Electrochemical Passivation Research Articles

Electrodeposition fabrication of corrosion−resistant Ni−based composite film on surface of Cu: Role of conductive YSZ and non−conductive Si3N4 nanoparticles

The Cu materials are playing an irreplaceable role in modern marine facilities, while one major issue affecting their service life is corrosion attack caused by external erosion of chloride ions, which leads to the quickly structural deterioration and reduced durability. To solve this obstinate issue, the corrosion−resistant Ni−based composite films with conductive Yttria–stabilized zirconia (YSZ, 2.5–15g/L) and non−conductive Si3N4 (2.5–15g/L) reinforcing phases were composite–electrodeposited on Cu substrate in direct current (DC) mode. It was believed that the electrical differences of incorporated nanoparticles have a significant impact on nucleation and growth behaviors during electrodeposition, which further altered the structure and property of Ni−based composite films. Therefore, the emphasis of this study was to establish the correlation between obtained structure, electrochemical, and immersion corrosion performances at different incorporation levels of YSZ/Si3N4 nanoparticles. The results demonstrate that by increasing the total doping contents, the Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) measurements exhibited an initial increase followed by a subsequent decrease on co−deposition dynamics, which was related to the dominant impact of conductive YSZ nanoparticle at electrocrystallization process. Meanwhile, the moderate incorporation level of 15g/L offered effective control over structural compactness through dispersion−strengthening and grain−refining, and the same ratio of YSZ/Si3N4 nanoparticles further maximized the improvement degree of microhardness, electrochemical passivation, and immersion stability of resulting films. Besides, the corrosion current density (jcorr) of Ni−YSZ−Si3N4 composite coating under optimum condition of 15g/L was two orders of magnitude smaller than that of Cu substrate after long−term immersion test, and the corresponding polarization resistance (Rp) also increased by 8.6 times. Overall, these substantial alterations obtained provide effective guideline for the design and preparation of corrosion−resistant Ni−based composite coating, which is beneficial to prolonging the service life of Cu components in saline environments.

Ultrafine Grain 316L Stainless Steel Manufactured by Ball Milling and Spark Plasma Sintering: Consequences on the Corrosion Resistance in Chloride Media

This paper reports experimental results concerning the corrosion of 316L austenitic stainless steels produced by ball milling and spark plasma sintering in NaCl electrolyte. Specimens with grain sizes ranging from 0.3 µm to 3 µm, without crystallographic texture, were obtained and compared with a cast that is 110 µm in grain size and an annealed reference. The potentiodynamic experiments showed that the reduction in grain size leads to a degradation of the electrochemical passivation behavior. This detrimental effect can be overcome by appropriate passivation in a HNO3 concentrated solution before consolidation. The Mott–Schottky measurements showed that the semiconducting properties of the passive layer do not vary significantly on the grain size, especially the donor density, which is responsible for the chemical passivation breakdown by chloride anions. The total electrical resistance of the layer, measured by impedance spectroscopy is always lower than the one of a cast and annealed 316L, but it slightly increases with a reduction in grain size in the ultrafine grain range. This is followed by a slight increase in the thickness of the oxide layer. The effect of chloride ions is very pronounced in terms of passivation breakdown if the powder is not passivated prior to sintering. This leads to the nucleation and growth of subsurface main pits and the formation of secondary satellite pits, especially for the smallest grain sizes. Passivation of the 316L powder before sintering has been found to be an effective way to prevent this phenomenon.

Portable Copper-Based Electrochemical SERS Sensor for Point-of-Care Testing of Paraquat and Diquat by On-Site Electrostatic Preconcentration.

