ChemSusChem

Publications in this journal

• Article: Oligocarbazole-Based Chromophores for Efficient Thin-Film Dye-Sensitized Solar Cells.

  Samuel De Sousa, Céline Olivier, Laurent Ducasse, Gwenaëlle Le Bourdon, Lionel Hirsch, Thierry Toupance
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  ABSTRACT: Carb your enthousiasm: Carbazole-based sensitizers with high extinction coefficients are synthesized for application in dye-sensitized solar cells (DSCs). The dyes perform efficiently with both iodine and cobalt electrolytes, showing power conversion efficiencies of up to 5.8 % on TiO2 films of 15 μm thickness, and retaining 90 % of their efficiency in devices with thinner films.
  ChemSusChem 05/2013;
• Article: Dehydrogenation of Dodecahydro-N-ethylcarbazole on Pt(111).

  Christoph Gleichweit, Max Amende, Stefan Schernich, Wei Zhao, Michael P A Lorenz, Oliver Höfert, Nicole Brückner, Peter Wasserscheid, Jörg Libuda, Hans-Peter Steinrück, Christian Papp
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  ABSTRACT: Sloshing hydrogen: Liquid organic hydrogen carriers are high-boiling organic molecules, which can be reversibly hydrogenated and dehydrogenated in catalytic processes and are, therefore, a promising chemical hydrogen storage material. One of the promising candidates is the pair N-ethylcarbazole/perhydro-N-ethylcarbazole (NEC/H12 -NEC). The dehydrogenation and possible side reactions on a Pt(111) surface are evaluated in unprecedented detail.
  ChemSusChem 05/2013;
• Article: Nafion-Resin-Modified Mesocellular Silica Foam Catalyst for 5-Hydroxymethylfurfural Production from D-Fructose.

  Zhen Huang, Wenya Pan, Haibo Zhou, Feng Qin, Hualong Xu, Wei Shen
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  ABSTRACT: Catalytic dehydration of D-fructose to 5-hydroxymethylfurfural (HMF) was investigated over a series of Nafion-modified mesocellular silica foam (MCF) materials. By using an impregnation method, Nafion resin was highly dispersed in the ultra-large pores of the MCFs. Highly efficient and selective dehydration of D-fructose to HMF was achieved in dimethyl sulfoxide solvent; an 89.3 % HMF yield with 95.0 % selectivity was obtained in the presence of the Nafion(15)/MCF catalyst. The effects of reaction temperature, reaction time, and solvent on the dehydration of D-fructose were systematically investigated. The catalyst could be regenerated through an ion-exchange method and a high yield was retained after being used five times. As a heterogeneous catalytic process, a possible reaction mechanism for the dehydration of D-fructose over Nafion-modified MCF catalysts was proposed.
  ChemSusChem 05/2013;
• Article: Composite Poly(ethylene oxide) Electrolytes Plasticized by N-Alkyl-N-butylpyrrolidinium Bis(trifluoromethanesulfonyl)imide for Lithium Batteries.

  Morten Wetjen, Maria Assunta Navarra, Stefania Panero, Stefano Passerini, Bruno Scrosati, Jusef Hassoun
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  ABSTRACT: We report a new class of quaternary polymer electrolyte membranes that comprise poly(ethylene oxide) (PEO), lithium trifluoromethanesulfonylimide (LiTFSI), N-alkyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PyrA,4 TFSI) as an ionic liquid, and a SiO2 filler. The results of differential scanning calorimetry indicate that the addition of SiO2 and different ionic liquids induces a decrease in the PEO melting enthalpy, which thereby increases the ionic conductivity and the Li transference number. The electrochemical stability is proved by using impedance spectroscopy and cyclic voltammetry. Galvanostatic cycling of Li/LiFePO4 cells, which comprise the quaternary polymer electrolytes, revealed their superior performance compared to conventional PEO-Li salt electrolytes. In the course of this investigation, a synergistic effect of the combined ionic liquid-ceramic filler modification could be proved at temperatures close to 50 °C.
  ChemSusChem 05/2013;
• Article: Structural Characterization of Anion-Calcium-Humate Complexes in Phosphate-based Fertilizers.

