Anodic Deposition Research Articles

Investigation of Low-Temperature Tribological Behavior of Multilayer a-C:H Coatings Deposited on 5A06 Aluminum Alloy

Abstract In this article, a multilayer gradient coating of Cr/CrN/CrNC/CrC/a-C:H was successfully fabricated on the surface of 5A06 aluminum alloy through the application of anodic layer ion beam deposition and medium-frequency pulse magnetron sputtering techniques. The tribological behavior of the coatings was investigated by means of dry reciprocating sliding tests, conducted at temperatures ranging from −100 °C to 25 °C in both air and oxygen atmospheres. The microstructure, mechanical properties, and wear characteristics were analyzed using scanning electron microscopy (SEM), X-ray energy dispersive spectrometer (EDS), Raman spectroscopy, and indentation testing. The research findings indicate that the tribological performance in ambient air is primarily influenced by the synergistic effects of transfer layer formation and surface graphitization. In oxygen environments, poor initial tribological performance at 25 °C and 0 °C was due to tribochemical reactions that disrupted the passivated C–H bonds. Low temperatures hindered the formation of friction interface transfer layers, graphitization, and chemical reactions at the interface. Nevertheless, the coating demonstrates satisfactory lubricating performance due to the presence of a considerable quantity of sp2-hybridized carbon atoms within the coating itself. In both atmospheres at low temperatures (−50 °C and −100 °C), the steady-state friction coefficient remains below 0.3, and the wear rate is less than 1 × 10−6 mm3/N m. Furthermore, the primary cause of abrasive wear is the residual hard oxide formed by the abrasives on the 0Cr18Ni9 stainless steel used as the mating material for the coating.

Simulation and experimental study on anodic electrochemical deposition of gold

Simulation and experimental study on anodic electrochemical deposition of gold

Molecular Structure Regulation Elicits Steric Hindrance of Ketone Additives with High Adsorbability for Oriented Deposition of Zn Anode.

The uncontrollable dendritic growth and interfacial parasitic reactions severely hinder the large-scale operation of aqueous zinc-ion batteries (AZIBs), root in the fundamental kinetics imbalance between the excessively rapid electrochemical reduction rate and retarded bulk mass transfer. To resolve this dilemma, a rationally structure-designed ketone additive, butane-2,3-dione (BD), was screened from a series of counterparts to achieve highly reversible Zn plating/stripping by moderating electroreduction kinetics. Specifically, the BD molecule preferentially adsorbs in the inner Helmholtz plane to repel solvated Zn-ions via the steric-hindrance effect. The modulated electroreduction kinetics alters zinc deposition behavior, guiding directional Zn (002) texture. Moreover, the constructed H2O-poor electric double layer mitigates parasitic reactions. Notably, the rebalancing of interfacial consumption rate and ion diffusion rate endows Zn anode with superb reversibility (average 99.7% during 1825 cycles) and great cycling durability (2827 h at 1 mA cm-2 and 1276 h at 5 mA cm-2). The outstanding electrochemical performance of Zn anode under harsh conditions (423 h, 50 mA cm-2 and 50 mAh cm-2, 76% depth of discharge) and assembled full cells coupled with multifarious cathodes (Zn//δ-MnO2 and Zn//NaV3O8·1.5H2O) further highlights the versatility of the steric-hindrance additive in AZIBs.

Positively Charged Quasi-Metal-Organic Framework to Reconstruct an Electric Double Layer for a Durable Zn Metal Anode.

To reveal the construction principle of an electric double layer (EDL) on a Zn anode, a positively charged artificial solid electrolyte interphase (SEI) is established by a quasi-metal-organic framework with open metal sites (OMSs). As illustrated by theoretical calculation and in situ Raman and Fourier transform infrared spectroscopy characterization, the OMSs are introduced successfully and unsaturated Ce sites bond with SO42- anions as transfer sites for Zn2+, leading to a homogeneous ion distribution within the inner Helmholtz plane (IHP). Therefore, the distribution of Zn2+-H2O-SO42- in the EDL has been adjusted due to the regulating effect by a SEI. Besides, the regulated EDL reduces the concentration of SO42- and free H2O in the IHP, thus promoting uniform Zn2+ deposition and anticorrosion properties of the Zn anode. As a result, the Q-Ce-808@Zn anode demonstrates exceptional cycling stability over 4200 h (1 mA cm-2) and 1300 h (20 mA cm-2).