With the advent of portable Raman spectrometers, the deployment of surface-enhanced Raman spectroscopy (SERS) in point-of-care testing (POCT) has been initiated. Within any analytical framework employing SERS, the acuity and selectivity inherent to the SERS substrate are of paramount importance. In this article, we utilize in situ electrochemical passivation technology to fabricate CuI passivation film, which serves as a flexible copper-based SERS substrate. Furthermore, portable electrochemical SERS (EC-SERS) sensors were prepared by combining this with laser direct writing technology. The detection signal was amplified using electrostatic preconcentration technology, showcasing impressive sensitivity, selectivity, and stability in pesticide detection. The detected concentrations of paraquat and diquat in tea reached as low as 3.36 and 2.43 μg/kg, respectively. Furthermore, the application of electrostatic preconcentration facilitated selective target molecule aggregation on the SERS sensor, markedly increasing Raman signal strength and enabling single-molecule detection. This research introduces an innovative POCT method for pesticides, promising to advance environmental monitoring's analytical capabilities.

Electrochemical behavior and passivation film characterization of TiZrHfNb multi-principal element alloys in NaCl-containing solution

In this work, the electrochemical behavior and passivation film characteristics of a TiZrHfNb multi-principal element alloy (MPEA) with an equal atomic ratio in Cl− solution were studied. The effect of constituent metals on the overall corrosion resistance of alloys focused on different aspects. Ti could reduce the point defect density of the passivation film, while Nb kept the passivation film stable at a high potential, Hf and Zr provided high resistance and charge transfer resistance to the passivation film, and hydroxides enhanced the repair ability of the passivation film. There was also a synergistic effect between the alloying elements.

Comparing Electrochemical Passivation and Surface Film Chemistry of 654SMO Stainless Steel and C276 Alloy in Simulated Flue Gas Desulfurization Condensates.

This research examines the behavior of electrochemical passivation and the chemistry of surface films on 654SMO super austenitic stainless steel and C276 nickel-based alloy in simulated condensates from flue gas desulfurization in power plant chimneys. The findings indicate that the resistance to polarization of the protective film on both materials initially rises and then falls with either time spent in the solution or the potential of anodic polarization. Comparatively, 654SMO exhibits greater polarization resistance than C276, indicating its potential suitability as a chimney lining material. Mott-Schottky analysis demonstrates that the density of donors in the passive film formed on 654SMO exceeds that on C276, potentially due to the abundance of Fe oxide in the passive film, which exhibits the characteristics of an n-type semiconductor. The primary components of the passive films on both materials are Fe oxides and Cr oxides. The formation of a thin passive film on C276 in the simulated condensates is a result of the low Gibbs free energy of nickel oxide and low Cr content. The slower diffusion coefficient of point defects leads to the development of a thicker and more compact passive film on the surface of 654SMO.

In-situ electrochemical passivation for constructing high-voltage PEO-based solid-state lithium battery

Polyethylene oxide (PEO) is one of the promising substrates for polymer solid electrolyte. However, when coupled with high energy density nickel-rich layered cathode materials, PEO faces the risk of catalytic decomposition by delithium nickel-rich materials. In this work, the in-situ electrochemical passivation strategy is employed to obtain high voltage PEO-based solid-state lithium battery. Trace commercial liquid electrolyte was added on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM811) electrode, and liquid electrolyte is prior to PEO electrolyte to react with the cathode during charge/discharge process, leading to the formation of cathode-electrolyte interface (CEI) layer. The CEI layer avoids the direct contact between PEO and NCM811, thus effectively prevents PEO from being decomposed by NCM811 under high voltage. As a result, the optimized NCM811||PEO||Li battery displays enhanced electrochemical performance, especially cycling performance. This simple but effective strategy not only simplifies the manufacturing process, but also has instructional guidance for high-voltage PEO-based battery.

Function of Cu-Sb or Al microalloying on the corrosion resistance of 9Cr steel exposed to simulated concrete pore solution

The role of Cu-Sb or Al on the passivation and Cl-induced depassivation of 9Cr steel in simulated concrete pore solution was systematically obtained via electrochemical tests and microstructure characterization. Both microalloying enhanced electrochemical passivation even if the solution pH dropped. Cu and Al participated in the formation of natural passive film, and the properties of passive film were optimized in terms of resistance, composition, and inner film thickness. However, the chloride threshold level (CTL) was not increased with Cu-Sb microalloying and even decreased with Al microalloying, which is understood from the stability of Al-containing products and the hazards of inclusions.

