Electrochemical Mechanism Research Articles

Synergistic structural engineering of 3D printed matchable electrodes for long-life rechargeable nickel–bismuth batteries

Aqueous rechargeable alkaline batteries have attracted increasing attention due to their reliable safety, low cost and high electrochemical potential. However, it remains challenging to construct remarkable rechargeable batteries with desirable electrode architectures and optimized electrochemical mechanisms. Herein, 3D printed high-loading bismuth-based anodes with synergistic enhancement of three-dimensional interconnection network structure and oxygen vacancies is achieved, for which intrinsic battery charge storage mechanism is in-depth unveiled. The synergistic structural engineering significantly enhances the overall charge carrier transport of 3D printed nickel-bismuth batteries, as evidenced by the conductivity of a single-wired electrode, enabling nickel-bismuth batteries to achieve a high areal capacity of 0.17 mA h cm−2 at 6 mA cm−2, a high energy density of 97.92 μWh cm−2 and a power density of 6.41 mW cm−2. Moreover, superior cycling stability is obtained. Ex situ characterization results reveal that Bi2O2.33 undergoes a phase transition after the initial charge and discharge, while the subsequent cycles rely on the reversible phase transition mechanism between Bi and Bi2O3 for basic charge storage. The exceptional performance and revealed mechanism of 3D printed batteries offer novel ideas and understanding for constructing future rechargeable nickel-bismuth batteries with state-of-the-art behaviors.

Development of V2O3 Nanostructures for Alkali Metal Ion Batteries: A Novel Approach through Mild Metal Vapor Reduction and Interface Engineering.

V2O3 has been extensively researched as a battery electrode material due to its ample reserves and high theoretical capacity. However, the synthesis of valence-sensitive V2O3 presents technical challenges as it requires a strict combination of high-temperature treatment and a narrow range of oxygen partial pressures. This study proposes a gentle Li vapor-assisted thermal reduction method to synthesize pure-phase V2O3 at a relatively low temperature of 480 °C without any hazardous gases. It has been discovered that reducing the temperature also improves the specific surface area of the nanoto-mesoscale hierarchical structures and enhances the reactive sites between their secondary grains. These advantages enable the V2O3 micronano particles to store higher levels of Li+, Na+, and K+, increase ionic transport, and tolerate volume expansion. It demonstrates a significant capacity of 767 mA h g-1 in lithium-ion batteries, 393 mA h g-1 in sodium-ion batteries, and 209 mA h g-1 in potassium-ion batteries. It has also been discovered that the crystal structure of V2O3 is easily adjustable by varying the synthesis temperature, which significantly affects the electrochemical storage mechanism. The V2O3 synthesized at 480 °C with low crystallinity exhibits a notable intercalation reaction, facilitating the electrochemical kinetics of reversible insertion/extraction of Li+, Na+, and K+. In contrast, the highly crystalline sample synthesized at 580 °C displays pseudocapacitance behavior instead of an intercalation reaction. The highly crystalline sample synthesized at 680 °C exhibits a thorough pseudocapacitance reaction possessing the capacitive functionality for the electrochemical storage of Na+ or K+ with larger ion radii. This study describes a new synthesis strategy and rational modification of vanadium-based electrodes for alkali metal ion batteries, leading to the development of reasonably priced rechargeable battery systems with applications extending beyond lithium-ion batteries.

Electrochemical corrosion and product formation mechanism of M42 high-speed steel in NaH2PO4-Na2SO4 passivating electrolyte

High-speed steel (HSS) rolls operate in harsh conditions, making them vulnerable to surface degradation. Material removal technology for repairing defective HSS roll surfaces is the most effective way to maintain their integrity and reduce production costs. Electrochemical corrosion machining, with its excellent machining capabilities, offers a promising method for repairing HSS roll surfaces. However, the outer working layer of these rolls is made of premium HSS containing passivating metallic elements, complicating its corrosion behavior, particularly in passivating electrolytes. To elucidate the corrosion behavior and uncover the underlying mechanisms of corrosion and product formation of HSS during electrochemical corrosion machining, this study investigates the electrochemical corrosion process and behavior of M42 HSS used in rolls within a NaH2PO4-Na2SO4 passivating electrolyte. Metallographic etching experiments indicated that M42 HSS comprises a tempered martensitic matrix along with M2C and M6C eutectic carbides. Characteristics of oxidative reactions for M42 HSS in the electrolyte were observed in cyclic voltammetry. By conducting anodic polarization tests, along with thermodynamic analysis and characterization techniques, the entire electrode system was thoroughly examined, including corrosion phenomena, varying processes, and underlying mechanisms of corrosion and product formation. Notably, this study is the first to construct a Pourbaix diagram for the M42 HSS-H2PO4−-SO42−–H2O system. The thermodynamic analysis revealed that the applied potential variation significantly influences corrosion behavior of M42 HSS, confirming by the characterization results. The adsorption phenomenon on the cathodic surface requires a higher potential (such as 6 V) to occur. Electrochemical reactions primarily occur on the anodic surface, while the cathodic surface (or in the electrolyte) mainly engages in chemical reactions with no electronic participation. Furthermore, the electrochemical corrosion process of HSS is driven by one or more corrosion mechanisms, such as galvanic corrosion, pitting, or intergranular corrosion. Therefore, these findings from this study contribute to the development of repairing HSS roll surfaces based on electrochemical corrosion machining in future engineering applications.