Bimetallic AuPd alloy nanoparticles on TiO2 nanotube arrays: a highly efficient photocatalyst for hydrogen generation

Decoration of TiO2nanotube (TNT) arrays by AuPd nanoparticles (NPs) produces a dramatic enhancement in the rate of hydrogen generation through photocatalytic water-splitting under solar illumination. XRD and TEM confirmed alloy formation in bimetallic AuPd NPs while XPS ruled out a core-shell architecture in the AuPd NPs. Well-dispersed, size-controlled AuPd NPs were formed by sequential physical vapor deposition of Au and Pd on TNTs followed by spontaneous thermal dewetting (TNT-AuPd). TNT-AuPd samples were characterized by small tensile microstrains. For comparison purposes and to derive physical insights, an identical method was used to form TNT-Au and TNT-Pd samples wherein TNTs were decorated by monometallic Au and Pd NPs respectively. In every case, an accumulation-type heterointerface between TiO2and the metallic/bimetallic NPs was indicated by binding energy shifts in the Ti2p high-resolution x-ray photoelectron spectra (HR-XPS). Initial and final state effects in the Au4f HR-XPS pointed to a large number of Au atoms in low coordinate sites such as edges, kinks and corners as well as a slower excited atom relaxation in the alloy. A similar preponderance of Pd atoms at low coordinate sites was found along with the presence of a small amount of palladium oxide. The alloying of Au with a low Pd content on TNT yields significant enhancement in hydrogen production under UV-visible light in aqueous triethanolamine solutions. TNT-AuPd demonstrated the highest photocatalytic H2production rate of 2920µmol g-1h-1, which is 8.9 times higher than that of TNTs, 2.1 times that of TNT-Au, and 1.69 times that of TNT-Pd under solar illumination. We studied H2generation under UV-filtered solar illumination with TNT-AuPd outperforming monometallic Au- and Pd-NP decorated TNTs, which is attributed to the enhancement of the catalytic activity of Pd in an Au environment, the presence of Pd and Au atoms at low coordinate sites, and photoinduced electron transfer between TNTs and AuPd alloy NPs, where AuPd acts as an efficient electron sink, in turn reducing carrier recombination losses. AuPd bimetallic nanoparticles on TNTs, prepared via a simple anodization and vapor deposition method, exhibit excellent stability across multiple cycles and offer valuable insights for the development of efficient photocatalysts with promising potential for emerging energy applications.

Multifunctional COF Colloid Regulates Anion Coordination in Solid Poly(Ionic Liquid)-Based Electrolyte for Lithium Metal Batteries.

The development of solid polymer electrolytes (SPEs) has been significantly impeded by two primary challenges: low ionic conductivity and the inhomogeneous deposition of lithium metal anode. Overcoming these limitations needs to reduce polymer crystallization and to design continuous, stable, fast ion transport pathways. In this study, the incorporation of covalent organic framework colloid (COF-C) as a multifunctional additive to SPEs is proposed, aiming to regulate lithium transport and construct stable electrolyte-electrode interphases. The interaction of COF-C with anions of poly(ionic liquid) (PIL) restricts the growth of PIL spherical crystals and reduces the crystallinity of the electrolyte. Acting as an anion receptor, COF-C promotes uniform Li+ distribution and enhances ion transport kinetics. Additionally, COF-C demonstrates to regulate the anions coordination and create stable solid-state electrolyte interphases between the lithium metal and SPEs. As a result, optimized SPE enables ionic conductivity of 2.70 × 10-4 S cm-1 at 25°C. The solid-state Li/PIL-COF-C/LiFePO4/ batteries demonstrate exceptional cycle stability, evidenced by a notable discharge specific capacity of 142.4 mAh g-1 at 1 C, along with a commendable capacity retention of 93.1% following 500 cycles. In addition, the PIL-COF-C can be adapted to a higher mass loading of LiFePO4.

Fabrication of ITO/FTO Free Flexible Solar Cells Based on ZnO Nanostructures on the Polyethylene Terephthalate/Al/Ti Substrate