Electrochemical passivation behavior and surface chemistry of 316 L stainless steel coatings on NV E690 steel fabricated by underwater laser direct metal deposition

The underwater direct metal deposition (UDMD) was employed to deposit 316 L stainless steel (SS316L) coatings on NV E690 steel. The chemical composition gradient from monolayer to trilayer SS316L induces an in-situ phase transformation, thereby enhancing the corrosion resistance. The steady-state passive film grew linearly with the applied potential and exhibited a bilayer structure: a high resistivity barrier layer and a low resistivity outer layer. The growth kinetics of the UDMD fabricated SS316L coatings align with the point defect model. Passive film is enriched in Cr while depleted in Fe and Ni, whereas the altered zone is enriched in Ni.

Highly dense passivation enhanced corrosion resistance of Ti2AlC MAX phase coating in 3.5 wt.% NaCl solution

This study aimed to investigate the dependence of electrochemical behavior upon the microstructural evolution of Ti2AlC MAX phase coating in 3.5 wt.% NaCl solution. The results showed that high-purity Ti2AlC coating with unique equiaxed nanocrystals exhibited remarkably higher impedance and lower current densities compared to those of uncoated Ti-6Al-4V substrate, which was attributed to the formed highly dense and continuously amorphous Al2O3 passive film on the coating surface. According to the combined DFT calculations, both the large diffusivity of Al atoms and the robust stability of Ti2AlxC with Al vacancies exceeding 50% contributed to the unusual achievement of electrochemical passivation characteristics, enabling the significant enhancement of anti-corrosion capability for Ti2AlC coating.

Electrochemical reactivity and passivation of organic electrolytes at spinel MgCrMnO4 cathode interfaces for rechargeable high voltage magnesium-ion batteries

Contact ion pairs determine oxidative stability and interface layer formation.

Electrochemical Passivation of Aluminum As a Current Collector for Solid-State Polymer Batteries : PEO/LiTFSI Polymer Electrolyte

Investigation of the electrochemical properties and passivation mechanism of aluminum as a current collector for solid-state polymer batteries is carried out. Herein, electrochemical stabilities of Polyethylene glycol (PEO) based solid-state electrolyte containing Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt are proved using electrochemical dynamic- and transient-mode polarization with surface scratching. These results indicate that Al metal undergoes passivation with a layer below 4.5 V vs. Li+/Li. And then Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) reveal double layers are formed during the passivation on Al metal surface, with the outer layer composed of metal fluorides (AlF3) and the inner layer composed of metal oxides (Al2O3). The formation of the AlF3 layer on Al metal surface is attributed to the reaction between Al2O3 and HF following as Al2O3 + 6HF → 2AlF3 + 3H2O. Therefore, successful passivation achieved by the formation of AlF3 on the Al2O3 surface of Al metal facilitates to be widely used as a current collector for lithium metal polymer batteries. Therefore, successful passivation by the formation of AlF3 on the Al2O3 surface of Al metal making it a promising choice for the positive electrode in lithium metal polymer batteries.

Identifying Stable Electrocatalysts Initialized by Data Mining: Sb2 WO6 for Oxygen Reduction.

Data mining from computational materials database has become a popular strategy to identify unexplored catalysts. Herein, the opportunities and challenges of this strategy are analyzed by investigating a discrepancy between data mining and experiments in identifying low-cost metal oxide (MO) electrocatalysts. Based on a search engine capable of identifying stable MOs at the pH and potentials of interest, a series of MO electrocatalysts is identified as potential candidates for various reactions. Sb2 WO6 attracted the attention among the identified stable MOs in acid. Based on the aqueous stability diagram, Sb2 WO6 is stable under oxygen reduction reaction (ORR) in acidic media but rather unstable under high-pH ORR conditions. However, this contradicts to the subsequent experimental observation in alkaline ORR conditions. Based on the post-catalysis characterizations, surface state analysis, and an advanced pH-field coupled microkinetic modeling, it is found that the Sb2 WO6 surface will undergo electrochemical passivation under ORR potentials and form a stable and 4e-ORR active surface. The results presented here suggest that though data mining is promising for exploring electrocatalysts, a refined strategy needs to be further developed by considering the electrochemistry-induced surface stability and activity.

