Electrochemical Tests Research Articles

The Physical and Chemical Properties of Carbon-supported Biosynthesized ZnO Nanostructure for High-performance Super-capacitor Applications

Objectives This research focuses on the green synthesis of ZnO nanostructures using P. macrosolen L. leaf extract and investigates the effects of calcination temperatures on their structural, morphological, optical, and electrochemical properties. Methods ZnO nanostructures were synthesized via a green, eco-friendly, and time-effective method. Characterizations included P-XRD for phase and crystallite size determination, FTIR spectroscopy for functional group analysis, FIB-SEM and HR-TEM for surface morphology, UV-Vis spectroscopy for optical properties, and electrochemical tests for evaluating super capacitor performance. Results XRD analysis confirmed the tetragonal Wurtzite hexagonal phase of ZnO nanostructures, with an average crystallite size of 35 nm calculated using the Debye-Scherrer equation. FTIR confirmed the formation of ZnO, while FIB-SEM and HR-TEM revealed a spongy, agglomerated surface morphology. UV-Vis analysis showed a reduction in the energy band gap with increasing calcination temperatures. Electrochemical analysis demonstrated that ZnO nanostructures calcinated at 580 °C exhibited superior charge/discharge capacities, cycling stability, and nearly 100% coulombic efficiency for up to 1000 cycles at a current density of 5 A/g, outperforming those prepared at 280 °C and 480 °C. Conclusion The biosynthesized ZnO nanostructures, especially those calcinated at 580 °C, show excellent potential as electrode materials for high-performance super capacitors due to their enhanced electrochemical performance and long-term cycling stability.

The magnesium sulfate whisker/Al2O3 superhydrophobic composite coating exhibits robust, corrosion-resistant, and delayed icing properties

The magnesium sulfate whisker/Al2O3 superhydrophobic composite coating exhibits robust, corrosion-resistant, and delayed icing properties

Modulating the structure of Cu in Cu2X/CNTs hollow tetrakaidecahedron to enhance high-efficiency H2O2 production.

Modulating the structure of Cu in Cu2X/CNTs hollow tetrakaidecahedron to enhance high-efficiency H2O2 production.

Multi-functional nitrile-based electrolyte additives enable stable lithium metal batteries with high-voltage nickel-rich cathodes.

A rechargeable lithium (Li) metal anode combined with a high-voltage nickel-rich layered cathode has been considered a promising combination for high-energy Li metal batteries (LMBs). However, they usually suffer from insufficient cycling life because of the unstable electrochemical stability of both electrodes. In this work, we report an advanced multi-functional additive, 1,3,6-hexanetricarbonitrile (HTCN), in a conventional carbonate-based electrolyte. This rationally designed electrolyte formation generates an ideal cathode electrolyte interphase (CEI) for LiNi0.8Co0.1Mn0.1O2 (NCM811) and a solid electrolyte interphase (SEI) for Li metal, successfully realizing stable ion transport kinetics. Then, theoretical calculations, physical characterization and electrochemical tests confirm that HTCN is more easily adsorbed on the NCM811 surface where it is oxidized to construct a stable CEI film involving the detachment of the CN group in a linear chain. Simultaneously, HTCN shows a more negative electron affinity and is easier to reduce, constructing a robust SEI film resulting from the detachment of the CN group in the side chain. Consequently, the assembled 50 μm-thin NCM811//Li (9.0 mg cm-2 of mass loading) delivers a desired energy density of ∼330 W h kg-1 at the cell level and an excellent cycling stability of 120 cycles with 88% capacity retention at 1C.

Construction of bimetallic oxy-hydroxides based on Ni(OH)2 nanosheets for sensitive non-enzymatic glucose detection via electrochemical oxidation and incorporation.