Here in, inverted structured bipolar heterojunction solar cell was fabricated on ITO-free flexible polymer (PET) substrate. A transparent and conducting polymer substrate in combination with nanostructures layers on the substrate was prepared using photoetching, and barrier layer of Al and metal layer of Ti were deposited on the photoetched surface using e-beam evaporation technique. Structural, morphological and electrical properties of the PET substrate and the deposited layers were studied by using various characterization techniques including XRD, FESEM, AFM, and electrical measurements. ZnO nanorods structure were grown on the Al/Ti deposited layer on PET substrate and XRD results confirm the formation of hexagonal wurtzite structure of ZnO on the top of Al/Ti layer with good crystallinity. Morphological properties studied by using FESEM reveal the rod shape morphology of the ZnO at a growth temperature of 70 °C, while, these rods were assembled together to form a flower structure at a higher growth temperature of 80 °C. Therefore, to tune the morphology of ZnO, temperature played a key role. After the successful deposition of cathode and anode, the final structure of the cell was fabricated. In order to study the performance comparison, the flexible cell on PET substrate was compared with the conventional ITO/Glass substrate based cell. It was found that the flexible cell showed comparable performance with a power conversion efficiency of 1.82%, and the bending cycle test depicted the excellent mechanical properties with good flexibility and power conversion efficiency of 1.78% even after 200 bending cycles. These studies revealed that the replacement of ITO, flexibility of the substrate, and the performance of the fabricated flexible cell would be an excellent inverted cell for future generation flexible device.

Stacking Pressure Modulated Deposition and Dissolution of Zinc Anode.

Aqueous zinc-ion batteries (ZIBs) are emerging as a promising candidate for large-scale energy storage, offering enhanced safety and low costs. Nevertheless, the disordered growth of zinc dendrites has resulted in low coulombic efficiency and the dangers of short circuits, limiting the commercialization of ZIBs. In this study, a planar growth of zinc along the (002) direction is achieved by regulating the moderate initial stacking pressure during cell cycling and facilitating a larger zinc deposition particle size. The pivotal role of stacking pressure on the zinc nucleation, growth, and dissolution processes is elucidated with in situ pressure X-ray diffraction (XRD), time of flight secondary ion mass spectrometry (TOF-SIMs), and scanning electronic microscopy (SEM). By adjusting the staking pressure from 20 to 300kPa, the battery cycle time increased 5 times. This work highlights the opportunity to precisely manipulate metal deposition/dissolution with stacking pressure for long-cycle life batteries.

Intelligent Strategy of Lithium Metal Reconstruction through Generation of a Protective Layer and Regulating Lithium Deposition.

Lithium metal has been considered as the most promising anode for next-generation batteries. However, its high reactivity with electrolyte and the growth of lithium dendrites hamper the application of lithium metal-based batteries. Herein, we demonstrate that lithium polyphosphides (LixPPs) can be dissolved in diethyl carbonate (DEC) and used as a reconditioner for generating a protective layer and regulating deposition of the Li metal anode. Since LixPPs are reduced prior to Li deposition in the lithiation process, their product can be a uniform and tight layer at the surface of the Li metal. The in situ-formed protection layer has superhigh Li ionic conductivity, and its thickness can be easily controlled by tuning the amount of LixPPs, thus facilitating the interface stability. The Li-Li symmetry batteries show stable cycling performance at 2 mA cm-2 and 1 mAh cm-2 over 5000 h. Interestingly, it exhibits a self-healing function on scratched Li metal.

Tailoring single atom materials for regulating metal anode deposition

Tailoring single atom materials for regulating metal anode deposition

Removal of artificial anionic dye by electrocoagulation and electro-oxidation combined system using aluminum and nano (Cu-Mn-Ni) composite electrodes

The combined system of electrocoagulation (EC) and electro-oxidation (EO) is one of the most promising methods in dye removal. In this work, a solution of 200 mg/l of Congo red was used to examine the removal of anionic dye using an EC-EO system with three stainless steel electrodes as the auxiliary electrodes and an aluminum electrode as anode for the EC process, Cu-Mn-Ni Nanocomposite as anode for the EO process. This composite oxide was simultaneously synthesized by anodic and cathodic deposition of Cu (NO3)2, MnCl2, and Ni (NO3)2 salts with 0.075 M as concentrations of each salt with a fixed molar ratio (1:1:1) at a constant current density of 25 mA/cm2. The characteristics structure and surface morphology of the deposited nano oxides onto the graphite substrates were determined by (XRD), (FE-SEM), (AFM), and (EDX). The results shown that nano Cu-Mn-Ni oxides were successfully deposited onto the anode and cathode. The crystal size and root mean square for the cathode were 30.79 nm and 79.36 nm, respectively, while for the anode, they were 24.19 nm and 41.88 nm, respectively. Furthermore, the combined system was examined for C.D, NaCl concentration, and time. In the EC-EO combined system, the cathode and anode were efficient when used as anodes for the EO process, besides aluminum. The cathode was more effective in the removal process than the anode due to its larger crystal size and the rough, granular shape of its surface. When current density (C.D) increased from 3 to 6 mA/cm², the removal efficiency shifted from 95% to 98%. However, excellent removal of 98% and 96.5% was attained with 1.665 and 2.0859 kWh/kg of dye as energy consumption in the presence and absence of NaCl salt, respectively by applying 6 mA/cm2 within 20 min of electrolysis.

