Solid State Electrochemistry

Nonstoichiometric molybdenum oxides (e-Mo x O y ) were synthesized by cathodic reduction of aqueous ammonium and sodium molybdate solutions. Surface morphology of electrolytic (e) deposits, the chemical composition, crystal lattice structure, and the characteristics of electrochemical Li + intercalation for such synthesized oxides were determined by the cation composition of molybdate solution and the conditions of deposit annealing. The electrochemical intercalation of Li + ions in these Mo-oxides was investigated in thinlayer ''ballast-free'' electrodes, as a pasted composite cathode in lithium batteries, and as an anode in lithiumion batteries, with liquid organic and polymer electrolytes. The reversible discharge capacity of e-Mo 4 O 11 synthesized from ammonium molybdate electrolyte in thin-layer ballast-free electrodes can exceed 225 mAh g À1 for more than 170 cycles.

In this review, a summary of our published results, completed with new unpublished data are considered together with some of other authors' publications, making an attempt to reveal the mechanism of the third element co-deposition in electroless NiP plating and to define its influence on the ternary coatings' properties. A model explaining the triple role of Cu added to the solution for electroless (EL) NiP plating is described: as a stabilizer [Cu(I)]; as an accelerator; and as a stability-affecting agent, forming a dispersed solid phase in the solution. The disproportionation reaction of Cu(I) has been taken into account. A planned experiment was performed using fulleffect factorial design with two levels of three process variables, and the response surfaces were constructed. The interaction between the factors was revealed. The results are in harmony with the aforementioned model. In low-tin Ni-Sn-P coatings, the alloy components are uniformly distributed both on the surface and through the thickness. In contrast, high-tin coatings exhibit three-dimensional areas enriched in Sn and impoverished in Ni and P. As the reason for their formation, the disproportionation reaction of Sn(II) is suggested, supposed to be locally predominant over the hypophosphite oxidation. EL deposition of pure Sn onto Ni-Sn-P substrates is shown. The inclusion of Cu or Sn in EL NiP increases the thermal stability of amorphous state, ensures the preservation of a paramagnetic behavior and improves the corrosion resistance.

Electrochemical characteristics for the nanoporous carbon|Et 4 NBF 4 +acetonitrile interface have been studied by cyclic voltammetry and impedance spectroscopy methods. The influence of the electrolyte concentration and thickness of the nanoporous electrode material on the shape of the cyclic voltammetry and impedance curves has been established and the reasons for these phenomena are discussed. A value of zero charge potential, depending slightly on the structure and concentration of the electrolyte, the region of ideal polarizability and other characteristics have been established. The nanoporous nature of the carbon electrodes introduces a distribution of resistive and capacitive elements, giving rise to complicated electrochemical behaviour. Analysis of the complex plane plots shows that the nanoporous carbon|Et 4 NBF 4 +acetonitrile electrolyte interface can be simulated by an equivalent circuit, in which two parallel conduction paths in the solid and liquid phases are interconnected by the doublelayer capacitance in parallel with the complex admittance of the hindered reaction of the charge transfer or of the partial charge transfer (i.e. adsorption stage limited) process. The values of the characteristic frequency depend on the electrolyte concentration and electrode potential, i.e. on the nature of the ions adsorbed at the surface of the nanoporous carbon electrode. The value of the solid state phase resistance established is independent of the thickness of the electrode material.

Electrochemical and corrosion behaviour of metals in alcohols are the subject of numerous investigations because of the application of mentioned solvents in chemical engineering, production of oxide nanoparticles (sol-gel techniques) and application of alcohols as fuels. Despite relatively rich bibliography related to electrocatalytic oxidation of alcohols on metal surface in mixed aqueous-alcohol solutions, the knowledge of the mechanism of reactions on metal/anhydrous alcohol interface is still not sufficient. Anodic oxidation of metal surface in alcohol leads to several electro-catalytic reactions with formation of surface compounds being the product of metal and alcohol oxidation. Identification of these products is very difficult. Therefore, our knowledge of the composition and structure of passive films or corrosion products on metal surface in anhydrous alcohol solvents is poor. Our paper presents the investigations of anodic behaviour of metals (Cu, Zn, Fe, Ni, Al and Ti) and semiconductors (p-Si) in methanol solutions of electrolytes, performed in our laboratory within the last 10 years. On the base of electrochemical measurements (linear sweep voltammetry, electrochemical impedance spectroscopy), spectroscopic investigations (X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and low-energy electron diffraction) and scanning electron microscopy techniques, the role of metal-alcohol intermediates in the formation of surface and soluble compounds is discussed. The practical application of electrochemical etching of metals as a method of production of micro-and nanoparticles of metals and oxides is also shown.

