersome, mainly due to their trapping in solid aggregates (including organic matter). Such aggregates need to be dispersed to release the MPs, which can be achieved through the assistance of ultrasonication (US) in the presence of an appropriate dispersing agent. However, mere dispersion of solid aggregates during the US might not result in the complete release of MPs adhered (AMPs) to MPs native (NMPs) to these samples. This is because MPs would adhere to the surface of the adjacent ones due to various physical-mechanical-thermal-chemical processes that prevail in landfills. Hence, guidelines for US-assisted extraction of MPs should be developed by considering an approach that would ensure (i) cleaning of NMPs’ surface and (ii) release of AMPs without damaging the former. This necessitates understanding the influence of US parameters such as energy applied (Eus), time (tus) and direct/indirect exposure of NMPs from landfills that would control CMP. In this context, the influence of above mentioned US parameters on the (i) surface cleaning of polyethylene NMPs and (ii) release of AMPs and their concentrations (CAMP) was investigated. It was observed that Eus equal to 500 kJ/L during the indirect method of US would result in surface cleaning of NMPs and complete release of AMPs without damaging the farmer’s structure. The present work acts as a precursor study to establish the guidelines for the US-assisted extraction of MPs in environmental samples. Also, a generalized relationship between Eus and CAMP, which can be employed to study the impact of landfill type on the release of MPs during the US was developed.

Ultrasonic-aided extraction and degossypolization of cottonseed meal protein: Optimization and characterization of functional traits and molecular structure

Cottonseed meal (CM) is a useful protein resource, but the presence of gossypol (a toxic compound) limits it utilization in industry. To reduce the gossypol content, the use of ultrasonication in extracting protein from CM was explored. Following single-factor experiments, operative limits of independent variables affecting removal ratio of total-gossypol (RRTG) and extractability of CM protein (CMP) were achieved as temperature (35–55 °C), sonication power (250–350 W), time (12–24 min), and NaOH concentration (2–6 g/L). Box-Behnken’s Design centered on a 3–level-4–factor was employed to optimize ultrasonication conditions on the yield and RRTG of CMP. The predictive models were statistically adequate (p < 0.0001) to reflect the experimental results of the responses as verified by insignificant lack-of-fit (p ≥ 0.1333) and high coefficient of determination (R2 ≥ 0.976) values. The optimized sonication conditions for two responses were 53 °C, 320 W, 21 min, and 4.6 g-NaOH/L. Under optimized conditions, the observed removal ratio of free- and total-gossypol and yield values were 93.21 %, 87.56 %, and 58.23 %, which substantially increased by 15.64 %, 12.88 %, and 29.56 %, respectively over control (alkaline extraction). Furthermore, sonicated isolate showed an increase in solubility and emulsion property relative to control, buttressed by particle sizing and zeta potential outcomes. Sodium dodecyl sulfide polyacrylamide gel electrophoresis (SDS-PAGE), Fourier Transform Infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and amino acid data showed notable changes in molecular weight, functional groups, surface topography, and hydrophobic amino acid content of CMP, respectively (i.e., after sonication), suggesting partial unfolding in CMP conformation. Accordingly, CMP isolates (especially the sonicated protein) could be considered edible because of the observed low gossypol content (< 0.045 %) and thus can be utilized as natural additives in food formulations.

Extraction of Common Small Microplastics and Nanoplastics Embedded in Environmental Solid Matrices by Tetramethylammonium Hydroxide Digestion and Dichloromethane Dissolution for Py-GC-MS Determination.

Determination of microplastics and nanoplastics (MNPs), especially small MPs and NPs (<150 μm), in solid environmental matrices is a challenging task due to the formation of stable aggregates between MNPs and natural colloids. Herein, a novel method for extracting small MPs and NPs embedded in soils/sediments/sludges has been developed by combining tetramethylammonium hydroxide (TMAH) digestion with dichloromethane (DCM) dissolution. The solid samples were digested with TMAH, and the collected precipitate was washed with anhydrous ethanol to eliminate the natural organic matter. Then, the MNPs in precipitate were extracted by dissolving in DCM under ultrasonic conditions. Under the optimized digestion and extraction conditions, the factors including sizes and concentrations of MNPs showed insignificant effects on the extraction process. The feasibility of this sample preparation method was verified by the satisfactory spiked recoveries (79.6-91.4%) of polystyrene, polyethylene, polypropylene, poly(methyl methacrylate), polyvinyl chloride, and polyethylene terephthalate MNPs in soil/sediment/sludge samples. The proposed sample preparation method was coupled with pyrolysis gas chromatography-mass spectrometry to determine trace small MPs and NPs with a relatively low detection limit of 2.3-29.2 μg/g. Notably, commonly used MNPs were successfully detected at levels of 4.6-51.4 μg/g in 6 soil/sediment/sludge samples. This proposed method is promising for evaluating small solid-embedded MNP pollution.

Polydopamine-engineered design of Nafion-free powder electrode with superhydrophilicity/superaerophobicity and superior adhesive structure for efficient overall water splitting

Absolute exploitation on the intrinsic catalytic property of powder electrocatalysts always faces the obstacles caused by the existing gas–liquid-solid three-phase interface problem and overwhelming dependence on Nafion usage. Herein, a general polydopamine (PDA)-engineering method is developed to construct Nafion-free powder electrode for efficient overall water splitting. The several nanometer scale PDA coating layers that are self-polymerized on catalyst surfaces, enable the superhydrophilicity/superaerophobicity for more exposed electroactive sites and smoother interfacial mass transfer, and meanwhile, render a superior structural stability inside working electrode with equivalent but more homogeneous adhesion compared with that of Nafion-used electrode. At 300 mA cm−2, the CoMoSxOy@PDA exhibits the low overpotential of 311 mV for OER and 343 mV for HER, and meanwhile demonstrates a cell voltage of only 1.89 V for over 200 h of stable operation and almost unaffected catalytic activity even under harsh ultrasonic working conditions. By theory calculations, the reduced reaction energy barrier for oxygen evolution and the optimized adsorption free energy for hydrogen evolution are revealed in depth.

Effect of ultrasonic field on the mechanism of electrodeposited Cu nucleation and growth

Electrodeposition technology is widely used in the surface treatment of copper foil. The unique “mechanical disturbance effect” and “cavitation effect” of ultrasonic field can effectively control the electrodeposition process of Cu and improve the quality of electrodeposited layer. In this paper, Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), Chronoamperometry (CA) and Chronocoulometry (CC) were used to study the electrochemical behavior of electrodeposited Cu in ultra-high acidity sulfate systems under different ultrasonic field powers. The nucleation and growth mechanism of Cu were discussed, and the surface morphology of electrodeposited layer was analyzed. The results show that the electrodeposition of Cu under the static condition (0 W) follows the diffusion controlled progressive nucleation and 3D growth mechanism, and the deposits are in the cylindrical shape with spherically agglomerated. The ultrasonic field significantly improves the mass transfer rate in the electrodeposition process, and the fine dispersion effect is obvious. The uniform and dense micro-nano layers are formed, following the 3D growth mechanism. With the increasing of ultrasonic field power, the nucleation mechanism gradually changes from the diffusion controlled progressive nucleation to the electrochemistry controlled instantaneous nucleation. In addition, there appear peeling, grooving and local microcracks on the electrodeposited layer under higher ultrasonic power condition, and it is easier to form a smooth and uniform electrodeposited layer with the ultrasonic power of 60 W compared to that with the ultrasonic power of 100 W.