Mechanism of Aluminium Electrochemical Oxidation and Alumina Deposition Using a Carbon Sphere Electrode

Using electromagnetic and electrochemical theories as a framework, this study examines the influence of carbon sphere electrodes on the distribution patterns of anodic oxidation and deposition current densities in metallic aluminium and porous anodic alumina. Theoretical calculations show that the current density symmetrically decreases from the centre outward under the effect of carbon sphere electrodes. Increasing the electrode distance improves the uniformity of the current distribution across the film, while decreasing the distance increases the rate of gradient change in current density. Simulation results reveal that at electrode spacings of 15 cm and 1 cm, the oxidation current density at the film centre is 1333 A/m2 and 2.9 × 105 A/m2, respectively. The current density gradually decreases outward along the radius, reaching 1330 A/m2 and 1.8 × 105 A/m2 at the edges, with observed current density gradient change rates of 500 A/m3 and 1.83 × 107 A/m3, respectively. Experimental results confirm that carbon sphere counter electrodes can create non-uniform oxidation and deposition electric fields. Microstructures with gradually varying symmetry can be generated by adjusting the electrode spacing, resulting in porous anodic alumina and composite films exhibiting iridescent, ring-like structural colours. The experimental findings align well with theoretical calculations and simulation results.

High-Responsivity Self-Powered Photoelectrochemical UV Photodetector Based on Integrated Self-Supporting SiC/ZnS Heterojunction Nanowire Arrays.

In the realm of photodetector (PD) technology, photoelectrochemical (PEC) PDs have garnered attention owing to their inherent advantages. Advances in this field depend on functional nanostructured materials, which are pivotal in improving the separation and transport of photogenerated electron-hole pairs to improve device efficiency. Herein, a highly photosensitive PEC UV PD is built using integrated self-supporting SiC/ZnS heterojunction nanowire array photoelectrodes through anodization and chemical deposition. Compared with the original SiC nanoarrays, the optimized SiC/ZnS-25 nanoarrays exhibit high photocurrent density (Dph, 809.2µAcm-2), rapid rise/decay times (τr/τd, 4/21ms), high responsivity (Rλ, 1.226AW-1), remarkable detectivity (D*, 2.517×1011Jones), and large external quantum efficiency (EQE, 40.57%) under 375nm UV light with a bias voltage of 0.6V. Furthermore, SiC/ZnS-25 delivers excellent self-powered performance, with Rλ, D*, and EQE reaching 0.91AW-1, 1.69×1011Jones, and 30.24%, respectively. In addition, the device exhibits excellent long-term operation and aging stability under a bias voltage of 0.6V and under self-powered conditions. The excellent photodetection behaviors of the SiC/ZnS PEC PD are mainly ascribed to the synergistic effect of the novel well-aligned nanowire geometry, heterojunction with ZnS nanofilms of optimal thickness, and integrated self-supporting configuration of the photoelectrode.

Self-enhanced photoelectrocatalytic removal of Ni-organic complex and Ni recovery by the in-situ forming anodic Ni deposit: P-n junction-driven photocatalytic oxidation and chemical oxidation

Self-enhanced photoelectrocatalytic removal of Ni-organic complex and Ni recovery by the in-situ forming anodic Ni deposit: P-n junction-driven photocatalytic oxidation and chemical oxidation

Revolutionizing copper pipe durability: Shielding against corrosion with graphene oxide through electrophoretic application

This research endeavors to utilize electrophoretic deposition (EPD) to coat copper (Cu) pipes with graphene oxide (GO) nanosheets, aiming to bolster their resistance against corrosion. To achieve this, a stable aqueous colloidal suspension of GO was meticulously prepared via liquid exfoliation in deionized water. This suspension served as an electrolytic solution for EPD. The EPD process involved the meticulous application of varied operational parameters such as deposition time, applied voltage, and GO nanosheet concentration to facilitate anodic deposition on the copper pipe’s surface. To gauge the efficacy of the GO coating, evaluations were conducted to assess adhesive force and stabilization using specialized coating adhesion scratch testing equipment. Further analysis of the resulting film on the Cu pipe was executed employing X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). These methods provided detailed insights into the characteristics and properties of the GO material post-deposition. The study yielded noteworthy outcomes, revealing the achievement of a uniform, unbroken, and consistent coating film on the Cu pipe. This was accomplished by employing specific parameters as 60 s of deposition time, a GO concentration of 0.5 mg/mL, and a voltage of 20 V. Impressively, when subjected to a corrosive solution containing 3.5% sodium chloride, the corrosion protection exhibited a remarkable twofold enhancement compared to untreated copper tubing, boasting an efficiency (η) of 90.48%. These findings suggest that the Cu pipe, coated with GO using the EPD technique, holds significant promise for utilization in demanding industrial settings susceptible to corrosion challenges.

