The production of syngas (H2 and CO)—a key building block for the manufacture of liquid energy carriers, ammonia and hydrogen—through the dry (CO2−) reforming of methane (DRM) continues to gain attention in heterogeneous catalysis, renewable energy technologies and sustainable economy. Here we report on the effects of the metal oxide support (γ-Al2O3, alumina-ceria-zirconia (ACZ) and ceria-zirconia (CZ)) on the low-temperature (ca. 500–750 ∘C) DRM activity, selectivity, resistance against carbon deposition and iridium nanoparticles sintering under oxidative thermal aging. A variety of characterization techniques were implemented to provide insight into the factors that determine iridium intrinsic DRM kinetics and stability, including metal-support interactions and physicochemical properties of materials. All Ir/γ-Al2O3, Ir/ACZ and Ir/CZ catalysts have stable DRM performance with time-on-stream, although supports with high oxygen storage capacity (ACZ and CZ) promoted CO2 conversion, yielding CO-enriched syngas. CZ-based supports endow Ir exceptional anti-sintering characteristics. The amount of carbon deposition was small in all catalysts, however decreasing as Ir/γ-Al2O3 > Ir/ACZ > Ir/CZ. The experimental findings are consistent with a bifunctional reaction mechanism involving participation of oxygen vacancies on the support’s surface in CO2 activation and carbon removal, and overall suggest that CZ-supported Ir nanoparticles are promising catalysts for low-temperature dry reforming of methane (LT-DRM).

Nutrient losses have to be avoided in agricultural systems for agronomic and environmental reasons. However, they are known to be potentially large and variable. Results from twenty nine trials aiming at quantifying nitrogen (N), phosphorus (P), potassium (K) and carbon (C) flows and losses from barn and manure storage for beef cattle (Belgian Blue double-muscled breed) were synthesized. They included variation in barn type (tied stall and deep litter), leading to contrasted manure types (respectively semi-solid manure and deep litter manure) of small groups (n = 4) of heifers or bulls. Despite uncertainties pointed out by non-zero P or K balances, we established for manure storage, a relation between K losses by flowing out as liquid and rainfalls: K lost (%K stored) = 100*(1-0.99*e((-0.00078*rainfalls) ((mm))); n = 28). We also emphasized, within the particular set of data treated, the effects of barn type (approached by STRAWr; kg straw kg(-1) DM in feed), manure storage duration (d), nitrogen in feed concentration (NFEED; g N kg(-1) DM) and storage temperature (degrees C) on N losses from the whole system (N lost (% N input) =-33.33 + 0.0869*storage duration+1.11*storage temperature+27.9*STRAWr+1.278*NFEED; r(2) = 0.700; n = 29) such as the strong relation between C and N losses during manure store per day of storage (N lost (% N stored d(-1))= 0.038 + 0.617*C lost (% C stored d(-1))). We also observed that, even if N and C inputs in the system were higher in deep litter systems due to straw supply, the amounts of N and C remaining in the manure after being stored were very similar, indicating higher losses of these nutrients from deep litter systems compared to tied stalls. These findings will further help in modeling cattle housing systems for nutrient cycling optimization. However, the relations established have to be validated for other tied stall and deep litter systems regarding the diversity in manure management for each barn type. Furthermore, when comparing manure provided under different housing systems, other agronomical (e.g. their sanitization due to heat increase when stored, ease of application to soil after storage) or environmental (e.g. greenhouse gas emissions) aspects have to be considered.

The thermal sintering under oxidative conditions of Rh nanoparticles supported on oxides characterized by very different oxygen storage capacities (OSC) and labilities was studied at 750 and 850 °C. Under sintering conditions, significant particle growth occurred for Rh/γ-Al2O3 (up to 120% at 850 °C). In striking contrast, Rh/ACZ (alumina–ceria–zirconia) and Rh/CZ (ceria–zirconia) exhibited marked resistance to sintering, and even moderate (ca. −10% at 850 °C) to pronounced (ca. −60% at 850 °C) redispersion of the Rh. A model is proposed based on a double-layer description of metal–support interactions assigned to back-spillover of labile oxygen ions onto the Rh particles, accompanied by trapping of atomic Rh by the resulting surface oxygen vacancies. This model accounts for the observed resistance to sintering and actual redispersion of Rh, consistent with both alternative sintering mechanisms, namely Ostwald ripening (OR) or particle migration and coalescence (PMC).

