Anodic Electrodeposition Research Articles

(Keynote) Facile Fabrication of High-Performance Lib Anode and Cathode Materials on Al and Ti By Smart Anodization and Hybrid Electrodeposition

Aluminum and titanium materials are well known as typical light metals which are widely applied to versatile products for their high corrosion resistance, conductive and decorative properties, etc. Recently, aluminum and titanium materials are paid extensive attention to battery industry, using as current collectors or electrode materials. Lithium-ion batteries (LIBs) are known as important power sources in many electric/electronic products such as cellular phones, digital cameras, portable computers, as well as electric vehicles (EVs) and hybrid electric vehicles (HEVs). To meet the ever-expanding needs for lithium-ion battery industry, it is an urgent task to develop new technologies for producing LIB materials with optimal performance-safety balance, and to substituting conventional sintering-casting process by cost-effective process in manufacture of LIBs. In this study, we report three new processes to fabricate cathode and anode materials for LIBs as below. Fabrication of Li-V-Mn-Ni-O composite films on Al by a hybrid electrodeposition for LIB Cathodes Fig.1a shows a cross-sectional scheme of Li-V-Mn-Ni-O composite films on Al foils. Different from the conventional sintering methods for producing LiCoO2-based LIB cathodes, we proposed a novel hybrid electrodeposition to fabricate Li-V-Mn-Ni-O composite films directly on Al, which is expected to increase the working potential with Li ions above 4 V vs. Li+/Li and to decrease the cost of active materials. The composite films were obtained by a cathodic electrodeposition in ethanol-water bath containing V5+、Ni2+, Mn2+, and Li+ ions. Before electrodeposition, an electro-etching pretreatment was adopted to enhance the adhesion between the Al substrate and the electrodeposits. It is found that the resultant composite films after annealing consists of V2O5, Li2MnO4, NiOOH, and metallic Li components. The cyclic voltammetric measurements detected three peaks at 3.2, 4.01, and 4.33 V vs. Li+/Li, which can be ascribed to the Li extraction reactions from the substance mentioned above, indicating the composite films worked as active materials as LIB cathodes. Formation of nanoporous TiO2-TiO-TiN composite films on Ti by a smart anodization for LIB anodes Nanoporous anodic TiO2 films are considered as promising LIB anode materials to solve the safe issue caused by lithium electrodeposition during charge/discharge process as use C-base anodes conventionally. However, the poor conductivity and low theoretic capacity of TiO2 materials are big concerns for practical uses for high density LIBs. Here, we formed successfully nanoporous TiO2-TiO-TiN composite films on Ti foils by a smart anodization in aqueous NO3 –-based solutions and found that the inclusion of conductive TiN component in TiO2 matrix film improved the electronic conductivity effectively (Fig.1.b). The TiO2-TiO-TiN composite films after being heated at 150–500 ºC can be used as binder-conductive reagent free LIB anodes and exhibited higher capacity than ordinary TiO2 films. Fabrication of TiO2-TiN/M-MOx (M = Sn, Mo) composite films on Ti by Hybrid electrolytic process In order to increase the capacity of anodic TiO2-TiN films, we conducted various electrodeposition of Sn-based and Mo-based materials with high theoretic capacities into the anodic TiO2-TiN matrix films, as shown in Fig.1c. The inclusion of highly conductive TiN component in TiO2 matrix film during anodization endows the necessary electronic conductivity for the successive cathodic hybrid electrodeposition of various active materials with high theoretic capacities. The one approach is to fill Sn and SnO2 nanoparticles into TiO2-TiN matrix films by using an acidic plating bath containing different Sn ions. This not only increased the areal specific capacity in 4–9 times compared to the anodic TiO2-TiN films, but also improved the conductivity of the composite films. Another approach is to fill Mo-based materials from a molybdate solution. It is found by XPS analysis that the resultant Mo-based deposits composed of molybdate oxides (MoO2-MoO3) and molybdate nitrides (Mo2N-MoN). The electrodeposition of Mo-based materials into TiO2-TiN films improved the conductivity of the composite films significantly due to the high conductive components of molybdate nitrides. As a result, TiO2-TiN/MoOx-MoyN composite films exhibited around 5 times higher discharge capacity than the TiO2-TiN films and excellent cycling performance with a retention of 97%, indicating a promising anode material with high power density and high safety for LIBs. Figure 1