Atomic-scale insights into the electrochemical mechanisms of aluminum-sulfur batteries: A first-principles study of Al-S clusters on graphene

Aluminum-sulfur (Al-S) batteries, known for their high energy density, cost-effectiveness, and sustainability, face challenges due to limited understanding of their atomic-level electrochemical mechanisms. This study uses first-principles calculations to explore the geometric and electronic structures of Al-S clusters and their interaction with graphene substrates. Key findings include charge transfer from graphene to Al-S clusters, especially in C@Al2S6 and C@Al2S3, and moderate adsorption strength crucial for reversible cycling. Thermodynamic analysis identifies the free energy change in the transition from C@Al2S6 to C@Al2S3, while AIMD simulations confirm structural stability, providing insights for optimizing Al-S battery performance.

Study on electrochemical polishing mechanism of TC4 titanium alloy

To achieve a high-quality and precise surface on TC4 titanium alloy for demanding engineering applications, electrochemical polishing (ECP) technology was employed to investigate the polishing process of TC4 titanium alloy in an ethylene glycol-sodium chloride green electrolyte. The macro and micro morphology, surface roughness, material removal rate, surface elements, surface corrosion resistance, and surface hardness of TC4 titanium alloy were measured before and after polishing. Single-factor experiments were conducted to explore the effects of processing gap, electrolyte temperature, polishing voltage, and polishing time on TC4 titanium alloy surface quality. Optimal polishing parameters were determined to be an electrode gap of 12 mm, a voltage of 20 V, a temperature of 40 °C, and a polishing time of 10 min. The experimental results indicated that after electrochemical polishing, the workpiece surface roughness Ra decreased from 256 nm to 25 nm, achieving a roughness reduction rate of 90.23%, the material removal rate was 3.348 μm min−1. The self-corrosion potential of the polished surface increased from −0.416 V to −0.375 V and the self-corrosion current density decreased from 4.447 × 10−7 A·cm−2 to 1.873 × 10−7 A·cm−2, the surface indentation hardness of the workpiece decreased from 5.8669 GPa to 4.6726 GPa. Based on the characterization of polished surface, the mechanism of electrochemical polishing of TC4 titanium alloy was proposed. The results demonstrate that electrochemical polishing of TC4 titanium alloy is highly efficient, involves no mechanical action, and causes no subsurface damage, making it a promising technology to meet medical requirements.

A room-temperature liquid eutectic GaSn anode with regulated wettability for lithium ion batteries

The alloy-type anodes in lithium ion batteries (LIBs) often suffer from the pulverization/failure of active materials caused by the drastic volume variations during cycling. Liquid Ga-based materials with low melting points and intrinsic self-healing feature are one of the best candidates for enhancing the Li storage property. Herein, a liquid eutectic GaSn (EGaSn) electrode was fabricated based upon a simple painting method and directly used as the anode for LIBs at room temperature. Furthermore, the wettability of liquid EGaSn alloy on the current collector in the Ar atmosphere was greatly improved through the construction of Ag3Ga modified layer on the stainless steel mesh (ssm) surface. And the Ag3Ga-EGaSn anode displays the much better Li storage performance (specific capacity, rate performance and cycling stability) than the untreated EGaSn anode. More importantly, operando XRD measurement clearly clarified the electrochemical reaction mechanism of Ag3Ga-EGaSn in LIBs. This work indicates a potential strategy to directly use liquid Ga-based electrode with regulated wettability for LIBs.

