Toward Effective CO Reduction in an Acid Medium: Electrocatalysis at CuO-Derived Polycrystalline Cu Sites Immobilized within the Network of WO Nanowires.

A hybrid catalytic system composed of copper (I)-oxide-derived copper nanocenters immobilized within the network of tungsten oxide nanowires has exhibited electrocatalytic activity toward CO reduction in an acid medium (0.5 mol dm HSO). The catalytic system facilitates conversion of CO to methanol and is fairly selective with respect to the competing hydrogen evolution.

Discrete, Cationic Palladium(II)-Oxo Clusters via f-Metal Ion Incorporation and their Macrocyclic Host-Guest Interactions with Sulfonatocalixarenes.

We report on the discovery of the first two examples of cationic palladium(II)-oxo clusters (POCs) containing f-metal ions, [Pd O M {(CH ) AsO } (H O) ] (M=Ce , Th ), and their physicochemical characterization in the solid state, in solution and in the gas phase. The molecular structure of the two novel POCs comprises an octahedral {Pd O } core that is capped by eight M ions, resulting in a cationic, cubic assembly {Pd O M } , which is coordinated by a total of 16 terminal dimethylarsinate and eight water ligands, resulting in the mixed Pd -Ce /Th oxo-clusters [Pd O M {(CH ) AsO } (H O) ] (M=Ce, Pd Ce ; Th, Pd Th ). We have also studied the formation of host-guest inclusion complexes of Pd Ce and Pd Th with anionic 4-sulfocalix[n]arenes (n=4, 6, 8), resulting in the first examples of discrete, enthalpically-driven supramolecular assemblies between large metal-oxo clusters and calixarene-based macrocycles.

Enhancement of Activity and Development of Low Pt Content Electrocatalysts for Oxygen Reduction Reaction in Acid Media.

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, then O-reduction often proceeds at a less positive potential, and produces higher amounts of undesirable HO-intermediate.

Differences in electrochemical response of prospective anticancer drugs IPBD and Cl-IPBD, doxorubicin and Vitamin C at plasmid modified glassy carbon.

For the comparison of the DNA interactions with drugs, two newly synthesized prospective anticancer drugs, 6-(1H-imidazo[4,5-b]phenasine-2-yl)benzene-1,3-diol (IPBD) and, its -Cl derivative (Cl-IPBD) have been compared with doxorubicin, a drug widely used in medicine, and with Vitamin C. These compounds were accumulated at a supercoiled scpUC19 plasmid layer formed on a glassy carbon electrode (GCE). Stability of the drug-plasmid/GCE layer was achieved by initial plasmid accumulation using prolonged potential cycling for ca.

Fe -Containing 96-Tungsto-16-Phosphate: Synthesis, Structure, Magnetism and Electrochemistry.

The 48-Fe -containing 96-tungsto-16-phosphate, [Fe (OH) (H O) (HP W O ) ] (Fe ), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {Fe P W } 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 Fe was synthesized by a simple one-pot reaction of an {Fe } coordination complex with the hexalacunary {P W } POM precursor in water.

15-Copper(ii)-containing 36-tungsto-4-silicates(iv) [CuO(OH)X(A-α-SiWO)] (X = Cl, Br): synthesis, structure, magnetic properties, and electrocatalytic CO reduction.

The 15-copper(ii)-containing 36-tungsto-4-silicates [Cu15O2(OH)10X(A-α-SiW9O34)4]25- (X = Cl, 1; Br, 2) have been prepared in 70% yield by reaction of the trilacunary 9-tungstosilicate precursor [A-α-SiW9O34]10- with Cu2+ ions in aqueous pH 8 medium. Both polyanions 1 and 2 were isolated as hydrated mixed potassium/sodium salts and characterized in the solid state by FT-IR, TGA, single-crystal XRD, and elemental analysis. DC magnetic susceptibility measurements from 1.

Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase.

Solar-Driven Water Oxidation and Decoupled Hydrogen Production Mediated by an Electron-Coupled-Proton Buffer.

Solar-to-hydrogen photoelectrochemical cells (PECs) have been proposed as a means of converting sunlight into H2 fuel. However, in traditional PECs, the oxygen evolution reaction and the hydrogen evolution reaction are coupled, and so the rate of both of these is limited by the photocurrents that can be generated from the solar flux. This in turn leads to slow rates of gas evolution that favor crossover of H2 into the O2 stream and vice versa, even through ostensibly impermeable membranes such as Nafion.

