Martin Oschatz

Friedrich Schiller University Jena

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Stefan Kaskel

TU Dresden

Lars Borchardt

Ruhr University Bochum

Markus Antonietti

Max Planck Institute of Colloids and Interfaces

Konstantin Schutjajew

Friedrich Schiller University Jena

Winfried Nickel

TU Dresden

Runyu Yan

Max Planck Institute of Colloids and Interfaces

Tobias Heil

Max Planck Institute for Solid State Research

Qing Qin

Anhui Normal University

Ralf Walczak

Max Planck Institute of Colloids and Interfaces

Eike Brunner

TU Dresden

Cooperative Institutions

TU Dresden

Max Planck Institute of Colloids and Interfaces

Friedrich Schiller University Jena

Max Planck Society

Technische Universität Berlin

Chinese Academy of Sciences

Helmholtz-Zentrum Berlin für Materialien und Energie

Centre National de la Recherche Scientifique

Georgia Institute of Technology

Fraunhofer Institute for Material and Beam Technology

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Micro‐ and Mesoporous Carbide‐Derived Carbon–Selenium Cathodes for High‐Performance Lithium Selenium Batteries

Advanced Energy Materials (2014)

Jung Tae Lee Hyea Kim Martin Oschatz Dong‐Chan Lee Feixiang Wu

Nanocomposites of selenium (Se) and ordered mesoporous silicon carbide‐derived carbon (OM‐SiC‐CDC) are prepared for the first time and studied as cathodes for lithium‐selenium (Li‐Se) batteries. The higher concentration of Li salt in the electrolytes greatly improves Se utilization and cell cycle stability. Se‐CDC shows significantly better performance characteristics than Se‐activated carbon nanocomposites with similar physical properties. Se‐CDC also exhibits better rate performance and cycle stability compared to similarly produced sulfur (S)–CDC for Li/S batteries.

Carbon fibers

Carbide-derived carbon

10.1002/aenm.201400981

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Citations (159)

Electrochemical Generation of Catalytically Active Edge Sites in C₂N‐Type Carbon Materials for Artificial Nitrogen Fixation

Small (2022)

Wuyong Zhang Shaoqi Zhan Qing Qin Tobias Heil Xiyu Liu

The electrochemical nitrogen reduction reaction (NRR) to ammonia (NH3 ) is a potentially carbon-neutral and decentralized supplement to the established Haber-Bosch process. Catalytic activation of the highly stable dinitrogen molecules remains a great challenge. Especially metal-free nitrogen-doped carbon catalysts do not often reach the desired selectivity and ammonia production rates due to their low concentration of NRR active sites and possible instability of heteroatoms under electrochemical potential, which can even contribute to false positive results. In this context, the electrochemical activation of nitrogen-doped carbon electrocatalysts is an attractive, but not yet established method to create NRR catalytic sites. Herein, a metal-free C2 N material (HAT-700) is electrochemically etched prior to application in NRR to form active edge-sites originating from the removal of terminal nitrile groups. Resulting activated metal-free HAT-700-A shows remarkable catalytic activity in electrochemical nitrogen fixation with a maximum Faradaic efficiency of 11.4% and NH3 yield of 5.86 µg mg-1cat h-1 . Experimental results and theoretical calculations are combined, and it is proposed that carbon radicals formed during activation together with adjacent pyridinic nitrogen atoms play a crucial role in nitrogen adsorption and activation. The results demonstrate the possibility to create catalytically active sites on purpose by etching labile functional groups prior to NRR.

Carbon fibers

Active carbon

10.1002/smll.202204116

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Citations (19)

Covalent triazine framework/carbon nanotube hybrids enabling selective reduction of CO₂ to CO at low overpotential

Green Chemistry (2020)

Andreas Laemont Sara Abednatanzi Parviz Gohari Derakhshandeh Florian Verbruggen Erika Fiset

Nitrogen-rich covalent triazine frameworks (CTFs) were grown in situ onto surface-functionalized carbon nanotubes. These novel hybrid catalysts electrochemically reduce CO₂ to CO with a faradaic efficiency up to 81% at an overpotential of 380 mV.