In-situ interfacial passivation and self-adaptability synergistically stabilizing all-solid-state lithium metal batteries

The function of solid electrolytes and the composition of solid electrolyte interphase (SEI) are highly significant for inhibiting the growth of Li dendrites. Herein, we report an in-situ interfacial passivation combined with self-adaptability strategy to reinforce Li0.33La0.557TiO3 (LLTO)-based solid-state batteries. Specifically, a functional SEI enriched with LiF/Li3PO4 is formed by in-situ electrochemical conversion, which is greatly beneficial to improving interface compatibility and enhancing ion transport. While the polarized dielectric BaTiO3-polyamic acid (BTO-PAA, BP) film greatly improves the Li-ion transport kinetics and homogenizes the Li deposition. As expected, the resulting electrolyte offers considerable ionic conductivity at room temperature (4.3 × 10−4 S cm−1) and appreciable electrochemical decomposition voltage (5.23 V) after electrochemical passivation. For Li-LiFePO4 batteries, it shows a high specific capacity of 153 mA h g−1 at 0.2 C after 100 cycles and a long-term durability of 115 mA h g−1 at 1.0 C after 800 cycles. Additionally, a stable Li plating/stripping can be achieved for more than 900 h at 0.5 mA cm−2. The stabilization mechanisms are elucidated by ex-situ XRD, ex-situ XPS, and ex-situ FTIR techniques, and the corresponding results reveal that the interfacial passivation combined with polarization effect is an effective strategy for improving the electrochemical performance. The present study provides a deeper insight into the dynamic adjustment of electrode-electrolyte interfacial for solid-state lithium batteries.

Investigating Mechanisms Leading to Enhanced Performance of Carbon-Coated Si Anodes By Chemical Vapor Deposition Method

Prior research on carbon-coated silicon (Si@C) for Si-based lithium-ion batteries have shown improved electrochemical performance upon coating. However, the underlying mechanisms responsible for the enhancement in performance have not been fully explored and are typically attributed to the protective influence of the carbon coating around the Si particles as well as the improved electronic conductivity of the electrode. In this work, we investigate the contribution of coating on the processing of the electrodes as well as on the formed solid electrolyte interphase (SEI). Si@C particles were prepared by chemical vapor deposition (CVD) technique to achieve a homogeneous carbon layer on the Si surface. The influence of coating time as well as processing temperature was investigated. X-ray photoelectron spectroscopy (XPS), neutron reflectivity (NR) measurements, and transmission electron microscopy (TEM) reveal the coating characteristics such as its extremely thin nature, ~2.5 nm, allowing us to rule out the protective function of carbon coating to prevent Si volume expansion as the governing mechanism for the improved electrochemical behavior. Instead, Raman mapping of the electrodes reveal a uniform distribution of Si and carbon conductive additive, indicating that the coating on the Si particles can facilitate slurry processing which yields to more homogeneous electrodes. Consequently, this leads to the commonly reported improved electronic connections within the electrodes as supported by electrochemical impedance spectroscopy (EIS) data. Furthermore, SEI studies using XPS reveal similar SEI characteristics of the Si electrodes after cycling in half and full cell format. In summary, we assign the improved performance of Si@C on the beneficial effect of carbon coating on the processing of Si electrodes, but not on the electrochemical passivation.