Due to their ease of synthesis and large specific surface area, Ni(OH)2 nanosheets have emerged as promising electrochemical sensing materials, attracting significant attention in recent years. Herein, a series of oxy-hydroxides based on Ni(OH)2 nanosheets, including NiOx/Ni(OH)2@NF and (MNi)Ox/Ni(OH)2@NF (M = Co, Fe, or Cr), are successfully synthesized via the electrochemical oxidation and incorporation strategies. Electrochemical tests demonstrate that these Ni(OH)2-based oxy-hydroxides exhibit excellent electrochemical oxidation activity for glucose in alkaline electrolyte. Among these, (CoNi)Ox/Ni(OH)2@NF displays higher sensitivity of 3590.3 μA mM-1 cm-2 across a broad linear range of 10 μM to 1.14 mM, with a rapid current response time of less than 4 s. The superior sensing performances of (CoNi)Ox/Ni(OH)2@NF are attributed to the formation of abundant Ni3+ species and reactive-O atoms due to the electrochemical oxidation, and the synergistic effects of Co/Ni active sites resulting from the electrochemical incorporation process. In addition, the (CoNi)Ox/Ni(OH)2@NF demonstrates good stability and reproducibility for glucose sensing. This work fully leverages the significance of surface reconstruction of Ni(OH)2, providing new insights for the application of transition metal-based oxy-hydroxide materials in bio-sensing.

Microscopic analysis of the destruction of passive film on stainless steel caused by sulfide in simulated cooling water

Abstract Sulfide often appears in circulating cooling water due to the presence of sulfate reducing bacteria and could affect corrosion behavior of cooling pipe metals such as stainless steel. Scanning Kelvin probe and scanning electrochemical microscope measurements, combined with electrochemical testing, were used to investigate the micro-electrochemical information of passive film and analyzed the influence of sulfide in simulated cooling water on corrosion resistance of stainless steel. Results showed that the presence of sulfide in water caused a negative shift in surface potential of stainless steel, an increase in surface potential difference, and an increase in local response current on the surface, resulting in a current peak that gradually increased over time. The analysis results of passive film composition showed that the presence of sulfide caused increase in the ratio of Fe/Cr and OH−/O2−, as well as the content of Cr(OH)3 and Fe(OH)3 in passive film, whereas caused a decrease of Cr2O3 content, and led to the formation of FeS2 in the passive film. These changes in the composition of the passive film made it easier for active sites to appear on the surface of stainless steel and enhanced the conductivity of the passive film and significantly reducing its protective performance.

Synthesis and characterization of graphene-based electrocatalysts for the detection of damaged starch ratio

In this study, the detection of damaged starch ratio on synthesized graphene-based electrocatalysts were evaluated based on the iodine oxidation mechanism. Electrocatalysts were synthesized by three different electrochemical exfoliation techniques. Synthesized catalysts were tested in a three-electrode system with electrolytes mixed with flours at different damaged starch ratios (at 16.5, 25 and 30 UCD values). For the electrochemical tests related to iodine absorption, electrolyte solutions were prepared according to Medcalf and Gilles principle; cyclic voltammetry and chronoamperometry were performed at 50 mV/s in the range of 0–1 V vs. SCE; and at a potential of 1 V vs. SCE. The synthesized catalysts showed reversible reaction properties by giving anodic and cathodic peaks of iodine in the three-electrode system. The exfoliated graphene samples were characterized via standard tools such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman and UV-vis spectroscopy. After all, it was seen that the G2 type electrocatalyst has the highest sensitivity to iodine absorption and potential for use in damaged starch detection.

Characterization of passive layer formation kinetics of Zn5Al hot-dip galvanized coatings using gel electrolytes

PurposeThe formation of a natural passive layer on hot-dip galvanized coatings increases their corrosion resistance. Although the basic mechanisms of passive layer formation are known, the quantitative determination of the evolution of its passive character, in particular its surface resistivity, and its development under atmospheric weathering remains largely unexplored for zinc-5% aluminum (Zn5Al) coatings.Design/methodology/approachZn5Al-galvanized test sheets were exposed to atmospheric weathering for four weeks during summer and winter, and the development of polarization resistance measured using a gel-type electrolyte over these periods. Further investigation included stripping away the formed passive layer midway through the exposure period and electrochemical characterization of the passive layer that re-formed after under continue weathering.FindingsThe results showed a steadily increasing resistivity of the corrosion product (passive) layer over the course of the weathering period; this was confirmed by supplementary macroscopic and microscopic analyses. Exposure conditions affected the speed of development. Polarization resistance values were higher by approximately 50 kΩcm2 during the winter compared to summer. Upon interruption of exposure and removal of the passive layer, it rebuilt up much more rapidly after exposure resumed in comparison with the initial layer.Originality/valueThe use of gel electrolyte for determining the polarization resistance of a metal surface is a novel and useful method. To the best of the authors’ knowledge, this study has, for the first time, established the suitability of this electrochemical test method for quantifying the coating resistance of Zn5Al galvanized steel after calibrating the measurement parameters.

