A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H /2 H interconversion from pH 0 to 9, with catalytic preference for H oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm , only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm , a new efficiency record for a hydrogen biofuel cell with base metal catalysts.

The oriented in situ crystallisation of microporous manganese(II) formate [Mn(HCO 2 ) 2 ] on different porous supports (e.g. porous alumina and graphite) has been investigated. The anisotropic growth of Mn(HCO 2 ) 2 was examined by Xray diffraction (XRD) and scanning electron microscopy (SEM). The intracrystalline diffusion of methanol in Mn(HCO 2 ) 2 was studied by observation of the sorption kinetics by interference microscopy (IFM). It was found that untreated discs of porous alumina and graphite supports exhibit poor densities of Mn(HCO 2 ) 2 crystals per supported area. Even lower crystal densities are found for activated supports such as for alumina after basic treatment and for oxidized graphite supports. Improved results have been achieved by replacing formic acid by sodium formate in the synthesis

The intracrystalline concentration profiles during molecular uptake of methanol by an initially empty, single crystal of microporous manganese(II) formate (Mn(HCO2)2), representing an ionic inorganic-organic hybrid within the MOF family, are monitored by interference microscopy. Within these profiles, a crystal section could be detected where over the total of its extension ( approximately 2 microm x 50 microm x 30 microm) molecular uptake ideally followed the pattern of one-dimensional diffusion. Analysis of the evolution of intracrystalline concentration in this section directly yields the permeability of the crystal surface and the intracrystalline diffusivity as a function of the concentration of the total range of 0

The effect of the nature of the transition metal on the structure and activity for hydrogen evolution of Metal-N-C catalysts synthesized via the pyrolysis of metal salts and a Zn-based metal organic framework was investigated. It is found that W, Mo, Cu and Zn lead to amorphous carbons with high specific area while Cr, Mn, Fe, Co and Ni lead to more graphitic carbons with a lower specific area. Metal salts with a high redox potential are fully reduced during pyrolysis while others are only partially reduced. Electrochemical activity toward hydrogen evolution was investigated at pH 1 and pH 13. Hydrogen evolution on these Metal-N-C catalysts is generally more facile at pH 1 than at pH 13, paralleling the trends observed for noble metal surfaces. The Co-, Ni-and Fe-N-C catalysts are the most active at pH 13 while Co-N-C and Cr-N-C are the most active at pH 1. The activity of the latter catalysts stems from metallic cobalt particles encapsulated in carbon and from a chromium carbo-nitride phase, respectively.

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High temperature proton exchange membrane fuel cells (HT‐PEMFC) have a promising market in micro‐combined heat and power (μ‐CHP) applications. Operating above 150 °C, they would better cope with return temperatures of typical heating systems than conventional PEMFCs and would allow simplification of system regulations dedicated to failure prevention.Single cell and 500 We HT‐PEMFC stack integrating Celtec P 1000 MEAs were fed with synthetic reformate and air and successfully operated at 160 °C under accelerated typical annual μ‐CHP profile. The single cell was unaffected by 500 h of current cycling while stop/start cycles induced some voltage loss. After 658 h of cumulated operation, stack performance loss was limited at 7.6%: its electrical efficiency (LHV) decreased from 30.6 to 28.3%. Moreover, four initial stop/start cycles weakly impacted its performance, indicating that selected shutdown/restart protocol is convenient for field application. Conversely, after additional start/stop cycles, degradation rate was increased by stop/start cycling and some specific cells (mostly associated with lower initial OCV) exhibited significantly higher degradation rates. Finally, voltage transient evolution during current step exhibits undershoot which magnitude is strongly depends on cell location in the stack: it increased at stack dead‐end and for cells exhibiting highest degradation rates.

No abstract

Two synthetic smectites (montmorillonite and beidellite) are studied by a water adsorption technique in order to assess their specific surface areas under atmospheric conditions. A route recently proposed for extracting the thermodynamic data from experimental adsorption isotherms is used. The variation of the specific surface area during water adsorption is obtained, which can be linked to the enlargement of the interlayer space determined using X-ray diffraction. This variation is compared to an idealized specific surface area obtained from TEM and X-ray measurements in agreement with crystallographic models. All these results are also compared with those obtained previously for a natural montmorillonite. A simple view of swelling is proposed.