Design of Non-Ammoniacal Solution for Electrodeposition of CuO on Cu2o Substrate

Semiconductor materials are attracting increasing attention as photoelectrodes and photovoltaic devices. Cuprous oxide (Cu2O), which has been intensively studied due to its high absorption coefficient, low cost, and low toxicity, is a p-type semiconductor with a bandgap energy of approximately 2.1 eV. However, Cu2O has a narrow solar absorption region due to its high bandgap energy. CuO (bandgap energy of 1.4 eV) has been combined with Cu2O to increase the absorption wavelength range [1]. Thermal oxidation of Cu2O surfaces for forming CuO/Cu2O bi-layer films has been reported [2]. However, this thermal oxidation creates nanopores and voids in the films and degrades the film performance. In this study, an electrochemical formation of CuO on a Cu2O surface is investigated. Previously reported methods of electrochemical CuO formation include an anodic electrodeposition using an ammoniacal aqueous solution [3]. In ammoniacal solutions, however, the Cu2O surface is unstable and can be dissolved as Cu(I)-ammine complexes. In this study, suitable non-ammoniacal ligands, which can be used to stabilize Cu2O during CuO electrodeposition, are examined through thermodynamic calculations, and the electrodeposition behavior of CuO films on Cu2O is experimentally investigated.An appropriate ligand, 2-aminoethanol, i.e., mono-ethanolamine (MEA), was obtained by drawing the pH speciation diagram using thermodynamic data [4, 5]. It is difficult to use MEAs to form complexes with Cu(I) and easy to form with Cu(II), and MEAs are relatively inexpensive and versatile. Figure 1 shows that CuO is stable at a pH region lower than the region where the Cu(II)-MEA complex is dominant, suggesting that it is feasible to achieve CuO electrodeposition using a local pH drop, through, for example, anodic oxygen evolution reaction.In a 0.05 M Cu(II) + 0.125 M MEA aqueous solution without NaOH addition (pH = 8.5), precipitates − probably hydroxide − were formed (Figure 2(b)). In contrast, when the pH was increased to 12.5, a deep blue aqueous solution was obtained without any precipitates (Figure 2(c)). While a set of existing stability constants [5] indicated the presence of CuO or Cu(OH)2 precipitates in the 0.05 M Cu(II) + 0.125 M MEA aqueous solution at a pH value of 12.5, a clear solution was obtained at [Cu(II)] = 0.05 M, [MEA] = 0.125 M, and pH = 12.5. A Cu2O substrate was immersed in this solution for 5 h to confirm the stability of Cu2O in the solution. From the results, almost no weight change was observed, unlike the case of ammoniacal solutions, when nitrogen degassing was carried out for 30 min before performing the immersion test to prevent the oxidation of Cu2O by dissolved oxygen. Potentiostatic electrodeposition of CuO was conducted on +0.45 V vs. Ag/AgCl reference electrode at 313 K. Cu2O/FTO —Cu2O was electrodeposited on fluorine-doped tin oxide (FTO) in advance [2]— and Pt plates were used as both the working electrode (WE) and the counter electrode. Figure 3 shows the X-ray diffraction (XRD) profiles of the Cu2O/FTO WE before and after the electrodeposition. Along with cubic Cu2O, monoclinic CuO was detected. Additionally, the cross-sectional field-emission scanning electron microscopy (FE-SEM) images depicted in Fig. 4 indicate a bi-layer structure. Therefore, we conclude that CuO was stacked, keeping the Cu2O layer intact. Figure 5 shows the visible spectroscopy near-infrared region (vis-NIR) absorbance spectra of the Cu2O and CuO/Cu2O films. The absorption edge of the Cu2O films was 630 nm, while that of the CuO/Cu2O films shifted to 900 nm, demonstrating that the CuO/Cu2O films had a broader absorption wavelength range than pure Cu2O or pure CuO films. In summary, a non-ammoniacal bath is surveyed from the thermodynamics database, and CuO/Cu2O bi-layer films are electrochemically fabricated.

A New Route to Carbon Film Coating by Anodic Electrodeposition from Ionic Liquid Containing Different Phenylsilane Derivatives

We propose a new direct anodic electrodeposition process for carbon coatings that is possible at room temperature in ionic liquid (IL) with phenylsilane derivatives, which include dimethylphenylsil...

