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In this work, a multifunctional binder with self‐healing, flame retardant, high conductivity, and abundant polar groups is prepared by the free radical polymerization method and applied to lithium–sulfur (Li‐S) batteries to achieve high safety and exceptional electrochemical performance. The self‐healing characteristic of binder induced by intermolecular hydrogen bonds and SS dynamic covalent bonds can repair volume expansion cracks. The polar groups and excellent conductivity endue binder with strong chemisorption on polysulfides and fast charge transportation, which can effectively inhibit the shuttle effect and accelerate polysulfides redox kinetics. More important, the considerable flame retardant performance of binder can improve the safety of the LiS batteries. As a result, the LiS cells using FHCP binder deliver an outstanding cycle stability of a high‐capacity retention rate of 85% after 100 cycles at 0.2 C, and a high reversible area specific capacity of 5.25 mAh cm–2 at a sulfur loading of 4.72 mg cm–2 and a correspondingly lean electrolyte condition (E/S ratio = 6 µL mg–1). [ABSTRACT FROM AUTHOR]

We report on the discovery of the first two examples of cationic palladium(II)‐oxo clusters (POCs) containing f‐metal ions, [PdII6O12M8{(CH3)2AsO2}16(H2O)8]4+ (M=CeIV, ThIV), 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 {Pd6O12}12− core that is capped by eight MIV ions, resulting in a cationic, cubic assembly {Pd6O12MIV8}20+, which is coordinated by a total of 16 terminal dimethylarsinate and eight water ligands, resulting in the mixed PdII‐CeIV/ThIV oxo‐clusters [PdII6O12M8{(CH3)2AsO2}16(H2O)8]4+ (M=Ce, Pd6Ce8; Th, Pd6Th8). We have also studied the formation of host‐guest inclusion complexes of Pd6Ce8 and Pd6Th8 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. The POCs were also found to be useful as pre‐catalysts for electrocatalytic CO2‐reduction and HCOOH‐oxidation. [ABSTRACT FROM AUTHOR]

We report on the discovery of the first two examples of cationic palladium(II)‐oxo clusters (POCs) containing f‐metal ions, [PdII6O12M8{(CH3)2AsO2}16(H2O)8]4+ (M=CeIV, ThIV), 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 {Pd6O12}12− core that is capped by eight MIV ions, resulting in a cationic, cubic assembly {Pd6O12MIV8}20+, which is coordinated by a total of 16 terminal dimethylarsinate and eight water ligands, resulting in the mixed PdII‐CeIV/ThIV oxo‐clusters [PdII6O12M8{(CH3)2AsO2}16(H2O)8]4+ (M=Ce, Pd6Ce8; Th, Pd6Th8). We have also studied the formation of host‐guest inclusion complexes of Pd6Ce8 and Pd6Th8 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. The POCs were also found to be useful as pre‐catalysts for electrocatalytic CO2‐reduction and HCOOH‐oxidation. [ABSTRACT FROM AUTHOR]

This paper reports on the application of poly (3,4‐ethylenedioxythiophene)/carbon nanotubes (PEDOT/CNT) material for the construction of a hybrid supercapacitor utilizing iodide redox‐active electrolyte. To address the advantages in terms of electrochemical performance, comparison has been made to the system using conventional activated carbon (AC) electrodes. Despite limited specific surface area of the polymer‐based material, the PEDOT/CNT cell demonstrates reasonably high electrical parameters (vs. highly porous AC), especially those normalized per volume or total mass of the device. Interestingly, it also exhibits more stable self‐discharge characteristics over operation time which shall be assigned to smaller fraction of free polyiodides generated in the cell in the presence of the low‐surface‐area polymer electrode, in addition to their strong confinement in the polymer network, thus suppressing redox‐shuttling. Pursuing the mechanistic studies, we have managed to detect (using the electrocatalytic WO3‐based voltammetric probe) the presence of undesirable iodates but at lower concentrations in a case of the PEDOT/CNT‐based capacitor. [ABSTRACT FROM AUTHOR]