Polypyrrole films doped with sulfonated β-cyclodextrin (PPy/sβ-CD) and carboxymethyl β-cyclodextrin (PPy/CMβ-CD) were formed on electropolymerisation of pyrrole in a solution of the cyclodextrin sodium salts. Lower rates of electropolymerisation were evident with the carboxymethyl β-CD and this was attributed to protonation of the carboxylate groups due to an increase in the interfacial pH at the electrode-solution interface. The PPy/sβ-CD and PPy/CMβ-CD films showed cation exchange behaviour with the ingress of Na + and its associated water molecules on reduction. The PPy/CMβ-CD film showed less electroactive behaviour which may be related to the lower number of anionic pendants on the CMβ-CD or to the possible precipitation of the less soluble neutral CD which arises due to the protonation of the carboxylate groups. The PPy/sβ-CD showed a high capacitance of 6.0 mF cm −2 corresponding to a specific capacitance of 71 F g −1 over a wide potential range extending from − 0.60 to 0.60 V vs SCE. Over-oxidation was observed at relatively low potentials, at about 0.60 V vs SCE. A diffusion coefficient of 6.47 × 10 −6 cm 2 s −1 and a rate constant of 3.73 × 10 −2 cm s −1 were obtained for the ferricyanide redox couple at the PPy/sβ-CD, indicating little or no inhibition of the ferricyanide redox reaction.

Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene varying the chain length in the range between 5 and 23 double bonds provide deeper insights into the redox properties of such systems. Furthermore, cyclic voltammetric studies of α,ω-diphenylpolyenes and phenylenevinylenes give clear evidence that the formation of the radical ions is followed by a rapid reversible dimerization between the oligomeric chains. The thermodynamic and kinetic parameters of the chemical reaction are presented. Applying these results to the properties of conducting polymers opens up new perspectives for interpreting charge storage and conductivity.

The electrochemical behaviour of self-assembled monolayer (SAM) of aliphatic hexadecanethiol was studied by cyclic voltammetry (CV), elimination voltammetry with linear scan (EVLS) and crystal quartz microbalance (QCM). SAMs were electrochemically created on gold-coated QCM crystal through the sulphur in 1-hexadecanethiol molecule head group. The effect of thiol concentration and potential scan rate on the SAM formation was studied. Formation of SAM was confirmed by CVand QCM. EVLS results revealed the kinetically controlled process followed with electrode reaction in adsorbed state characteristic for SAM formation at lower concentration. The electrode reaction of a totally adsorbed electroactive species was indicated by means of a peak-counter peak signal at higher thiol concentration.

A stoichiometric MgAl 2 O 4 spinel powder was synthesized by a microwave-assisted combustion synthesis (MWCS) route. For the purpose of comparison, another stoichiometric MgAl 2 O 4 spinel powder was also prepared following the conventional combustion synthesis (CCS) method. The batch size had a strong influence on the specific surface area of the material, which in turn is highly dependent on the preparation method adopted. The surface areas of these synthesized powders were found to decrease from 36.78 to 0.1 m 2 /g for MWCS and 126 to 8.06 m 2 /g for CCS samples, respectively, when the batch size was increased from 2 to 100 g. This could be attributed to sintering of the samples due to high adiabatic temperature generated as a result of increased heat accumulation with bigger batch quantities. Between the two powders synthesized by the two different routes, the powders obtained by MWCS and CCS routes were found to contain grains/crystals in range of 20-50 and 100-250 nm size, respectively. The thermogravimetry/differential thermal analysis (TG-DTA) and X-ray diffraction (XRD) studies reveal that microwave-assisted combustion synthesis route yields materials with higher degree of compositional stability and phase purity as compared to the conventional combustion synthesis method.