Improved Norfloxacin degradation by urea precipitation Ti/SnO2–Sb anode under photo-electro catalysis and kinetics investigation by BP-neural-network-physical modeling

The photo-electro catalysis has emerged as efficient and sustainable degradation method for antibiotics, where metal oxide anode plays a critical role. Exploring novel preparation method for anodes catalysis to achieve larger active sites and diverse oxidants production can directly enhance the degradation performance. Therefore, in this work, a new urea precipitation method for anode formation was studied. Both novel urea precipitation Ti/SnO2–Sb anode (TSSA-U) and traditional electro-deposition Ti/SnO2–Sb anode (TSSA-E) were prepared for Norfloxacin degradation by photo-electro catalysis in saline water. A unique tubular Ti/SnO2–Sb units formatted by urea precipitation resulted in higher porosity. This led to dominating advantage for TSSA-U on photo/electrochemical activity and degradation performances by individual photo/electro catalysis, compared to TSSA-E. However, this gap of degradation performances shrank when synergistic effect of photo-electro catalysis involved. The highest TOC removal ratio of 91.1% was obtained from TSSA-U under photo-electro catalysis. Besides, a novel BP-neural-network-physical modeling (BP-ANN-P) was developed for analysis. According to this modeling, both direct (adsorption-degradation, radiation, etc.) and indirect (mainly •Cl) routes contributed significantly in degradation work by TSSA-U, where indirect route shared 41.8–90.1% of total degradation ratio. An increasing of current density (from 5 to 25 mA cm−2) enhanced the kinetics for both routes. Indirect route preferred pH = 3–7 with direct route enhanced by neutral condition. Moreover, indirect route also showed better adaptability with higher initial NOR loadings.Both urea precipitation and BP-ANN-P have shown their value for high performance material formation and data analysis, respectively. Notably, higher catalysis performance and better analysis connect to low energy cost, shorter running time and more efficient judgement and selection, which meets the requirement of cleaner production and environmental sustainability.

Electrochemical deposition and characterization of iridium oxide films on Ti2AlC support for oxygen evolution reaction

Two types of iridium oxide films formed at the Ti2AlC substrate were investigated: (1) anodically electrodeposited iridium oxide film from the solution based on IrCl3xH2O; (2) iridium oxide film prepared by cycling thin layer of electrodeposited Ir in the 0.5 M H2SO4 from − 0.25 to 1.20 V. It was shown that during anodic electrodeposition of iridium oxide film (1) coulombic efficiency decreases with increasing anodic potential, being only 3% at E = 0.7 V vs. SCE and 26% at E = 0.62 V vs. SCE. A pair of peaks corresponding to the transition Ir(III)-oxide/Ir(IV)-oxide was present on the CVs recorded in 0.5 M H2SO4. While cycling pure Ir thin layer in the solution of 0.5 M H2SO4 from − 0.25 to 1.20 V (2) up to 100 cycles, typical CV response was characterized with the prepeak and a pair of peaks corresponding to the Ir(III)/Ir(IV)-oxide transition. With the increase of cycles number to 150, additional peak at potential of 1.0 V appeared. This peak was formed on the account of pair of peaks corresponding to the Ir(III)/Ir(IV)-oxide transition. The oxygen evolution reaction (OER) was investigated at both iridium oxide films. It was shown that the Tafel slope for the OER was ~ 40 mV dec−1 for the first polarization curve, confirming that the rds was a reaction S–OH → S–Oads + H+ + e−. As the number of recorded polarization curves increased, the activity of both types of iridium oxide films decreased, due to dissolution of iridium oxide films at the potentials of the OER. It is shown that anodically electrodeposited iridium oxide film is more active for the OER than that obtained by cycling electrodeposited iridium layer. However, both iridium oxide films exhibited insufficient stability.

Hierarchical NiCo2O4-MnOx-NF monolithic catalyst synthesized by in-situ alternating anode and cathode electro-deposition strategy: Strong interfacial anchoring force promote catalytic performance

It is of great significance to explore and develop in-situ preparation strategies to improve the activity and service life of monolithic catalysts. In this work, the strategy of alternating anode and cathode electro-deposition was creatively proposed, a hierarchical monolithic catalyst that three-dimensional nickel foam with an open-pore structure at the bottom, structural flexible MnOx crystal in the middle layer, and vertically oriented small size NiCo2O4 spinel phase at the top was successfully prepared. Consequently, NiCo2O4-MnOx-NF-250 monolithic catalyst exhibits lowest T90 of 196 °C, and T’90 of 204 °C (after ultrasonic exfoliation experiment) at 6000 h−1 gaseous hourly space velocity (GHSV) for 100 ppm benzene combustion. It has been convinced that a monolithic catalyst with high activity and strong anchoring force was successfully prepared by a simple strategy of alternating anode and cathode electro-deposition, which not only provides a strategy for designing monolithic catalyst but also paves the way for industrial benzene removal.

