Though Metal Organic Frameworks (MOF's) and MOF-derived solids have been employed in various applications, especially catalysis, there is still a constant search for better performing MOF-based hybrid catalysts. In this work, we employed sacrificial template method in synthesizing MIL-53(Al) type - porous Alumina (MA) composites that exhibit different physico-chemical and catalytic properties compared to parent solids (MIL-53 and mesoporous Al2O3). Structural investigations demonstrated that composites possess combined structure of both the parent solids. Novel composites possess hierarchical (meso- & micro-) pores, with average pore width in the range of similar to 14-16 nm. NH3 adsorption calorimetry and isopropanol test enabled deducing the possible nature and strength of acid-basic sites in composites. 'MA' composites show intermediate chemical properties and synergistic multifunctional catalytic behaviour compared to parent solids. This work reveals, for the first time, extensively tunable physico-chemical properties of a novel class of solids: "the MIL-53(Al) type - porous alumina composites" that can have a huge potential as multifunctional catalysts.

The influence of the B type cation from the ABO3 perovskite formulation La0.75Sr0.25XO3 (LSX, where X is Fe, Mn or Cr) on the C and H2S tolerance and its catalytic activity for the methane/water reaction has been studied.

Two commercial activated carbons, namely STIX and AP4, were selected to investigate their ability for siloxane adsorption and further thermal regeneration in relation with their different physico-chemical properties. In the frame of biogas purification, the studied siloxanes were L2, L3, L4 (linear molecules) and D4, D5 (cyclic molecules). The maximum capacity of adsorption was estimated by gas chromatography and gravimetric methods. AP4 presents better adsorptive properties comparing with STIX irrespective of the type of siloxane. Thermal regeneration after siloxanes adsorption was followed up to 400 degrees C by both gas chromatography and in situ DRIFTS. Except L2, the siloxane polymerization proceeds on the AC containing alkali metals (K, Na) as revealed by the observed release of their decomposition products during the thermodesorption treatment. The same sites are responsible for the cleavage of SieO bonds in linear molecules and formation of L2 as primary product above 100 degrees C. The presence of such sites, possibly strong basic sites, is detrimental to the regenerability of the spent adsorbent and to the adsorption which could be limited by partial blockage of the AC porosity. Interestingly the regenerability of the alkali-free AC depends only on the volatility of the siloxane.

•Specific hydrophilic sites in AC induce D4 adsorption capacity loss in humid atmosphere.•D4 polymerizes on ACs containing hydrophilic sites/alkali impurities.•The polymerization induces incomplete thermal regeneration and could also hamper D4 adsorption.

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A commercial activated carbon (AC) was characterized by physicochemical methods. The AC adsorption/desorption properties and the adsorbent regenerability were evaluated for the removal of octamethylcyclotetrasiloxane (D4), a common siloxane impurity in biogases. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) was employed to investigate the adsorption of D4 on AC at room temperature and its thermodesorption up to 300 degrees C. The AC was activated in N-2 at varying temperatures within the 25-300 degrees C interval. The striking feature is the polymerization of D4 observed during the desorption experiment followed by the release of PolyDimethylSiloxane (PDMS) in the gas phase. The thermal treatment before adsorption is proposed to influence the D4-AC interaction. (c) 2017 Elsevier B.V. All rights reserved.

The CO oxidation reaction on carbon-supported Pt nanoparticles (average size of 2.8 to 7.7 nm) was studied under flowing conditions at atmospheric pressure and temperatures between 300 and 353 K by coupling quadrupole mass spectrometry (QMS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The Pt loading was varied between 20 and 60 wt%. Gases diluted in He (0.5 mol%) were used together with Ar as a tracer. Reactions with CO and O2 introduced separately onto the samples were studied by QMS, applying successive step changes of the reaction mixtures. Variations in the rate of the reactions were observed and correlated with changes of the calculated coverage of the Pt surface by CO and/or O adspecies at varying steps of the experiment. The transient reaction of CO(g) with adsorbed O (Oad) was fast and mass transport-limited while that of O2(g) with adsorbed CO (COad) was sluggish. Following the same experimental procedures, FTIR spectra of adsorbed CO after varying steps were recorded, confirming the variations of COad and Oad as determined by QMS and indicating changes in the CO distribution over varying types of Pt surface sites. The influence of the adlayer composition (co-adsorption of COad and Oad), the particle size/structure and some possible surface reconstruction effects on the CO oxidation rate were evidenced and discussed. The structure of the Pt nanoparticles supported on carbon appears as an important factor for the efficiency of the so-called O2 bleeding as a CO mitigation strategy in polymer electrolyte membrane fuel cells.