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Green biosynthesis of nanoparticles and their applications in sensor field is of great interest to the researchers. We report herein a simple green approach for the synthesis of silver nanoparticles (Ag-NPs) using Acacia nilotica Willd twig bark and its application for the detection of 4-nitro phenol (4-NP). The synthesized Ag-NPs were characterized by Transmission electron microscopy, X-ray diffraction and elemental analysis. The size of synthesized Ag-NPs was in the range of 10-50 nm. The Ag-NPs modified electrode shows a high sensitivity and selectivity towards the sensing of 4-NP. The fabricated modified electrode shows a low detection limit of 15 nM on the wider linear response range from 100 nM to 350 μM with the sensitivity of 2.58±0.05 μAμM −1 cm −2 . In addition, the fabricated sensor shows good repeatability and reproducibility.

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H 2 O 2 formed during the enzymatic process.

Passivity of metals and alloys is a phenomenon of utmost technical importance as it prevents many construction materials from rapid deterioration. For the majority of metals, passivity is based on the spontaneous formation of a thin oxide layer (the passive ®lm), in a speci®c environment. This ®lm can slow corrosion (dissolution) reactions by many orders of magnitude. The present review tries to give an overview of several important aspects and factors that in¯uence ®lm formation, stability and breakdown. Emphasis is on chemical stability and its connection to thermodynamic, kinetic and electronic aspects of the metal/oxide/environment system. Although some metals (e.g. Fe) and alloys (e.g. Fe/Cr) are treated with greater depth, the focal point is the description of general mechanistic approaches ± for speci®c systems the reader is referred to secondary literature.

Density functional theory (DFT) calculations are performed to analyze curvature effects in the oxidative longitudinal unzipping of carbon nanotubes (CNTs) of different diameters. The reactions considered involve the adsorption of permanganate, followed by the oxidation of the nanotube, which results in dione and hole formation. The study was performed with armchair CNTs of different diameters and with corrugated graphene layers, which emulate the curvature of CNT of larger radii, with the finding that the curvature and the pyramidalization angle of the these structures strongly affects the stability of the intermediate dione structure formed during the unzipping process. Permanganate adsorption energies increase for more curved surfaces promoting the oxidation reaction in surfaces of small radius, making this reaction spontaneous for small radius. The second permanganate adsorbs on the parallel carbon-carbon bond to first diona formation resulting the longitudinal unzipping of the CNT.

The interaction of safranin O (SO) with doublestranded calf thymus DNA was investigated electrochemically, using a DNA-modified glassy carbon (GC-DNA) electrode. The results were compared with those obtained using a bare GC electrode. The formal potential of SO was more negative when using the GC-DNA electrode, although the rate of heterogeneous electron transfer was not altered. The GC-DNA electrode enabled preconcentration of the SO on the electrode surface, despite the fact that the mass transfer effects in the thin DNA layer adsorbed on the surface were still observed. The diffusion coefficient of SO and the binding ratio for the oxidized and reduced forms of the bound species were obtained. A binding isotherm for SO at the GC-DNA electrode was plotted from coulometric titrations, giving a binding constant of 5.8×10 4 L mol −1 .

In this study, Co 3 O 4 /SiO 2 nanocomposites have been successfully synthesized by citrate-gel method by utilizing SiO 2 matrix for Co 3 O 4 embedment. Spectroscopy analyses confirm the formation of high crystalline Co 3 O 4 nanoparticles; meanwhile, microscopy findings reveal that the Co 3 O 4 nanoparticles are embedded in SiO 2 matrix. Electrochemical properties of the Co 3 O 4 /SiO 2 nanocomposites were carried out using cyclic voltammetry (CV), galvanostatic chargedischarge, and electrochemical impedance spectroscopy (EIS) in 5 M KOH electrolyte. The findings show that the charge storage of Co 3 O 4 /SiO 2 nanocomposites is mainly due to the reversible redox reaction (pseudocapacitance). The highest specific capacitance of 1,143 F g −1 could be achieved at a scan rate of 2.5 mV s −1 in the potential region between 0 and 0.6 V. Furthermore, high-capacitance retention (>92 %) after 900 continuous charge-discharge tests reveals the excellent stability of the nanocomposites. It is worth noting from the EIS measurements that the nanocomposites have low ESR value of 0.33 Ω. The results manifest that Co 3 O 4 /SiO 2 nanocomposites are the promising electrode material for supercapacitor application.

