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[en] Iron phthalocyanine supported on graphite nanofibers (GNF-FePc) were synthesized using a simple solvothermal process and characterized using various structural analyses. GNF-FePc were employed as bifunctional electrocatalysts in the air cathode of lithium-oxygen batteries. Galvanostatic charge–discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy were performed to assess the Performance of Li-air batteries. The air-cell delivered a high specific capacity of ∼5500 mAh/g at the first cycle which remained close to 90% of that value after 4 cycles. The reversibility was nearly 100% for all the four cycles with comparatively lower over potential.
[en] We explored the electrocatalytic activity of PEDOT:PSS modified GC (PEDOT:PSS/GC) electrode for electrocatalysis of NpO_2"2"+/NpO_2"+ redox couple in nitric acid and its performance is compared with conventionally used electrodes (GC, Au and Pt electrodes). (author)
[en] Highlights: • Highly electrocatalytic Se/Au/Pd nanoparticles have been developed. • Se/Au/Pd nanoparticles exhibit higher activity than commercial Pd/C catalysts. • Photoelectrochemical effect of Se results in enhanced electrocatalytic activity. • Se/Au/Pd nanoparticles show their critical role in self-powered sensing systems. • A self-powered electrochemical sensing system for glucose detection is developed. Bimetallic nanoparticles (NPs) have received increasing attention for their outstanding catalytic activity which the corresponding monometallic NPs can hardly achieve. In this paper, we developed a facile approach to prepare Se-supported Au/Pd NPs with high and photo-assisted electrocatalytic activity. Cyclic voltammetry (CV) measurements showed that the electrocatalytic activity of the Se-supported Au/Pd NPs was dependent on the Pd content. This result indicates that the interface between Pd and Au plays a vital factor in the electrocatalytic activity, while the individual metal components in the Se/Au/Pd system are of minor relevance for such activity. The Se-supported Au/Pd NPs exhibited mass activities of 4.25 (A/mgPd) and 1.21 (A/mgAu+Pd) toward ethanol oxidation, which were higher than that of the commercial Pd/C catalyst (0.36 A/mgPd). The electrocatalytic activity of Se-supported Au/Pd NPs was further enhanced by 2.4 times under solar light irradiation due to the photoelectrochemical effect of the Se NPs. It was further demonstrated in this paper that the presence of Se-supported Au/Pd NPs is crucial in self-powered electrochemical sensing systems as the overall sensitivity is significantly improved.
[en] Graphene is a flat monolayer of sp2 bonded carbon atoms tightly packed into a two-dimensional honeycomb lattice. Graphene sheets have attracted great attention for both fundamental science and applied research due to their high specific surface area, high conductivity, superior optics and mechanical properties. Graphene oxide (GO) is one of the most common precursors for the preparation of graphene. The presence of oxygen-containing functional groups in GO makes it hydrophilic and thus it can be easily dispersed into aqueous solutions. Electrochemical reduction of GO is the reagent free process to prepare graphene, which will henceforth be called as reduced graphene oxide (rGO). In the present study, the aqueous dispersion of GO was drop-casted on glassy carbon (GC) electrode under optimized conditions. Then it was electrochemically reduced in saturated sodium carbonate (Na2CO3) solution. The electron transfer reaction of U(VI)/U(V) redox couple was investigated at rGO in saturated Na2CO3 solution
[en] Electrocatalysis is a very effective SCC mitigation approach in oxidizing environments provided there is a stoichiometric excess of reductants over oxidants. This paper summarizes the mechanisms and criteria for effective SCC mitigation, with particular focus on the critical location for the catalyst in a crack and recent experimental support for these concepts. Optimization of electrocatalysis by On-Line NobleChemTM is described, with emphasis on experimental evidence for mitigation at ≤ 0.1 ppb Pt. (author)
[en] Magneli phases have been introduced as an unique electron conductive and interactive support for electro-catalysis both in hydrogen (HELR) and oxygen (OELR) electrode reactions in water electrolysis and Low Temperature PEM Fuel Cells (LT PEM FC). The Strong Metal-Support Interaction (SMSI) that imposes the former implies: (i) the hypo-hyper-d inter-bonding effect and its catalytic consequences, and (ii) the interactive primary oxide (M-OH) spillover from the hypo-d-oxide support as a dynamic electrocatalytic contribution. The stronger the bonding, the more strained appear d-orbitals, thereby the less strong the intermediate adsorptive strength in the rate determining step (RDS), and consequently, the faster the facilitated catalytic electrode reaction arises. At the same time the