Enhancement of Synaptic Performance through Synergistic Indium Tungsten Oxide-Based Electric-Double-Layer and Electrochemical Doping Mechanisms

This study investigated the potential of indium tungsten oxide (IWO) channel-based inorganic electrolyte transistors as synaptic devices. We comparatively analyzed the electrical characteristics of indium gallium zinc oxide (IGZO) and IWO channels using phosphosilicate glass (PSG)-based electrolyte transistors, focusing on the effects of electric-double-layer (EDL) and electrochemical doping. The results showed the superior current retention characteristics of the IWO channel compared to the IGZO channel. To validate these findings, we compared the DC bias characteristics of SiO2-based field-effect transistors (FETs) with IGZO and IWO channels. Furthermore, by examining the transfer curve characteristics under various gate voltage (VG) sweep ranges for PSG transistors based on IGZO and IWO channels, we confirmed the reliability of the proposed mechanisms. Our results demonstrated the superior short-term plasticity of the IWO channel at VG = 1 V due to EDL operation, as confirmed by excitatory post-synaptic current measurements under pre-synaptic conditions. Additionally, we observed superior long-term plasticity at VG ≥ 2 V due to proton doping. Finally, the IWO channel-based FETs achieved a 92% recognition rate in pattern recognition simulations at VG = 4 V. IWO channel-based inorganic electrolyte transistors, therefore, have remarkable applicability in neuromorphic devices.

A Study on the Problem of AC Corrosion of Power Umbilical Cables Caused by Electromagnetic Induction Phenomena

During the normal laying and operation of a three-core umbilical cable, AC current can easily lead to AC electrochemical corrosion on the outer surface of the steel tube. To explore the electrochemical corrosion mechanism and the factors affecting the three-core umbilical cable, this paper optimizes the internal induced potential calculation method for three-core umbilical cables. It analyzes the changes in the characteristics of the induced potential and explores the variations in the density of induced current under different conditions. The research results show that by optimizing the calculation method for the induction potential of the umbilical cable’s steel pipe, for the electromagnetic significance of the smallest repeating unit, the induction potential on the steel pipe’s surface exhibited a cyclic change. The peak part of the induction potential is most likely to experience electrochemical corrosion. Additionally, reducing the radius of the outer insulation aperture of the steel pipe and improving the conductivity of seawater will increase the density of the induced current in the insulation aperture, thereby increasing the risk of electrochemical corrosion. As the cable pitch and AC frequency increase, the current density in the steel pipe pores will also rise.

Transition metal catalysts coordinated with electrochemistry for preparation of graphene

It is still crucial to produce mass high-quality graphene through simple and low-cost methods for its wide applications. Herein, a simple and fast method by combining inexpensive transition metal catalysts with electrochemistry to exfoliate natural flake graphite is reported. The electrode is prepared in a sandwich structure, where the titanium mesh will enwrap the nickel net coated with graphite powder. This method can quickly achieve the large-scale preparation of graphene within 15 min. The quality of graphene with large lateral size and few layers has been characterized by XRD, SEM, TEM, Raman, and AFM. The possible electrochemical exfoliation mechanism has been proposed. Oxygen evolution reaction occurs at the anode due to the transition metal catalysts, and hydrogen ions (H+) are generated along with oxygen, H+ and SO42− ions will form a local strong acid. The formation of strong acidic H2SO4 in-situ around electrode will oxidize the edge of the graphite, allowing the intercalation of SO42−, H2O, SO2 and O2 into the graphite sheets, which will inflate the graphite and exfoliate of graphite into graphene. This strategy is reliable, environmentally friendly, and suitable for industrial production.

Mass Transfer Limitation within Molecular Crowding Electrolyte Reorienting (100) and (101) Texture for Dendrite‐Free Zinc Metal Batteries

AbstractAqueous zinc metal batteries are emerging as a promising alternative for energy storage due to their high safety and low cost. However, their development is hindered by the formation of Zn dendrites and side reactions. Herein, a macromolecular crowding electrolyte (MCE40) is prepared by incorporating polyvinylpyrrolidone (PVP) into the aqueous solutions, exhibiting an enlarged electrochemical stability window and anti‐freezing properties. Notably, through electrochemical measurements and characterizations, it is discovered that the mass transfer limitation near the electrode surface within the MCE40 electrolyte inhibits the (002) facets. This leads to the crystallographic reorientation of Zn deposition to expose the (100) and (101) textures, which undergo a “nucleation‐merge‐growth” process to form a uniform and compact Zn deposition. Consequently, the MCE40 enables highly reversible and stable Zn plating/stripping in Zn/Cu half cells over 600 cycles and in Zn/Zn symmetric cells for over 3000 hours at 1.0 mA cm−2. Furthermore, Na0.33V2O5/Zn and α‐MnO2/Zn full cells display promising capacity and sustained stability over 500 cycles at room and sub‐zero temperatures. This study highlights a novel electrochemical mechanism for achieving preferential Zn deposition, introducing a unique strategy for fabricating dendrite‐free zinc metal batteries.