Anthraquinone groups were electrochemically grafted to glassy carbon (GC) electrodes via methylene linker to study the oxygen reduction reaction (ORR) in alkaline medium. Two different anthraquinone derivatives, 2bromomethyl-anthraquinone or 2-chloromethylanthraquinone, were used to modify the GC electrode surface. Several modification conditions encompassing potential cycling and electrolysis at a fixed potential were employed in order to vary the surface concentration of MAQ groups (Γ MAQ ) and to study the dependence of the O 2 reduction behaviour on electrografting procedure. Cyclic voltammetry confirmed the presence of anthraquinone moieties attached to the GC electrode and Γ MAQ varied in the range of (0.5-2.4)× 10 −10 mol cm −2 . Oxygen reduction was studied on MAQmodified GC electrodes of various surface coverage using the rotating disc electrode (RDE) and rotating ring-disc electrode (RRDE) methods. The RDE and RRDE results of O 2 reduction reveal that GC/MAQ electrodes show rather similar electrocatalytic behaviour towards the ORR yielding hydrogen peroxide as the final product.

Substitution of classical lead anodes containing 6±8% of antimony, 4±6% of tin or 0.75±1.00% of silver in the zinc electrowinning and hard chromium plating bath with platinized and activated titanium anodes is discussed in this paper. Depending on the type of electrochemical processes, the main eects of this substitution are as follows: smaller electrical energy consumption, better current eciency, increased cell capacity, smaller electrode gap, higher purity of the deposit and savings in manpower and chemicals. Ti/Pt, Ti/Pt-IrO 2 , Ti/RuO 2 , Ti/Pt-IrO 2 -MnO 2 , Ti/Pt-IrO 2 -PbO 2 , Ti/Pt-IrO 2 -RuO 2 , Ti/MnO 2 , Ti/RuO 2 -MnO 2 and Ti/PbO 2 coated titanium anodes have been tested in synthetic as well as in industrial electrolytes. At working current densities some activated titanium anodes showed lower overpotential than the lead anode. These electrodes have continued to perform in this way during a one-year test in synthetic and industrial electrolytes so far. No signs of corrosion of the electrodes have been noticed during the test.

We report here several synthesis routes and their respective drawbacks/advantages for the preparation of pure LiFePO 4 . We demonstrate the possibility of using LiFePO 4 for electrochemical applications, with respect that an effective carbon coating was realized onto the smallest particles. Actually, to bypass the weak ionic conductivity of lithium iron phosphate, the thinnest would be the particles; the highest would be the performance under severe electrochemical conditions.

Nanorods, nanocolumnar-based ceria thin films were electrodeposited onto (FTO) or (ITO) glass substrates, at room temperature. Cubic fluorite type ceria nanostructured films of high crystal quality were synthesized on both substrates, as confirmed by X-ray diffraction and Raman spectroscopy. It was found that a substrate is a structure-directing agent for the growth process of ceria. Columnar-like particles were grown on

The availability and application of solid-state reference electrodes for potentiometric electrochemical sensors are briefly reviewed. For a long time, considerable efforts have been made to combine solid-state indicator electrodes with equivalent reference electrodes to take advantage of the absence of liquid system components to full capacity. In spite of various suggestions to solve the problem, no type of solidstate reference electrode is so far available with properties completely identical to conventional ones.

For a long time, the world has been waiting for a sustainable, inexpensive, and efficient material for application in electronic and energy conversion purposes. Cu 2 O thin films made by electrodeposition clearly fulfill the sustainability and cost prerequisites , and are broadly believed that they could lead to the fabrication of highly efficient devices if well prepared and designed. Here, we review the fundamentals for electrochemical synthesis and the electrodeposition aspects and procedures for growing Cu 2 O. The properties of electrodeposited Cu 2 O in thin films and nanostructures will be discussed in view of the literature, with emphasis on the electrical and optical properties and applications in photocatalysis and photovoltaics.

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Glass pH electrodes are being utilized for the measurement of pH values using liquid internal reference systems, which had been introduced on principle nearly hundred years ago and are still existing. To avoid several drawbacks in the practical usage of these kinds of chemical sensors, every effort has been made to develop an all-solidstate electrode with properties that are comparable to those of the conventional glass electrode. Metal oxide electrodes like RuO 2 or IrO x are a low-priced alternative. Different concepts for substituting the conventional (aqueous) reference system by solid systems and also for changing the classical bulb shape design to a planar structured one have been proposed. A suitable reference system can be achieved by means of modification of classic reference electrodes by employing a new type of mixed conducting oxides. Both metal oxide and glass electrodes can be screen-printed on substrate materials like ceramics and plastics etc. to get miniaturized all-solid-state electrodes. pH sensors based on field effect transistors (FET) become more important. However, up to now an equivalent FET compatible reference electrode is not available.