Stoichiometric and sub-stoichiometric lanthanum barium titanates (LBT) of perovskite structure type, substituted or not with Mn and/or Ce at the Ti-site, were prepared by sol–gel route with heat treatment in air. All the compounds display a cubic Pm-3m symmetry, which remains stable in reducing atmosphere. Whereas Mn substitution highly promotes the reducibility of the material, the electrical and electrochemical performance of Mn-doped compounds is decreased with respect to non-doped sub-stoichiometric LBT. In contrast, the electrical conductivity and resistance polarization of Ce-substituted LBT are close to those of non-doped LBT and Ce-substituted LBT appears especially efficient in improving the catalytic properties for methane steam reforming and avoiding carbon formation.

Pure and 5% Mn doped layered perovskites La4SrTi5O17, members of the La4Srn-4(Ti,Mn)nO3n+2 series with n = 5, have been synthesized and investigated as anode materials for Solid Oxide Fuel Cells. The use of XRD, neutron and electron diffraction techniques allows clarifying some divergences concerning the structural characterization within the family, not only in air but also in anodic-like N2/H2(97/3) atmosphere. The electrical conductivity of both compounds is very low in air but those values increase by two orders of magnitude in diluted hydrogen. The study of catalytic properties for methane steam reforming as well as in-depth analysis of the SOFC anodic behaviour of both materials are described, for which a microstructure optimization of the electrode allows to demonstrate the potential interest of the lamellar materials upon the classical three-dimensional cubic-like LSTs.

•Ir-CeO2 (0.1wt% Ir) was prepared by one-step solution combustion synthesis.•2nm-sized particles of Ir are obtained after an oxido-reducing treatment.•Ir-CeO2, highly active in CH4 reforming, is resistant to the irreversible poisoning by H2S.•This catalyst outperforms its Ir-impregnated and Rh-containing counterparts.

Among energy conversion systems, high temperature Fuel Cells are considered of great interest for delocalized, renewable and clean electricity and heat power production. The high operating temperature (500°C - 800°C) is likely to allow the use of various types of hydrocarbons instead of hydrogen as the fuel with high efficiency and flexibility. Theoretically, the fuel can be catalytically converted into hydrogen directly at the anodic side. Practically, the most important drawback is the formation of carbon deposits on the anode, poisoning the electrocatalytic activity of the electrode. Hence, one of the main current challenges remains the increase of the life-time of these systems (especially avoiding carbon deposition and anode pollution), and long term reliable operation with fuel flexibility. Such performances have not been achieved yet. We recently demonstrated the fundamental importance of the fuel utilization on the carbon deposition limits. The quantity of steam released by the anode is directly proportional to the current density, and then to the fuel utilization UF. Below a given value of UF, the system does not produce enough steam to ensure the internal catalytic conversion of the hydrocarbon flux, resulting in irreversible degradation of the cell by carbon methane cracking. This observation and the deep understanding of the anode operation in methane allowed us to achieve long term operation with pure hydrocarbons without carbon deposition at the surface of conventional Ni-YSZ anodes. The thermodynamical limits of carbon deposition as a function of fuel utilization were also investigated. Current developments and technological simplifications based on new principles of operation and original architectures designed in this finality will be presented. In particular the presentation will emphasize on the Gradual Internal Reforming and Electro-catalytic separation principles applied to the design of original anodic systems, and on the demonstration of the reliability of the systems in different pure hydrocarbons or carbon-based fuels (no H2O, CO2, O2 or carrier gas addition) [1-4]. The effect of the fuel utilization on the limits of carbon deposition will be discussed and the long term durability in pure dry methane will be demonstrated. The perspectives of direct operation of SOFC on waste fuels in order to decrease the amount of CO2 rejects in delocalized energy production systems will be discussed. 1. J-M. Klein et al., Journal of Power Sources 193, (2009) 331 2. S. D. Nobrega et al., Journal of Power Sources (2012) 156-159 4. S. Georges et al., ECS Transactions 57(1) (2013) 3023-3030 4. S.D. Nobrega et al., Journal of the Electrochemical Society, 161(3) (2014) F354-F359 5. J. Puig et al., Fuel Cells 14 (6) (2014) 1014-1021 6. K. Girona et al., Canadian Journal of Chemical Engineering 93 (2) (2015) 285-296

Solid oxide fuels cells with and without anodic catalytic layer and specific anodic current collectors were developed in order to be fueled by dry methane. Due to the cell architecture integrating a 0.1wt% Ir-CGO catalyst layer onto the anode, platinum, gold and cupper screen-printed meshes were designed and optimized to ensure efficient current collection between the anode surface and the catalyst membrane. Current density and ageing in H2 and in pure dry CH4 respectively were compared to conventional pressed grid collecting systems. Similar performances were achieved using bulk grids or gold, platinum and copper screen-printed meshes. Operation in pure dry methane is compared with and without the catalytic layer as a function of the fuel utilization. It is demonstrated that long term operation is possible provided that sufficient faradic efficiency is achieved.

