- Email: [email protected]
MCFC catalyst for indirect internal reforming of ethanol
Finally, a research group led by Jiirgen Garche at the Centre for Solar Energy & Hydrogen Research (Zentrum fi~r Sonnenenergie- und Wasserstoff-Forschung, ZSW) in Ulm is undertaking the practical fuel cell test.
Conclusions It is still not certain whether 'alloyed' nanoparticles, consisting of several types of metal atoms that are uniformly distributed in the particle, really do work with optimum effect in the fuel cell catalyst. The Miilheim synthesis group is therefore also working with systems in which both types of metal are placed on top of each other. On the interface, both types of atoms are positioned in close contact. Further improvement in catalytic activity, resistance to poisoning and long-term stability are expected above all from the specific interactions of both types of atoms on the boundary surface. Each type of catalyst exhibits an individual and highly complex behaviour along with its own strengths and weaknesses, which until now have been virtually impossible to predict. In order to find an optimum catalyst for a specific use, it is therefore necessary to carry out experiments using different chemical compositions. One particular area developed by the researchers in Miilheim is the innovative
ResearchTrends Composite PBI membranes Composite membranes 80-100"pm thick and with good mechanical properties were prepared using silicotungstic acid and silica as inorganic materials and polybenzimidazole (PBI) as binding polymer. Treatment of the composite membranes with phosphoric acid enhances the proton conductivi~ Silica has the double function of entrapping the heteropolyacid to avoid its dissolution in water, and retaining water to improve proton conduction. The as-prepared membrane with 50 wt% inorganic material is mechanically stable, with a proton conductivity of 1.2 × 10-3 S/cm at 160°C and 100% relative humidi W.The same membrane, after phosphoric acid treatment, gives a proton conductivity of 2.23 x 10-3 S/cm for the same conditions. E Staiti, M. Minutoli: J. of Power Sources 94(1) 9-13 (15 February 2001).
MCFC catalysts for indirect internal reforming of ethanol The feasibility of coupling a processor for
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production of nanoparticle precursors using combinations of two or even three different metals; this option had not previously been available for fuel cell catalysts. In conclusion, nanostructured metal colloids are very promising precursors for manufacturing multimetallic fuel cell catalysts that are truly nanosized (i.e. <2 nm) and have high metal loadings (20 wt% of metal).
References 1. H. Btinnemann, W. Brijoux, R. Brinkmann, R. Fretzen, T. Joussen, R. K/Sppler, P. Neiteler and J. Richter (1994) Preparation, characterization, and application of fine metal particles and metal colloids using hydrotriorganoborates, J. of Molecular Catalysis 86(1-3) 129-177 (1994). 2. H. B6nnemann, G. Braun, W. Brijoux, R. Brinkmann, A. Schulze Tilling, K. Seevogel and K. Siepen (1996) Nanoscale colloidal metals and alloys stabilized by solvents and surfactants: Preparation and use as catalyst precursors, J. of Organometallic Chemistry520(1/2) 143-162. 3. H. B6nnemann and W. Brijoux, in: A. Fiirsmer (Ed.) (1996) Active metals, VCH, Weinheim, 339-379. 4. H. B/Snnemann, W. Brijoux and T. Joussen (1993) Microcrystalline-to-amorphous metal and/or alloy powders dissolved without protective colloid in organic solvents. US Patent
internal indirect reforming of ethanol/water with MCFCs has been verified experimentally. Several tests were performed on two different Rh/A1203 catalysts to measure catalytic activity in ethanol steam reforming, both on alumina and supported catalysts. Ethanol could be decomposed and the steam reforming process obtained at well determined conditions of temperature and catalyst load. At 650°C the 5% Rh/Al203 catalyst produced a hydrogen-rich gas ideal for MCFC applications, free from ethylene or other undesirables. Good results were also obtained in long-term tests. S. Freni: J. of Power Sources 94(1) 14-19 (15 February 2001).
Performance of H2S-fueled SOFC Promising initial values for current and power output using this system show that hydrogen sulfide is a potentially suitable fuel for a zirconia-based SOFC operating at intermediate temperatures (750-800°C). However, Pt deposited on YSZ is not a suitable anode material for an H2S stream, as the formation of PtS contaminates the anode surface and
5580492 (assigned to Studiengesellschaft Kohle mbH, Germany). 5. H. Btnnemann, W. Brijoux, R. Brinkmann, E. Dinjus, T. Joussen and B. Korall (1991) Reduction of metal salts with tetraalkylammonium hydrotriorganoborates, Angewandte Chemie International Edition 30(10) 13441346. 6. H. Btnnemann, W. Brijoux, R. Brinkmann and J. Richter (2000) Process for producing tenside-stabilized colloids of mono- and bimetals of the group VIII and Ib of the periodic system in the form of precursors for catalysts which are isolable and water soluble at high concentration. US Patent 6090746 (assigned to Studiengesellschaft Kohle mbH, Germany). 7. H. B6nnemann and W. Brijoux, in:W. Moser (Ed.) (1996) Advanced catalysts and nanostructured materials, Academic Press, San Diego, Chap. 7, 165-196. 8. U.A. Paulus, U. Endruschat, G.J. Feldmeyer, T.J. Schmidt, H. Boennemann, and R.J. Behm i (2000) New PtRu alloy colloids as precursors for fuel cell catalysts, J. of Catalysis 195(2) 383-393. For more information, contact: Dr Ryan aichards, Abteilung Heterogene Katalyse, Max Planck Institut for Kohlenforschung,KaiserWilhelm Platz 1, D-45470 MLilheim a.d. Ruhr,Germany.Tel: +49 208 306 2360, Fax: +49 208 306 2983, Email: [email protected], http://www.mpi-muelheim.mpg.de
increases interface resistance between Pt and YSZ, ultimately leading to detachment of the Pt anode from the YSZ membrane. Electrochemical polarization significantly accelerates degradation of the Pt anode. Superior current output and longer MEA lifetime are found when using dilute H2S feed rather than a pure feed. Alternative anode catalysts are required, that do not deteriorate over time in an H2S atmosphere. M. Liu, P. He, J.L. Luo, A.R. Sanger, K.T. Chuang: J. of Power Sources 94(1) 20-25 (15 February 2001).
Two-phase flow/transport in PEM air cathode Two-phase flow and transport of reactants and products in the air cathode of PEM fuel cells was studied analytically and numerically. When the cell operated above the threshold current density, liquid water appeared and a two-phase zone formed within the porous cathode. A two-phase, multi-component mixture model in conjunction with a finite-volume-based CFD technique was applied to simulate the cathode operation in this regime. The polarization curve and water and
Fuel Cells Bulletin No. 37
Conclusions It is still not certain whether 'alloyed' nanoparticles, consisting of several types of metal atoms that are uniformly distributed in the particle, really do work with optimum effect in the fuel cell catalyst. The Miilheim synthesis group is therefore also working with systems in which both types of metal are placed on top of each other. On the interface, both types of atoms are positioned in close contact. Further improvement in catalytic activity, resistance to poisoning and long-term stability are expected above all from the specific interactions of both types of atoms on the boundary surface. Each type of catalyst exhibits an individual and highly complex behaviour along with its own strengths and weaknesses, which until now have been virtually impossible to predict. In order to find an optimum catalyst for a specific use, it is therefore necessary to carry out experiments using different chemical compositions. One particular area developed by the researchers in Miilheim is the innovative
ResearchTrends Composite PBI membranes Composite membranes 80-100"pm thick and with good mechanical properties were prepared using silicotungstic acid and silica as inorganic materials and polybenzimidazole (PBI) as binding polymer. Treatment of the composite membranes with phosphoric acid enhances the proton conductivi~ Silica has the double function of entrapping the heteropolyacid to avoid its dissolution in water, and retaining water to improve proton conduction. The as-prepared membrane with 50 wt% inorganic material is mechanically stable, with a proton conductivity of 1.2 × 10-3 S/cm at 160°C and 100% relative humidi W.The same membrane, after phosphoric acid treatment, gives a proton conductivity of 2.23 x 10-3 S/cm for the same conditions. E Staiti, M. Minutoli: J. of Power Sources 94(1) 9-13 (15 February 2001).
MCFC catalysts for indirect internal reforming of ethanol The feasibility of coupling a processor for
(~
production of nanoparticle precursors using combinations of two or even three different metals; this option had not previously been available for fuel cell catalysts. In conclusion, nanostructured metal colloids are very promising precursors for manufacturing multimetallic fuel cell catalysts that are truly nanosized (i.e. <2 nm) and have high metal loadings (20 wt% of metal).
References 1. H. Btinnemann, W. Brijoux, R. Brinkmann, R. Fretzen, T. Joussen, R. K/Sppler, P. Neiteler and J. Richter (1994) Preparation, characterization, and application of fine metal particles and metal colloids using hydrotriorganoborates, J. of Molecular Catalysis 86(1-3) 129-177 (1994). 2. H. B6nnemann, G. Braun, W. Brijoux, R. Brinkmann, A. Schulze Tilling, K. Seevogel and K. Siepen (1996) Nanoscale colloidal metals and alloys stabilized by solvents and surfactants: Preparation and use as catalyst precursors, J. of Organometallic Chemistry520(1/2) 143-162. 3. H. B6nnemann and W. Brijoux, in: A. Fiirsmer (Ed.) (1996) Active metals, VCH, Weinheim, 339-379. 4. H. B/Snnemann, W. Brijoux and T. Joussen (1993) Microcrystalline-to-amorphous metal and/or alloy powders dissolved without protective colloid in organic solvents. US Patent
internal indirect reforming of ethanol/water with MCFCs has been verified experimentally. Several tests were performed on two different Rh/A1203 catalysts to measure catalytic activity in ethanol steam reforming, both on alumina and supported catalysts. Ethanol could be decomposed and the steam reforming process obtained at well determined conditions of temperature and catalyst load. At 650°C the 5% Rh/Al203 catalyst produced a hydrogen-rich gas ideal for MCFC applications, free from ethylene or other undesirables. Good results were also obtained in long-term tests. S. Freni: J. of Power Sources 94(1) 14-19 (15 February 2001).
Performance of H2S-fueled SOFC Promising initial values for current and power output using this system show that hydrogen sulfide is a potentially suitable fuel for a zirconia-based SOFC operating at intermediate temperatures (750-800°C). However, Pt deposited on YSZ is not a suitable anode material for an H2S stream, as the formation of PtS contaminates the anode surface and
5580492 (assigned to Studiengesellschaft Kohle mbH, Germany). 5. H. Btnnemann, W. Brijoux, R. Brinkmann, E. Dinjus, T. Joussen and B. Korall (1991) Reduction of metal salts with tetraalkylammonium hydrotriorganoborates, Angewandte Chemie International Edition 30(10) 13441346. 6. H. Btnnemann, W. Brijoux, R. Brinkmann and J. Richter (2000) Process for producing tenside-stabilized colloids of mono- and bimetals of the group VIII and Ib of the periodic system in the form of precursors for catalysts which are isolable and water soluble at high concentration. US Patent 6090746 (assigned to Studiengesellschaft Kohle mbH, Germany). 7. H. B6nnemann and W. Brijoux, in:W. Moser (Ed.) (1996) Advanced catalysts and nanostructured materials, Academic Press, San Diego, Chap. 7, 165-196. 8. U.A. Paulus, U. Endruschat, G.J. Feldmeyer, T.J. Schmidt, H. Boennemann, and R.J. Behm i (2000) New PtRu alloy colloids as precursors for fuel cell catalysts, J. of Catalysis 195(2) 383-393. For more information, contact: Dr Ryan aichards, Abteilung Heterogene Katalyse, Max Planck Institut for Kohlenforschung,KaiserWilhelm Platz 1, D-45470 MLilheim a.d. Ruhr,Germany.Tel: +49 208 306 2360, Fax: +49 208 306 2983, Email: [email protected], http://www.mpi-muelheim.mpg.de
increases interface resistance between Pt and YSZ, ultimately leading to detachment of the Pt anode from the YSZ membrane. Electrochemical polarization significantly accelerates degradation of the Pt anode. Superior current output and longer MEA lifetime are found when using dilute H2S feed rather than a pure feed. Alternative anode catalysts are required, that do not deteriorate over time in an H2S atmosphere. M. Liu, P. He, J.L. Luo, A.R. Sanger, K.T. Chuang: J. of Power Sources 94(1) 20-25 (15 February 2001).
Two-phase flow/transport in PEM air cathode Two-phase flow and transport of reactants and products in the air cathode of PEM fuel cells was studied analytically and numerically. When the cell operated above the threshold current density, liquid water appeared and a two-phase zone formed within the porous cathode. A two-phase, multi-component mixture model in conjunction with a finite-volume-based CFD technique was applied to simulate the cathode operation in this regime. The polarization curve and water and
Fuel Cells Bulletin No. 37