Study of the electrochemical stability of the difenoconazole pesticide by cyclic voltammetry and UV-Vis spectrophotometry

Difenoconazole is a triazole fungicide that inhibits the activity of fungi and is widely used to protect fruits, vegetables and grains. Its health and safety issues need to be further studied. In this study, experiments were conducted to investigate the degradation kinetics and electrochemical degradation pathways of difenoconazole to harmless inorganic products using two electrochemical methods; cyclic voltammetry and constant current electrolysis, in association with UV-Vis spectrophotometric analysis. The results of electrochemical tests indicated the participation of difenoconazole pesticide molecules in charge transfer processes with a priori adsorption of its molecules on the surface of the platinum electrode. UV-Vis spectrophotograms of the pesticide solution indicated a decrease in the absorbance value corresponding to difenoconazole during constant current electrolysis processes. The study elaborates on a mechanism for direct electrochemical degradation of pesticide molecules on the platinum electrode surface.

Hydroxyapatite-reinforced Al-Mg composites for corrosion resistance in hanks' balanced salt solution

Aluminum-Magnesium (Al-Mg) matrix composites were fabricated using powder metallurgy. Ceramic particles such as synthetic hydroxyapatite and snail shell hydroxyapatite were used as reinforcing particles. Snail shell hydroxyapatite often shows superior corrosion resistance over manufactured hydroxyapatite because of its distinct structural integrity, biological compatibility, and trace element concentration. Aluminummagnesium matrix composites are lightweight metals with advantageous mechanical, physical, and density properties, making them suitable for applications in the automotive, aerospace, biomedical, and sports industries. However, their limited corrosion resistance has restricted their broader development and application. This study characterizes corrosion behavior of Al-Mg composites reinforced with HAss and HA bioceramic. Given that plastic deformation can improve corrosion resistance, powder metallurgy is one of the most promising techniques for improving a material's mechanical properties. Following HAss reinforcement testing, Al-Mg composites were contrasted. A compression pressure of 650 MPa was used to produce the samples at room temperature. Corrosion was measured using the potentiodynamic polarization electrochemical test in Hank's Balanced Salt Solution (HBSS). Out of all the AlMg/HAss composites, the 0.55Al-0.05Mg/0.40HAss composite exhibited the maximum corrosion resistance (9.58×10-4 mmpy), per the test results. 7.72×10-6 mmpy was the Al-Mg/HA composite's ideal corrosion resistance when combined with the 0.80Al-0.05Mg/0.15HA composite. The application of powder metallurgy in the production of the composites significantly improved their corrosion resistance. The Al-Mg/HAss AMC can also be used in biomaterials.

Sustainable Porous Activated Carbon from the Bark of Wood Apple Tree as Electrode Material for Supercapacitor Application

The remarkable microstructural characteristics of porous carbons make them attractive as electrode materials for supercapacitors. The production of porous carbon from biowaste materials has gained considerable attention because of their affordability and natural abundance. This work approaches the preparation of porous carbon using the bark of wood apple tree precursor. The X-ray diffraction analysis, Fourier transform infrared spectroscopy and scanning electron microscopy techniques were performed to evaluate the physico-chemical parameters of prepared activated carbon material. In three-electrode electrochemical tests, the activated carbon WABAC3 provides the specific capacitance of 345 F g–1 at a current density of 1 A g–1 in 1 M Na2SO4 electrolyte with remarkable rate capability. It provides the cyclic stability of 91% of initial capacitance after 5000 continuous GCD cycles at a current density of 5 A g–1.