Electrodeposition of chitosan enables synthesis of copper/carbon composites for H2O2 sensing

This work presents a novel approach in synthesizing copper (Cu)/carbon composite materials by electrodeposition of the biopolymer chitosan, a renewable carbon precursor, on a copper anode, followed by pyrolysis of the electrodeposited chitosan gel. The amount of copper in the Cu/carbon composite material can be controlled by modifying the pH of the chitosan solution from which the electrodeposition is performed. This further influences the physical properties of the composite material. Here we show a 14 fold increase in electrical conductivity of the Cu/carbon composite, when compared to the material without copper inclusions. Metal/carbon composite materials have a wide range of applications already reported in the literature. As a proof of concept, we demonstrate the electrochemical sensing capability of this Cu/carbon material for non-enzymatic detection of hydrogen peroxide, achieving a sensitivity of 58.9 μA/mM cm2, which is comparable to state of the art non-enzymatic hydrogen peroxide sensors. The anodic electrodeposition of chitosan proves to be a simple and straightforward medium for synthesis of Cu/carbon composites. We speculate that this method can be extended to obtain other metal/carbon composites as a low-cost alternative for the fabrication of functional composite electrodes.

Preparation and characterization of ZnO/PEG-Co(II)-PbO2 nanocomposite electrode and an investigation of the electrocatalytic degradation of phenol

A ZnO/PEG (polyethylene glycol) -Co(II)-PbO2 nanocomposite electrode was constructed by using the anodic electrodeposition method and used for the electrocatalytic degradation phenol. The results showed that the electrode surface formed numerous PbO2 nanosphere structures, and the average size of a single nanosphere is approximately 0.4 μm. XRD and EDS results showed the active layer consisted of β-PbO2, and contained small amounts of cobalt and carbon. The electrochemical measurements showed that the electrode possessed a lower activation energy (Ea = 17.517 kJ∙mol−1) and charge transfer resistance (Rct = 7.564 Ω cm2) and a larger exchange current density (i°=1.476 × 10-4 mA cm-2). The phenol degradation process was controlled by the adsorption process and kinetic parameters were obtained with an initial concentration of 100 mg L−1. The electrode possessed a shorter half-life, larger reaction rate constant, and degradation efficiency (RE = 91.1 %) after 180 min. Reaction order was also calculated, and the degradation followed the pseudo-first-order reaction kinetics. HPLC results showed that the degradation pathway is as follows: firstly, phenol is gradually decomposed into o-diphenol, p-diphenol and benzoquinone under hydroxyl radicals attack. Then, benzoquinone is broken into maleic acid and fumaric acid. Finally, these acidic compounds are broken into oxalic acid, which is eventually mineralized.

Electrodeposition of lead from methanesulfonic acid and methanesulfonate ionic liquid derivatives

The effects are reported of electrolyte composition on the electrochemistry of PbII and electrodeposition morphology of Pb in aqueous methanesulfonic acid (MSA) and two methanesulfonate-based ionic liquids: 1-butyl-3-methylimidazolium methanesulfonate and N,N-dimethylbutylammonium methanesulfonate. Cyclic voltammetry and chronoamperometry indicated that the reduction of PbII ions to Pb was a diffusion-controlled process proceeding via an overall two-electron transfer process at −0.67 V vs. Ag (1 M MSA) and involved 3-D progressive nucleation. Scanning electron microscopy showed a strong influence of deposition potential and electrolyte composition on the morphology of Pb deposits. Experimental data was used to model predictions of the specific electrical energy consumption for cathodic PbII electrodeposition coupled with either anodic oxygen evolution or PbO2 electrodeposition.

Extraction of tellurium and high purity bismuth from processing residue of zinc anode slime by sulfation roasting-leaching-electrodeposition process