The catalytic and structural properties of five different nanoparticle catalysts with varying Au/Ni composition were studied by six different methods, including in situ X-ray absorption spectroscopy and density functional theory (DFT) calculations. The as-prepared materials contained substantial amounts of residual capping agent arising from the commonly used synthetic procedure. Thorough removal of this material by oxidation was essential for the acquisition of valid catalytic data. All catalysts were highly selective toward N2 formation, with 50-50 Au:Ni material being best of all. In situ X-ray absorption near edge structure spectroscopy showed that although Au acted to moderate the oxidation state of Ni, there was no clear correlation between catalytic activity and nickel oxidation state. However, in situ extended X-ray absorption fine structure spectroscopy showed a good correlation between Au-Ni coordination number (highest for Ni50Au50) and catalytic activity. Importantly, these measurements also demonstrated substantial and reversible Au/Ni intermixing as a function of temperature between 550 °C (reaction temperature) and 150 °C, underlining the importance of in situ methods to the correct interpretation of reaction data. DFT calculations on smooth, stepped, monometallic and bimetallic surfaces showed that N + N recombination rather than NO dissociation was always rate-determining and that the activation barrier to recombination reaction decreased with increased Au content, thus accounting for the experimental observations. Across the entire composition range, the oxidation state of Ni did not correlate with activity, in disagreement with earlier work, and theory showed that NiO itself should be catalytically inert. Au-Ni interactions were of paramount importance in promoting N + N recombination, the rate-limiting step.

Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-dopedceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 degrees C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H(2)0 mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Ni Au surface alloy that inhibited carbonisation and poisoning of the active nickel surface. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The essential role of oxygen in enabling heterogeneously catalyzed Glaser Hay coupling of phenylacetylene on Ag(100) was elucidated by STM, laboratory and synchrotron photoemission, and DFT calculations. In the absence of coadsorbed oxygen, phenylacetylene formed well-ordered dense overlayers which, with increasing temperature, desorbed without reaction. In striking contrast, even at 120 K, the presence of oxygen led to immediate and complete disruption of the organic layer due to abstraction of acetylenic hydrogen with formation of a disordered mixed layer containing immobile adsorbed phenylacetylide. At higher temperatures phenylacetylide underwent Glaser Hay coupling to form highly ordered domains of diphenyldiacetylene that eventually desorbed without decomposition, leaving the bare metal surface. DFT calculations showed that, while acetylenic H abstraction was otherwise an endothermic process, oxygen adatoms triggered a reaction-initiating exothermic pathway leading to OH(a) + phenylacetylide, consistent with the experimental observations. Moreover, it was found that, with a solution of phenylacetylene in nonane and in the presence of O-2, Ag particles catalyzed Glaser-Hay coupling with high selectivity. Rigorous exclusion of oxygen from the reactor strongly suppressed the catalytic reaction. Interestingly, too much oxygen lowers the selectivity toward diphenyldiacetylene. Thus, vacuum studies and theoretical calculations revealed the key role of oxygen in the reaction mechanism, subsequently borne out by catalytic studies with Ag particles that confirmed the presence of oxygen as a necessary and sufficient condition for the coupling reaction to occur. The direct relevance of model studies to a mechanistic understanding of coupling reactions under conditions of practical catalysis was reaffirmed.