This paper reviews the literature describing the eects of conducting polymer coatings on the corrosion rate of ferrous alloys (iron, steel and stainless steel). The literature is interpreted in terms of the proposed mechanisms of corrosion protection: barrier, inhibitor, anodic protection and the mediation of oxygen reduction. The most intriguing aspect of the reported literature are the studies demonstrating corrosion protection when deliberate defects were introduced into the coating to expose the bare metal. These studies show that protection afforded by conducting polymer coatings is not due to simple barrier protection or inhibition alone. Many studies illustrate that the polymer/metal interface is modi®ed to produce passivating oxide layers and that charge transfer reactions occur between the metal and polymer. These studies support the proposed anodic protection mechanism, as do the reports of signi®cant ennoblism. On the other hand, there is considerable variation in the reported shift in corrosion potential and these highlight the in¯uence of substrate preparation, coating composition and mode of application and the nature of the electrolyte on the corrosion protection provided by the conducting polymer. For example, the evidence suggests that the emeraldine base form of polyaniline is superior to the emeraldine salt in terms of corrosion protection for steel. However, the number of direct comparisons is small and the reasons for the dierences are not well understood. Also not well understood are the role of the counterion release and local pH changes on pinhole protection. It is also argued that the conducting polymer reduces the likelihood of large increases in pH at the polymer/metal interface and so stabilizes the coating against cathodic disbondment. Further work is clearly needed to increase the protection period by further studies on the corrosion protection mechanism so that the polymer composition and processing methods may be optimized.

Structural defects play major role in catalysis and electrocatalysis. Nanocrystalline (or nanostructured) materials composed of nanometer-sized crystallites joined via grain boundaries have been recognized for their specific structure and properties, differentiating them from single crystals, coarsely grained materials or nanometer-sized supported single-grained particles (Gleiter, Nanostruct Mater 1:1-19, 1992). In this paper, we use Pt electrodes, prepared by electrodeposition on glassy carbon and gold supports, as model nanocrystalline materials to explore the influence of grain boundaries and other structural defects on electrocatalysis of CO and methanol oxidation. We build on the recently established correlations between the nanostructure (lattice parameter, grain size, and microstrains) of electrodeposited Pt and the deposition potential (Plyasova et al., Electrochim. Acta 51:4447-4488, 2006) and use the latter to obtain materials with variable density of grain boundary regions. The activity of electrodeposited Pt in the oxidation of methanol and adsorbed CO exceeds greatly that for Pt(111), polycrystalline Pt, or single-grained Pt particles. It is proposed that active sites in nanostructured Pt are located at the emergence of grain boundaries at the surface. For methanol electrooxidation, the electrodes with optimal nanostructure exhibit relatively high rates of the "direct" oxidation pathway and of the oxidation of strongly adsorbed poisoning intermediate (CO ads), but not-too-high methanol dehydrogenation rate constant. These electrodes exhibit an initial current increase during potentiostatic methanol oxidation explained by the CO ads oxidation rate constant exceeding the methanol decomposition rate constant.

Characterizations were carried out to study on a new plasticized solid polymer electrolyte that was composed of blends of poly(vinyl chloride) (PVC), liquid 50% epoxidized natural rubber (LENR50), ethylene carbonate, and polypropylene carbonate. This freestanding solid polymer electrolyte (SPE) was successfully prepared by solution casting technique. Further analysis and characterizations were carried out by using scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimeter (DSC), Fourier transform infrared (ATR-FTIR), and impedance spectroscopy (EIS). The SEM results show that the morphologies of SPEs are compatible with good homogeneity. No agglomeration was observed. However, upon addition of salt, formation of micropores occurred. It is worth to note that micropores improve the mobility of ions in the SPE system, thus increased the ionic conductivity whereas the crystallinity analysis for SPEs indicates that the LiClO 4 salt is well complexed in the plasticized PVC-LENR50 as no sharp crystallinity peak was observed for 5-15% wt. LiClO 4 . This implies that LiClO 4 salt interacts with polymer host as more bonds are form via coordination bonding. In DSC study, it is found that the glass temperature (T g ) increased with the concentration of LiClO 4 . The lowest T g was obtained at 41.6°C when incorporated with 15% wt. LiClO 4 . The features of complexation in the electrolyte matrix were studied using ATR-FTIR at the peaks of C0O, C-O-C, and C-Cl. In EIS analysis, the highest ionic conductivity obtained was 1.20× 10 −3 S cm −1 at 15% wt. LiClO 4 at 353 K.