Overpotential

Triazine

Carbon fibers

10.1039/d0gc00090f

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Citations (17)

Towards stable and high‐capacity anode materials for sodium‐ion batteries by embedding of Sb/Sn nanoparticles into electrospun mesoporous carbon fibers

Electrochemical Science Advances (2021)

Tian Liu Runyu Yan Elinor Josef Haijian Huang Long Pan

Abstract Antimony and tin are promising anode materials for sodium‐ion batteries due to their high theoretical sodium storage capacities. However, significant volume change during cycling limits their long‐term stability and rate performance. Composite engineering can minimize this problem. A versatile method for the synthesis of Sb nanoparticles inside the mesopores of carbon fibers prepared through electrospinning and subsequent carbothermal reduction is presented in this work. The mesopore architecture can host up to 61 wt% of Sb nanoparticles and buffer the volume changes during cycling. Smaller pores in the carbon provide the pathways for reversible insertion/extraction of sodium. This binder‐free material provides high rate capability and a long‐term cycling performance when used as an anode in half‐cells. When cycled at 0.5 A g −1 , the composite shows an initial capacity of 520 mA h g −1 with 507 mA h g −1 remaining after 500 cycles. Even at a high current density of 20 A g −1 , a capacity of 197 mA h g −1 is still achieved. Sn nanoparticles can be embedded in the mesopores of the carbon fibers by a similar method. These Sn‐based anodes also show remarkable electrochemical performance, indicating that this approach represents a generally applicable strategy for synthesizing advanced battery anodes.

Electrospinning

Carbon fibers

Sodium-ion battery

10.1002/elsa.202100010

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Citations (2)

Synthesis of Polymer Janus Particles with Tunable Wettability Profiles as Potent Solid Surfactants to Promote Gas Delivery in Aqueous Reaction Media

ACS Applied Materials & Interfaces (2021)

Bradley D. Frank Milena Perovic Saveh Djalali Markus Antonietti Martin Oschatz

Janus particles exhibit a strong tendency to directionally assemble and segregate to interfaces and thus offer advantages as colloidal analogues of molecular surfactants to improve the stability of multiphasic mixtures. Investigation and application of the unique adsorption properties require synthetic procedures that enable careful design and reliable control over the particles' asymmetric chemistry and wettability profiles with high morphological uniformity across a sample. Herein, we report on a novel one-step synthetic approach for the generation of amphiphilic polymer Janus particles with highly uniform and tunable wettability contrasts, which is based on using reconfigurable bi-phasic Janus emulsions as versatile particle scaffolds. Two phase-separated acrylate oils were used as the constituent droplet phases and transformed into their solidified Janus particle replicas via UV-induced radical polymerization. Using Janus emulsions as particle precursors offers the advantage that their internal droplet geometry can be fine-tuned by changing the force balance of surface tensions acting at the individual interfaces via surfactants or the volume ratio of the constituent phases. In addition, preassembled functional surfactants at the droplet interfaces can be locked in position upon polymerization, which enables both access toward postfunctionalization reaction schemes and the generation of highly uniform Janus particles with adjustable wettability profiles. Depending on the particle morphology and wettability, their interfacial position can be adjusted, which allows us to stabilize either air bubbles-in-water or water droplets-in-air (liquid marbles). Motivated by the interfacial activity of the particles and particularly the longevity of the resulting particle-stabilized air-in-water bubbles, we explored their ability to promote the delivery of oxygen inside a liquid-phase reaction medium, namely, for the heterogeneous Au-NP-mediated catalytic oxidation of d-glucose. We observed a 2.2-fold increase in the reaction rate attributed to the increase of the local concentration of oxygen around catalysts, thus showcasing a new strategy to overcome the limited solubility of gases in aqueous reaction media.

Janus Particles

Particle (ecology)

10.1021/acsami.1c07259

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Citations (33)

Hierarchical Carbide‐Derived Carbon Foams with Advanced Mesostructure as a Versatile Electrochemical Energy‐Storage Material

Advanced Energy Materials (2013)