Fabrication and Multi-Functional Performance of TiO2/TiO2-TiN/MoS2 Composite Films on Ti through Smart Anodization and Anodic Electrodeposition

Nanoporous TiO2-based materials as LIB anodes exhibit robust safety and long-term stability without the formation of lithium dendrites during charge/discharge cycling, owing to their relatively high operating potential (approximately 1.7 V vs. Li/Li+) and extremely small volume expansion (<4%). Recently, an anodizing process of Ti materials is proposed to successfully fabricate various nanoporous anodic TiO2-TiN-based films with large surface area and short diffusion paths for intercalation/extraction of Li+ ions and interfacial transport, which attract tremendous attention as promising anode materials for Li-ion batteries, surpassing traditional carbon-based anodes. Moreover, electrodeposition is a well-known process to deposit various substances, such as metals, metal oxides, and metal sulfide on electrical substrates, which can significantly enhance various performances including electrical conductivity, capacity, corrosion resistance, lubricity, etc. Molybdenum disulfide (MoS2) is widely used as solid lubricant with a low friction coefficient and LIB anode materials with a high theoretical capacity around 669 mA h g⁻¹. In this study, we propose a novel approach to deposit MoS2 into anodic nanoporous TiO2-TiN films to create a new nanostructured TiO2/TiO2-TiN/MoS2 composite film on Ti as multifunctional materials toward high-performance LIB anodes, all-solid-state batteries, as well as versatile mechanical parts with good lubricity and high corrosion/wear resistance.A two-step anodizing method was applied to form a bi-layered nanoporous TiO2-based film, i.e., a top tier with mesoporous larger pores and a matrix tier with nanoporous structure and improved conductivity. Briefly, a thin flat TiO2 top film with large-pore-size was firstly formed through anodization in a SO4 2--based solution. Subsequently, a thick nanoporous TiO2-TiN film was fabricated beneath the TiO2 top film by anodizing in a NO3 --based solution. Next, the porous TiO2/TiO2-TiN composite films were used as matrix films to fill MoS2 through anodic electrodeposition in a MoS4 2-based solution. The morphology, chemical composition, chemical states, and crystalline structures of the resultant anodized and electrodeposited films were analyzed by FE-SEM, EDX, XRD, XPS, and Raman. Moreover, the performances of the specimens as LIB anodes were evaluated through charge/discharge tests and various electrochemical experiments, and the lubricative properties and corrosion/wear resistance were measured by friction tests and various electrochemical methods.Fig.1a illustrates the schematic formation process of the composite film by successive anodization in sulfuric- and nitric-based solutions and anodic MoS2 deposition. Following the anodic deposition, Mo-based substances were precipitated into the bi-layered nanoporous TiO2/TiO2-TiN composite films on Ti. Fig.1b showed the surface and fractural cross-section FE-SEM images of the TiO2/TiO2-TiN film before MoS2 electrodeposition, depicting a mesoporous structure with large pore size ranging from 50 to 200 nm at the top layer and a thick nanoporous under layer with pore diameters of 30–50 nm consistent to our previous studies. Fig.1c shows the surface FE-SEM image and EDS analysis result of the TiO2/TiO2-TiN/MoS2 composite film after MoS2 electrodeposition. A smooth layered surface with tiny particles was observed throughout the specimen. EDS analysis detected Ti, Mo, S, and O elements, indicating the formation of molybdenum sulfide on the TiO2-based anodic films. Raman spectroscopy detected strong peaks of MoS2 and several weak peaks of Mo oxides. The XRD and XPS measurements further confirmed the presence of MoO2 and MoO3 in the composite films after heating at 523K for 1 h in air, which attributed to the oxidation of MoS2 under high temperature. Consequently, the TiO2/TiO2-TiN/MoS2-MoOx composite films after heating exhibited a high capacity of 848 μA h cm-2 as LIB anode materials, and the as-prepared TiO2/TiO2-TiN/MoS2 delivered a low friction coefficient of around 0.25 in a friction test, thus demonstrating the effectiveness and efficiency of the designed two-step anodization and electrodeposition process in achieving multifunctional performance. Figure 1