N-Doping Fe-C@Nb2CTx MXenes with High Stability and Strong Activity for Sodium-Ion Storage and Overall Water Splitting.

The development of highly stable and strongly active electrode materials for sodium-ion batteries (SIBs) and overall water splitting (OWS) is critical in sustainable energy storage and conversion systems. Here, a new electrode material N-Fe-C@Nb2CTx is introduced, with a layered sandwich structure consisting of N-doping Fe-MOF derived-nanorods (Fe-C) and Nb2CTx MXenes. Specifically, Nb2CTx obtained by etching Nb2AlC with HF acid is used as the main body to construct the layered sandwich structure with Fe-C as the filler. Benefiting from this structure, Fe-MOF grows in situ within Nb2CTx, which restrains MXenes aggregation and stacking and also alleviates the bulk effect of sodium-ion embedding/de-embedding, thus improving its stability. Again, the more exposed active sites from the layered sandwich structure and N-doping introduction ensure high reactivity as electrode materials. In addition, Fe-C nanorods strengthen the linkage between the Nb2CTx layers and N-doping enhances the ion/electron transport rate, thereby boosting the effective mass transfer and electrical conductivity. Density functional theory (DFT) calculations show that Fe-C and N-doping help increase the density of states (DOS) and material electrical conductivity. Meanwhile, the generated oxygen species (*OH and *O) in OER are captured by in situ FT-IR test. As a result, the N-Fe-C@Nb2CTx electrochemical test displays good electrochemical performance in SIBs and OWS.

Redox-Active Water-Soluble Low-Weight and Polymer-Based Anolytes Containing Tetrazine Groups: Synthesis and Electrochemical Characterization.

Polymer-based aqueous redox flow batteries (RFBs) are attracting increasing attention as a promising next-generation energy storage technology due to their potential for low cost and environmental friendliness. The search for new redox-active organic compounds for incorporation into polymer materials is ongoing, with anolyte-type compounds in high demand. In response to this need, we have synthesized and tested a range of new water-soluble redox-active s-tetrazine derivatives, including both low molecular weight compounds and polymers with different architectures. S-tetrazines are some of the smallest organic molecules that can undergo a reversible two-electron reduction in protic media, making them a promising candidate for anolyte applications. We have successfully modified linear polyacrylic acid and poly(N-isopropylacrylamide-co-acrylic acid) microgels with pendent 1,2,4,5-tetrazine groups. Electrochemical testing has shown that the new tetrazine-containing monomers and, importantly, the water-soluble redox polymers, both linear and microgel, demonstrate the chemical reversibility of the reduction process in an aqueous solution containing acetate buffer. This expands the range of water-soluble anodic materials suitable for water-based organic RFBs. The reduction potential value can be adjusted by changing the substituents in the tetrazine core. It is also worth noting that the choice of electrode material plays an important role in the kinetics of the tetrazine reaction: the use of carbon electrodes is particularly beneficial.

Interfacial Microstructure and Cladding Corrosion Resistance of Stainless Steel/Carbon Steel Clad Plates at Different Rolling Reduction Ratios

Optical microscope (OM), energy dispersive spectrometer (EDS), electron backscatter diffractometer (EBSD), electrochemical test, and transmission electron microscope (TEM) were employed to conduct interface microstructure observation and cladding corrosion resistance analysis on 304 SS/CS clad plates that have four different reduction ratios. The increase in rolling reduction ratio leads to larger grain size, gradually refined microstructure, and a decreased thickness of the interfacial martensite area. As the concentration disparity of the C element between carbon steel (CS) and 304 stainless steel (SS) is small, no evident carburization layer or decarburization layer can be detected. The ferrite microstructure on the CS side has greater stress distribution and greater local orientation deviation, and deformed grains are dominant. Austenite undergoes strain-induced martensitic transformation with the transformation mechanism of γ→twinning→a’-martensite. The martensite microstructure within the interface region grows in the direction of the interior of austenite grains. The reduction ratio increases sharply, leading to an increase in dislocation density, which promotes the nucleation, growth, and precipitation of carbides and seriously reduces the corrosion resistance of the cladding. Subsequently, the reduction ratio keeps on increasing. However, the degree of change in the reduction ratio diminishes. High temperature promotes the dissolution of carbides and improves the corrosion resistance. From this, it can be understood that by applying the process conditions of raising the reduction ratio and keeping a high temperature at the carbide dissolution temperature, a clad plate that has excellent interface bonding and remarkable corrosion resistance can be acquired.

