Electrochemical Tests Research Articles

IMPROVEMENT OF CORROSION RESISTANCE OF 2024 ALUMINUM ALLOY BY Y(NO3)3⋅6H2O MODIFICATION AND HOLE SEALING TREATMENT

In order to obtain better corrosion resistance, the micro-arc oxidation (MAO) coating after adding (Y(NO3)[Formula: see text]H2O was sealed by TiO2 sol–gel method. Dynamic polarization curves and electrochemical impedance spectroscopy show that the prepared samples (Y(NO3)[Formula: see text]H2O content was 1.5[Formula: see text]g/L) have good corrosion resistance ([Formula: see text]A[Formula: see text]) in 3.5[Formula: see text]wt.% NaCl aqueous solution. Afterward, the samples with a concentration of 1.5 g/L of Y(NO3)[Formula: see text]H2O were sealed by TiO2 sol–gel. Through SEM, XRD and electrochemical test, it is found that the surface of the film is smooth, the phase is mainly in the form of Anatase-TiO2 and has better corrosion resistance ([Formula: see text]A[Formula: see text]). This showed that sealing the doped 2024 aluminum alloy MAO film can significantly reduce the corrosion sensitivity and corrosion rate of the film.

MOF-Based Construction of Oxygen Vacancies ZnMn2O4 for Superior Zinc Storage.

Manganese-based oxides are widely used as cathode materials for aqueous zinc-ion batteries (ZIBs) due to their high theoretical specific capacity, abundant reserves, and high operating voltage. However, their practical applications are limited by inherent issues such as active material dissolution, structural collapseor changes, and slow reaction kinetics. In this study, a cathode material for zinc batteries, ZnO-ZnMn2O4 (MZ), is synthesized based on a metal-organic framework (MOF). Synergistic strategies involving atomic composition modulation and defect engineering are employed to address the inherent issues of ZnMn2O4, stabilize the material structure, inhibit the disproportionation of Mn3+, and reduce the Jahn-Teller effect. Additionally, the material benefits from enhanced oxygen vacancies and a smaller particle size, which promote faster reaction kinetics. Electrochemical tests show that MZ-550 delivers a high specific capacity of 314.5 mA h g-1 at 100 mA g-1 and cycling stability, with a capacity retention of 96.6% after 1500 cycles at 1000 mA g-1. In addition, the material demonstrates outstanding electrochemical performance under extreme conditions, with specific capacities of 86.4 mA h g-1 at -20 °C and 331.1 mA h g-1 at 40 °C. This study provides insights for the development of high-performance cathode materials for ZIBs in advanced energy storage systems.

Metal‐Free Electrocatalysts for H2O2 Electrosynthesis: From Sites Identification to Electrochemical Advanced Oxidation Process

AbstractCarbonaceous materials, especially the metal‐free carbons, have attracted widespread attention owing to their risk‐free nature with metal dissolving during the electrocatalysis process, but their further developments are still hindered by missing a suitable scenario on practical applications. Herein, we demonstrate a successful case of using the oxygen‐containing‐groups‐modified carbons for the H2O2 electrosynthesis and the derivative electrochemical advanced oxidation process. The active sites with the more C─O rather than C═O groups are easily obtained by controlling the temperature and time in the wet chemical treatment. Identified by theoretical calculations and electrochemical testing, the modified carbons with the highest ratio of C─O/C═O groups exhibit high activity with above 90% H2O2 selectivity over the entire potential during 2e‐transfer oxygen reduction reaction, attributing to their enlarged charge delocalization. In addition, the corresponding gas diffusion electrodes with the high‐speed and high‐stability H2O2 electrosynthesis (2.78 µg s−1 cm−2 with the above 80% current efficiency) are applied for the electro‐peroxone process on the simulant and practical phenolic wastewater, where the chemical oxygen demand removal reaches above 90%. The long‐term operation in the harsh electrochemical environment for over 200 h also confirms its great potential for practical electrochemical applications.

Sn(II)-Pyrophosphate Complex with Low Plating/Stripping Potential for Sn-I Flow Battery Applications.