Passivation effects on corrosion and cavitation erosion resistance of UNS S32205 duplex alloy in 3.5% NaCl

ABSTRACT The electrochemical and electronic properties of UNS S32205 duplex alloy passive film were studied with EIS and Mott–Schottky techniques, respectively. The role of Fe and Cr oxides in the passive film formation was checked using XPS. The cavitation behaviour was evaluated using an optical microscope OM. The studies were carried out in a 3.5% NaCl solution saturated with CO2 on various types of passive films: the air-formed (AF), the long-term aged (LTA), and the passivated (P1 and P2). The results showed that the electrochemical passivation treatment at passive region 1 improved the corrosion and cavitation behaviour compared to AF, while the long-term aging process made it worse. Passivation at passive region 2 was harmful and recorded the worst results under corrosion and cavitation erosion conditions. Thus, exposing the equipment made of this alloy to the passivation treatment at special conditions makes it more resistant to corrosion and cavitation erosion.

High-entropy Electrolyte Enables High Reversibility and Long Lifespan for Magnesium Metal Anodes.

The stable cycling of Mg-metal anodes is limited by several problems, including sluggish electrochemical kinetics and passivation at the Mg surface. In this study, we present a high-entropy electrolyte composed of lithium triflate (LiOTf) and trimethyl phosphate (TMP) co-added to magnesium bis(trifluoromethane sulfonyl)imide (Mg(TFSI)2/1,2-dimethoxyethane (DME) to significantly improve the electrochemical performance of Mg-metal anodes. The as-formed high-entropy Mg2+-2DME-OTf--Li+-DME-TMP solvation structure effectively reduced the Mg2+-DME interaction in comparison with that observed in traditional Mg(TFSI)2/DME electrolytes, thereby preventing the formation of insulating components on the Mg-metal anode and promoting its electrochemical kinetics and cycling stability. Comprehensive characterization revealed that the high-entropy solvation structure brought OTf- and TMP to the surface of the Mg-metal anode and promoted the formation of a Mg3(PO4)2-rich interfacial layer, which is beneficial for enhancing Mg2+ conductivity. Consequently, the Mg-metal anode achieved excellent reversibility with a high Coulombic efficiency of 98% and low voltage hysteresis. This study provides new insights into the design of electrolytes for Mg-metal batteries.

High‐entropy Electrolyte Enables High Reversibility and Long Lifespan for Magnesium Metal Anodes

AbstractThe stable cycling of Mg‐metal anodes is limited by several problems, including sluggish electrochemical kinetics and passivation at the Mg surface. In this study, we present a high‐entropy electrolyte composed of lithium triflate (LiOTf) and trimethyl phosphate (TMP) co‐added to magnesium bis(trifluoromethane sulfonyl)imide (Mg(TFSI)2/1,2‐dimethoxyethane (DME) to significantly improve the electrochemical performance of Mg‐metal anodes. The as‐formed high‐entropy Mg2+‐2DME‐OTf−‐Li+‐DME‐TMP solvation structure effectively reduced the Mg2+‐DME interaction in comparison with that observed in traditional Mg(TFSI)2/DME electrolytes, thereby preventing the formation of insulating components on the Mg‐metal anode and promoting its electrochemical kinetics and cycling stability. Comprehensive characterization revealed that the high‐entropy solvation structure brought OTf− and TMP to the surface of the Mg‐metal anode and promoted the formation of a Mg3(PO4)2‐rich interfacial layer, which is beneficial for enhancing Mg2+ conductivity. Consequently, the Mg‐metal anode achieved excellent reversibility with a high Coulombic efficiency of 98 % and low voltage hysteresis. This study provides new insights into the design of electrolytes for Mg‐metal batteries.