The catalytic activity of commercial carbon-supported PtFe (PtFe/C) nanoparticles admixed with mesoporous polyoxometalate Cs3H3PMo9V3O40, (POM3-3–9), has been evaluated towards oxygen reduction reaction (ORR) in acid medium. The polyoxometalate cesium salt co-catalyst/co-support has been prepared by titration using the aqueous solution of phosphovanadomolibdic acid. The synthesized material has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results confirm formation of the polyoxometalate salt with the characteristic Keggin-type structure. The composite catalyst has been prepared by mixing the POM3-3–9 sample with the commercial PtFe/C by sonication. The diagnostic rotating ring-disk voltammetric studies are consistent with good performance of the system with low Pt loading during ORR. The fuel cell membrane electrode assembly (MEA) utilizing the PtFe/POM-based cathode has exhibited comparable or better performance (at relative humidity on the level of 100, 62, and 17%), in comparison to the commercial MEA with higher Pt loading at the cathode. Furthermore, based on the cell potential and power density polarization curves, noticeable improvements in the fuel cell behavior have been observed at the low relative humidity (17%). Finally, the accelerated stress test, which uses the potential square wave between 0.4 V and 0.8 V, has been performed to evaluate MEA stability for at least 100 h. It has been demonstrated that, after initial losses, the proposed catalytic system seems to retain stable performance and good morphological rigidity. [ABSTRACT FROM AUTHOR]

Poly(4‐vinylpyridine)‐modified copper(I) oxide photocathodes, bare or decorated with palladium nanoparticles, can be used for the visible‐light‐driven selective reduction of CO2, mostly to methanol and carbon monoxide (in the absence of Pd cocatalyst) or formic acid and carbon monoxide (in the presence of Pd cocatalyst). The photocathode materials, which are composed of hierarchically deposited (onto transparent fluorine‐doped conducting glass electrode) Cu2O (inner layer) and poly(4‐vinylpyridine) (P4VP) polyelectrolyte film (outer‐layer), with or without dispersed Pd nanoparticles, have been fabricated and examined using electrochemical methodology, atomic force microscopy, and various spectroscopic techniques, including the Raman approach. While the physicochemical characteristics of Cu2O, including the oxide identity and its semiconducting properties, are not largely affected by the interfacial modification with P4VP, the photostability of the hybrid photocathode is significantly improved. The P4VP‐modified Cu2O exhibits reasonable durability during photoelectrochemical reduction of CO2 upon illumination with sunlight in semi‐neutral medium (Na2SO4). While Cu2O can be identified using Raman spectroscopy as the sole bulk component of the semiconducting film, the XPS data imply that the Cu2O surface is likely to be partially reduced during prolonged operation. Introduction of palladium cocatalyst seems to improve distribution (collection and transport) of photoelectrons at the photoelectrochemical interface and affects the CO2‐electroreduction mechanism. [ABSTRACT FROM AUTHOR]

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]

Electrocatalytic activity of Pt and bimetallic PtRu nanoparticles (both Vulcan supported and unsupported) toward electrooxidation of dimethyl ether (DME), a potential small organic molecule fuel, in an acid medium (0.5 mol dm−3 H2SO4) has been significantly enhanced by dispersing them over a thin film of zirconia (ZrO2). The enhancement effects concern increases of the DME electrocatalytic current densities recorded under both cyclic voltammetric and chronoamperometric conditions. Similar effects have been observed for the oxidation of methanol. Regarding the dissimilar DME electrooxidation mechanisms at Pt and PtRu catalytic centers, the activating capabilities of zirconia seem to originate from the high population of reactive –OH groups favoring mobility of protons and the capability of inducing the oxidative removal of poisoning (CO-type) intermediates both at platinum and ruthenium catalytic sites. In the presence of the zirconia matrix, the onset potential for the oxidation of DME (particularly at PtRu) is shifted more than 50 mV toward less positive potentials. Mutual metal-support interactions are also postulated. [ABSTRACT FROM AUTHOR]