Exploring electrolyte formulations that can effectively reduce the plating/stripping potentials of metallic electrodes holds great significance in advancing the development of high-voltage redox flow batteries. In this study, we introduce a novel Sn-based chelated electrolyte, namely, Sn(P2O7)26-, by directly reacting the Sn2+ solution with an excess of P2O74- solution. Electrochemical tests prove that the incorporation of high-concentration P2O74- ligands could shift the plating/stripping potential to -0.67 V. Thus, the demonstrated Sn-I flow battery reveals an average cell voltage of nearly 1.2 V and maintains stable cycling over 250 cycles at a high current density of 80 mA cm-2, with an average energy efficiency of about 70%. Moreover, no dendrite formation formed during the Sn deposition on the carbon felt. This study offers broad prospects for the future development of high-voltage Sn-based flow batteries.

Preoxidation Assisted Alkali Activation Constructs Polyacrylonitrile-Based Porous Carbon for Supercapacitors.

The porous structural tailoring of polyacrylonitrile-based carbon materials is the key to maximize capacitive performance. Herein, hierarchical porous carbons (HPC) with high specific surface area and controllable porosity are synthesized by preoxidation assisted alkali activation strategy using polyacrylonitrile as the precursor. The results show that high preoxidation temperature is beneficial to increase the specific surface area and pore volume of HPC. The optimized HPC-300 has a high BET specific surface area of 3161 m2 g-1, a micropore volume of 1.45 cm3 g-1, and an AD/AG of 3.56. Electrochemical test shows that the specific capacitances of HPC-300 in 6 M KOH electrolyte at 1 A g-1 and 10 A g-1 are 314.1 F g-1 and 213.0 F g-1, respectively, with a capacitance retention of 67.8 %. The assembled supercapacitors based on HPC-300 deliver an energy density of 11.7 Wh kg-1 at a power density of 250.0 W kg-1 in KOH electrolyte and 21.1 Wh kg-1 at 450.0 W kg-1 in Na2SO4 electrolyte and possess a capacitance retention of 98.1 % over 20,000 charge-discharge cycles. This preoxidation coupled activation method provides a potential strategy for the preparation of PAN-based porous carbon with high specific surface area and capacitance.

Corrosion behaviour of 6016 aluminium/steel resistance spot welding joints in salt spray environment

The corrosion behaviour of lightweight aluminium/steel joints formed through resistance spot welding with multi-ring domed electrodes was investigated. A detailed examination of the RSW joint between 6016 aluminium and DP780 galvanised steel was conducted using electrochemical corrosion tests in a 3.5% NaCl solution and spray acceleration tests. The bonding process involved the formation of an interfacial Fe–Al intermetallic layer, with oxide inclusions near the aluminium nugget. Unlike the interfacial intermetallic layer, microcracks and Si-rich regions at the aluminium-side interface front were found to be particularly vulnerable to corrosion during salt spray exposure. This study demonstrates that the microstructure and interface oxides are key factors affecting corrosion resistance of the joint nugget and provides insights into optimising the RSW process.

Preparation and Properties of Cd/Ni Complexes Based on 2,6‐Bis(4′‐carboxyl‐phenyl)pyrazine Ligand

ABSTRACTTwo transition metal complexes (complex 1 = {[Cd (DCPP)·(H2O)]·(DMF)}n and complex 2 = {[Ni (DCPP)·(H2O)]·(DMF)}n) with the same structure and different functions were synthesized based on 2,6‐bis(4′‐carboxybenzene)pyrazine ligand (H2DCPP) by solvothermal method, and their structure and properties were analyzed and characterized by a variety of characterization methods. Complex 1 was used as a fluorescence sensor to recognize cations and anions in water; it had excellent recognition and anti‐interference ability with Fe3+ and Cr2O72− among cations and anions. Complex 2 (2‐CPE) was used as electrochemical material to perform electrochemical tests on hydrogen peroxide and sodium nitrite with good electrocatalytic effect. This work provides a synthesis strategy for fluorescence and electrochemical sensing materials, respectively.

Research on Interfacial Construction and Energy Storage Performance of Polymetallic Heterostructure Based on Zn-Ni 3d Orbital Modulation and DFT Study.