  Roberto Baigorri, Oscar Urrutia, Javier Erro, Marcos Mandado, Ignacio Pérez-Juste, José María Garcia-Mina
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  ABSTRACT: Fertilizers based on phosphate-metal-humate complexes are a new family of compounds that represents a more sustainable and bioavailable phosphorus source. The characterization of this type of complex by using solid (31) P NMR in several fertilizers, based on single superphosphate (SSP) and triple superphosphate (TSP) matrices, yielded surprising and unexpected trends in the intensity and fine structure of the (31) P NMR peaks. Computational chemistry methods allowed the characterization of phosphate-calcium-humate complexes in both SSP and TSP matrices, but also predicted the formation of a stable sulfate-calcium-humate complex in the SSP fertilizers, which has not been described previously. The stability of this complex has been confirmed by using ultrafiltration techniques. Preference towards the humic substance for the sulfate-metal phase in SSP allowed the explanation of the opposing trends that were observed in the experimental (31) P NMR spectra of SSP and TSP samples. Additionally, computational chemistry has provided an assignment of the (31) P NMR signals to different phosphate ligands as well as valuable information about the relative strength of the phosphate-calcium interactions within the crystals.
  ChemSusChem 05/2013;
• Article: Magnetism in Lithium-Oxygen Discharge Product.

  Jun Lu, Hun-Ji Jung, Kah Chun Lau, Zhengcheng Zhang, John A Schlueter, Peng Du, Rajeev S Assary, Jeffrey Greeley, Glen A Ferguson, Hsien-Hau Wang, Jusef Hassoun, Hakim Iddir, Jigang Zhou, Lucia Zuin, Yongfeng Hu, Yang-Kook Sun, Bruno Scrosati, Larry A Curtiss, Kahlil Amine
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  ABSTRACT: Nonaqueous lithium-oxygen batteries have a much superior theoretical gravimetric energy density compared to conventional lithium-ion batteries, and thus could render long-range electric vehicles a reality. A molecular-level understanding of the reversible formation of lithium peroxide in these batteries, the properties of major/minor discharge products, and the stability of the nonaqueous electrolytes is required to achieve successful lithium-oxygen batteries. We demonstrate that the major discharge product formed in the lithium-oxygen cell, lithium peroxide, exhibits a magnetic moment. These results are based on dc-magnetization measurements and a lithium-oxygen cell containing an ether-based electrolyte. The results are unexpected because bulk lithium peroxide has a significant band gap. Density functional calculations predict that superoxide-type surface oxygen groups with unpaired electrons exist on stoichiometric lithium peroxide crystalline surfaces and on nanoparticle surfaces; these computational results are consistent with the magnetic measurement of the discharged lithium peroxide product as well as EPR measurements on commercial lithium peroxide. The presence of superoxide-type surface oxygen groups with spin can play a role in the reversible formation and decomposition of lithium peroxide as well as the reversible formation and decomposition of electrolyte molecules.
  ChemSusChem 05/2013;
• Article: Polymer Bulk Heterojunction Solar Cells with PEDOT:PSS Bilayer Structure as Hole Extraction Layer.