Mn Oxide / IrO2 / Ti Anodes Prepared By Calcination for Oxygen Evolution in Seawater Electrolysis

INTRODUCTIONIn the future, hydrogen production will be performed by direct electrolysis of seawater. However, every time hydrogen is produced, it is necessary to avoid generating chlorine because it has a negative impact on the ecosystem. We have been developing an oxygen evolution anode for seawater electrolysis that produces only oxygen without chlorine. It has been found that anodically deposited g-MnO2-type Mn1-xMoxSnyO2+xanodes showed the oxygen evolution efficiency for more than 4000 hours in the electrolysis of 0.5 M NaCl [1]. The anodic deposition method has required many steps and further cleaning of the electrolytic diaphragm. For these reasons, in order to commercialize oxygen evolution anodes for seawater electrolysis, it is essential to establish a simple manufacturing method. We are considering fabricating Mn oxide as an active material on an IrO2 intermediate layer formed on a titanium substrate using calcination method.In this study, Mn oxide electrodes were fabricated by coating various concentrations of manganese nitrate butanol solutions on the IrO2intermediate layer and at various calcination temperatures. We have investigated the crystal structure and Mn oxide weight that would have the highest activity for oxygen evolution efficiency.EXPERIMENTALTitanium metal substrates were immersed to roughen enhancing the anchor effect of the substrate on the electrocatalyst layer in concentrated H2SO4. IrO2 intermediate layer was formed by coating on one side of the titanium substrate in 0.26 M Chloroiridic acid with a brush, dried at 363 K for 10 min in air. The other side was coated in the same procedure and dried. And then these substrates was calcined at 723 K for 10 min in air. This procedure was repeated three times but the final calcination of the specimen was continued for 60 min at 723 K in air for calcination. Mn oxide electrocatalyst for oxygen evolution was formed by coating on the IrO2 / Ti in 0.073～0.52 M Mn(NO3)2 butanolsolution with a brush and drying at 353 K for 90 min in the same way as when forming the IrO2 intermediate layer. Calcination was performed at 473, 573, and 723 K. Impurities formed without becoming manganese oxides were electrolytically cleaned in 0.5 M NaCl until no dissolution of the impurities was observed.The performance of the electrode was examined by electrolysis of 0.5 M NaCl solution at 1000Am-2. The oxygen evolution efficiency was estimated by the difference between the total charge passed during electrolysis and the formation charge of chlorine analyzed by iodometric titration. Polarization curves were measured galvanostatically. Correction for IR drop was made with the electrochemical impedance spectroscopy (EIS) method.The characterization of the electrode was carried out by XRD and EPMA.RESULTS AND DISCUSSIONXRD diffraction clarified that Mn₂O₃ were consisted at 723 K, Ramsdellite-type MnO₂ at 673 K, and IrO2 at 573 K.Figure 1 shows the relationship between Mn oxide weight and oxygen evolution efficiency. The oxygen evolution efficiency of the anode consisted of only IrO2 was about 8%. It found that the oxygen evolution efficiency was different due to the difference in calcination temperature, that is, the difference in crystal structure to Mn oxide weight of about 2.5 mgcm-2. The oxygen evolution efficiency of the anode with Ramsdellite-type MnO₂ formed at 573 K was about 57 % at 1.8 mgcm-2. The oxygen evolution efficiency of anodes formed at 473 and 723 K with the equivalent weight was about 52 and 32 % respectively. Previous research has shown that anodes containing the γ-MnO2 formed by anodic deposition have high catalytic activity for oxygen evolution [2]. The γ-MnO2 contains stacking faults in which β-MnO2 is mixed into the ramsdellite-MnO2[3]. The electrode with 4.5 mgcm-2 of Mn₂O₃ at 723 K shows the maximum oxygen generation efficiency, which is about 83%.A future challenge is to add substances such as molybdenum as additional elements to obtain higher oxygen evolution efficiency. In conventional electrode fabrication using anodic deposition, the addition of molybdenum significantly has improved oxygen generation efficiency.REFERENSE[1]Z. Kato, J. Bhattarai , N. Kumagai, K. Izumiya, and K. Hashimoto, Applied. Surface. Science. 257 (2011) 8230.[2] A. A. El-Moneim, N. Kumagai, K. Asami, and K. Hashimoto , Materials Transactions, Vol. 46, No. 2 (2005) pp. 309[3] Jian-Bao LI, K. Koumoto and H. Yanagida, Journal of the Ceramic Society of Japan, 96 [1] (1988)74 Figure 1