Magnetron sputtering under oblique angle deposition was used to produce Ni-containing ultra thin film anodes comprising alternating layers of gadolinium doped ceria (GDC) and yttria stabilized zirconia (YSZ) of either 200 nm or 1000 nm thickness. The evolution of film structure from initial deposition, through calcination and final reduction was examined by XRD, SEM, TEM and TOF-SIMS. After subsequent fuel cell usage, the porous columnar architecture of the two-component layered thin film anodes was maintained and their resistance to delamination from the underlying YSZ electrolyte was superior to that of corresponding single component Ni-YSZ and Ni-GDC thin films. Moreover, the fuel cell performance of the 200 nm layered anodes compared favorably with conventional commercially available thick anodes. The observed dependence of fuel cell performance on individual layer thicknesses prompted study of equivalent but more easily fabricated hybrid anodes consisting of simultaneously deposited Ni-GDC and Ni-YSZ, which procedure resulted in exceptionally intimate mixing and interaction of the components. The hybrids exhibited very unusual and favorable IV characteristics, along with exceptionally high power densities at high currents. Their discovery is the principal contribution of the present work.

We report on the synthesis of undoped ∼5 μm YSZ-Ni porous thin films prepared by reactive pulsed DC magnetron sputtering at an oblique angle of incidence. Pre-calcination of the amorphous unmodified precursor layers followed by reduction produces a film consisting of uniformly distributed tilted columnar aggregates having extensive three-phase boundaries and favorable gas diffusion characteristics. Similarly prepared films doped with 1.2 at.% Au are also porous and contain highly dispersed gold present as Ni-Au alloy particles whose surfaces are strongly enriched with Au. With hydrogen as fuel, the performance of the undoped thin film anodes is comparable to that of 10–20 times thicker typical commercial anodes. With a 1:1 steam/carbon feed, the un-doped anode cell current rapidly falls to zero after 60 h. In striking contrast, the initial performance of the Au-doped anode is much higher and remains unaffected after 170 h. Under deliberately harsh conditions the performance of the Au-doped anodes decreases progressively, almost certainly due to carbon deposition. Even so, the cell maintains some activity after 3 days operation in dramatic contrast with the un-doped anode, which stops working after only three hours of use. The implications and possible practical application of these findings are discussed.

A detailed study of ammonia synthesis from hydrogen and nitrogen in a planar dielectric barrier discharge (DBD) reactor was carried out. Electrical parameters were systematically varied, including applied voltage and frequency, electrode gap, and type of ferroelectric material (BaTiO3 versus PZT). For selected operating conditions, power consumption and plasma electron density were estimated from Lissajous diagrams and by application of the Bolsig + model, respectively. Optical emission spectroscopy was used to follow the evolution of plasma species (NH*, N*, N-2(+) and N-2*) as a function of applied voltage with both types of ferroelectric material. PZT gave both greater energy efficiency and higher ammonia yield than BaTiO3: 0.9 g NH3 kWh(-1) and 2.7% single pass N-2 conversion, respectively. This performance is substantially superior to previously published findings on DBD synthesis of NH3 from N-2 and H-2 alone. The influence of electrical working parameters, the beneficial effect of PZT and the importance of controlling reactant residence time are rationalized in a reaction model that takes account of the principal process variables

Previous theoretical studies of C3B have suggested that boron-doped graphite is a promising H-2- and Li-storage material, with large maximum capacities. These characteristics could lead to exciting applications as a lightweight H-2-storage material for automotive engines and as an anode in a new generation of batteries. However, for these applications to be realized a synthetic route to bulk C3B must be developed. Here we show the thermolysis of a single-source precursor (1,3-BBr2)(2)C6H4) to produce graphitic C3B, thus allowing the characteristics of this elusive material to be tested for the first time. C3B was found to be compositionally uniform but turbostratically disordered. Contrary to theoretical expectations, the H-2- and Li-storage capacities are lower than anticipated, results that can partially be explained by the disordered nature of the material. This work suggests that to model the properties of graphitic materials more realistically, the possibility of disorder must be considered.