  Wanjung Kim, Namhun Kim, Jung Kyu Kim, Insun Park, Yeong Suk Choi, Dong Hwan Wang, Heeyeop Chae, Jong Hyeok Park
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  ABSTRACT: A high current density obtained in a limited, nanometer-thick region is important for high efficiency polymer solar cells (PSCs). The conversion of incident photons to charge carriers only occurs in confined active layers; therefore, charge-carrier extraction from the active layer within the device by using solar light has an important impact on the current density and the related to power conversion efficiency. In this study, we observed a surprising result, that is, extracting the charge carrier generated in the active layer of a PSC device, with a thickness-controlled PEDOT:PSS bilayer that acted as a hole extraction layer (HEL), yielded a dramatically improved power conversion efficiency in two different model systems (P3HT:PC60 BM and PCDTBT:PC70 BM). To understand this phenomenon, we conducted optical strength simulation, photocurrent-voltage measurements, incident photon to charge carrier efficiency measurements, ultraviolet photoelectron spectroscopy, and AFM studies. The results revealed that approximately 60 nm was the optimum PEDOT:PSS bilayer HEL thickness in PSCs for producing the maximum power conversion efficiency.
  ChemSusChem 05/2013;
• Article: Effect of the Structural Characteristics of Binary Pt-Ru and Ternary Pt-Ru-M Fuel Cell Catalysts on the Activity of Ethanol Electrooxidation in Acid Medium.

  Ermete Antolini
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  ABSTRACT: In view of their possible use as anode materials in acid direct ethanol fuel cells, the electrocatalytic activity of Pt-Ru and Pt-Ru-M catalysts for ethanol oxidation has been investigated. This minireview examines the effects of the structural characteristics of Pt-Ru, such as the degree of alloying and Ru oxidation state, on the electrocatalytic activity for ethanol oxidation.
  ChemSusChem 05/2013;
• Article: Pseudocapacitive Hausmannite Nanoparticles with (101) Facets: Synthesis, Characterization, and Charge-Transfer Mechanism.

  Matthew P Yeager, Wenxin Du, Qi Wang, N Aaron Deskins, Matthew Sullivan, Brendan Bishop, Dong Su, Wenqian Xu, Sanjaya D Senanayake, Rui Si, Jonathan Hanson, Xiaowei Teng
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  ABSTRACT: Hausmannite Mn3 O4 octahedral nanoparticles of 18.3±7.0 nm with (101) facets have been prepared by an oxygen-mediated growth. The electrochemical properties of the Mn3 O4 particles as pseudocapacitive cathode materials were characterized both in half-cells and in button-cells. The Mn3 O4 nanoparticles exhibited a high mass-specific capacitance of 261 F g(-1) , which was calculated from cyclic voltammetry analyses, and a capacitive retention of 78 % after 10 000 galvanostatic charge-discharge cycles. The charge-transfer mechanisms of the Mn3 O4 nanoparticles were further studied by using synchrotron-based in situ X-ray absorption near edge spectroscopy and XRD. Both measurements showed concurrently that throughout the potential window of 0-1.2 V (vs. Ag/AgCl), a stable spinel structure of Mn3 O4 remained, and a reversible electrochemical conversion between tetrahedral [Mn(II) O4 ] and octahedral [Mn(III) O6 ] units accounted for the redox activity. Density functional theory calculations further corroborated this mechanism by confirming the enhanced redox stability afforded by the abundant and exposed (101) facets of Mn3 O4 octahedra.
  ChemSusChem 05/2013;
• Article: Superhydrophobic Activated Carbon-Coated Sponges for Separation and Absorption.

  Hanxue Sun, An Li, Zhaoqi Zhu, Weidong Liang, Xinhong Zhao, Peiqing La, Weiqiao Deng
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  ABSTRACT: Highly porous activated carbon with a large surface area and pore volume was synthesized by KOH activation using commercially available activated carbon as a precursor. By modification with polydimethylsiloxane (PDMS), highly porous activated carbon showed superhydrophobicity with a water contact angle of 163.6°. The changes in wettability of PDMS- treated highly porous activated carbon were attributed to the deposition of a low-surface-energy silicon coating onto activated carbon (confirmed by X-ray photoelectron spectroscopy), which had microporous characteristics (confirmed by XRD, SEM, and TEM analyses). Using an easy dip-coating method, superhydrophobic activated carbon-coated sponges were also fabricated; those exhibited excellent absorption selectivity for the removal of a wide range of organics and oils from water, and also recyclability, thus showing great potential as efficient absorbents for the large-scale removal of organic contaminants or oil spills from water.
  ChemSusChem 05/2013;
• Article: Catalytic Characteristics of AgCu Bimetallic Nanoparticles in the Oxygen Reduction Reaction.