In this study, ZnCo2O4 nanosheets and NiCo2O4 nanowires were successfully grown on nickel foam as anode materials for lithium-ion batteries by a low-temperature hydrothermal and immersion method. The nanosheets offered an enlarged electrically active surface area, and the nanowires provided support for the nanosheets, thereby forming a heterojunction interface. The ZnCo2O4/NiCo2O4 heterojunction demonstrated favorable electrochemical performance in electrochemical tests. In terms of its rated performance, the capacity of the composite electrode recovered to 1050 mAh g-1 when the current density ranged from 0.1 to 1 A g-1; its capacity was maintained even when the current density returned to 0.1 A g-1 after 60 cycles. The diffusion coefficient of lithium ions (DLi+) increased due to the reduction of the interfacial contact resistance under the interfacial electric field of the heterostructure, and they were continuously activated during repeated cycles. This further significantly enhanced the electrochemical activity of the electrode. The analysis results based on the density functional theory revealed the hybridization of the 3d orbitals of Ni and Zn and the augmented electronic state occupancy of the orbitals near the Fermi energy level. This process was accompanied by the migration of electrons, leading to a decrease in the band gap. Meanwhile, the Li+ diffusion barrier decreased, and the conductivity of the electrode materials was enhanced.

Tribo and Corrosion Resistance of Ni-W-P Coatings Synergistically Enhanced by Cationic hBN and Cationic cBN.

In this work, polydopamine (PDA) modification of hBN is used to create DRhBN+ particles having a two-dimensional lamellar structure, which are then applied on Ni-W-P coatings. Additionally, pulsed electrodeposition is used to successfully create composite coatings of Ni-W-P/DRhBN+, Ni-W-P/DRcBN+, and Ni-W-P/DRhBN+-DRcBN+. The properties of the four composite coatings are contrasted. The results demonstrate that the PDA coating on hBN particles improves the dispersion of DRhBN+ particles in the bath by introducing -NH3+ and catechol groups. Moreover, because of the grain refinement impact of the DRhBN+ and DRcBN+ particles, the surface of the composite coating with these additions is dense and flat. It should be noted that the innovative composite coating, which takes advantage of the synergistic effects of the two modified particles, performs best overall. According to microhardness tests, the composite coating may reach a hardness of up to 917.6 HV. Surprisingly, the friction loss of the composite coating during reciprocating friction testing is negligible, and its average coefficient of friction (COF) is as low as 0.199. The DRhBN+ and DRcBN+ particles' diffuse reinforcement, their effect on grain refinement, and the DRhBN+ particles' self-lubricating ability as a solid lubricant are all responsible for the improved performance. Electrochemical impedance spectroscopy and polarization curve tests further demonstrate that the composite coating, which combines both kinds of particles, has an icorr of 1.34 μA/cm2, a corrosion rate of Vcorr 14 μm/year, and an Rt value of 54230 Ω·cm2. These findings demonstrate the exceptional corrosion resistance of the Ni-W-P/DRhBN+-DRcBN+ composite coating.

Instantaneous Self-Healing Chitosan Hydrogels with Enhanced Drug Leakage Resistance for Infected Stretchable Wounds Healing.

Self-healing hydrogels are intelligent wound dressings to repair structural damage caused by limb movement, demonstrating advantages in stretchable wound management. Chitosan is widely used in the preparation of hydrogels due to the biocompatibility and biodegradability. However, the self-healing efficiency and mechanical strength of chitosan hydrogels are not ideal. To address the issues, three self-healing hydrogels: the single schiff base network hydrogels (OH), the double schiff-base bond network hydrogel (OHD), and borate ester bond/schiff base bond (OHPB) are designed. The self-healing time of OHPB is only 0.7 s measured by real-time electrochemical test, while the self-healing time of OH and OHD is 3.5 h and 1.5 h. Furthermore, OHPB hydrogel exhibits the desirable mechanical strength and tissue adhesion. Following the destruction-repair process, CIP and exosome loaded OHPB (ec⊂OHPB) hydrogel displays approximate 100% drug leakage resistance to achieve long-term antibacterial, cells migration promotion and M2 polarization. ec⊂OHPB hydrogel significantly accelerates infected stretchable wounds healing by relieving inflammation, facilitating angiogenesis and collagen deposition, promoting epidermal remodeling. Consequently, OHPB hydrogel with instantaneous self-healing property and enhanced drug leakage resistance performance makes it possible to broaden the application prospects of chitosan hydrogel dressings.