(Digital Presentation) Effects of the Morphological Changes Associated with a Li Metal Anode on Deposition and Dissolution Cycle in Bis(fluorosulfonyl)Amide-Based Ionic Liquids

Lithium metal has been considered as a promising candidate for the negative electrode of secondary batteries for several decades because its capacity (3860 mAh g–1) is higher than those of currently used electrode materials. However, the lithium metal anode has been known to exhibit poor cycle performance or give rise to short circuits due to the dendritic or whisker-like morphology of lithium formed during deposition and dissolution. Analysis of the morphology of lithium deposits, especially the cross-section, is considered to be important for contributing to research on improving the charge-discharge ability of lithium metal anode. The formation of a uniform and highly Li+conductive solid electrolyte interphase (SEI) on the lithium metal surface leading to dense and low porosity lithium deposits and a reversible deposition-dissolution reaction of lithium is a significant challenge. It has been suggested that the bis(fluorosulfonyl)amide (FSA–)-derived SEI in ionic liquid (IL) electrolyte containing a high concentration of LiFSA can improve cycle performance and suppress dendritic growth [1,2]. We have reported the cycle performance of lithium and the formation of a SEI for electrolytes comprised of LiFSA in MOEMPFSA (MOEMP+: 1-methyl-1-methoxyethylpyrrolidinium) or BMPFSA (BMP+: 1-methyl-1-butylpyrrolidinium) [3]. The resistance of the SEI in LiFSA-MOEMPFSA (1:1 molar ratio) was lower than that in LiFSA-BMPFSA (1:1 molar ratio), and the deposition and dissolution performance of a lithium metal anode was improved in LiFSA-MOEMPFSA compared to LiFSA-BMPFSA. This is thought to be due to the variation in SEI composition with IL cation structure. Previous studies have demonstrated the cycle performance at a capacity of 1 or 4 mAh cm–2 [3,4] for lithium metal. However, these values are rather low when considering the proposed application as a negative electrode material for next-generation batteries, and it is essential to study a larger capacity. In the present study, the morphological changes of Li during deposition and dissolution cycle at 10 mAh cm–2 and the relationship between cycle performance and the morphology of deposited Li was investigated. The electrolytes were prepared by mixing MOEMPFSA or BMPFSA and LiFSA at 50.0-50.0 mol%. The water contents in the ionic liquid electrolytes were less than 50 ppm, as determined by Karl Fischer titration. The preparation of 10 mAh cm–2 deposited Li on Cu was conducted using a Cu|Li planar electrode cell (laminate-like) at 0.1, 0.5 and 1.0 mA cm–2. Celgard 3501 was used as the separator. The cross-sections of the deposited lithium on Cu were revealed by processing with Ar ion milling at –80 °C. The observation of the cross-section of deposited lithium on Cu was carried out with a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) and without exposure to air. The SEM images of the cross-sections of a 10 mAh cm–2 lithium deposit on Cu at 0.1 or 0.5 mA cm–2 in LiFSA-MOEMPFSA reveal a denser and lower porosity than that at 1.0 mA cm–2. It is suggested that columnar growth of lithium was observed due to particle growth rather than nucleation at lower current density. The morphology of the 10 mAh cm–2 lithium deposits on Cu at 0.5 mA cm–2 in LiFSA-MOEMPFSA was denser than that in LiFSA-BMPFSA. This is thought to be due to the differences in the resistance of the SEI derived from MOEMPFSA and BMPFSA. The denser and lower porosity deposited lithium is considered to be promising for operation at as high a capacity as 10 mAh cm–2, and is expected to contribute to the improvement of the reversibility of the lithium anode with suppressing dendritic growth.AcknowledgmentsThis study was supported by the Green Technologies of Excellence (GteX, JPMJGX23S0) program of the Japan Science and Technology Agency (JST). MOEMPCl was supplied by Nisshinbo Holdings Inc.References R. Furuya, T. Hara, T. Fukunaga, K. Kawakami, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 168, 100516 (2021).G. Girard, M. Hilder, N. Dupre, D. Guyomard, D. Nucciarone, K. Whitbread, S. Zavorine, M. Moser, M. Forsyth, D. MacFarlane, and P. Howlett, ACS Appl. Mater. Interfaces, 10, 6719 (2018).N. Serizawa, R. Yamashita, and Y. Katayama, J. Phys. Chem. C, 127, 10434 (2023). Y. Maeyoshi, K. Yoshii, and H. Sakaebe, J. Electrochem. Soc., 90, 047001 (2022).