  Kihyun Shin, Da Hye Kim, Hyuck Mo Lee
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  ABSTRACT: Intensive research on oxygen reduction reaction (ORR) catalysts has been undertaken to find a Pt substitute or reduce the amount of Pt. Ag nanoparticles are potential Pt substitutes; however, the weak oxygen adsorption energy of Ag prompted investigation of other catalysts. Herein, we prepared AgCu bimetallic nanoparticle (NP) systems to improve the catalytic performance and compared the catalytic performance of Ag, Cu, AgCu (core-shell), and AgCu (alloy) NP systems as new catalyst by investigating the adsorption energy of oxygen and the activation energy of oxygen dissociation, which is known to be the rate-determining step of ORR. By analyzing HOMO-level isosurfaces of metal NPs and oxygen, we found that the adsorption sites and the oxygen adsorption energies varied with different configurations of NPs. We then plotted the oxygen adsorption energies against the energy barrier of oxygen dissociation to determine the catalytic performance. AgCu (alloy) and Cu NPs exhibited strong adsorption energies and low activation-energy barriers. However, the overly strong oxygen adsorption energy of Cu NPs hindered the ORR.
  ChemSusChem 05/2013;
• Article: CO2 Sorbents with Scaffold-like CaAl Layered Double Hydroxides as Precursors for CO2 Capture at High Temperatures.

  Po-Hsueh Chang, Tai-Jung Lee, Yen-Po Chang, San-Yuan Chen
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  ABSTRACT: A highly stable high-temperature CO2 sorbent consisting of scaffold-like Ca-rich oxides (CaAlO) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing CaAlNO3 layered double hydroxide (LDH) precursors through a sol-gel process with Al(O(i) P)3 and Ca(NO3 )2 with Ca(2+) /Al(3+) ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca(2+) /Al(3+) ratios of 2:1. However, both LDH and Ca(OH)2 phases were produced at higher ratios. Both TEM and SEM observations indicated that the CaAlNO3 LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO-based CaAlO mixed oxide (CAMO), composed of CaO and Ca12 Al14 O33 , was still present. The CAMO exhibited high specific surface areas (up to 191 m(2) g(-1) ) and a pore size distribution of 3-6 nm, which allowed rapid diffusion of CO2 into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO2 absorption at 700 °C. Thermogravimetric analysis results indicated that a CO2 capture capacity of approximately 49 wt % could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94-98 % of the initial CO2 capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments.
  ChemSusChem 05/2013;
• Article: Ruthenium Catalysts for Hydrogenation of Aromatic and Aliphatic Esters: Make Use of Bidentate Carbene Ligands.

  Felix A Westerhaus, Bianca Wendt, Andreas Dumrath, Gerrit Wienhöfer, Kathrin Junge, Matthias Beller
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  ABSTRACT: Committed carbenes: The convenient application of bidentate carbene ligands is described for the hydrogenation of carboxylic acid esters. The ligand precursors are easily synthesized through the dimerization of N-substituted imidazoles with diiodomethane. The catalyst is generated in situ and exhibits good activity and functional group tolerance for the hydrogenation of aromatic and aliphatic carboxylic acid esters.
  ChemSusChem 05/2013;
• Article: New Insights into the Oxygen Reduction Reaction Mechanism on Pt (111): A Detailed Electrochemical Study.