Nanocomposite semi-solid redox ionic liquid electrolytes with enhanced charge-transport capabilities for dye-sensitized solar cells.

The ability of Pt nanostructures to induce the splitting of the II bond in iodine (triiodide) molecules is explored here to enhance electron transfer in the iodine/iodide redox couple. Following the dispersal of Pt nanoparticles at 2 % (weight) level, charge transport was accelerated in triiodide/iodide-containing 1,3-dialkylimidazolium room-temperature ionic liquid. If both Pt nanoparticles and multi-walled carbon nanotubes were introduced into the ionic-liquid-based system, a solid-type (nonfluid) electrolyte was obtained.

CO₂ electroreduction at bare and Cu-decorated Pd pseudomorphic layers: catalyst tuning by controlled and indirect supporting onto Au(111).

We report here the results of electrochemical studies on CO2 electroreduction at multilayered catalyst composed of the monatomic layer of copper covering palladium overlayers (0.8-10 monolayers) deposited on the well-defined Au(111) surface. These multilayered systems were obtained by successive underpotential deposition steps: Pd on Au(111) as well as Cu on Pd/Au(111).

Enhanced water splitting at thin film tungsten trioxide photoanodes bearing plasmonic gold-polyoxometalate particles.

Tungsten trioxide (WO3) is one of a few stable semiconductor materials liable to produce solar fuel by photoelectrochemical water splitting. To enhance its visible light conversion efficiency, we incorporated plasmonic gold nanoparticles (Au NPs) derivatized with polyoxometalate (H3PMo12O40) species into WO3. The combined plasmonic and catalytic effect of Au NPs anchored to the WO3 surface resulted in a large increase of water photooxidation currents.

Assembly of crosslinked oxo-cyanoruthenate and zirconium oxide bilayers: Application in electrocatalytic films based on organically modified silica with templated pores.

Electrochemical deposition of crosslinked oxo-cyanoruthenate, Ru-O/CN-O, from a mixture of RuCl and KRu(CN) is known to yield a film on glassy carbon that promotes oxidations by a combination of electron and oxygen transfer. Layer-by-layer (LbL) deposition of this species and of a film formed by cycling of the electrode potential in a ZrO solution systematically increases the number of catalytically active sites of the Ru-O/CN-O on the electrode. The evaluation of the electrocatalytic activity was by cyclic voltammetric oxidation of cysteine at pH 2.

Electrocatalytic oxidation of small organic molecules in acid medium: enhancement of activity of noble metal nanoparticles and their alloys by supporting or modifying them with metal oxides.

Different approaches to enhancement of electrocatalytic activity of noble metal nanoparticles during oxidation of small organic molecules (namely potential fuels for low-temperature fuel cells such as methanol, ethanol and formic acid) are described. A physical approach to the increase of activity of catalytic nanoparticles (e.g.

Electrochemically assisted fabrication of size-exclusion films of organically modified silica and application to the voltammetry of phospholipids.

Modification of electrodes with nm-scale organically modified silica films with pores diameters controlled at 10- and 50-nm is described. An oxidation catalyst, mixed-valence ruthenium oxide with cyano crosslinks or gold nanoparticles protected by dirhodium-substituted phosophomolybdate (AuNP-RhPMo), was immobilized in the pores. These systems comprise size-exclusion films at which the biological compounds, phosphatidylcholine and cardiolipin, were electrocatalytically oxidized without interference from surface-active concomitants such as bovine serum albumin.

Toward more efficient bioelectrocatalytic oxidation of ethanol for amperometric sensing and biofuel cell technology.

The integrated, structured, and multifunctional bioelectrocatalytic system for effective oxidation of ethanol is developed here. The concept is based on the layer-by-layer (LbL) assembly through electrostatic attraction of positively charged, multiwalled carbon nanotubes and the controlled combination of dehydrogenase enzymes. More specifically, the LbL technique was employed for sequential immobilization of two dehydrogenase enzymes and poly(diallyldimethylammonium chloride)-covered multiwalled carbon nanotubes onto a glassy carbon electrode substrate.

Enhanced oxygen reduction at Pd catalytic nanoparticles dispersed onto heteropolytungstate-assembled poly(diallyldimethylammonium)-functionalized carbon nanotubes.