Uniform, highly porous, columnar thin films incorporating YSZ and NiO prepared by magnetron sputtering with deposition at glancing incidence exhibited stoichiometries close to that of the Y-Zr-Ni sputter target. Characterization by means of SEM, XRD, XPS and RBS revealed that the uniformly distributed nickel component in the as-deposited films consisted of NiO, and that the YSZ component was essentially amorphous. Annealing such films at 850 degrees C in hydrogen resulted in crystallization of the YSZ phase with preservation of the columnar morphology, while the NiO underwent reduction to metallic Ni, which partially segregated to the film surface. The hydrogen-annealed thin film anodes exhibited high conductivity, comparable to that of conventionally-prepared anodes, in both hydrogen and hydrogen/water mixtures at temperatures relevant to SOFC operation. They were also robust against strain-induced separation from the substrate under limited thermal cycling in both oxidizing and reducing atmospheres and are promising candidates for use as anodes in their own right and as strain-accommodating buffer layers between conventional anodes and the electrolyte for use in SOFC applications. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Comme souligne par Mazoyer et Roudart (2002), la mise en place de systemes de polyculture – elevage a permis d’accroitre la productivite des terres cultivees grâce au transfert de fertilite du saltus vers l’ager. Neanmoins, cette association n’a permis des augmentations significatives de rendements que suite au developpement d’une culture attelee lourde. En effet, celle-ci a permis la recolte de fourrages pour maintenir le cheptel en stabulation hivernale. Le fumier produit durant cette phase a alors pu etre transfere sur les terres afin d’y etre enfoui par labour. Suite a la fabrication d’engrais de synthese et au developpement de la traction mecanique, une specialisation des systemes et une dissociation des productions animales et vegetales a, a nouveau, eu lieu parallelement a une forte augmentation de la productivite du travail.

Phenylacetylene (PA) and iodobenzene (IB) are prototypical reactants in Sonogashira cross-coupling. Their adsorption behavior and reactivity on the Au(100) surface were studied by STM, temperature-programmed desorption and reaction, and DFT calculations that included the effect of dispersion forces. The two species exhibited very different behavior. Thus, even at 200 K, PA rearranged Au surface atoms so as to lift the hex reconstruction and adsorb in 4-fold-symmetric islands on the unreconstructed 100 surface. On the other hand, IB adsorbed on the reconstructed hex surface, again as islands, forming three different coexisting close-packed structures. The DFT results are in good accord with these findings, demonstrating the strong preference of PA and IB for the (100) and hex surfaces, respectively. Moreover, the calculated adsorption energies were in satisfactory agreement with values estimated from the desorption data. Adsorbed separately, both PA and IB underwent homocoupling yielding diphenyl diacetylene and biphenyl, respectively; in the former case, reaction appeared to originate at island boundaries. On the well-annealed surface, coadsorbed PA and IB behaved independently, generating only products of homocoupling. However, on the Ar+ roughened surface, Sonogashira cross-coupling also occurred, yielding diphenyl acetylene. These findings are discussed in terms of the island-forming propensity of the reactants, amplified by the labile nature of the Au 100 surface under adsorption and the marked preference of the two reactants for different substrate structures, factors that act to inhibit the formation of a mixed adlayer and suppress reactivity. The implications for the behavior of practical Au nanoparticle catalysts are considered.

Plasma-assisted catalysis of the reaction between CO2 and C2H6 in a single-pass, ferroelectrically moderated dielectric barrier discharge reactor has been studied at near ambient temperature l as a function of physicochemical and electrical reaction variables. The presence of small amounts of a vanadia/alumina catalyst dispersed on the BaTiO3 ferroelectric markedly enhanced the production of formaldehyde, the focus of this work. A maximum HCOH selectivity of 11.4% (defined with respect to the number of ethane carbon atoms consumed) at similar to 100% ethane conversion was achieved, the other products being CO, H2O, H-2, CH4 and a small amount of C3H8. N2O was also an effective partial oxidant (HCOH selectivity 8.9%) whereas use of O-2 led to complete combustion, behavior that may be rationalized in terms of the electron impact excitation cross sections of the three oxidants. Control experiments with the coproducts CH4 and C3H8 showed that these species were not intermediates in HCOH formation from C2H6. Analysis of reactor performance as a function of discharge characteristics revealed that formaldehyde formation was strongly favored at low frequencies where the zero-current fraction of the duty cycle was greatest, the implication being that plasma processes also acted to destroy previously formed products. A tentative reaction mechanism is proposed that accounts for the broad features of formaldehyde production.