Mass Transfer Limitation within Molecular Crowding Electrolyte Reorienting (100) and (101) Texture for Dendrite-Free Zinc Metal Batteries.

Aqueous zinc metal batteries are emerging as a promising alternative for energy storage due to their high safety and low cost. However, their development is hindered by the formation of Zn dendrites and side reactions. Herein, a macromolecular crowding electrolyte (MCE40) is prepared by incorporating polyvinylpyrrolidone (PVP) into the aqueous solutions, exhibiting an enlarged electrochemical stability window and anti-freezing properties. Notably, through electrochemical measurements and characterizations, it is discovered that the mass transfer limitation near the electrode surface within the MCE40 electrolyte inhibits the (002) facets. This leads to the crystallographic reorientation of Zn deposition to expose the (100) and (101) textures, which undergo a "nucleation-merge-growth" process to form a uniform and compact Zn deposition. Consequently, the MCE40 enables highly reversible and stable Zn plating/stripping in Zn/Cu half cells over 600 cycles and in Zn/Zn symmetric cells for over 3000 hours at 1.0 mA cm-2. Furthermore, Na0.33V2O5/Zn and α-MnO2/Zn full cells display promising capacity and sustained stability over 500 cycles at room and sub-zero temperatures. This study highlights a novel electrochemical mechanism for achieving preferential Zn deposition, introducing a unique strategy for fabricating dendrite-free zinc metal batteries.

Accelerated microbiologically influenced corrosion of copper by sulfate‐reducing bacterium Desulfovibrio desulfovibrio

AbstractThe corrosion behavior and electrochemical damage mechanisms induced by sulfate‐reducing bacteria (SRB) on copper (Cu) were investigated in this study. Electrochemical impedance spectroscopy revealed that SRB accelerated the corrosion of Cu, albeit with a mitigating effect observed due to the formation of a protective and dense biofilm. However, upon the rupture of this protective film, the corrosion tendency of Cu significantly increased. Surface analysis corroborated these findings, with the predominant corrosion product identified as Cu2S, a result further supported by thermodynamic calculations. The accelerated corrosion of Cu was primarily attributed to the physiological metabolism of SRB, which generates hydrogen sulfide as the principal agent driving corrosion processes.

Learning Model Based on Electrochemical Metallization Memristor with Cluster Residual Effect

Although a memristor model, subjected to electrochemical metallization mechanism, has been proposed based on the spontaneous decay of clusters in the previous work, it does not agree with the human forgetting accurately. Therefore, an improved model is meaningfully presented for the memristor with the cluster spontaneous decay by adding the residual effect. The former is due to the inward contraction of atoms driven by surface energy, while the latter is because of the balance of attractive and repulsive forces between atoms. The model fits well with the actual device. The forgetting is caused by the spontaneous decay. Memory retention is generated due to the added effect, which is also the internal cause of good agreement with the actual forgetting. Additionally, short‐term plasticity is converted to long‐term plasticity through the repeated learning. The efficiency of experiential learning using this model is much higher than that using the previous. It is shown that the physical mechanism of spontaneous decay in the cluster‐based channel is different from that in vacancy‐based or atom‐based channel. The model working under a non‐ideal condition with the temperature influence is discussed. Potential applications based on the model are stated.

A surface and corrosion characterisation of micro arc oxidation treated friction stir welded ZM21 and ZE41 magnesium alloy: a comparison study