Both Keggin-type phosphotungstic acid (HPW) and Pd are not prominent catalysts towards the oxygen reduction (ORR), but their composite Pd-HPW catalyst produces a significantly higher electrochemical activity for the ORR in acidic media. The novel composite catalyst was synthesized by self-assembly of HPW on multi-walled carbon nanotubes (MWCNTs) via the electrostatic attraction between negatively charged HPW and positively charged poly(diallyldimethylammonium (PDDA)-wrapped MWCNTs, followed by dispersion of Pd nanoparticles onto the HPW-PDDA-MWCNT assembly. The as-prepared catalyst was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Phosphomolybdate-modified multi-walled carbon nanotubes as effective mediating systems for electrocatalytic reduction of bromate.

Electrocatalytic properties (towards reduction of bromate in 0.5moldm(-3) H(2)SO(4)) of multi-walled carbon nanotubes (CNTs) modified with phosphododecamolybdate (PMo(12)) monolayers have been diagnosed using cyclic voltammetry and amperometry. The ability of negatively charged PMo(12)-modified CNTs to attract electrostatically ultra-thin, positively charged conducting polymer (PEDOT or polypyrrole) structures is explored to grow in controlled manner hybrid organic-inorganic network electrocatalytic films.

ABTS-modified multiwalled carbon nanotubes as an effective mediating system for bioelectrocatalytic reduction of oxygen.

The ability of such a common redox mediator as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) to undergo sorption on carbon surfaces is explored here to convert multiwalled carbon nanotubes (CNTs) into a stable colloidal solution of ABTS-modified carbon nanostructures, the diameters of which are approximately 10 nm (as determined by transmission electron microscopy). Subsequently, inks composed of fungal laccase (Cerrena unicolor) mixed with the dispersion of ABTS-modified CNTs and stabilized with Nafion, were deposited on glassy carbon and successfully employed to the reduction of oxygen in McIlvain buffer at pH 5.2.

Analysis of charge transport in gels containing polyoxometallates using methods of different sensitivity to migration.

Two methods have been used for examination of transport of charge in gels soaked with DMF and containing dissolved polyoxometallates. The first method is based on the analysis of both Cottrellian and steady-state currents and therefore is capable of giving the concentration of the electroactive redox centres and their transport (diffusion-type) coefficient. The second method provides the real diffusion coefficients, i.

Monitoring of conductivity changes in passive layers by scanning electrochemical microscopy in feedback mode: localization of pitting precursor sites on surfaces of multimetallic phase materials.

Scanning electrochemical microscopy (SECM) in feedback mode was applied to monitor changes in the electronic conductivity of a passive layer existing on a nanocrystalline Nd-Fe-B-type permanent magnet of the following composition, Nd13.5Fe79.5Si1B6 (where subscripts denote at.

Hybrid bioelectrocatalyst for hydrogen peroxide reduction: immobilization of enzyme within organic-inorganic film of structured Prussian Blue and PEDOT.

Fabrication of structured film (on glassy carbon substrate) composed of compact Prussian Blue (that has been prepared by alternate immersions and through assembling within ultra-thin layers of 4(pyrrole-1-yl)-benzoic acid, PPyBA) and poly(3,4-ethylendioxythiophene), PEDOT, is described. This functionalized film has been characterized by fast charge propagation, and it has served as a redox conducting template for permanent attachment of a model enzyme, horseradish peroxidase, HRP. The resulting organic-inorganic system acts as an effective hybrid bioelectrocatalyst for electroreduction of hydrogen peroxide, a model reactant for biosensors and biofuel cells.

Polyoxometallates as inorganic templates for electrocatalytic network films of ultra-thin conducting polymers and platinum nanoparticles.

We develop a concept of fabrication of the multilayer network films on electrodes by exploring the ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo(12)O(40)(3-)), to form stable anionic monolayers (templates) on carbon and metals including platinum. By repeated alternate treatments in the solution of PMo(12)O(40)(3-) (or in the colloidal suspension of polyoxometallate-protected Pt-nanoparticles) and in the solution of monomer (e.g.

Iterative absolute electroanalytical approach to characterization of bulk redox conducting systems.

A novel electroanalytical approach is proposed here, and it is demonstrated with the direct and simultaneous determination of two unknowns: the concentration of redox sites and the apparent diffusion coefficient for charge propagation in a single crystal of dodecatungstophosphoric acid. This Keggin-type polyoxometalate serves as a model bulk redox conducting inorganic material for solid-state voltammetry. The system has been investigated using an ultramicrodisk working electrode in the absence of external liquid supporting electrolyte.