Molecular dynamics simulations of ternary PtxPdyAuz fuel cell nanocatalyst growth

International audienceMolecular dynamics simulation of PEMFC cathodes based on ternary Pt70Pd15Au15 and Pt50Pd25Au25 nanocatalysts dispersed on carbon indicate systematic Au segregation from the particle bulk to the surface, leading to an Au layer coating the cluster surface and to the spontaneous formation of a Pt@Pd@Au core-shell structure. For Au content below 25at%, surface Ptx Pdy active sites are available for efficient oxygen reduction reaction, in agreement with DFT calculations and experimental data. Simulations of direct core@shell system prepared in conditions mimicking those of plasma sputtering deposition pointed out an increase of the number of accessible PtxPd y surface active sites. Core-shell nanocatalyst morphology changes occur due to impinging Pt kinetic energy confinement and dissipation

Selective Electrooxidation of Glycerol Into Value-Added Chemicals: A Short Overview

A comprehensive overview of the catalysts developed for the electrooxidation of glycerol with the aim of producing selectively value-added compounds is proposed in the present contribution. By presenting the main results reported in the literature on glycerol electrooxidation in acidic and alkaline media, using different kinds of catalytic materials (monometallic catalysts based on platinum group metals and non-noble metals, multimetallic alloys, or modification of surfaces by adatoms, etc.) and under different experimental conditions, some general trends concerning the effects of catalyst composition and structure, of reaction medium and of the electrode potential to enhance the activity for the glycerol oxidation reaction and of the selectivity toward a unique value-added product will be presented and discussed. The objective is to provide a guideline for the development of electrochemical systems which allow performing the electrooxidation of glycerol at the rate and selectivity as high as possible

Crystal structure of the membrane attack complex assembly inhibitor BGA71 from the Lyme disease agent Borrelia bavariensis

Funding Information: This work was supported by the European Regional Development Fund (ERDF) grant Nr. 1.1.1.2/VIAA/1/16/144 “Structural and functional studies of Lyme disease agent Borrelia burgdorferi outer surface proteins to reveal the mechanisms of pathogenesis with the intention to create a new vaccine”. Diffraction data have been collected on BL14.1 at the BESSY II electron storage ring operated by the Helmholtz-Zentrum, Berlin. We would particularly like to acknowledge the help and support of Manfred S. Weiss and Christian Feiler during the experiment. Publisher Copyright: © 2018, The Author(s).Borrelia (B.) bavariensis, B. burgdorferi, B. afzelii, B. garinii, B. spielmanii, and B. mayonii are the causative agents in Lyme disease. Lyme disease spirochetes reside in infected Ixodes ticks and are transferred to mammalian hosts during tick feeding. Once transmitted, spirochetes must overcome the first line of defense of the innate immune system either by binding complement regulators or by terminating the formation of the membrane attack complex (MAC). In B. bavariensis, the proteins BGA66 and BGA71 inhibit complement activation by interacting with the late complement components C7, C8, and C9, as well as with the formed MAC. In this study, we have determined the crystal structure of the potent MAC inhibitor BGA71 at 2.9 Ǻ resolution. The structure revealed a cysteine cross-linked homodimer. Based on the crystal structure of BGA71 and the structure-based sequence alignment with CspA from B. burgdorferi, we have proposed a potential binding site for C7 and C9, both of which are constituents of the formed MAC. Our results shed light on the molecular mechanism of immune evasion developed by the human pathogenic Borrelia species to overcome innate immunity. These results will aid in the understanding of Lyme disease pathogenesis and pave the way for the development of new strategies to prevent Lyme disease.publishersversionPeer reviewe

Cellobiose Dehydrogenase Aryl Diazonium Modified Single Walled Carbon Nanotubes: Enhanced Direct Electron Transfer through a Positively Charged Surface

One of the challenges in the field of biosensors and biofuel cells is to establish a highly efficient electron transfer rate between the active site of redox enzymes and electrodes to fully access the catalytic potential of the biocatalyst and achieve high current densities. We report on very efficient direct electron transfer (DET) between cellobiose dehydrogenase (CDH) from Phanerochaete sordida (PsCDH) and surface modified single walled carbon nanotubes (SWCNT). Sonicated SWCNTs were adsorbed on the top of glassy carbon electrodes and modified with aryl diazonium salts generated in situ from p-aminobenzoic acid and p-phenylenediamine, thus featuring at acidic pH (3.5 and 4.5) negative or positive surface charges. After adsorption of PsCDH, both electrode types showed excellent long-term stability and very efficient DET. The modified electrode presenting p-aminophenyl groups produced a DET current density of 500,mu A cm(-2) at 200 mV vs normal hydrogen reference electrode (NHE) in a 5 mM lactose solution buffered at pH 3.5. This is the highest reported DET value so far using a CDH modified electrode and comes close to electrodes using mediated electron transfer. Moreover, the onset of the electrocatalytic current for lactose oxidation started at 70 mV vs NHE, a potential which is 50 mV lower compared to when unmodified SWCNTs were used. This effect potentially reduces the interference by oxidizable matrix components in biosensors and increases the open circuit potential in biofuel cells. The stability of the electrode was greatly increased compared with unmodified but cross-linked SWCNTs electrodes and lost only 15% of the initial current after 50 h of constant potential scanning

Nickel cobalt hydroxide nanoflakes as catalysts for the hydrogen evolution reaction

International audienc

PdAu/C catalysts prepared by plasma sputtering for the electro-oxidation of glycerol

International audienc