primary oxide spillover transferred from the hypo-d-oxide support directly interferes and reacts either individually and directly to contribute to finish the oxygen reduction, or with other interactive species, like CO to contribute to the CO tolerance. In such a respect, the conditions to provide Au to act as the reversible hydrogen electrode have been proved either by its potentiodynamic surface reconstruction in a heavy water solution, or by the nano-structured SMSI Au on anatase titania with characteristic strained d-orbitals in such a hypo-hyper-d-interactive bonding (Au/TiO2). In the same context, the monoatomic network dispersion of Pt upon Magneli phases makes it possible to produce an advanced interactive supported electro-catalyst for cathodic oxygen reduction (ORR). The strained hypo-hyper-d-inter-electronic and inter-d-orbital metal/hypo-d-oxide support bonding relative to the strength of the latter, has been inferred to be the basis of the synergistic electrocatalytic effect both in the HELR and ORR. (authors)
[en] The electrochemical hydrogen absorption of electrodes containing Zr0.9Ti0.1(Ni0.5Mn0.25Cr0.20V0.05)2 is studied in alkaline media by monitoring the activation and discharge capacity along charge-discharge cycling.The considered alloy is tested in both as melted and annealed condition in order to investigate the catalytic effect of small amounts of micro segregated secondary phases of the Zr-Ni system. Since these catalytic phases are only present in the as melted alloys, tests are also carried out using a composite material elaborated from powders of the annealed alloy with the addition of 18 wt.% of the suspected catalytic phases, melted separately.The hydrogen absorption-desorption behavior for the different cases is discussed and correlated with the metallurgical characterization of the materials.The catalytic effects are studied employing cyclic voltammetry and electrochemical impedance techniques. The results are analyzed in terms of a developed physicochemical model
[en] A lot of methods exist to directly reduce carbon dioxide into hydrocarbons: the photoelectrochemical process is certainly the most interesting, essentially due to the similarities with photosynthesis. As the human activities produce a great quantity of CO2, this one can then be considered as an infinite source of carbon. The products of this reaction are identical to those obtained during a Fischer-Tropsch reaction, that is to say hydrocarbons, alcohols and carboxylic acids. These works deal with the electrochemical reduction of CO2 in standard conditions of temperature and pressure. The photochemical part has been replaced by a current generator as electrons source and a KHCO3 aqueous solution as protons source. The first catalytic results clearly show that it is possible to reduce CO2 into light hydrocarbons, typically from C1 to C9. (O.M.)
[en] We developed a new way to form the well-defined nanocomposite of Au NPs and exfoliated LDH nanosheet by in situ chemical reduction with NaBH_4. The optical and structural studies indicate that the Au NPs are highly dispersed and immobilized on the surface of LDH nanosheets. The Au/LDH nanosheet exhibited an excellent electrocatalysis toward glucose oxidation reaction. The results strongly demonstrate that the nanoscopic natures and dense positive charges of LDH nanosheet effectively stabilized the Au NPs to maintain their inherent properties during the synthesis and the electrocatalysis. The use of the double hydroxide nanosheets as nanoscopic support materials for the transition-metal NPs will dramatically improve their functionalities in heterogeneous catalysis. Recently, two-dimensional nanosheet of exfoliated layered double hydroxide (LDH) has emerged as a new type of solid support to immobilize the diverse metal NPs because of the large metal hydroxide area, good biochemical stability, and highly charged positive potential of 1- to 2-nm thick LDH layers. LDHs consist of a continuous stack of positively charged metal hydroxide layers with counter anions and water molecules placed in interlayer spaces
[en] The data obtained until now seem to indicate that the hydrogen production by hydrogenases induces a proton-hydride coupling. In taking the structures of theses enzymes active sites (determined by X-ray diffraction) as a basis, it can be thought that this proton-hydride coupling is facilitated by the juxtaposition of two protonation sites, the metallic center M and the basic group of an E ligand of the coordination sphere. Contrarily to the supposed running of the hydrogenases enzymes, the homogeneous catalysts of the protons reduction, described in the literature, present a reactivity which is either on an alone metallic site or on a metal-metal bond. This work deals then with the preparation of complexes having two juxtaposed protonation sites. Some iron dinuclear compounds have been synthesized and their properties studied. (O.M.)