There are 14 articles/chapters written by 35 contributors in Part 1 of this book on electron transfer (ET), which is volume 106 of the immortal series entitled Advances in Chemical Physics. The ®rst two chapters provide an overview of the history of ET starting from the 1940s and continuing up to the present time. These chapters are written by two pioneers in the ®eld, Prof. R.M. Marcus and Prof. N. Sutin. They deliver an overview of the subject and de®ne the fundamental issues.

The composite coatings containing of nanocrystalline Ni matrix and hard nano-sized γ-Al 2 O 3 were electrodeposited in a system with a rotating disk electrode. The bath composition (nickel salts and buffer concentration, presence of surface-active agents and inert particles) influence on kinetics of Ni electrodeposition as well as on structural properties (morphology, phase composition, texture, residual stresses) and microhardness of Ni/Al 2 O 3 coatings has been investigated. SEM and TEM studies show more uniform arrangement of Al 2 O 3 particles in the matrix, however a tendency to agglomeration is observed. Surfactant application to a saccharine containing bath effectively improves the dispersion of nanoparticles into the nickel matrix. The addition of Al 2 O 3 particles results in decrease of the average Ni crystallite size. The introduction of additive into electrolyte solution resulted in change of stress character of composite coatings (from tensile to compressive). The microhardness of Ni matrix was enhanced (about 40%) due to incorporation of ceramic particles.

The following document covers the determination of the diffusion coefficient of two powder materials: LiFePO 4 and LiMn 2 O 4 by using potentiostatic intermittent titration technique (PITT) and impedance spectroscopy methodology and compares relevant results with the following relation: D ¼ R 2 I 0 3aQ , which is obtained by solving Fick's spherical coordinate equation (where I 0 is the initial step current in the PITT experiment, R is the particle radius, Q is the charge that intercalated during the step, and α is the percentage of the theoretical intercalated charge). This procedure allowed the verification of the validity of the spherical model for the powder materials, the accuracy of the expression proposed for the diffusion coefficient determination, and the correctness of the measures that had been taken.

Carbonaceous materials are widely used in electrochemistry. All allotropic forms of carbons-graphite, glassy carbon, amorphous carbon, fullerenes, nanotubes, and doped diamond-are used as important electrode materials in all fields of modern electrochemistry. Examples include graphite and amorphous carbons as anode materials in high-energy density rechargeable Li batteries, porous carbon electrodes in sensors and fuel cells, nano-amorphous carbon as a conducting agent in many kinds of composite electrodes (e.g., cathodes based on intercalation inorganic host materials for batteries), glassy carbon and doped diamond as stable robust and high stability electrode materials for all aspects of basic electrochemical studies, and more. Amorphous carbons can be activated to form very high specific surface area (yet stable) electrode materials which can be used for electrostatic energy storage and conversion [electrical double-layer capacitors (EDLC)] and separation techniques based on electro-adsorption, such as water desalination by capacitive de-ionization (CDI). Apart from the many practical aspects of activated carbon electrodes, there are many highly interesting and important basic aspects related to their study, including transport phenomena, molecular sieving behavior, correlation between electrochemical behavior and surface chemistry, and more. In this article, we review several important aspects related to these electrode materials, in a time perspective (past, present, and future), with the emphasis on their importance to EDLC devices and CDI processes.

Molybdenum oxide thin films were prepared electrochemically onto the selenium predeposited tin oxide-coated glass substrates using 0.22 M sodium citrate (C 6 H 5 Na 3 O 7 ) solution (pH 8.3) and sodium molybdate as a precursor. Cyclic voltammetry was used to determine the deposition potential effects on molybdenum compound speciation, while quantitative thin film composition was obtained from X-ray photoelectron spectroscopy depth profiles. Thin molybdenum film growth and composition was potential dependant. Predominant molybdenum species was Mo(IV) at all deposition potentials and deposition times. Optical properties of the molybdenum oxide thin films were determined using UV-VIS spectroscopy. The absorption edge varied between 560 and 650 nm, whereas optical band gap values-between 1.79 and 2.19 eV-well within the limits for solar light-induced chemical reactions.