  Ana M Gómez-Marín, Juan M Feliu
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  ABSTRACT: The oxygen reduction reaction (ORR) is undoubtedly the most important fuel-cell cathodic reaction. In this work, a detailed electrochemical analysis of the ORR on Pt (111) in nonadsorbing electrolytes was performed, which included the high-potential region Eup =1.15 V while ensuring the electrode surface structure stability. Our results suggest that the reduction of a soluble intermediate species formed during the ORR is the rate-determining step in the whole reaction mechanism. This species does not undergo any other electrochemical reaction at E>0.9 V and may accumulate close to the electrode surface. Together with dissolved O2 , this intermediate may modify the oxide-growth dynamics on Pt (111). Hence, both species interact with the electrode surface through complex catalytic networks. Under certain experimental conditions, oxygenated species from the oxidation of Pt (111) may enhance the overall ORR current. These results propose an alternative to explain the current state of the art for this fundamental process.
  ChemSusChem 05/2013;
• Article: Reactivity of Azole Anions with CO2 from the DFT Perspective.

  Huarong Tang, Chao Wu
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  ABSTRACT: Azole anions are key components in CO2 capture materials that include ionic liquids and porous solids. Herein, we use density functional theory (DFT) and a Langmuir-type adsorption model to study azole anion-CO2 interactions. Linear CO2 has to be bent by approximately 45° to form an NC bond within the azole ring. The energy cost of bending renders CO2 absorption much more difficult compared to SO2 absorption. For different azole anions, the number of nitrogen atoms in the ring and the natural bond orbital energy of the reacting nitrogen lone pair, both linearly correlate with the calculated reaction enthalpy and are useful handles for new sorbent designs. Unlike for SO2 , the azole parent architecture (unsubstituted) does not allow successive CO2 absorption under mild conditions (<0.12 MPa and at room temperature). Experimental CO2 and SO2 absorption isotherms are reproduced by using the Langmuir model parameterized with the calibrated DFT reaction enthalpies. This study provides insight for designing azole-based CO2 -capture materials.
  ChemSusChem 05/2013;
• Article: Oxygen-functionalized few-layer graphene sheets as active catalysts for oxidative dehydrogenation reactions.

  Viviane Schwartz, Wujun Fu, Yu-Tung Tsai, Harry M Meyer, Adam J Rondinone, Jihua Chen, Zili Wu, Steven H Overbury, Chengdu Liang
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  ABSTRACT: Invited for this month's cover is the group from the Center for Nanophase Materials Sciences (CNMS) at the Oak Ridge National Laboratory. The illustration is of the catalytic activity of the reported oxygen-functionalized few-layer graphenes, whereas the micrograph background image is of the same graphenes recorded by the authors using a new helium-ion microscope at the CNMS. Read the full text of the article at 10.1002/cssc.201200756.
  ChemSusChem 05/2013; 6(5):732.
• Article: Conversion of Cellulose and Cellobiose into Sorbitol Catalyzed by Ruthenium Supported on a Polyoxometalate/Metal-Organic Framework Hybrid.

  Jinzhu Chen, Shengpei Wang, Jing Huang, Limin Chen, Longlong Ma, Xing Huang
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  ABSTRACT: Cellulose and cellobiose were selectively converted into sorbitol over water-tolerant phosphotungstic acid (PTA)/metal- organic-framework-hybrid-supported ruthenium catalysts, Ru-PTA/MIL-100(Cr), under aqueous hydrogenation conditions. The goal was to investigate the relationship between the acid/metal balance of bifunctional catalysts Ru-PTA/MIL-100(Cr) and their performance in the catalytic conversion of cellulose and cellobiose into sugar alcohols. The control of the amount and strength of acid sites in the supported PTA/MIL-100(Cr) was achieved through the effective control of encapsulated-PTA loading in MIL-100(Cr). This design and preparation method led to an appropriately balanced Ru-PTA/MIL-100(Cr) in terms of Ru dispersion and hydrogenation capacity on the one hand, and acid site density of PTA/MIL-100(Cr) (responsible for acid-catalyzed hydrolysis) on the other hand. The ratio of acid site density to the number of Ru surface atoms (nA /nRu ) of Ru-PTA/MIL-100(Cr) was used to monitor the balance between hydrogenation and hydrolysis functions; the optimum balance between the two catalytic functions, that is, 8.84<nA /nRu <12.90, achieves maximum conversion of cellulose and cellobiose into hexitols. Under the applied reaction conditions, optimal results (63.2 % yield in hexitols with a selectivity for sorbitol of 57.9 % at complete conversion of cellulose, and 97.1 % yield in hexitols with a selectivity for sorbitol of 95.1 % at complete conversion of cellobiose) were obtained using a Ru-PTA/MIL-100(Cr) catalyst with loadings of 3.2 wt % for Ru and 16.7 wt % for PTA. This research thus opens new perspectives for the rational design of acid/metal bifunctional catalysts for biomass conversion.
  ChemSusChem 04/2013;
• Article: Glucose Dehydration to 5-Hydroxymethylfurfural in a Biphasic System over Solid Acid Foams.