Methane appears to be a fuel of great interest for solid oxide fuel cell (SOFC) systems because it can be directly converted into hydrogen by Internal Reforming within the SOFC anode. To cope with carbon formation, a new SOFC cell configuration combining a catalyst layer with a classical anode was developed. The rate of the CH4 consumption in the catalyst layer (Ir-CGO) was determined experimentally for small values of steam to carbon ratios. This paper proposes a modelling and a simulation, using the CFD-Ace software package, of the behaviour of a SOFC operated in Gradual Internal Reforming (GIR) conditions. This model of SOFC takes into account the kinetics of the steam reforming reaction in the catalyst layer in order to assess the influence of the steam to carbon ratio and the cell polarization. Because the risk of carbon formation is greater under GIR operation, a detailed thermodynamic analysis was carried out. Thermodynamic equilibrium calculations allowed us to predict the conditions of carbon formation occurrence.

Solution combustion generates mesoporous ceria with strongly anchored Ir nanoparticles, which are efficient methane reforming catalysts.

, and delivering a rather stable power output. Such a fuel-flexible SOFC was achievedby using both an anodic catalytic layer, which efficiently converts the primary fuel into hydrogen, and by the operation in gradualinternal reforming conditions, which prevented degradation due to carbon formation.© 2014 The Electrochemical Society. [DOI: 10.1149/2.107403jes] All rights reserved.Manuscript submitted October 24, 2013; revised manuscript received January 9, 2014. Published January 17, 2014.

CO adsorption on carbon-supported Pt nano-particles under operando conditions was studied by quadru-pole mass spectrometry and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). The Pt catalyst was also studied by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). It was shown by HRTEM and XPS that Pt nanoparticles can be fully reduced by H-2 at room temperature instead of by conventional high-temperature treatment. The Pt dispersion was determined by XRD, HRTEM, and CO chemisorption techniques with an excellent agreement among them. The room-temperature H-2/O-2 titration method was also used, but if assuming H/Pt-s = O/Pt-s = 1, it led to the underestimation of the dispersion compared to the other techniques. The existence of adsorption sites inaccessible to H-2 (or O-2) but accessible to CO because of a stronger interaction with Pt was proposed to explain the results. It was also concluded that H/Pt-s was lower than unity (H/Pt-s = 0.72) and, as a major consequence, that Pt nanoparticles with 2.7 nm diameter still have a bulk-like behavior in contrast with what was reported in the literature for 1 nm Pt particles. CO adsorption on Pt/C at 298 K after H-2 treatment was studied by operando DRIFTS. The C-O stretching vibration (nu CO) bands were ascribed to CO adsorbed on Pt surface at (111)-terrace, (100)-terrace, edge, and kink sites in linear and bridge forms. An unexpected nu CO band at 1703 cm(-1) was observed upon CO adsorption and tentatively attributed to CO on surface Pt sites interacting through its oxygen end with the carbon support. It was also shown that the adsorption of CO and H-2 in successive repeated steps was necessary to reach a stable state of the adsorbed CO phase. Possible reconstruction of Pt nanoparticles at room temperature during this process is discussed.

Electrolyte (yttria-stabilised zirconia, YSZ) supported solid oxide fuel cells (SOFCs) were fabricated using spin coating of standard LSM cathode and Ni-YSZ cermet anode. A ceria-based catalytic layer was deposited onto the anode with a special current collector design. Such a single cell configuration allows operation by gradual internal reforming of direct carbon-containing fuels. First, the fabricated single cells were operated with hydrogen to determine the optimised conditions of fuel concentration and flow rate regarding faradaïc efficiency. Then, the fuel was switched to dry ethanol and the cells were operated for several hours (100h) with good stability. Post-operation electron microcopy analyses revealed no carbon formation in the anode layer. The results indicate that the gradual internal reforming mechanism is effective, opening up the way to multi-fuel SOFCs, provided that a suitable catalyst layer and cell design are available.

Based on a multiscale modeling framework, we focus on understanding the impact of CO adsorption on the intrinsic stability properties of PtxCoy nanoparticles under PEMFC anode operating conditions. Firstly, CO adsorption effect on PtxCoy has been studied by using Monte Carlo (MC) simulation. Then, the MC results were coupled with a non-equilibrium thermodynamics kinetics model (MEMEPhys®) to simulate the effect of CO poisoning on the activity and durability of PtxCoy nanoparticles as HOR catalysts. The results are compared with simulations carried out on Pt, where potential self-oscillatory behaviour is observed and experimentally confirmed. The PtxCoy HOR activity and stability properties reveal to be strongly dependent on the nanoparticle size and composition. For certain nanoparticle sizes, simulations show that PtCo nanoparticles provide better CO tolerance than Pt3Co. However, the CO tolerance of PtCo degrades faster than that of Pt3Co in long-term operation. From both modeling and experimental approaches, it is demonstrated for the first time that this observation is due to the fact that CO adsorption enhances Cobalt dissolution.