This report shows the synthesis of a new family of "core-shell" carbon nitride (CN)-based electrocatalysts (ECs) for the oxygen reduction reaction (ORR) in acid medium. The ECs comprise "cores" of carbon black nanoparticles (NPs) that are covered by a CN "shell" embedding the active sites. The latter include Pt as the "active metal" and Co as the "co-catalyst." The interplay between the synthesis parameters, the chemical composition, and the ORR performance of the final ECs is elucidated. In particular, the ORR performance and reaction mechanism are studied both in an: (i) "ex-situ" setup, by means of cyclic voltammetry with thin-film rotating ring-disk electrode (CV-TF-RRDE) measurements; and (ii) "in-situ" experiment, i.e., in single proton exchange membrane fuel cells (PEMFCs) tested under operating conditions. A structural hypothesis is proposed that explains both the "ex situ" and the "in situ" ORR results on the basis of: (i) the relative amounts of the reactants used in the precursor synthesis; and (ii) the main temperature of the pyrolysis process (Tf) adopted in the preparation of the ECs. It is shown that the understanding of the fundamental features of the physicochemical processes involved in the preparation of the ECs is crucial in order to improve the proposed synthesis route and to yield ORR ECs exhibiting a performance level beyond the state of the art. [ABSTRACT FROM AUTHOR]

Silver-iron carbon nitride, which has been prepared by pyrolysis (under inert atmosphere) of silver hexacyanoferrate(II) deposited on graphene nanoplatelets, is considered here as electrocatalyst for oxygen reduction in alkaline medium (0.1 M potassium hydroxide electrolyte) in comparison to simple silver nanoparticles and iron carbon nitride (prepared separately in a similar manner on graphene nanoplatelets). The performance of catalytic materials has been examined using such electrochemical diagnostic techniques as cyclic voltammetry and rotating ring-disk electrode voltammetry. Upon application of the graphene nanoplatelet-supported mixed silver-iron carbon nitride catalyst, the reduction of oxygen proceeds at more positive potentials, as well as the amounts of hydrogen peroxide (generated during reduction of oxygen at potentials more positive than 0.3 V) are lower relative to those determined at pristine silver nanoparticles and iron carbon nitride (supported on graphene nanoplatelets), when they have been examined separately. The enhancement effect shall be attributed to high activity of silver toward the reduction/decomposition of H2O2 in basic medium. Additionally, it has been observed that the systems based on carbon nitrides show considerable stability due to strong fixation of metal complexes to CN shells.ᅟ [ABSTRACT FROM AUTHOR]

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 1.8–300 K established the ground state to be paramagnetic with a magnetic moment corresponding to 15 uncoupled Cu2+ (S = 1/2) ions. EPR measurements and simulations were consistent with this analysis. Electrochemical studies were performed for polyanions 1 and 2 dissolved in solution to elucidate the electroactivity of both copper and tungstate sites. Using 2 as a representative example, the electrocatalytic activity towards CO2 reduction upon deposition on a glassy carbon electrode surface, while retaining selectivity relative to hydrogen evolution, was demonstrated. [ABSTRACT FROM AUTHOR]

A hybrid matrix composed of a porous polyaniline underlayer, a robust bacterial biofilm and a multiwalled carbon nanotube overlayer has been demonstrated to function as highly active support for dispersed Pt catalytic nanoparticles during the electroreduction of carbon dioxide in neutral medium (phosphate buffer at pH 6.1). In contrast with bare Pt nanoparticles (deposited at a glassy carbon substrate), application of the hybrid system produces sizeable CO2-reduction currents in comparison to those originating from hydrogen evolution. The result is consistent with an enhancement in the reduction of carbon dioxide. However, the biofilm-based matrix tends to inhibit the catalytic properties of platinum towards proton discharge (competitive reaction) or even oxygen reduction. The hydrated structure permits easy unimpeded flow of aqueous electrolyte at the electrocatalytic interface. Although application of the polyaniline underlayer can be interpreted in terms of stabilization and improvement of the biofilm adherence, the use of carbon nanotubes facilitates electron transfer to Pt catalytic sites. It is apparent from the voltammetric stripping-type analytical experiments that, although formation of some methanol and methanoic acid cannot be excluded, carbon monoxide seems to be the main CO2-reduction product. [ABSTRACT FROM AUTHOR]