Magnesium alloys have gained attention as promising materials in industrial applications, for their high specific strength and low density. Magnesium alloys have desirable mechanical properties, but their poor corrosion resistance prevents their safe implementation. Alloys such as ZM21 and ZE41, possess unique properties that provide improved machinability and increased red-hot strength, respectively, while remaining prone to corrosion. To improve corrosion resistance, surface treatments and coating processes are employed. Comparing the corrosion characteristics of ZM21 and ZE41 is vital for aerospace and automotive applications, directly affecting component durability, reliability, and performance against corrosion. Magnesium alloys are frequently joined through friction stir welding (FSW), hence, similar importance is provided to studying the corrosion performance of welds, since FSW introduces microstructural changes that alter corrosion performance of welded joints. The paper discusses electrochemical corrosion mechanisms and analyzes the effect of Micro Arc Oxidation (MAO) coating on electrode potential, passivity, and electrical resistance of ZM21 and ZE41 plates welded through FSW. MAO treatments were performed on both base material and FSW joints. The corrosion performance of MAO-coated FSWed ZM21 and ZE41 alloys was compared through the Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarisation (PDP) tests. The PDP test revealed that MAO treatment enhanced the corrosion resistance of both base and FSWed ZM21 and ZE41 magnesium alloys. There was an improvement in potential polarization (Rp) values from 565 Ω cm2 to 11245 Ω cm2 for ZM21 and from 1184.4 Ω cm2 to 11435.69 Ω cm2 for ZE41 alloys. While exhibiting improvements in corrosion resistance, MAO-treated ZE41 performed better than MAO-treated ZM21. PDP results were verified through confirmatory EIS results. Therefore, MAO treatments are effective methods to improve the corrosion performance of Mg alloys. Evaluation of MAO coating performance on various FSW Mg alloys and studying their corrosion performance is crucial for engineering material selection.

A highly stable insertion type V1-xTixP solid solution as an anode material for high-rate lithium-ion batteries

As electric vehicles (EVs) grow in popularity, the demand for lithium-ion batteries (LIBs) simultaneously grows, and the fast-charging capability is becoming increasingly important. However, it is generally believed that graphite anode still suffers from a poor rate capability for fast-charging applications, and other insertion-type oxide anodes with a high rate capability exhibit too high Li+-ion insertion/extraction potential, which cannot meet a requirement for high energy density anodes. In this work, the hexagonal structure of V1-xTixP (x = 0.0, 0.25, and 1.0) phases were introduced as insertion-type anode materials for LIBs with a low reaction potential of Li+-ion insertion/extraction. The crystal structure and the corresponding electrochemical reaction mechanism of insertion-type anodes of TiP, VP, and MoP were compared. A facile strategy forming a substitutional solid solution is suggested to improve the electrochemical properties of anode materials by combining the end members among insertion-type VP, TiP, and MoP as forming V1-xTixP and V1-xMoxP compounds. V1-xTixP (x = 0.25) electrode, substituting V atoms with Ti atoms in VP structure, shows excellent long-term cycle stability at 1 A/g with a cycle retention of 87.7 % during 2500 cycles, delivering a two times higher capacity of 211.1 mAh g−1 compared to that of the commercial graphite electrode.

A numerical analysis of the mechano-electrochemical effects on localised corrosion in pipelines using a multi-physical field coupling approach

In this study, we used a multi-physics coupling approach integrating the electrochemical and solid mechanics fields to develop a three-dimensional finite element model. This model was specifically designed to investigate the effects of mechano-electrochemical (M-E) effects on pipeline corrosion. The boundary conditions for the finite element simulation were established using experimental data, enabling the model to effectively predict the corrosion potential and current density, which aligned well with the experimental findings. Subsequently, the validated model was applied to examine the M-E effects near the pipe corrosion defects, considering various depths of corrosion defects and axial strain. Our results indicate that the stress concentration at the core of the defect increases with increasing axial tensile strain and deepening corrosion. The investigation of the correlation between the corrosion potential and net current density revealed that mechanical forces significantly impact metal corrosion rates, thus influencing pipeline longevity. When the metal structure of the pipeline is deformed within the elastic deformation range, the impact of the M-E effects on corrosion is minimal. However, when a tensile strain is applied or the defect geometry induces plastic deformation at the defect site, a notable increase in the local corrosion activity is observed.

Glycosylated flavonoid kaempferitrin: Electroanalytical detection and the proposal of an oxidation mechanism supported by quantum chemical calculations