Model excreted nitrogen (N), phosphorus (P), carbon and potassium (K) distributions in cattle manures in function of the barn type

Metal-catalyzed Sonogashira coupling reactions that lead to the formation of new C-C bonds are of strategic importance in synthetic organic chemistry [1]. They provide a powerful and flexible method for systematically and efficiently constructing complex molecular architectures from suitably tailored building blocks. This chemistry is almost always carried out homogeneously using expensive organometallic complexes of palladium as catalysts. It is now the most important method for preparing arylalkynes and conjugated enynes, which are key precursors in the synthesis of natural products, pharmaceuticals, and molecular organic materials. The ability to carry out such reactions heterogeneously by means of suitable low cost nanoparticle catalysis is a highly desirable goal because of the well-known operational advantages of heterogeneous over homogeneous methodology. Moreover, the availability of inexpensive and air-stable nanoparticle catalysts capable of carrying out Sonogashira coupling with low-cost aryl chlorides (as opposed to expensive aryl iodides) would greatly expand the possibilities for scale-up and technological implementation of Sonogashira coupling [2] Here, by means of single crystal experiments involving STM and temperature programmed reaction (TPR) supported by DFT calculations, . we show that the Ag(100) surface catalyzes Sonogashira coupling of chlorobenzene (ClBz) and phenyl acetylene (PA), thus meeting both the above stated objectives. It is found that both reactants show a pronounced tendency to form islands on extended terraces, thus inhibiting cross-coupling activity which is thought to occur where island boundaries are proximate (Figure 1A and B). Consistent with this view, deliberately roughening the surface so as to limit island size results in the onset of Sonogashira coupling. In this way, simultaneous co-adsorption of PA and ClBz from an approximately equimolar vapour under UHV conditions followed by TPR measurements showed that homocoupling of PA to diphenyldiacetylene (DPDA) and of Chlorobenzene to biphenyl (BP) occurred. Most importantly, Sonogashira cross coupling of the two reactants to yield diphenylacetylene (DPA) was also observed (Figure 1C). These findings open the door to the design and development of optimized Ag nanoparticle catalyst systems.

Evaluation of the third Action Programme. Recommendations for regulatory and scientific research. In accordance with the Nitrates Directive, the third "Durable Nitrogen Management Plan" (PGDA) will be soon reviewed in Wallonia (Belgium). The second "Nitrate - Water" workshop took place between 28th May and 1st June 2012. The workshop was attended by both Belgian scientists (Universite catholique de Louvain - UCL, Walloon Agricultural Research Center CRA-W, Universite de Liege - ULg, Gembloux Agro-Bio Tech) and French scientists (National Institute for Agricultural Research - INRA). In the light of the results of experiments presented by scientists at this workshop, modifications to the PGDA are now recommended. These concern organic and mineral nitrogen fertilization for crops and meadows; catch crops; soil nitrate-nitrogen residue limitation in autumn, at the start of the nitrate leaching period; the management of meadow ploughing and a modification of the dairy cow standard for nitrogen production.

Lors de la destruction d’une prairie permanente, la mineralisation de la matiere organique accumulee dans le sol entraine un enrichissement important en azote mineral les annees qui suivent la destruction. Les resultats montrent que durant les deux annees de cultures de mais qui suivent une destruction de printemps, les rendements sont eleves, au maximum du potentiel regional, et les reliquats depassent tres largement les valeurs attendues pour la culture consideree. D’autres resultats montrent que les risques de pertes d’azote sont eleves pour la destruction de prairie permanente avant l’hiver, meme en region froide. Afin de reduire les risques de pertes d’azote entre deux cultures, il convient donc, non seulement de piloter la fertilisation de maniere plus precise notamment par des analyses de sol, mais egalement de generaliser l’interdiction de destruction avant l’hiver et de realiser des successions culturales permettant de prelever l’azote disponible en grande quantite et sur une periode la plus longue possible.