Enhanced CO2 Photoreduction Performance of WO3−x

Converting CO2 greenhouse gases into high-value-added fuels via semiconductor photocatalysts is an ideal solution to address current environmental and energy issues. Due to its unique physicochemical traits and flexible structure, WO3 is widely employed in photocatalysis. Nevertheless, it commonly faces problems such as limited light absorption and low reaction selectivity. Here, we effectively tackle the existing issue by introducing an oxygen defect strategy to synthesize two-dimensional WO3−x nanosheets with rich oxygen vacancies. Due to localized surface plasmon resonance (LSPR), these nanosheets may exhibit broad light absorption and efficient CO2 adsorption and activation. In the photocatalytic reduction of carbon dioxide (CO2) to carbon monoxide (CO), WO3−x nanosheets exhibited 100% selectivity and 16.1 μmol g−1 h−1 yield, 6.2 times higher than WO3. Oxygen vacancies improve WO3’s band structure and increase its capacity to absorb visible light. Based on electrochemical tests and fluorescence spectroscopy analysis, the outstanding functionality of WO3−x nanosheets is related to the improved separation and transport of photocurrents and the restricted radiative recombination of the resulting electron pairs and holes.

Sulfonated Styrene-Grafted Polyvinylidene Fluoride Copolymers for Proton Exchange Membranes for AQDS/Bromine Redox Flow Batteries.

This study presents the preparation and electrochemical testing of sulfonated styrene-grafted poly(vinylidene fluoride) (pVDF) copolymers as proton exchange membranes (PEMs) for semi-organic redox flow batteries (RFBs) based on 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/bromine. The copolymers are synthesized via a two-step procedure, involving i) atom transfer radical polymerization of styrene (Sty) for the grafting to the pVDF backbone and ii) the sulfonation of the polystyrene grafted side chains. Copolymers with different amounts of sulfonated styrene (SSty) in the side chains (i.e., degree of sulfonation (DS)) are obtained and used for the preparation of PEMs by solution casting. The PEMs are characterized to assess their thermal, mechanical, water absorption, and ion exchange properties, to evaluate the effect of DS on membrane properties, and to select the membrane with the best overall performance for application in single cell tests. Electrochemical testing reveals that the pVDF-g-(Sty26-co-SSty14) membrane exhibits low crossover of redox species, favorable ohmic resistance, and energy efficiency. Results from single cell tests, as compared with commercial benchmarks such as Nafion 115 and Aquivion E87-12s, highlight the potential of such copolymers as alternative membranes for RFBs.

Engineering Corrosion-Resistant Microstructures in AZ31D Magnesium Alloy through Friction Stir Processing

In this study friction stir processing (FSP) was utilized to refine the microstructure of thick AZ31D magnesium (Mg) alloy, followed by evaluation of its microstructure and corrosion behavior in a NaCl environment. The application of a tapered threaded pin profile resulted in enhanced material mixing, significant grain refinement and reduced defect formation due to minimal heat input and minimized thermal gradients across the stir zone (SZ). The SZ, dominated by the pin profile, exhibited a fine, equiaxed, and uniform grain structure throughout its thickness the average grain size reduced from 13.8 µm to 5.19 µm after second pass of FSP confirmed through field-emission scanning election microscopy (FE-SEM) analysis. This structural refinement significantly enhanced the corrosion performance of the FSPed alloys, as compared to the base material (BM), demonstrated by electrochemical testing in 3.5% NaCl solution. The FSPed alloy surface showed uniform corrosion behavior, instead of intergranular corrosion with deep mud cracking patterns observed in the BM. This improved corrosion resistance was due to the uniformity of the produced microstructure via FSP, which reduced localised corrosion sites. These findings suggest that FSP is a promising technique for improving the durability of Mg alloys in corrosive environments, potentially benefiting applications in the automotive and aerospace industries.

