TY - JOUR A1 - Kraehnert, R. A1 - Ortel, Erik A1 - Paul, B. A1 - Eckhardt, B. A1 - Kanis, M. A1 - Liu, R. A1 - Antoniou, A. T1 - Electrochemically dealloyed platinum with hierarchical pore structure as highly active catalytic coating N2 - Micro structured reactors are attractive candidates for further process intensification in heterogeneous catalysis. However, they require catalytic coatings with significantly improved space-time yields compared to traditional supported catalysts. We report the facile synthesis of homogeneous nanocrystalline Pt coatings with hierarchical pore structure by electrochemical dealloying of amorphous sputter-deposited platinum silicide layers. Thickness, porosity and surface composition of the catalysts can be controlled by the dealloying procedure. XPS analysis indicates that the catalyst surface is primarily composed of metallic Pt. Catalytic tests in gas-phase hydrogenation of butadiene reveal the typical activity, selectivity and activation energy of nanocrystalline platinum. However, space time yields are about 13 to 200 times higher than values reported for Pt-based catalysts in literature. The highly open metallic pore structure prevents heat and mass transport limitations allowing for very fast reactions and reasonable stability at elevated temperatures. KW - Pt catalysts KW - Pt–Si layers KW - Scanning Electron Microscopy (SEM) KW - Transmission Electron Microscopy (TEM) KW - pore structure KW - electrochemical dealloying PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-351393 DO - https://doi.org/10.1039/C4CY00851K SN - 2044-4753 SN - 2044-4761 VL - 5 IS - 1 SP - 206 EP - 216 PB - RSC Publ. CY - Cambridge AN - OPUS4-35139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Polte, J. A1 - Bernsmeier, D. A1 - Eckhardt, B. A1 - Paul, B. A1 - Bergmann, A. A1 - Strasser, P. A1 - Emmerling, Franziska A1 - Kraehnert, R. T1 - Pd/TiO2 coatings with template-controlled mesopore structure as highly active hydrogenation catalyst N2 - Micro-structured reactors offer excellent mass and heat transport capabilities and can therefore sustain very high reaction rates and space–time-yields also for highly exothermic catalytic reactions. However, such high rates cannot be reached when the reactors are coated or filled with conventional catalysts powders. We present a strategy for the direct synthesis of highly active wall-coated supported catalysts via co-deposition of a pore template (here micelles formed from PEO-b-PPO-b-PEO) and a precursors for the metal oxide (TiCl4) along with a compatible precursor for the active metal (PdCl2). The obtained catalytic coatings possess a template-controlled open pore structure and excellent mechanical stability. Moreover, the active metal is highly dispersed and well-distributed across the coating also at high Pd loadings. The corresponding high activity along with rapid mass transfer enabled by the open pore system results in the best space–time-yields in the gas-phase hydrogenation of butadiene reported so far in literature for a supported catalyst. KW - Titanium oxide films KW - Palladium nanoparticle KW - Wall-coated supported catalysts KW - Template-controlled mesoporous materials KW - Hydrogenation of 1,3-butadiene PY - 2015 DO - https://doi.org/10.1016/j.apcata.2014.12.044 SN - 0926-860X SN - 1873-3875 VL - 493 SP - 25 EP - 32 PB - Elsevier CY - Amsterdam AN - OPUS4-32465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eckhardt, B. A1 - Ortel, Erik A1 - Bernsmeier, D. A1 - Polte, J. A1 - Strasser, P. A1 - Vainio, U. A1 - Emmerling, Franziska A1 - Kraehnert, R. T1 - Micelle-templated oxides and carbonates of zinc, cobalt, and aluminium and a generalized strategy for their synthesis N2 - Catalysis, energy storage, and light harvesting require functional materials with tailored porosity and nanostructure. However, common synthesis methods that employ polymer micelles as structure-directing agents fail for zinc oxide, for cobalt oxide, and for metal carbonates in general. We report the synthesis of the oxides and carbonates of zinc, cobalt, and aluminum with micelle-templated structure. The synthesis relies on poly(ethylene oxide)-block-poly(butadiene)-block-poly(ethylene oxide) triblock copolymers and a new type of precursor formed by chemical complexation of a metal nitrate with citric acid. A general synthesis mechanism is deduced. Mechanistic insights allow for the prediction of optimal processing conditions for different oxides and carbonates based on simple thermogravimetric analysis. Employing this synthesis, films of ZnO and Co3O4 with micelle-controlled mesoporosity become accessible for the first time. It is the only soft-templating method reported so far that also yields mesoporous metal carbonates. The developed synthesis is generic in nature and can be applied to many other metal oxides and carbonates. KW - EISA KW - Pore templating KW - Metal oxide KW - Metal carbonate KW - Zinc oxide KW - Cobalt oxide PY - 2013 DO - https://doi.org/10.1021/cm400535d SN - 0897-4756 SN - 1520-5002 VL - 25 IS - 14 SP - 2749 EP - 2758 PB - American Chemical Society CY - Washington, DC AN - OPUS4-29113 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Fischer, A. A1 - Chuenchom, L. A1 - Polte, Jörg A1 - Emmerling, Franziska A1 - Smarsly, B.M. A1 - Kraehnert, R. T1 - New triblock copolymer templates, PEO-PB-PEO, for the synthesis of titania films with controlles mesopore size, wall thickness, and bimodal porosity N2 - The synthesis and properties of a series of new structure-directing triblock copolymers with PEO-PB-PEO structure (PEO = poly(ethylene oxide) and PB = polybutadiene) and their application as superior pore-templates for the preparation of mesoporous titania coatings are reported. Starting from either TiCl4 or from preformed TiO2 nanocrystalline building blocks, mesoporous crystalline titanium oxide films with a significant degree of mesoscopic ordered pores are derived, and the pore size can be controlled by the molecular mass of the template polymer. Moreover, the triblock copolymers form stable micelles already at very low concentration, i.e., prior to solvent evaporation during the evaporation-induced self-assembly process (EISA). Consequently, the thickness of pore walls can be controlled independently of pore size by changing the polymer-to-precursor ratio. Thus, unprecedented control of wall thickness in the structure of mesoporous oxide coatings is achieved. In addition, the micelle formation of the new template polymers is sufficiently distinct from that of typical commercial PPO-PEO-PPO polymers (Pluronics; PPO = poly(propylene oxide)), so that a combination of both polymers facilitates bimodal porosity via dual micelle templating. KW - Mesoporous materials KW - Titanium oxide films KW - Anatase nanoparticles KW - PEO-PB-PEO KW - Dual templating PY - 2012 DO - https://doi.org/10.1002/smll.201101520 SN - 1613-6810 SN - 1613-6829 VL - 8 IS - 2 SP - 298 EP - 309 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-26277 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -