Formic acid (HCOOH) has a great potential as a safe and a convenient hydrogen carrier for fuel cell applications. However, efficient and CO-free hydrogen production through the decomposition of formic acid at low temperatures (<363 K) in the absence of additives constitutes a major challenge. Herein, we present a new heterogeneous catalyst system composed of bimetallic PdAg alloy and MnO x nanoparticles supported on amine-grafted silica facilitating the liberation of hydrogen at room temperature through the dehydrogenation of formic acid in the absence of any additives with remarkable activity (330 mol H 2 ·mol catalyst −1 ·h −1 ) and selectivity (>99%) at complete conversion (>99%). Moreover this new catalytic system enables facile catalyst recovery and very high stability against agglomeration, leaching, and CO poisoning. Through a comprehensive set of structural and functional characterization experiments, mechanistic origins of the unusually high catalytic activity, selectivity, and stability of this unique catalytic system are elucidated. Current heterogeneous catalytic architecture presents itself as an excellent contender for clean hydrogen production via room-temperature additive-free dehydrogenation of formic acid for on-board hydrogen fuel cell applications.

Influence of ceria on the NOx storage and reduction behavior of NSR catalysts was investigated in a systematic manner over γ-Al2O3, Ba/Al, Ce/Al, Ba/Ce/Al, Pt/Al, Pt/Ce/Al and Ba/Pt/Ce/Al systems using BET, XRD, Raman spectroscopy and in situ FTIR. Although ceria promotion does not seem to have a substantial influence on the overall NOx storage capacity, it does have a clearly positive effect on the NOx reduction via H2(g) during catalytic regeneration under rich conditions which is associated with the enhancement in the total amount of activated hydrogen on the catalyst surface and lowering of the thermal threshold for hydrogen activation. A strong metal support interaction (SMSI) between Pt sites and the BaOx/CeOx domains leads to a complex redox interplay including oxidation of the precious metal sites, reduction of ceria, formation of BaO2 species as well as the formation of Pt-O-Ce interfacial sites on the Ba/Pt/Ce/Al surface. Ceria domains also act as anchoring sites for Pt species, limit their surface diffusion, enhance dispersion and hinder sintering at elevated temperatures. On the Ba/Pt/Ce/Al catalyst surface, reduction of the stored nitrates under relatively mild conditions via H2(g) initially leads to the formation of surface -OH and -NHx species and gas phase N2O, as well as the destruction of surface nitrate species, leaving bulk nitrates mostly intact. Reduction proceeds with the conversion of N2O(g) into N2(g) along with the partial loss of surface -OH and -NHx groups, dehydration and the loss of bulk nitrates. © 2013 Elsevier B.V

a b s t r a c tPerovskite-based materials (LaMnO 3 , Pd/LaMnO 3 , LaCoO 3 and Pd/LaCoO 3 ) were synthesized, characterized (via BET, XRD, Raman spectroscopy, XPS and TEM) and their NO x (x = 1,2) adsorption characteristics were investigated (via in-situ FTIR and TPD) as a function of the nature of the B-site cation (i.e. Mn vs Co), Pd/PdO incorporation and H 2 -pretreatment. NO x adsorption on of LaMnO 3 was found to be significantly higher than LaCoO 3 , in line with the higher SSA of LaMnO 3 . Incorporation of PdO nanoparticles with an average diameter of ca. 4 nm did not have a significant effect on the amount of NO 2 adsorbed on fresh LaMnO 3 and LaCoO 3 . TPD experiments suggested that saturation of fresh LaMnO 3 , Pd/LaMnO 3 , LaCoO 3 and Pd/LaCoO 3 with NO 2 at 323 K resulted in the desorption of NO 2 , NO, N 2 O and N 2 (without O 2 ) below 700 K, while above 700 K, NO x desorption was predominantly in the form of NO + O 2 . Perovskite materials were found to be capable of activating N-O linkages typically at ca. 550 K (even in the absence of an external reducing agent) forming N 2 and N 2 O as direct NO x decomposition products. H 2 -pretreatment yielded a drastic boost in the NO oxidation and NO x adsorption of all samples, particularly for the Cobased systems. Presence of Pd further boosted the NO x uptake upon H 2 -pretreatment. Increase in the NO x adsorption of H 2 -pretreated LaCoO 3 and Pd/LaCoO 3 surfaces could be associated with the electronic changes (i.e. reduction of B-site cation), structural changes (surface reconstruction and SSA increase), reduction of the precious metal oxide (PdO) into metallic species (Pd), and the generation of oxygen defects on the perovskite. Mn-based systems were more resilient toward B-site reduction. Pd-addition suppressed the B-site reduction and preserved the ABO 3 perovskite structure.