To cite some of his research activities, it should be mentioned that Roberto Marassi was a pioneer in the field of electrochemical energy storage for more than 40 years, pursuing research in such areas as molten salts or ionic liquids, Na-S batteries, Li-ion batteries, low-temperature fuel cells, and vanadium redox flow batteries, in addition to his interests in electroanalytical chemistry. But Roberto is remembered mainly for his availability to interact with other people, especially the young scientists, as well as for his sincere enthusiasm for the progress in electrochemical science and technology. Roberto Marassi was one of the scientists who, by developing new or by extending existing methods or materials, significantly advanced the understanding of electrochemical energy conversion processes as well as of the fundamentals of electrocatalysis and electroanalysis. [Extracted from the article]

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. By using solid-state voltammetric (both sandwich-type and microelectrode-based) methodology, the apparent diffusion coefficients for charge transport increased to approximately 1×10−6 cm2 s−1 upon the incorporation of the carbon-nanotube-supported iodine-modified Pt nanostructures. A dye-sensitized solar cell comprising TiO2 covered with a heteroleptic RuII-type sensitizer (dye) and the semisolid triiodide/iodide ionic liquid electrolyte admixed with carbon-nanotube-supported Pt nanostructures yielded somewhat higher power conversion efficiencies (up to 7.9 % under standard reporting conditions) than those of the analogous Pt-free system. [ABSTRACT FROM AUTHOR]

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. Shielding the Au NPs with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface. [ABSTRACT FROM AUTHOR]

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. Shielding the Au NPs with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface. [ABSTRACT FROM AUTHOR]

Electrocatalytic oxidation of ethanol in acid medium (0.5 mol dm[sup -- 3] H[sub 2]SO[sub 4]) was significantly enhanced by not only supporting bimetallic PtRu nanoparticles on nanostructured metal oxides (TiO[sub 2] or WO[sub 3]), but also by depositing such catalytic systems on planar nanoporous platinized electrode substrates. Incorporation of TiO[sub 2] or WO[sub 3] into the electrocatalytic interface was likely to improve proton mobility and to provide -OH groups capable of inducing the removal of poisoning species, such as CO, from the Pt sites in the bimetallic PtRu catalyst. Synergistic interactions between ruthenium and titania were also possible. Regularly porous nanostructured platinum substrate also permitted development of submicro 'reactors' where reactant molecules, electrolyte ions, and all active components (TiO[sub 2] or WO[sub 3], Pt substrate, PtRu catalytic sites) could co-exist and become easily accessible. While WO[sub 3] was able to undergo fast reversible redox transitions to non-stoichiometric oxides, efficient utilization of inert (non-electroactive) TiO[sub 2] required admixing with carbon nanotubes to ensure easy charge distribution and good conductivity at the electrocatalytic interface. [ABSTRACT FROM AUTHOR]

A multifunctional mediating system for bioelectrocatalytic oxidation of glucose is described. It comprises a conducting polymer, poly(3,4-ethylenodioxythiophene), carbon nanotubes modified with 4-(pyrrole-1-yl) benzoic acid that provide carboxyl groups that aid immobilization of glucose oxidase in a conductive three-dimensional network, tetrathiafulvalene that mediates electron exchange with the enzyme. This composite produces a system that is capable of effective oxidation of glucose to gluconic acid at pH 7. The current is concentration dependent to at least 60 mM and maintains 77 % of initial response for 35 days. Data supporting the utility of this system for electrochemical sensing and biofuel cell technology are presented. [ABSTRACT FROM AUTHOR]

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) viathe 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). TEM images show that Pd nanoparticles were uniformly dispersed on the surface of MWCNTs even when the Pd loading was increased to 60 wt%. Electrochemical activity of the catalysts for the ORR was evaluated by steady state polarization measurements using a rotating disk electrode. Compared with the acid treated MWCNTs, Pd nanoparticles supported on the HPW-assembled MWCNTs show a much higher ORR activity that is comparable to conventional Pt/C catalysts. The high electrocatalytic activities could be related to high dispersion of Pd nanoparticles as well as synergistic effects originating from the high proton conductivity of HPW. The Pd/HPW–PDDA–MWCNTs system as the cathode catalyst in proton exchange membrane fuel cells is demonstrated. [ABSTRACT FROM AUTHOR]