A novel strategy for fabrication, activation and cleaning of fully 3D printed flexible planar electrochemical platforms

AbstractIn recent years, 3D printing of carbon‐based conductive filaments has received growing attention for assembling electrodes to be used in a wide variety of electroanalytical devices and applications. Despite the large amount of work present in literature concerning the development of three‐dimensional (3D) conductive structures, its potential as dry deposition method for assembling two‐dimensional (2D) electrodes to be used in planar configuration is still largely unexplored. In fact, the possibility to rapidly change the geometry of the electrochemical circuits, associated with the reduction of waste and the absence of solvents, which are instead important components of ink and paste formulations, makes this strategy a valid green and efficient alternative to other deposition approaches such as screen‐printing technology. We report here a rapid and solvent‐free method for assembling fully 3D printed flexible planar electroanalytical platforms (3DEPs) to be used with microliters of liquid. At the same time, a novel protocol for the surface pre‐treatment of 3D printed electrodes based on ultrasonication in aqueous NaOH solution followed by electrochemical activation using the same medium, is presented. In addition, the same procedure has proved to be efficient for cleaning the electrode surface after electrochemical passivation, thus confirming the validity of both time‐efficient and environmentally‐friendly assembling and activation/cleaning procedures developed which allow efficient and reusable electrodes to be produced. Finally, 3DEPs were tested by a proof‐of‐concept quantification of a commonly used food dye (Brilliant Blue, E‐133) in commercial solutions used for homemade food coloring.

Effect of rare–earth (Ce, La) compounds on the microstructure, mechanical and electrochemical corrosion characteristics of electroplated Ni films

For optimizing the microstructure and performance of Ni–electroplating film, the soluble rare–Earth (RE) compounds CeCl3 or LaCl3 were introduced, which were electrodeposited on Cu substrate by direct current (DC) and pulse current (PC) methods, respectively. The surface characteristics of morphology, composition, and phase of obtained different deposits were investigated, and the relationship between the structure and the performance of internal stress, hardness, and electrochemical responses was discussed. The results show that both RE compounds were conducive to eliminating the surface pits by inhibiting the hydrogen evolution reaction, while did not co–deposit into the Ni film. Moreover, the preferred orientation of Ni (111) crystalline plane was altered into Ni (200) by LaCl3, and its combination with PC–electrodeposition further had a better grain refinement effect than CeCl3. Due to the formation of a relatively dense and fine deposit, the PC–electrodeposited Ni/LaCl3 film exhibited the highest hardness of 320 HV, lowest tensile stress of 55 MPa, and best electrochemical passivation protection, which effectively improved the comprehensive performance of Ni film and demonstrated a good prospect for industrial applications.

Boron-Doped Activated Carbon Supports for Cobalt-Catalyzed Oxygen Evolution in Alkaline Electrolyte.

Activated carbons (ACs) are the most widely used and attractive support materials for electrocatalytic applications because of their significant surface areas, high electrical conductivities, and moderate affinities toward supported metal catalysts. However, the corrosive behavior of ACs at oxidative potentials causes an inevitable reduction in the active surface area of supported catalysts, resulting in the continuous deterioration of their electrocatalytic performance. Therefore, the introduction of corrosion-resistant durable catalyst supports is essential for sustainable and efficient electrocatalysis. Here, we modified ACs to obtain different boron (B)-doped structures via doping-temperature controls to investigate the corrosion resistance of B-doped ACs. With increasing doping temperature, the B-doped ACs exhibited a decreased defect density and enhanced crystallinity owing to the accelerating dopant-induced graphitization. We found that the substitution of B atoms into the carbon lattice improved the structural integrity of the carbon structure, and cyclic voltammetry (CV) tests suggested that the highly B-substituted structures caused electrochemical surface passivation against carbon corrosion. Moreover, B-doped ACs significantly contributed to the increase in loading mass of cobalt (Co)-based catalyst on them and the electrochemical durability toward the oxygen evolution reaction as catalyst-support hybrid. The B22 (B-doped AC obtained at a 2200 °C B-doping temperature)-supported Co catalyst with the lowest oxidation current exhibited a voltage change of 32 mV at a current density of 10 mA/cm2 (ΔEj=10) after 10,000 cycles, which was a factor of ∼7 higher cycle durability and stability than that of the conventional IrO2 catalyst (ΔEj=10 = 205 mV). Here, we propose that surface engineering by B-doping to improve the structural integrity of ACs is an attractive method for designing durable electrocatalytic support materials.