An improved polymer electrolyte membrane fuel cell-based amperometric hydrogen sensor has been developed. The sensor operates at room temperature, and the electrolyte used in the sensor is Nafion which is a protonconducting solid polymer electrolyte. Platinum black is used as both anode and cathode. The sensor functions as a fuel cell, H 2 /Pt//Nafion//Pt/O 2 , and a mechanical barrier limits the supply of hydrogen to the sensing side electrode. The limiting current is found to be linearly related to the hydrogen concentration. The sensor can be used to measure hydrogen in argon in parts per million and percentage levels. The basic principle, details of assembly, and response behavior of the sensor are discussed.

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The electrodeposition of ternary zinc-nickel-iron alloy was studied in acidic sulfate bath. The comparison between Zn, Ni, and Fe deposition and Zn-Ni and Zn-Ni-Fe co-deposition revealed that the remarkable inhibition of Ni and Fe deposition takes place due to the presence of Zn 2+ in the plating bath. The increase in corrosion resistance of ternary deposits is not only attributed to the formation of γ-Ni 2 Zn 11 phase but also to iron co-deposition and formation of iron phase. It was also found that the bath temperature has a great effect on the surface appearance and the deposit composition. The investigation was carried out using cyclic voltammetry and galvanostatic techniques for electrodeposition, while linear polarization resistance and anodic linear sweeping voltammetry techniques were used for corrosion study. Morphology and chemical composition of the deposits were characterized by means of scanning electron microscopy and atomic absorption spectroscopy.

The article comments upon some basic concepts related to the electrocrystallization phenomena. Short stories about the founders of the classical nucleation and crystal growth theory M. Volmer, W. Kossel, I.N. Stranski, R. Kaischew, and L. Krastanow are also included.

In this paper, the morphology, the conformation, and the electrochemical performance of TiO 2 nanotubes and LiFePO 4 have been studied by using scanning electron microscope, XRD, and charge/discharge cycles. The electrochemical tests comprised low rate cycling, cycling at C rate, and cycling at different rates. This work was finalized to the fabrication of lithium-ion batteries based on the TiO 2 /LiFePO 4 redox couple. Battery cells were assembled and electrochemical tests were performed to evaluate cell capacity, power, and energy. Further tests were carried out to evaluate the capacity retention as a function of cycle number and discharge current.

ABSTRACT Micro- and mesoporous carbide-derived carbons (CDCs) were synthesised from TiC powder via a gas-phase reaction using HCl and Cl2 within the temperature range of 700–1,100 °C. Analysis of X-ray diffraction results show that TiC-CDCs consist mainly of graphitic crystallites. The first-order Raman spectra showed the graphite-like absorption peaks at ~1,577 cm−1 and the disorder-induced peaks at ~1,338 cm−1. The low-temperature N2 sorption experiments were performed, and specific surface areas up to 1,214 and 1,544 m2 g−1 were obtained for TiC-CDC (HCl) synthesised at T = 800 °C and TiC-CDC (Cl2) synthesised at T = 900 °C, respectively. For the TiC-CDC powders synthesised, a bimodal pore size distribution has been established with the first maximum in the region up to 1.5 nm and the second maximum from 2 to 4 nm. The energy-related properties of supercapacitors based on 1 M (C2H5)3CH3NBF4 in acetonitrile and TiC-CDC (Cl2) and TiC-CDC (HCl) as electrode materials were also investigated by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge and constant power methods. The specific energy, calculated at U = 3.0 V, are maximal for TiC-CDC (Cl2 800 °C) and TiC-CDC (HCl 900 °C), which are 43.1 and 31.1 W h kg−1, respectively. The specific power, calculated at cell potential U = 3.0 V, are maximal for TiC-CDC (Cl2 1,000 °C) and TiC-CDC (HCl 1,000 °C), which are 805.2 and 847.5 kW kg−1, respectively. The Ragone plots for CDCs prepared by using Cl2 or HCl are quite similar, and at high power loads, the TiC-CDC material synthesised using Cl2 at 900 °C, i.e. the material with optimal pore structure, delivers the highest power at constant energy.