We describe a sol-gel approach by which iron hexacyanoferrate is immobilized in silica in a manner suited to investigation by electrochemistry in the absence of a contacting liquid phase. Such physicochemical parameters as concentration of redox sites ( Co) and apparent (effective) diffusion coefficient ( Dapp) are estimated by performing cyclic voltammetric and potential step experiments in two time regimes, which are characterized by linear and spherical diffusional patterns, respectively. Values of Dapp and Co thereby obtained are 2.0 × 10−6 cm2 s−1 and 1.4 × 10−2 mol dm−3. The Dapp value is larger than expected for a typical solid redox-conducting material. Analogous measurements done in iron(III) hexacyanoferrate(III) solutions of comparable concentrations, 1.0 × 10−2 and 5.0 × 10−3 mol dm−3, yield Dapp on the level of 5–6 × 10−6 cm2 s−1. Thus, the dynamics of charge propagation in this sol-gel material is almost as high as in the liquid phase. The residual water in the silica, along with the pore structure, are important to the overall mechanism of charge transport, which apparently is limited by physical diffusion rather than electron self-exchange. Under conditions of a solid state voltammetric experiment which utilizes an ultramicroelectrode, encapsulated iron hexacyanoferrate redox centers seem to be in the dispersed colloidal state rather than in a form of the rigid polymeric film. [ABSTRACT FROM AUTHOR]

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 O2-reduction often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO2, WO3, Ta2O5, Nb2O5, and ZrO2), stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction in oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. Alternatively, the Pt-based bi- and multi-metallic catalysts, including PtM alloys or M-core/Pt-shell nanostructures, where M stands for certain transition metals (e.g., Au, Co, Cu, Ni, and Fe), can be considered. The catalytic efficiency depends on geometric (decrease in Pt–Pt bond distances) and electronic (increase in d-electron vacancy in Pt) factors, in addition to possible metal–support interactions and interfacial structural changes affecting adsorption and activation of O2-molecules. Despite the stabilization of carbons, doping with heteroatoms, such as sulfur, nitrogen, phosphorus, and boron results in the formation of catalytically active centers. Thus, the useful catalysts are likely to be multi-component and multi-functional. [ABSTRACT FROM AUTHOR]

Voltammetry of silicotungstic acid (STA), H4SiW12O40, that was encapsulated in silica was performed in the absence of a contacting liquid phase. Two one-electron reductions that are separated by 200 mV were observed, which is the same behavior as in aqueous solution. At scan rates, v, below 10 mV s−1 with a 10 μm dia. carbon fiber indicator electrode, plateaus with limiting currents which are independent of v were observed, which is indicative of spherical diffusion from a field that is much larger than the electrode area. At v > 20 V s−1, peaks were observed with currents directly proportional to v½. For a gel aged for 2 days, an effective diffusion coefficient, Deff, of 3 × 10−7 cm2 s−1 was estimated by voltammetry and chronoamperometry; the concentration of the redox sites thereby determined was about 0.5 M. The Deff values that were obtained in this study were larger than expected for a solid electrolyte, which suggests an important role of residual water. In support of this model, gels that were aged in a humidistat at 33% humidity at room temperature for 2 and 5 days lost 16% and 13%, respectively, of their mass when dried at 120°. [ABSTRACT FROM AUTHOR]

Using Prussian blue (PB) electrodeposited on gold-covered foil as a model system, we have demonstrated the usefulness of the time-derivative measurements of absorbance versus potential (linear potential-scan voltabsorptometry) for spectroelectrochemical characterization of thin electrochromic films. The time-derivative signals were monitored for PB at 680 and 420 nm in potassium, sodium and lithium electrolytes. Information obtained from cyclic voltabsorptometry is equivalent or complementary to that from conventional cyclic voltammetry. In the case of PB films investigated in lithium electrolyte, the voltabsorptometric time-derivative peaks are better defined than the respective voltammetric peaks. The combination of voltabsorptometry with voltammetry enables molar absorptivity and/or film loading to be determined. Also, concentration changes of differently colored mixed-valence redox centers can be monitored as a function of applied potential. [ABSTRACT FROM AUTHOR]