Influence of Specific Ball‐Milling Energy on Mechanical and Corrosion Properties of Zn–0.2 Graphene Nanoplatelet Composites

The specific amount of ball‐milling energy (SBME) plays a significant role in achieving a homogenous dispersion of graphene nanoplatelets (GNPs) in metal matrix composites (MMCs). The dispersion of GNPs in the metal matrices, induced by SBME, can be adjusted to improve the mechanical and corrosion properties of the MMCs. Herein, high‐energy ball milling is utilized to disperse 0.2 wt% of GNPs into zinc (Zn) powders using different SBMEs. Ball‐milled powder mixtures (BMPMs) obtained at different SBMEs are cold‐compacted at 500 MPa and sintered at 420 °C. The morphology of the BMPMs and the microstructure of the Zn–0.2GNP composites (Zn‐based MMCs [ZMCs]) are evaluated utilizing X‐ray diffraction and scanning electron microscopy. Compression and electrochemical testing are performed on ZMCs to analyze the mechanical and corrosion properties. Results indicated that the GNPs are uniformly dispersed in the Zn powders at the optimal SBME of 32.82 kJ g−1. The microhardness, compressive yield strength, ultimate compressive strength, compressive strain, and reduced elastic modulus of the ZMC fabricated at 32.82 kJ g−1 SBME are 68.7 HV, 123, 247 MPa, 22.9%, and 89.04 GPa, respectively, improvements of 66%, ≈160, ≈201, ≈51, and ≈26% compared to the reference sample ball milled at 0.91 kJ g−1 SBME. The corrosion rate of the ZMCs declined with increasing SBMEs.

ZnO/Cu2S PN-junctions with built-in electric field for enhanced CO2 electroreduction

A full stack strategy, including facilitating the capture of CO2 molecules on catalysts, regulating intermediates, and releasing products, is highly needed to break the bottleneck for CO2 electroreduction to CO. The electric field is expected to promote capture of CO2, reduce energy barriers of reaction, and efficiently release CO, boosting the overall CO2 reduction reaction (CO2RR) activities. In this work, ZnO/Cu2S PN-junctions with a built-in electric field were fabricated. Kelvin probe force microscopy measurements confirmed that the presence of the built-in electric field facilitates the adsorption of more CO2 molecules onto the catalyst surface. Furthermore, theoretical calculations and electrochemical testing demonstrated that the built-in electric field lowers the reaction energy barrier and effectively modulates the reaction intermediates, contributing to enhanced catalytic performance. This work provides a full stack strategy to improve CO2RR performance and thinking for gas-fed catalytic reactions.

KOH-Assisted Molten Salt Route to High-Performance LiNi0.5Mn1.5O4 Cathode Materials.

A simple and cost-effective route based on a KOH-assisted molten salt method is designed here to synthesize LiNi0.5Mn1.5O4 spinel. Pure-phase LiNi0.5Mn1.5O4 can be successfully prepared using chlorides as raw materials and adding KOH at 700 °C. The structure, morphology, and performance are discussed in detail. The measurements reveal that using KOH-assisted synthesis can optimize the crystal structure of the obtained LiNi0.5Mn1.5O4 samples, resulting in grain refinement while maintaining the predominantly octahedral structure that grows along the (111) crystal plane. This new synthesis pathway provides excellent performance in terms of cycle life. Electrochemical tests show that the KOH-assisted sample exhibits higher initial specific capacities (124.1 mAh·g-1 at 0.2 C and 111.4 mAh·g-1 at 3 C) and superior cycling performances (capacity retention of 85.0% after 200 cycles at 0.2 C and 95.70% after 100 cycles at 3 C). This provides a potential solution for the practical application of high-voltage LiNi0.5Mn1.5O4 lithium-ion batteries.