Martin Oschatz Lars Borchardt Katja Pinkert Sören Thieme Martin R. Lohe

Highly porous carbide‐derived carbon (CDC) mesofoams (DUT‐70) are prepared by nanocasting of mesocellular silica foams with a polycarbosilane precursor. Ceramic conversion followed by silica removal and high‐temperature chlorine treatment yields CDCs with a hierarchical micro‐mesopore arrangement. This new type of polymer‐based CDC is characterized by specific surface areas as high as 2700 m 2 g −1 , coupled with ultrahigh micro‐ and mesopore volumes up to 2.6 cm 3 g −1 . The relationship between synthesis conditions and the properties of the resulting carbon materials is described in detail, allowing precise control of the properties of DUT‐70. Since the hierarchical pore system ensures both efficient mass transfer and high capacities, the novel CDC shows outstanding performance as an electrode material in electrochemical double‐layer capacitors (EDLCs) with specific capacities above 240 F g −1 when measured in a symmetrical two‐electrode configuration. Remarkable capacities of 175 F g −1 can be retained even at high current densities of 20 A g −1 as a result of the enhanced ion‐transport pathways provided by the cellular mesostructure. Moreover, DUT‐70 can be infiltrated with sulfur and host the active material in lithium–sulfur battery cathodes. Reversible capacities of 790 mAh g −1 are achieved at a current rate of C/10 after 100 cycles, which renders DUT‐70 an ideal support material for electrochemical energy‐storage applications.

Carbon fibers

Carbide-derived carbon

10.1002/aenm.201300645

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Citations (99)

Preparation of hard carbon/carbon nitride nanocomposites by chemical vapor deposition to reveal the impact of open and closed porosity on sodium storage

Carbon (2021)

Konstantin Schutjajew Paolo Giusto Eneli Härk Martin Oschatz

The sodium-ion battery is a promising successor for the lithium-ion battery. Its energy density is limited by the anode, where sodium ideally is stored at low potentials vs. Na/Na+. The understanding of the fundamental relationships between material properties and sodium storage is often lagging behind materials development. There is a discord regarding the involvement of so-called "closed pores" in carbons in sodium storage. To investigate their influence, a chemical vapor deposition (CVD) process to deposit polymeric carbon nitride (p-C3N4) on hard carbon fibres of both, open and closed microporosity, is developed. High storage capacity at a low potential is only possible, when suitable, sealed pores are present. In fibers without notable gas-accessible surface, p-C3N4 is deposited on the external area, whereas in open-microporous samples the p-C3N4 phase grows in micropores. Consequently, except for the untreated fibres with closed pores, the composite with a pore gradient along the fibers is the only one in the study that is able to accommodate sodium at low potentials. Neither the remaining graphitic domains, nor the introduced p-C3N4 are able to accommodate sodium in a quasimetallic state. Finally, not only the sodium storage but also the solid-electrolyte interphase (SEI) build-up is influenced by the additional p-C3N4 layer.

Carbon fibers

Carbon nitride

10.1016/j.carbon.2021.09.051

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Citations (23)

Towards stable lithium-sulfur battery cathodes by combining physical and chemical confinement of polysulfides in core-shell structured nitrogen-doped carbons

Carbon (2020)

Runyu Yan Martin Oschatz Feixiang Wu

Polysulfide

Carbon fibers

Lithium–sulfur battery

Particle (ecology)

10.1016/j.carbon.2020.01.046

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Citations (89)

Self-Supporting Hierarchical Porous PtAg Alloy Nanotubular Aerogels as Highly Active and Durable Electrocatalysts

Chemistry of Materials (2016)

Wei Liu Danny Haubold Bogdan Rutkowski Martin Oschatz René Hübner

Developing electrocatalysts with low cost, high activity, and good durability is urgently demanded for the wide commercialization of fuel cells. By taking advantage of nanostructure engineering, we fabricated PtAg nanotubular aerogels (NTAGs) with high electrocatalytic activity and good durability via a simple galvanic replacement reaction between the in situ spontaneously gelated Ag hydrogel and the Pt precursor. The PtAg NTAGs have hierarchical porous network features with primary networks and pores from the interconnected nanotubes of the aerogel and secondary networks and pores from the interconnected thin nanowires on the nanotube surface, and they show very high porosities and large specific surface areas. Due to the unique structure, the PtAg NTAGs exhibit greatly enhanced electrocatalytic activity toward formic acid oxidation, reaching 19 times higher metal-based mass current density as compared to the commercial Pt black. Furthermore, the PtAg NTAGs show outstanding structural stability and electrochemical durability during the electrocatalysis. Noble metal-based NTAGs are promising candidates for applications in electrocatalysis not only for fuel cells, but also for other energy-related systems.

10.1021/acs.chemmater.6b01394

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Citations (88)

Application of Thermal Response Measurements to Investigate Enhanced Water Adsorption Kinetics in Ball‐Milled C₂N‐Type Materials

ChemistryOpen (2022)

Shengjun Du Desirée Leistenschneider Jing Xiao Jan Dellith Erik Troschke

Abstract Sorption‐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, C 2 N‐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 C 2 N‐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 C 2 N 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.

Thermal Stability

10.1002/open.202200193

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Citations (13)