Anode slime and its processing residue contains a variety of valuable elements, which are the main source of tellurium and bismuth. A systematic study on the extraction of tellurium and bismuth from processing residue of zinc anode slime and electrodeposition to obtain high purity bismuth was carried out. Sulfation roasting thermodynamics, leaching thermodynamics, and reduction potential involved in the extraction were calculated and used as theoretical guidance for the experiment. In the process of extracting tellurium and bismuth: the minimum amount of sulfuric acid and the appropriate low temperature of sulfation roasting conditions for processing residue of zinc anode slime are explained that the ratio of sulfuric acid to anode slime was 0.54:1, and the temperature was 435 °C. The leaching process of the roasting product was optimized. The optimal water leaching conditions were a liquid to solid ratio of 6:1 and a reaction time of 0.5 h at 25 °C. The optimal alkali leaching condition is 10% NaOH liquid to solid ratio of 6:1 and reaction time of 0.5 h at 25 °C. Tellurium and bismuth were separated, and tellurium was enriched from a low content of anode slime raw materials. The recovery rate of tellurium and bismuth were 84.9% and 97.1%, respectively. The reduced deposition process of bismuth ions on the cathode was characterized by cyclic voltammetry in the nitric acid. In the stable deposition state, electrodeposition overpotential of the bismuth ion on the titanium plate was 0.1068 V. Tributyl phosphate (TBP) was used as extraction solvent and nitric acid solution was used as stripping solution to purify the impurities in the basic bismuth sulfate. After extraction process, the removal rates of tellurium (Te), arsenic (As), copper (Cu), and antimony (Sb) were 96.5%, 93.3%, 99.1% and 100%, respectively. The content of other impurity elements also reduced greatly. The electrical separation process further reduced the content of impurities in the electrolyte, in which the concentration of tellurium was reduced to less than 1 ppm. A standard-compliant high purity elemental bismuth was obtained by electrodeposition from purified electrolyte.

Electrodeposition of Metal Oxides on Spray-Coated Nanostructured Carbon Framework As High Performance Electrode Materials for Asymmetric Pseudocapacitors

Combining transition metal oxides and nanostructured hierarchical carbon materials is considered as one of the best strategy to achieve high performance supercapacitors electrodes [1]. Here is reported a novel way to increase energy densities while maintaining high power densities exploiting pseudocapacitance and nanostructuration of electrode materials.In the first part of this study, carbon nanotubes/graphene/manganese dioxide nanostructured films were designed as pseudocapacitors electrodes (Fig. A). While MnO2 is a well-known pseudocapacitive cathode material and will increase energy densities [2], nanostructured carbon materials provide high electronic conductivity and specific surface. The challenge is to assemble these three materials (CNTs/G/MnO2) into a nanostructured electrode with controlled homogeneity, morphology, and composition. First, carbon nanotubes and graphene foils are associated in a specific multi-layered organization onto a current collector by dynamic spray gun deposition. It creates a controlled porous network in the electrodes. This deposition method used for nanostructuration of thin films generates homogeneous mats with tunable thickness. This structuration of the carbon nanomaterials is reproducible, easily scalable and low-cost considering that it is compatible with large surfaces. The CNTs/G multilayered structure provides a good accessibility with an appropriate porosity for ion insertion (pores of 2 to 6 nm), a high specific surface area (~360 m2/g), and an electrically conductive network (~3600 S/m), all necessary to confer high power densities. Our approach consists in synthesizing MnO2 by anodic electrodeposition directly onto the conductive nanostructured carbon framework. Electrodeposition is very versatile [3] and simply. The morphology of the manganese dioxide (shape, particles size, and mass loading) can be controlled and the electrochemical performances can be tuned by adjusting the deposition conditions. The MnO2 nanoparticles are deposited through the thickness (seen in cross section Figure A) of the carbon mat with controlled sizes ranging from 50 to 200 nm.Materials are characterized by SEM, XPS, microporosity analysis and electrochemistry. Results demonstrate that the capacitance can reach up to 220 F/g for binder free electrodes with a MnO2 mass loading of 55%. The pseudocapacitive oxide insures a faradaic contribution that enhances the specific capacitance by a factor 5 compared to the carbon nanomaterials structure only. The electrodes present an outstanding stability of 96% over 3 000 cycles in aqueous electrolytes (Na2SO4 1M). Then an asymmetric system with activated carbon as the negative electrode is developed to demonstrate the energy density increase compared to a symmetric system with activated carbon as electrodes. When adding MnO2 to the cathode the exploitable potential window can be widen up to 1.4V and the energy density increases from 1 Wh/kg to 6 Wh/kg for a power density of 0.7 kW/kg. Stability of 85% in capacitance was demonstrated for 20 000 cycles on this system.The second part of the contribution is devoted to molybdenum oxide (MoO3) that has been recently introduced as an appropriate anode material for pseudocapacitors in view of its low cost nature and high electrochemical activity [4,5]. It has been reported to be suitable in terms of potential window as a negative counterpart to manganese oxide in asymmetric pseudocapacitors [6]. This study focuses on the development of a carbon nanotubes/molybdenum oxide composite by spray-coating and cathodic electrodeposition (Fig. B). The growth of this specific metal oxide is quite complex with several possible intermediaries presenting different oxidation states depending on the environment [7]. Studies on the impact of the chemical and electrochemical conditions on the morphology, crystallinity, and homogeneity of the oxide layer are performed and thermal treatments aiming to enhance these parameters and stabilize the electrochemical performances are explored. Solubility of the deposited MoOx has been found to be a major issue in aqueous electrolytes and in that regard tests have been performed in organic electrolytes with lithium salts to insure stability of the final system. First results obtained for a simple binary MoOx-CNTs electrode already present a good maximum specific capacitance of 110 F/g. [1] National Science Review, 4, 1 (2017) 71–90 [2] Prog. Mater. Sci. 74 (2015) 51-124. [3] Ceram. Int. 44 (2018) 10863-10870. [4] Chem. Commun., 2011, 47, 10058–10060 5] Materials Letters 66 (2012) 102–105 [6] Adv. Funct. Mater. 2013, 23, 5074–5083 [7] Analytica Chimica Acta 496 (2003) 39–51 Figure 1