Benzoxazine/Micro‐Arc Oxidation High‐Temperature‐Resistant Composite Coating With Superior Corrosion Protection Performance on Magnesium Alloy

ABSTRACTIn this study, to seal the pores of a micro‐arc oxidation (MAO) coating, benzoxazine (BZ) is used to form a highly heat‐resistant MAO/BZ composite coating with excellent anti‐corrosion performance on a magnesium alloy. The as‐prepared BZ coating, which has a static water contact angle of 111.52° ± 2.6°, is bonded firmly to the MAO coating and can withstand a temperature of 300°C. The results of electrochemical tests indicate that the composite coating prepared by BZ with a concentration of 40% demonstrates a low corrosion current density of 9.01 × 10−12 A cm−2 in a 3.5 wt.% NaCl aqueous solution. Moreover, the composite coating exhibits an outstanding corrosion resistance after a neutral salt spray test for 82 days. Furthermore, it is concluded that an increased concentration of BZ can significantly increase the coating thickness with a dense curing crosslinking structure, which is a key factor in the corrosion protection of MAO coatings.

Transferring from Eu3+ to Eu2+ in Eu2O3-LiCl-KCl molten salt: an optical and electrochemical investigation

ABSTRACT Europium is an important element in the nuclear industry, which is usually applied in the high-temperature melt system. Therefore, due to relatively limited progress in understanding europium among all lanthanide elements, this study aims to disclose the important behavior of Eu3+ (Eu2O3) in the LiCl-KCl molten salt system employing optical and electrochemical strategies and to provide a theoretical basis for the subsequent electrolytic separation of Eu from other metals in nuclear waste. The optical behavior and electrochemical behavior of Eu2O3 in LiCl-KCl molten salt were tested by Raman, UV-vis diffuse reflectance spectra and CV, SWV, CP and other electrochemical methods. Through spectroscopic studies, it was found that Eu2O3 formed a new phase EuOCl in LiCl-KCl melt at 973 K. With the increase of Eu2O3 ratio, the band gap of products first increased and then decreased. Through electrochemical studies, it was found that Eu3+ underwent a single electron exchange process in LiCl-KCl melt, corresponding to the conversion between Eu(III) and Eu(II). The process was a quasi-reversible diffusion-controlled process. A series of electrochemical tests were carried out to determine the diffusion coefficient D of Eu (III) and Eu (II) as (1.94 ± 0.05) × 10−5 cm2 s−1 and (1.95 ± 0.05) × 10−5 cm2 s−1, respectively. This work reveals the electrolytic process of Eu3+ in molten system, which may influence on the spent fuel treatment.

The Impact of Pre- and Post-Treatment Processes on Corrosion Resistance of Micro-Arc Oxidation Coatings on Mg Alloys: A Systematic Review.

As one of the lightest metallic structural materials, magnesium (Mg) alloys possess numerous distinctive properties and are utilized across a broad spectrum of applications. However, the poor corrosion resistance of Mg alloys limits their application. Micro-arc oxidation (MAO) is an effective surface treatment method that enhances the corrosion resistance of Mg alloys. Nevertheless, the intrinsic porous structure of MAO coatings hinders significant improvement in corrosion resistance. Research indicates that the pre- and post-treatment processes associated with MAO markedly enhance the densification of the oxide coatings, thereby improving their overall performance. This paper aims to provide a comprehensive review and analysis of the effects of various pre- and post-treatment processes, highlighting key advancements and research gaps in improving MAO coatings on Mg alloys. An in-depth analysis of the crucial role of pre-treatment in optimizing interfacial bonding and post-treatment in enhancing coating density is conducted using electrochemical testing and scanning electron microscopy (SEM). Finally, the future development of pre- and post-treatment processes are discussed.

Enhancing Mechanical and Biodegradation Properties of Zn-0.5Fe Alloys Through Rotary Forging.

