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- ItemCeria/silicon carbide core–shell materials prepared by miniemulsion technique(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2011) Borchardt, Lars; Oschatz, Martin; Frind, Robert; Kockrick, Emanuel; Lohe, Martin R.; Hauser, Christoph P.; Weiss, Clemens K.; Landfester, Katharina; Büchner, Bernd; Kaskel, StefanFor the first time we present the synthesis of CeO2/Si(O)C core–shell particles prepared by the miniemulsion technique. The Si(O)C core was obtained by means of a polycarbosilane precursor (SMP10), which was subsequently functionalized with ceria and pyrolyzed to the ceramic. The size of these particles could easily be adjusted by varying the surfactants and the surfactant concentration, or by the addition of comonomers. Hence particle sizes ranged from 100 to 1000 nm, tunable by the preparation conditions. All materials were characterized by photon cross correlation spectroscopy, scanning electron microscopy and elemental mapping investigations. Furthermore, first catalytic tests were carried out by temperature programmed oxidation (TPO) of methane, and the activity of this material in lowering the onset temperature of methane combustion by 262 K was documented.
- ItemGold Aerogels: Three-Dimensional Assembly of Nanoparticles and Their Use as Electrocatalytic Interfaces(Washington, DC : Soc., 2016) Wen, Dan; Liu, Wei; Haubold, Danny; Zhu, Chengzhou; Oschatz, Martin; Holzschuh, Matthias; Wolf, André; Simon, Frank; Kaskel, Stefan; Eychmüller, AlexanderThree-dimensional (3D) porous metal nanostructures have been a long sought-after class of materials due to their collective properties and widespread applications. In this study, we report on a facile and versatile strategy for the formation of Au hydrogel networks involving the dopamine-induced 3D assembly of Au nanoparticles. Following supercritical drying, the resulting Au aerogels exhibit high surface areas and porosity. They are all composed of porous nanowire networks reflecting in their diameters those of the original particles (5–6 nm) via electron microscopy. Furthermore, electrocatalytic tests were carried out in the oxidation of some small molecules with Au aerogels tailored by different functional groups. The beta-cyclodextrin-modified Au aerogel, with a host–guest effect, represents a unique class of porous metal materials of considerable interest and promising applications for electrocatalysis.
- ItemHydrophilic non-precious metal nitrogen-doped carbon electrocatalysts for enhanced efficiency in oxygen reduction reaction(Cambridge : Royal Society of Chemistry, 2015) Hao, Guang-Ping; Sahraie, Nastaran Ranjbar; Zhang, Qiang; Krause, Simon; Oschatz, Martin; Bachmatiuk, Alicja; Strasser, Peter; Kaskel, StefanExploring the role of surface hydrophilicity of non-precious metal N-doped carbon electrocatalysts in electrocatalysis is challenging. Herein we discover an ultra-hydrophilic non-precious carbon electrocatalyst, showing enhanced catalysis efficiency on both gravimetric and areal basis for oxygen reduction reaction due to a high dispersion of active centres.
- ItemNickel cobalt oxide hollow nanosponges as advanced electrocatalysts for the oxygen evolution reaction(Cambridge : Soc., 2015) Zhu, Chengzhou; Wen, Dan; Leubner, Susanne; Oschatz, Martin; Liu, Wei; Holzschuh, Matthias; Simon, Frank; Kaskel, Stefan; Eychmüller, AlexanderA class of novel nickel cobalt oxide hollow nanosponges were synthesized through a sodium borohydride reduction strategy. Due to their porous and hollow nanostructures, and synergetic effects between their components, the optimized nickel cobalt oxide nanosponges exhibited excellent catalytic activity towards oxygen evolution reaction.
- ItemEmulsion soft templating of carbide-derived carbon nanospheres with controllable porosity for capacitive electrochemical energy storage(Cambridge : Royal Society of Chemistry, 2015) Oschatz, Martin; Zeiger, Marco; Jaeckel, Nicolas; Strubel, Patrick; Borchardt, Lars; Reinhold, Romy; Nickel, Winfried; Eckert, Jürgen; Presser, Volker; Kaskel, StefanA new approach to produce carbide-derived carbon nanospheres of 20-200 nm in diameter based on a novel soft-templating technique is presented. Platinum catalysis is used for the cross-linking of liquid (allylhydrido)polycarbosilane polymer chains with para-divinylbenzene within oil-in-water miniemulsions. Quantitative implementation of the pre-ceramic polymer can be achieved allowing precise control over the resulting materials. After pyrolysis and high-temperature chlorine treatment, resulting particles offer ideal spherical shape, very high specific surface area (up to 2347 m^2/g^-1), and large micro/mesopore volume (up to 1.67 cm^3/g^-1). The internal pore structure of the nanospheres is controllable by the composition of the oil phase within the miniemulsions. The materials are highly suitable for electrochemical double-layer capacitors with high specific capacitances in aqueous 1 M Na2SO4 solution (110 F/g^-1) and organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile (130 F/g^-1).
- ItemApplication of Thermal Response Measurements to Investigate Enhanced Water Adsorption Kinetics in Ball-Milled C2N-Type Materials(Weinheim : Wiley-VCH-Verl., 2022) Du, Shengjun; Leistenschneider, Desirée; Xiao, Jing; Dellith, Jan; Troschke, Erik; Oschatz, MartinSorption-based water capture is an attractive solution to provide potable water in arid regions. Heteroatom-decorated microporous carbons with hydrophilic character are promising candidates for water adsorption at low humidity, but the strong affinity between the polar carbon pore walls and water molecules can hinder the water transport within the narrow pore system. To reduce the limitations of mass transfer, C2N-type carbon materials obtained from the thermal condensation of a molecular hexaazatriphenylene-hexacarbonitrile (HAT-CN) precursor were treated mechanochemically via ball milling. Scanning electron microscopy as well as static light scattering reveal that large pristine C2N-type particles were split up to a smaller size after ball milling, thus increasing the pore accessibility which consequently leads to faster occupation of the water vapor adsorption sites. The major aim of this work is to demonstrate the applicability of thermal response measurements to track these enhanced kinetics of water adsorption. The adsorption rate constant of a C2N material condensed at 700 °C remarkably increased from 0.026 s−1 to 0.036 s−1 upon ball milling, while maintaining remarkably high water vapor capacity. This work confirms the advantages of small particle sizes in ultramicroporous materials on their vapor adsorption kinetics. It is demonstrated that thermal response measurements are a valuable and time-saving method to investigate water adsorption kinetics, capacities, and cycling stability.