Electrochemical Deposition of a Metal–Organic Framework and Subsequent Conversion to Cobalt Selenide

Here, we prepared a cobalt–metal organic framework (MOF) by anodic electrodeposition at room temperature and transformed it first to Co3O4 by calcination. The MOF-derived Co3O4 was then employed as...

Anodic electrodeposition of ligand-free iridium oxide on titanium with high mass loading and study of electrochemical treatments

A high yielding anodic electrodeposition of IrOx particles was conducted on Ti substrates as an electrocatalyst in brine electrolysis. The formation of a stable ligand-free IrOx.nH2O was performed by hydrolyzing IrCl3·3H2O in alkaline solution followed by acid condensation process. The conversion of hydrolyzed Ir to the IrOx.nH2O particles at different pH and aging times are evaluated by the UV–visible spectroscopy. Stable IrOx suspension was prepared at pH 11 in 10 h aging time. Potentiostatic and dynamic potential sweep methods were used for the electrodeposition of IrOx. The cyclic voltammetry analysis on the formation of IrOx indicates that an anodic potential of 0.6 V (vs. SCE) is required for IrOx deposition. The results show that the electrodeposition process based on dynamic potential sweeps enhances the yield of IrOx and the electrocatalytic activity toward the oxygen evolution. The presence of both Ir(III) and Ir(IV) which was observed using X-ray photoelectron spectroscopy confirms the reversible transition of Ir(III)/Ir(IV) occurs during the growth of IrOx on the surface.

Electrodeposition of MnO2 on spray-coated nanostructured carbon framework as high performance material for energy storage

Carbon nanotubes/graphene/manganese dioxide nanostructured thin films are developed as supercapacitors electrodes in this contribution. The effects of nanostructuration and pseudocapacitance on electrochemical performances are investigated. The challenge is to assemble these materials in a composite electrode achieving controlled homogeneity, morphology, and composition. Mixing carbon nanotubes (CNTs) and graphene sheets in a hierarchical organization can increase the accessibility of the electrolyte to the entire active surface by creating a controlled porous network inside the electrode. The carbon nanomaterials are deposited on a current collector by dynamic spray gun deposition, an easily scalable, reproducible and industrially suitable method used for nano-structuration of thin films. MnO2 nanocrystals are obtained by anodic electrodeposition directly on this conductive nanostructured carbon framework. This binder free electrode is characterized by SEM, TEM, XPS, XRD, microporosity, Raman spectroscopy, and electrochemistry. Results show that the specific capacitance of the samples can reach 209 F/g thanks to a strong control of the MnO2 morphology, particle size and to adequate Mn/C ratios. The electrode has very good stability with capacitance retention of 96% after 3000 charge/discharge cycles.

Electrochemically anchored manganese hexacyanoferrate nanocubes on three-dimensional porous graphene scaffold: Towards a potential application in high-performance asymmetric supercapacitors

An efficient two-step strategy is proposed to fabricate binderless and high-performance pseudocapacitive material/carbonaceous material composite electrodes for practical applications in energy-storage power sources. Taking value of this superior architecture, we demonstrate a three-dimensional (3D) reduced graphene oxide-supported manganese hexacyanoferrate (MnHCF/rGO) hybrid electrode. Firstly, a 3D conductive rGO scaffold is constructed via electrophoretic deposition (EPD) of graphene oxide nanoplatelets (GONPs) on graphite substrate and a subsequent electrochemical reduction to enhance their electrical conductivity. Then, MnHCF nanocubes are orderly grown onto the rGO nanosheets by an anodic galvanostatic pulse electrodeposition (GPED). This 3D porous electrode structure provides more active sites for electrochemical reactions, facilitates electron and ion transport and prevents the aggregation of MnHCF nanocubes during charge-discharge cycling. The as-prepared rGO-supported MnHCF electrode demonstrates a high specific capacitance of 612 F g−1 at 1.0 A g−1 as well as outstanding cycling stability (93.8% capacitance retention after 2000 cycles). Furthermore, an asymmetric supercapacitor device consisting of the MnHCF/rGO positive electrode and pure rGO negative electrode delivers a high energy density of 45.3 Wh Kg−1 at a power density of 916 W kg−1 in the wide operation voltage of 1.9 V and remarkable cycling stability (91.2%, 4000 cycles).