Corrosion Characteristics of Typical Gangue Minerals in Biometallurgical Systems.

Electrochemical and shake flask tests were used to examine the corrosion characteristics of typical gangue minerals in biometallurgical systems and their impact on microbial communities. The results show that the solubility order of the three gangue minerals is feldspar, mica, and quartz in descending order. Their corrosion processes are mainly controlled by cathodic electron-donating processes. They are subjected to triple resistance, which is defined as solution-resistant, colloidal silica passivation, and iron precipitation (ferric hydroxide or jarosite passivation). Fe3+ and microorganisms both greatly improve the corrosion capacity of the system for the three gangue minerals. The community diversity may rise to 9.3, 8.6, and 4.4 times that of the initial HQ0211 strain, respectively, in the presence of feldspar, mica, and quartz.. The proportions of autotrophic microorganisms Leptospirillum, Sulfobacillus, and Acidiplasma decreased significantly, and the mixed trophic archaeon Ferroplasma and heterotrophic archaeon Cuniculiplasma became the dominant microorganisms in the system. Finally, the dissolution mechanism of gangue minerals in biometallurgical systems is discussed. The results enrich the theory of the gangue mineral corrosion process, which can lay a foundation for the effective regulation of biometallurgical processes.

Laser Welding of Micro-Wire Stent Electrode as a Minimally Invasive Endovascular Neural Interface.

Minimally invasive endovascular stent electrodes are an emerging technology in neural engineering, designed to minimize the damage to neural tissue. However, conventional stent electrodes often rely on resistive welding and are relatively bulky, restricting their use primarily to large animals or thick blood vessels. In this study, the feasibility is explored of fabricating a laser welding stent electrode as small as 300 μm. A high-precision laser welding technique was developed to join micro-wire electrodes without compromising structural integrity or performance. To ensure consistent results, a novel micro-wire welding with platinum pad method was introduced during the welding process. The fabricated electrodes were integrated with stent structures and subjected to detailed electrochemical performance testing to evaluate their potential as neural interface components. The laser-welded endovascular stent electrodes exhibited excellent electrochemical properties, including low impedance and stable charge transfer capabilities. At the same time, in this study, a simulation is conducted of the electrode distribution and arrangement on the stent structure, optimizing the utilization of the available surface area for enhanced functionality. These results demonstrate the potential of the fabricated electrodes for high-performance neural interfacing in endovascular applications. The approach provided a promising solution for advancing endovascular neural engineering technologies, particularly in applications requiring compact electrode designs.

Corrosion Properties of Cold-Sprayed Cr3C2-25(Ni20Cr) Coatings After Heat Treatment.

The corrosion resistance of a Cr3C2-25(Ni20Cr) cermet coating applied to an Al7075 substrate (Cr3C2-25(Ni20Cr)/Al7075) was investigated. The coating was produced using a cold spraying (CS) method. The main aim of the research was to determine the effect of heat treatment on the properties of cermet coatings on the Al7075 substrate. The mechanical properties of the Cr3C2-25(Ni20Cr)/Al7075 composite were assessed through microhardness (HV) measurements. The surface morphology and microstructure of the specimens were examined using a scanning electron microscope (SEM). Electrochemical testing in an acidic chloride solution was employed to evaluate the corrosion behavior of the materials. The cermet coating effectively protected the Al7075 substrate from the aggressive corrosive environment. Heat treatment homogenized the structure of the cermet coating, eliminating microcracks and pores on the Cr3C2-25(Ni20Cr)/Al7075 surface. Notably, annealing at 300 °C in air significantly enhanced the corrosion resistance of the cermet coating. The corrosion rate was reduced by more than five times compared to the non-heat-treated Cr3C2-25(Ni20Cr)/Al7075 coating.