The rising prevalence of orthopedic conditions, driven by an aging population, has led to a growing demand for advanced implant materials. Traditional metals such as stainless steel and titanium alloys are biologically inert and often necessitate secondary surgical removal, imposing both economic and psychological burdens on patients. Biodegradable zinc-based alloys offer promising alternatives due to their moderate degradation rates, biocompatibility, and tissue-healing properties. However, existing studies on Zn-Fe alloys primarily focus on composition optimization, with limited investigation into how processing methods influence their performance. This study explores the effects of rotary forging on the microstructure and mechanical properties of Zn-0.5Fe alloys. By refining grain structure and promoting dynamic recrystallization, rotary forging achieves significant improvements in ductility (60% elongation, a 114% increase compared to the extruded state) while maintaining corrosion resistance. Electrochemical and immersion tests reveal that rotary forging produces a denser and more protective corrosion layer, thereby improving the degradation performance of the material in simulated body fluid. Cytotoxicity and fluorescence staining tests confirm excellent biocompatibility, validating the material's suitability for medical applications. These findings elucidate the mechanisms by which rotary forging enhances the properties of Zn-0.5Fe alloys, providing a novel approach to tailoring biodegradable implant materials for orthopedic applications.

Pulse width effects on microstructure and electrochemical properties of DLC coatings deposited on high-strength Al alloy

Abstract This study employed cage-like hollow discharge plasma-enhanced chemical vapor deposition (PECVD) to synthesize diamond-like carbon (DLC) films on the 2024 aluminum alloy. The DLC coatings were deposited using varying pulse widths. The microstructural and mechanical properties of the films were evaluated using scanning electron microscopy (SEM), x-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Nano Indenter G200 device, and a tribometer model (MS-T3001). The anticorrosion behavior of the coatings in a 3.5 wt% NaCl solution was investigated using a range of electrochemical techniques. The results showed that increasing the pulse width to 20 μs led to the deposition of thicker films due to enhanced plasma density and deposition rate. Corrosion measurements revealed lower corrosion and passive current densities as pulse width increased. This behavior can be attributed to the thicker DLC film, which effectively reduces the presence of pores and inhibits corrosive species from attacking the bare alloy. Additionally, this study calculated and reported the thermodynamic corrosion parameters, including enthalpy of activation (∆H), entropy of activation, and activation energy (∆E) for the sample.

Investigation and evaluation of the efficiency of palm kernel oil extract for corrosion inhibition of brass artifacts

Brass (Cu–Zn alloy) used in the crescent of the Al-Maradani Mosque pulpit is subjected to corrosion under certain conditions, such as exposure to polluted air, oxidizing acids, and compounds containing sulphur or ammonia. This study aimed to evaluate the effectiveness of palm kernel oil extract (PKO) as a green corrosion inhibitor for protecting brass artifacts. The crescent was analyzed using metallographic microscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) to identify its alloy composition, microstructure and corrosion products. The analyses confirmed the crescent was made of a brass alloy (Cu–Zn) and formed by hammering, with corrosion layers composed primarily of cuprite and clinoatacamite, covered by dust containing calcite and quartz. The corrosion protection efficiency of the PKO was evaluated using brass coupons, simulating the artifact of the alloy. Electrochemical methods, including the open circuit potential (OCP), Tafel, and electrochemical impedance spectroscopy (EIS), were used to assess the performance of palm kernel oil on brass coupons at different concentrations (1, 3, 5, 7%). Electrochemical tests showed that corrosion inhibition efficiency increased with higher palm kernel oil concentrations, with the 7% concentration exhibiting the highest corrosion protection, up to 99.7%.

COBALT DOPED IRON BASED PEROVSKITE CATALYSTS FOR EFFICIENT REDUCTION OF NITRATE TO AMMONIA

Electrochemical nitrate reduction reaction (NO3RR) has received universal attention to synthesize value‐added ammonia, which requires high‐efficiency catalysts to reduce the reaction barrier. Herein, cobalt doped SrFeO3 nanofibers (SCFO) with abundant oxygen vacancies via electrospinning technique is proposed to convert nitrate to ammonia. Such catalyst achieves an optimum Faradaic efficiency of 81.5% and a high NH₃ yield of 16.1 mg h⁻¹ mg‐1cat. in a 0.1 M PBS + 0.1 M NaNO₃ solution at ‐0.9 V reversible hydrogen electrode (RHE). Moreover, the in‐situ electrochemical test and DFT calculations confirm the potential‐determining step (PDS) for SCFO is *NO‐*N with an energy barrier of only 1.28 eV.