Stirring-mediated anomalous dielectric behaviour of electrodeposited and in situ oxidized FeAl2O4 thin films

Spinel ferrites, due to high permeability and stability, possess remarkable features that make them a favourable candidate for spintronic applications. Electrodeposition method is used for the synthesis of iron aluminium oxide (FAO) thin films. A series of samples are prepared by keeping deposition time constant at 10 min, and in situ oxidation time varied as 5 min, 10 min, 15 min and 20 min by anodic electrodeposition. These electrodeposited FAO thin films are annealed at 500 Oe applied magnetic field at 300 °C in vacuum. At 5-min oxidation time, mixed structural phases, i.e. FeAl2O4 and Al2O3, are observed, whereas phase-pure FeAl2O4 is observed at 10-min oxidation time. A further increase in oxidation time to 15 min and 20 min results in reappearance of mixed phases. Phase-pure FeAl2O4 thin film at oxidation time of 10 min exhibits bond angle of ~ 158.59° with + ive tilt ~ 4.59°. A decrease in bond angle (i.e. ~ 139.20°) with − ive tilt ~ − 14.8° is observed with an increase in oxidation time to 20 min. SEM micrographs show the formation of octahedral and dodecahedral grains for 10-min oxidation time with grain size in the range of 2–3 μm. FTIR and Raman analysis confirms the formation of FeAl2O4 thin film at 10-min oxidation time with the appearance of bands at 610.94 cm−1 and 753 cm−1, respectively. Magnetic hysteresis curves show a ferromagnetic behaviour of iron aluminium oxide thin films. Thin film prepared using 10-min oxidation time shows a relatively higher value of saturation magnetization Ms (17.89 emu/cm3). Anomalous dielectric behaviour is observed for FeAl2O4 thin films due to the resonance phenomena at higher frequencies. Dielectric constant of ~ 37.96 at log f = 5.0 is observed for 10-min oxidation time. Temperature-dependent dielectric study is also carried out in the temperature range of 30–210 °C. Fitting of Cole–Cole plots through ZView software shows a strong dependence of dielectric constant on grain boundary resistance. This is to be emphasized that detailed study on the dielectric and impedance properties of electrodeposited iron aluminium oxide thin films is rare to be found. Having knowledge of room temperature and temperature-dependent dielectric properties of iron aluminium oxide thin films will help in extending the field of application to the microelectronic industry.

Anodically electrodeposited NiO nanoflakes as hole selective contact in efficient air processed p-i-n perovskite solar cells

Nanostructured NiO as hole selective contact for perovskite solar cells is deposited on ITO from the potentiostatic anodic electrodeposition of NiOOH. Along with the large surface extension due to the honeycomb-like morphology, the electrodeposition route imparts different electrochemical features in respect to the classic sol-gel derived NiO, which are two interesting features for optoelectronic applications. CH3NH3PbI3 is deposited in ambient atmosphere on the NiO substrates to fabricate p-i-n perovskite solar cells, with PCBM and solution processed BCP as electron selective contact and silver as counter electrode. We found that the performances are strongly dependent on the deposition potential, with the PCE increasing when going from 1.00 V to 1.10 V vs Ag/AgCl. The best efficiency obtained is 16.1%, thanks to a fill-factor of 78%. Notably, the electrodeposited layer outperformed the sol-gel spin-coated one, proving the effectiveness of electrosynthesis to achieve competitive selective contacts for perovskite photovoltaics.

Electron Transfer Kinetics at Graphene Quantum Dot Assembly Electrodes.

Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (hexabenzocoronene (HBC) and carbon quantum dot (CQD)) onto a conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrode states at different potentials, and tunneling rate constant (Marcus-Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc+) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than -0.5 V versus Ag/Ag+. Enabled by these large densities, the electron transfer rates at the Fc/Fc+ thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This study is expected to accelerate the discovery of improved synthetic carbon electrodes by providing fast screening methodology of their electrochemical behavior.