Effects of reaction temperature and feed composition on reactant conversion, product distribution and catalytic stability were investigated on syngas production by reforming of glycerol, a renewable waste, with CO 2 on Rh/ ZrO 2 and Rh/CeO 2 catalysts. For the first time in the literature, fresh and spent catalysts were characterized by in-situ FTIR, Raman spectroscopy, transmission electron microscopy and energy dispersive X-ray analysis techniques in order to unravel novel insights regarding the molecular-level origins of catalytic deactivation and aging under the conditions of glycerol dry reforming. Both catalysts revealed increased glycerol conversions with increasing temperature, where the magnitude of response became particularly notable above 650 and 700°C on Rh/ZrO 2 and Rh/CeO 2 , respectively. In accordance with thermodynamic predictions, CO 2 transformation occurred only above 700°C. Syngas was obtained at H 2 /CO ∼0.8, very close to the ideal composition for Fischer-Tropsch synthesis, and carbon formation was minimized with increasing temperature. Glycerol conversion decreased monotonically, whereas, after an initial increase, CO 2 conversion remained constant upon increasing CO 2 /glycerol ratio (CO 2 /G) from 1 to 4. In alignment with the slightly higher specific surface area of and smaller average Rh-particle size on ZrO 2 , Rh/ZrO 2 exhibited higher conversions and syngas yields than that of Rh/CeO 2. Current characterization studies indicated that Rh/CeO 2 revealed strong metal-support interaction, through which CeO 2 seemed to encapsulate Rh nanoparticles and partially suppressed the catalytic activity of Rh sites. However, such interactions also seemed to improve the stability of Rh/CeO 2 , rendering its activity loss to stay below that of Rh/ZrO 2 after 72 h time-on-stream testing at 750°C and for CO 2 /G = 4. Enhanced stability in the presence of CeO 2 was associated with the inhibition of coking of the catalyst surface by the mobile oxygen species and creation of oxygen vacancies on ceria domains. Deactivation of Rh/ZrO 2 was attributed to the sintering of Rh nanoparticles and carbon formation.

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Faceted colloidal nanoparticles are currently of immense interest due to their unique electronic, optical, and catalytic properties. However, continuous flow synthesis that enables rapid formation of faceted nanoparticles of single or multi-elemental composition is not trivial. We present a continuous flow synthesis route for the synthesis of uniformly sized Pd nanocubes and PdPt core–shell nanoparticles in a single-phase microfluidic reactor, which enables rapid formation of shaped nanoparticles with a reaction time of 3 min. The PdPt core–shell nanoparticles feature a dendritic, high surface area with the Pt shell covering the Pd core, as verified using high-resolution scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. The Pd nanocubes and PdPt core–shell particles are catalytically tested during NO2 reduction in the presence of H2 in a flow pocket reactor. The Pd nanocubes exhibited low-temperature activity (i.e., <136 °C) and poor selectivity performance toward production of N2O or N2, whereas PdPt core–shell nanoparticles showed higher activity and were found to achieve better selectivity during NO2 reduction retaining its basic structure at relatively elevated temperatures, making the PdPt core–shell particles a unique, desirable synergic catalyst material for potential use in NO x abatement processes.

a b s t r a c tTiO 2 -Al 2 O 3 binary oxide surfaces were utilized in order to develop an alternative photocatalytic NO x abatement approach, where TiO 2 sites were used for ambient photocatalytic oxidation of NO with O 2 and alumina sites were exploited for NO x storage. Chemical, crystallographic and electronic structure of the TiO 2 -Al 2 O 3 binary oxide surfaces were characterized (via BET surface area measurements, XRD, Raman spectroscopy and DR-UV-Vis Spectroscopy) as a function of the TiO 2 loading in the mixture as well as the calcination temperature used in the synthesis protocol. 0.5 Ti/Al-900 photocatalyst showed remarkable photocatalytic NO x oxidation and storage performance, which was found to be much superior to that of a Degussa P25 industrial benchmark photocatalyst (i.e. 160% higher NO x storage and 55% lower NO 2 (g) release to the atmosphere). Our results indicate that the onset of the photocatalytic NO x abatement activity is concomitant to the switch between amorphous to a crystalline phase with an electronic band gap within 3.05-3.10 eV; where the most active photocatalyst revealed predominantly rutile phase together and anatase as the minority phase.

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