Application of Porous Electrode for Energy Efficient Electrocoagulation

Electrocoagulation (EC) has been recognized as a promising electrochemical water treatment technology. Porous electrodes were investigated for enhanced EC removal efficiency and reduced energy consumption associated with their high surface area. In this study, we characterized EC performance in both batch and continuous flow EC reactors for treating secondary effluent wastewater. Here, we highlight the possible use of porous electrodes to revolutionize EC by enhancing pollutant removal efficiency, such as virus attenuation, while maintaining Faradaic efficiency and significantly reducing energy consumption. To gain a deeper understanding of porous electrode functionality, we conducted advanced analysis employing neutron computed tomography to characterize internal structural changes in the porous foam electrode after EC water treatment. Combining this method with microscopic analysis, we validated that the internal surface area of porous electrodes is involved in electrochemical dissolution at the anode and reductive deposition at the cathode. This technique provided valuable insights into electrochemical processes occurring within porous electrodes, shedding light onto their role in pollutant removal mechanisms. Moreover, we systematically investigated the size effect of electrode porosity in virus attenuation, energy requirements, Faradaic efficiency, and the efficiency of removing pollutants such as silica and hardness to determine the optimal porosity for high EC performance. Through comprehensive studies of continuous flow EC reactor systems, we will discuss the scalability and practicality of porous electrode-based EC systems for real-world applications. This study underscores the pivotal role of porous electrodes in improving EC processes and achieving efficient pollutant removal with reduced energy consumption.

Anodic Dissolution of Al–Fe and Al-Fe-Si Alloys in Emimcl–AlCl3 Electrolyte

Al casting alloys, which contain large amounts of Fe, Si, and Cu, are used for automotive engine components. Recycling used Al casting alloys further leads to effective use of resources and reduction of environmental load.We have reported that various Al alloys can be purified and upgraded by electrorefining using ionic liquids.1,2) In this study, we investigated the anodic dissolution and cathodic deposition behavior of Al–Fe binary alloys and Al–Fe–Si ternary alloys with controlled intermetallic compound.Pure Fe (99.99%Fe), pure Al (99.999%), Al–1.5%Fe, and Al–1.5%Fe–3.5%Si casting alloys were used as anode samples. Ionic liquid preparation and all electrochemical measurements were performed in an Ar-filled glove box. The ionic liquid electrolyte was prepared by mixing 1-ethyl-3-methylimidazolium chloride (EmImCl) and AlCl3 with a molar ratio of 1 : 2. In the electrochemical measurements, Al–1.5%Fe and Al–1.5%Fe–3.5%Si alloys were used for the working electrode, Pt and Cu plates for the counter electrode, and Al wire for the reference electrode. Anodic polarization measurements and constant potential electrolysis were performed at an experimental temperature of 323 K. Anodic polarization curves were measured from the immersion potential to 1.5 V vs Al/Al(III) at a scanning rate of 1 mV s− 1. Constant potential electrolysis was performed at potentials of 0.4, 0.7, 0.9, and 1.4 V at a charge density of 100 C cm− 2. After constant potential electrolysis, samples were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS).Intermetallic compounds were identified as Al6Fe in the Al–1.5%Fe alloy and β-AlFeSi in the Al–1.5%Fe–3.5%Si alloy by XRD measurements. In the anodic polarization curves of these alloys, oxidation waves were observed at 0.9 V and 1.4 V in the Al–1.5%Fe–3.5%Si alloy, which were higher than the dissolution potential of pure Fe. SEM–EDS analysis of the Al–1.5%Fe–3.5%Si alloy after electrolysis showed a decrease in Al concentration and an increase in Fe and Si concentrations in β-AlFeSi at 0.9 V. At 1.4 V, Al and Fe concentrations decreased and Si concentration increased.These results indicate that anodic dissolution of Fe in β-AlFeSi in EmImCl–AlCl3 ionic liquid occurs at 1.4 V, which is more noble than the dissolution potential of 0.5 V for pure Fe, and that the addition of Si to the Al–Fe alloy suppressed the anodic dissolution of Fe.From the above, in the Al–Fe–Si alloy containing β-AlFeSi formed by adding Si in the Al–Fe alloy, the dissolution of Fe into the electrolyte is suppressed, and the purity of Al at the cathode is improved. Acknowledgement Part of this work was supported by the New Energy and Industrial Technology Development Organization (NEDO). We would like to express our gratitude to all parties concerned. Reference 1) J. Nunomura et al., J. Electrochem. Soc., 169, 082518 (2022).2) J. Nunomura et al., Electrochim. Acta, 460, 142601 (2023).