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The 48‐FeIII‐containing 96‐tungsto‐16‐phosphate, [FeIII48(OH)76(H2O)16(HP2W12O48)8]36− (Fe48), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {FeIII6P2W12} units that are linked in an end‐on fashion forming a macrocyclic assembly that contains more iron centers than any other polyoxometalate (POM) known to date. The novel Fe48 was synthesized by a simple one‐pot reaction of an {Fe22} coordination complex with the hexalacunary {P2W12} POM precursor in water. The title polyanion was characterized by single‐crystal XRD, FTIR, TGA, magnetic and electrochemical studies. [ABSTRACT FROM AUTHOR]

Nanostructured mixed metal (W, Zr) oxide matrices (in a form of layered intercalated films of WO 3 and ZrO 2 ) are considered here for supporting and activating catalytic platinum nanoparticles toward electrooxidation of ethanol. Remarkable increases of electrocatalytic (voltammetric, chronoamperometric) currents measured in 0.5 mol dm −3 H 2 SO 4 (containing 0.5 mol dm −3 ethanol) have been observed. Comparison has been made to the behavior of methanol and acetaldehyde under analogous conditions. The enhancement effects are interpreted in terms of specific interactions between platinum nanoparticles and the metal oxide species, high acidity of the mixed oxide sites, as well as high population of surface hydroxyl groups and high mobility of protons existing in close vicinity of Pt catalytic sites. The metal oxide nanostructures are expected to interact competitively (via the surface hydroxyl groups) with adsorbates of the undesirable reaction intermediates, including CO, facilitating their desorption (“third body effect”), or even oxidative removal (e.g., of CO to CO 2 ). The fact that the partially reduced tungsten oxide (H x WO 3 ) component is characterized by fast electron transfers coupled to proton displacements tends to improve the overall charge propagation at the electrocatalytic interface. [ABSTRACT FROM AUTHOR]

We report here the results of electrochemicalstudies on CO2electroreduction at multilayered catalystcomposed of themonatomic layer of copper covering palladium overlayers (0.8–10monolayers) deposited on the well-defined Au(111) surface. These multilayeredsystems were obtained by successive underpotential deposition steps:Pd on Au(111) as well as Cu on Pd/Au(111). Low index orientation ofAu substrate was chosen to compare Pd overlayers with bulk Pd(111),which is known to reduce CO2to CO adsorbates in acidicsolutions. The process of CO2electroreduction was studiedby using classical transient electrochemical methods. Catalytic activityof bare Pd layers was investigated in acidic and neutral solutions.In the latter case, much higher activity of Pd overlayers was observed.The results showed that the palladium layer thickness significantlychanged the catalytic activities of both bare Pd overlayers and theone Cu monolayer covered electrodes toward CO2electroreduction.Results show that catalytic activity can be finely tuned by usingthe multilayered near-surface-alloy approach. [ABSTRACT FROM AUTHOR]

Electrochemical properties of thin films and microcrystalline precipitates of nickel(II) hexacyanoferrate(II, III), NiHCNFe, are strongly dependent on the method of their preparation and experimental conditions of their investigation. The films have been generated on both inert (gold) and parent metal (nickel) substrates. Interpretation of voltammetric responses of nickel hexacyanoferrate microstructures on electrodes is supported with the data of elemental analysis estimations obtained using atomic absorption and surface examination based on X-ray energy dispersive spectroscopy. Both electrodeposited films and mechanically-attached precipitates of nickel hexacyanoferrate constitute mixed structures in which the relative ratios of K and Ni to Fe reflect composition of a solution for modification, choice of the deposition potential and time, and the time and potential limits of exposure of the system to voltammetric potential cycling in potassium salt supporting electrolyte. We demonstrate here that the more positive set of peaks of nickel hexacyanoferrate is related to the electroactivity of the form containing relatively larger amount of potassium and smaller of nickel. On the other hand, the more negative set of the system’s peaks shall be attributed to the form that is largely potassium depleted and containing more nickel relative to iron. In this context, the use of the previously proposed approximate formulas, K2Ni[FeII(CN)6] and KNi1.5[FeII(CN)6], for the predominant nickel hexacyanoferrate (reduced) forms is justified. [Copyright &y& Elsevier]