Bioactivity enhancement of cerium-containing titanium oxide nanotubes. Relationship between surface reactivity and nanostructuring process

The present study is focused on the development of a novel surface by electrochemical modification of titanium substrates (Ti) to enhance bone-bonding ability. A Ce-containing conversion coating was formed on Titanium oxide nanotubes (Ti_TiO2NT) (Ti_TiO2NT_CeOx) in an innovative and straightforward approach by anodic deposition. Both Ti_TiO2NT and Ti_TiO2NT_CeOx materials depict a regular and highly ordered nanotubular morphology with open tops cavities. At a molecular level, cerium ions form a stable link with titanium through a Ti–O–Ce bridging bond in a partially ordered crystal lattice of anatase, inducing a strong passivation effect. Finally, bone-bonding ability of the modified surfaces was evaluated with a bioactivity test, revealing that cerium species induce calcium phosphate precipitation with more efficiency than bare Ti and even Ti_TiO2NT surfaces. The cerium doping strongly affects the electrochemical behavior of Ti_TiO2NT_CeOx surfaces, enhancing the metal passivity. These results prove that nanoscale tailoring of Ti surface by anodic electrodeposition using cerium (i.e., 2.5 wt%) is a suitable method to retain the geometry of the original NTs and provide a reproducible, stable, nanotubular, highly ordered, bioactive and corrosion resistant material, appropriate for applications in regenerative medicine.

Understanding the Effect of Polymer Surface Layers on Magnesium Insertion in PEDOT/MnO2 Coaxial Nanowires

Rechargeable magnesium batteries are a possible alternative technology to lithium-ion batteries. However, there are challenges associated with all parts of magnesium battery systems – anode, cathode, and electrolyte. Regarding cathodes, the divalent Mg ion has slow insertion kinetics in many common metal oxide materials due to strong electrostatic interactions with the host ionic lattice. These materials are desirable due to their high voltage and thus the potential to contribute to a high energy density battery, therefore strategies to aid Mg2+ insertion in metal oxides are an important research focus. Two strategies to improve Mg2+ insertion include utilizing nanostructured cathode materials as well as introducing water, either in the electrolyte or crystal water within the metal oxide structure. Previous work demonstrated that manganese dioxide (MnO2) nanowires deposited via anodic electrodeposition effectively intercalated Mg ions when water was present in a ratio of 6:1 (H2O:Mg2+) in Mg(ClO4)2/propylene carbonate electrolyte (1). Without water in the electrolyte to solvate the Mg2+ and shield the charge, Mg2+ does not insert into the MnO2. Further, an investigation of the charge storage mechanism for this process determined that a conversion reaction on the MnO2 surface in addition to Mg insertion into the bulk both were dependent on the presence of water (2). Following this work, there were two additional characteristics of interest regarding MnO2 cathodes cycled in water-containing organic electrolyte: manganese dissolution and electronic conductivity. A previously published one-step co-electrodeposition process of MnO2 and poly(3,4-ethylenedioxythiophene)(PEDOT) provided a tunable structure to test both effects (3). With the PEDOT surface layer, there are two possible advantages: first is confining the MnO2 layer to minimize Mn dissolution, and second is addition of the more electronically conductive PEDOT layer for fast electron transport along the comparatively resistive MnO2 material. Here, coaxial PEDOT/MnO2 nanowires served as a test structure to investigate how a PEDOT surface layer affected Mg ion insertion into the MnO2 at the core and to develop additional understanding of the properties of MnO2 and how structural alterations could influence the electrochemical reactions. By altering the voltage of electrodeposition, the thickness of the PEDOT layer was varied. Cyclic voltammetry and galvanostatic charge/discharge tests were done to evaluate the Mg insertion capabilities, power performance, and cyclability of coaxial nanowires with PEDOT thicknesses ranging from 10-90 nm. Transmission electron microscopy and scanning electron microscopy were used to monitor structural properties and changes. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to monitor changes in manganese content. This work will address how PEDOT thickness influences the ability of Mg2+ to insert into MnO2, how it affects Mn dissolution, and how the increased electronic conductivity of PEDOT impacts performance when cycling at higher current densities. These results could help inform better design of future cathode materials for rechargeable Mg battery systems. 1. J. Song, M. Noked, E. Gillette, J. Duay, G. Rubloff and S. B. Lee, Physical Chemistry Chemical Physics, 17, 5256 (2015).2. E. Sahadeo, J. Song, K. Gaskell, N. Kim, G. Rubloff and S. B. Lee, Physical Chemistry Chemical Physics, 20, 2517 (2018).3. R. Liu and S. B. Lee, Journal of the American Chemical Society, 130, 2942 (2008).