  Vitaly V Ordomsky, John van der Schaaf, Jaap C Schouten, T Alexander Nijhuis
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  ABSTRACT: A solid acid foam-structured catalyst based on a binderless zirconium phosphate (ZrPO) coating on aluminum foam was prepared. The catalyst layer was obtained by performing a multiple washcoating procedure of ZrPO slurry on the anodized aluminum foam. The effect of the pretreatment of ZrPO, the concentration of the slurry, and the amount of coating on the properties of the foam was studied. The catalytic properties of the prepared foams have been evaluated in the dehydration of glucose to 5-hydroxymethylfurfural (HMF) in a biphasic reactor. The catalytic behavior of ZrPO foam-based catalysts was studied in a rotating foam reactor and compared with that of bulk ZrPO. The effect of a silylation procedure on the selectivity of the process was shown over bulk and foam catalysts. This treatment resulted in a higher selectivity due to the deactivation of unselective Lewis acid sites. Addition of methylisobutylketone leads to extraction of HMF from the aqueous phase and stabilization of the selectivity to HMF over bulk ZrPO. A more intensive contact of the foam with the aqueous and organic phases leads to an increase in the selectivity and resistance to deactivation of the foam in comparison with a bulk catalyst.
  ChemSusChem 04/2013;
• Article: Effect of CeO2 Addition to Al2 O3 Supports for Pt Catalysts on the Aqueous-Phase Reforming of Glycerol.

  M M Rahman, Tamara L Church, Andrew I Minett, Andrew T Harris
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  ABSTRACT: A series of Pt catalysts supported on Al2 O3 that was doped with different amounts of CeO2 was developed, characterized, and tested in the aqueous-phase reforming (APR) of glycerol to H2 . Catalyst 3Pt/3CeAl, which bore 3 wt % Pt on a support that contained 3 wt % CeO2 , showed the highest carbon conversion to gas (85 %) and the highest H2 yield (80 %) for a feedstock of 1 wt % glycerol in water at 240 °C and 40 bar. A CeO2 /Al2 O3 support with only 1 wt % Pt also showed high H2 selectivity and carbon conversion to gas, as well as a much lower CH4 yield than the benchmark 3Pt/Al catalyst, clearly demonstrating that doping the support with 3 wt % CeO2 improved the APR of glycerol. H2 chemisorption results showed that the highest metal dispersion (58 %) and active surface area (4.3 m(2) g(-1) ) were achieved for the support that contained 3 wt % CeO2 , and this effect appeared to be primarily responsible for the high H2 yield and carbon conversion to gas. No CO was observed in the product gas; therefore, this gas could potentially be used directly in proton exchange membrane fuel cells. Thus, including CeO2 in the Al2 O3 catalyst support enhanced both the activity and selectivity towards H2 of a Pt catalyst for the APR of glycerol.
  ChemSusChem 04/2013;