We describe the electrochemical behavior of solid copper hexacyanoferrate (powder) investigated in the absence of contact with a liquid external supporting electrolyte. In addition to a typical hexacyanoferrate(III,II) redox transition, the system is characterized by a second electrode process which appears at more negative potentials. Diagnostic experiments, which include spectrochemical and solid-state voltammetric characterization, support our view that the latter redox reaction most likely originates from reduction of the system''s lattice copper(II) ions. The overall dynamics of charge transport in the material, when discussed in terms of effective diffusion, is moderately high (on the level of 10−8 cm2 s−1). Comparison has been also made to the electrochemical behavior of solid Prussian blue and to the voltammetric characteristics of conventional electrodes modified with thin films of copper hexacyanoferrate. [Copyright &y& Elsevier]

This work reports the synthesis, the physicochemical characterization and the electrochemical studies of new electrocatalysts (ECs) for the oxygen reduction reaction (ORR) that: (i) exhibit a hierarchical architecture; and (ii) do not comprise platinum. The active sites of the ECs consist of Fe and Sn species stabilized in “ coordination nests ” of a carbon nitride (CN) matrix. The latter exhibits a rough, microporous morphology and acts as a “ shell ” covering a graphene “ core ”. This paper: (i) discusses the role played by Fe as the “ active metal ” in this family of ECs; and (ii) examines in detail how the physicochemical properties and, correspondingly, the electrochemical performance are affected by a suitable activation procedure A meant to boost the ORR kinetics. The results lead to an improved fundamental understanding on the features of the active sites, including the impact of both A and the pH of the environment in their performance and ORR mechanism. These insights clarify the most desirable features to be included in high-performing ECs belonging to this family, paving the way to the synthesis of next-generation, efficient ECs for the ORR that do not comprise platinum. [ABSTRACT FROM AUTHOR]

Abstract: Tungsten trioxide, unhydrated with hexagonal structure (h-WO3), has been prepared by hydrothermal method at a temperature of 180°C in acidified sodium tungstate solution. Thus prepared h-WO3 has been characterized by X-ray diffraction (XRD) method and using electrochemical techniques. The morphology has been examined by scanning and transmission electron microscopies (SEM and TEM) and it is consistent with existence of nanorods of 50–70nm diameter and up to 5μm length. Cyclic voltammetric characterization of thin films of h-WO3 nanorods has revealed reversible redox behaviour with charge–discharge cycling corresponding to the reversible lithium intercalation/deintercalation into the crystal lattice of the h-WO3 nanorods. In propylene carbonate containing LiClO4, two successive redox processes of hexagonal WO3 nanorods are observed at the scan rate of 50mV/s. Such behaviour shall be attributed to the presence of at least two W atoms of different surroundings in the lattice structure of h-WO3 nanorods. On the other hand, in aqueous LiClO4 solution, only one redox process is observed at the scan rate of 10mV/s. The above observations can be explained in terms of differences in the diffusion of ions inside two types of channel cavities existing in the structure of the h-WO3 nanorods. Moreover, the material can be applied as active support for the catalytic bi-metallic Pt–Ru nanoparticles during electrooxidation of ethanol in acid medium (0.5moldm−3 H2SO4). [Copyright &y& Elsevier]

Abstract: The solid-state electrochemistry and thermochromism of cobalt hexacyanoferrate (CoHCF) in a composite matrix comprising silica sol–gel and generation-4 poly(amidoamine) dendrimer was investigated and compared to analogous studies of CoHCF powders. The thermochromic behaviour over the range, 25–85°C, of the reduced form in the sol–gel matrix differed from that of the powder. The results suggested that even in the presence of KCl in this matrix, the dominate form of the reduced CoHCF was Co2 IIFeII(CN)6 rather than K2CoIIFeII(CN)6. In contrast, the thermochromic behaviour of the oxidized form of CoHCF was the same as that reported for the powders. The observed cyclic voltammetric behaviour of CoHCF in the sol–gel composite matrix was the same as that of powders in terms of the electrode processes, but the influence of scan rate on the current was dependent upon the cell configuration. With the CoHCF-doped composite contacted to a solution phase, this behaviour was consistent with anion intercalation/de-intercalation control, but in a solid-state cell, a transition from a surface-controlled to a mass-transport controlled current was observed. [Copyright &y& Elsevier]