In this work, the electrochemical behavior of the glycosylated flavonoid kaempferitrin was studied, and an electroanalytical methodology was developed for its determination in infusions of Bauhinia forficata using a boron-doped diamond electrode (BDD). The electrochemical behavior of the flavonoid was studied by cyclic voltammetry, and two irreversible oxidation peaks at 0.80 and 1.0 V vs Ag/AgCl were observed. The influence of the pH on the voltammograms was examined, and higher sensitivity was found at pH 7.0. The electrochemical process corresponding to peak 1 at 0.80 V is predominantly diffusion-controlled, as the study shows at varying scan rates. An analytical plot was obtained by square wave voltammetry at optimized experimental conditions (frequency = 100 s−1, amplitude = 90 mV, and step potential = 8 mV) in the concentration range from 3.4 μmol L−1 to 58 μmol L−1, with a linearity of 0.99. The limit of detection and limit of quantification values were 1.0 μmol L−1 and 3.4 μmol L−1, respectively. Three samples of Bauhinia forficata infusions (2 g of sample in 100 mL of water) were analyzed, and the KF values found were 5.0 × 10−4 mol L−1, 3.0 × 10−4 mol L−1, and 7.0 × 10−4 mol L−1, with recovery percentages of 98 %, 106 % and 94 %, respectively. Finally, experiments were performed with two other flavonoids (chrysin and apeginin) to compare and propose an electrochemical oxidation mechanism for kaempferitrin, which was supported by quantum chemical calculations.

Optimized Phase and Crystallinity of Cr2(NCN)3 Dominating Electrochemical Lithium Storage Performance.

Cr2(NCN)3 is a potentially high-capacity and fast-charge Li-ion anode owing to its abundant and broad tunnels. However, high intrinsic chemical instability severely restricts its capacity output and electrochemical reversibility. Herein we report an effective crystalline engineering method for optimizing its phase and crystallinity. Systematic studies reveal the relevancy between electrochemical performance and crystalline structure; an optimal Cr2(NCN)3 with high phase purity and uniform crystallinity exhibits a high reversible capacity of 590 mAh g-1 and a stable cycling performance of 478 mAh g-1 after 500 cycles. In-operando heating XRD reveals its high thermodynamical stability over 600 °C, and in-operando electrochemical XRD proves its electrochemical Li storage mechanism, consisting of the primary Li-ion intercalation and subsequent conversion reactions. This study introduces a facile and low-cost method for fabricating high-purity Cr2(NCN)3, and it also confirms that the Li storage of Cr2(NCN)3 can be further improved by tuning its phase and crystallinity.

Electrochemical Oxidation Mechanism of Pyrite in a Copper(II)-Citrate-Sodium Thiosulfate Composite System

Pyrite is an important gold carrier during gold leaching, but it is readily oxidized, which causes environmental problems such as acidic mine drainage. Thus, it is necessary to study the oxidation mechanism of pyrite in a gold-leaching electrolyte. The surface oxidation reaction of pyrite is a multi-electron transfer electrochemical oxidation process. Based on this, electrochemical technology was used to explore the electrochemical oxidation mechanism of pyrite in a Cu2+-Cit3−-S2O3 2− system. The surface oxidation products of the pyrite were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The experiments showed that the thiosulfate concentration did not change the oxidation mechanism of pyrite at 0.30 V under the conditions of this experiment. Increasing the concentration and potential of thiosulfate accelerated the oxidation rate of pyrite. The electrochemical oxidation of pyrite in the Cu2+-Cit3−-S2O3 2− system occurred in two stages. At low potentials in a passivated state, the process was diffusion-controlled, and the surface oxidation rate was slow. When the potential exceeded 0.50 V, the passivation film on the surface was penetrated, allowing the oxidation reaction on the surface of pyrite to continue. The results of this experiment are useful for deepening the understanding of the oxidation mechanism of pyrite in electrolytes.

Electrochemical Preparation of Ti2CrV Alloy in CaCl2 Melt

Ti2CrV alloy shows good hydrogen storage characteristics at room temperature and ambient pressure. The present study investigated the feasibility of direct electrochemical reduction of TiO2-Cr2O3-V3O5 to Ti2CrV in CaCl2 melt at 900 °C by the FFC Cambridge process. The electrolysis was conducted in a two-electrode assembly with the sintered mixed oxide cathode and HD graphite anode at a constant cell voltage of 3.1 V for different time intervals to elucidate the reduction mechanism of the metal oxide mixture. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques. Cyclic voltammetry studies using metallic cavity electrode containing mixed metal oxide powder were also carried out to determine the electrochemical reduction behavior in CaCl2 melt at 900 °C. It was observed that the presence of pre-formed Cr and V metal in the vicinity of titanium oxide helped in its faster reduction. The complete metallization of the sintered mixed oxide pellet occurred after 15 h of electrolysis. The electrochemical reduction mechanism was observed to proceed through various intermediates such as chromium-rich Cr-V, vanadium-rich V-Cr, CaTiO3, TiO, Ti6O, Ti-V, and C15-TiCr2.