Hydrophilic non-precious metal nitrogen-doped carbon electrocatalysts for enhanced efficiency in oxygen reduction reaction

Exploring 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

Textural Characterization of Micro- and Mesoporous Carbons Using Combined Gas Adsorption and n-Nonane Preadsorption

Porous carbon and carbide materials with different structures were characterized using adsorption of nitrogen at 77.4 K before and after preadsorption of n-nonane. The selective blocking of the microporosity with n-nonane shows that ordered mesoporous silicon carbide material (OM-SiC) is almost exclusively mesoporous whereas the ordered mesoporous carbon CMK-3 contains a significant amount of micropores (25%). The insertion of micropores into OM-SiC using selective extraction of silicon by hot chlorine gas leads to the formation of ordered mesoporous carbide-derived carbon (OM-CDC) with a hierarchical pore structure and significantly higher micropore volume as compared to CMK-3, whereas a CDC material from a nonporous precursor is exclusively microporous. Volumes of narrow micropores, calculated by adsorption of carbon dioxide at 273 K, are in linear correlation with the volumes blocked by n-nonane. Argon adsorption measurements at 87.3 K allow for precise and reliable calculation of the pore size distribution of the materials using density functional theory (DFT) methods

New Routes Towards Nanoporous Carbon Materials for Electrochemical Energy Storage and Gas Adsorption

The chemical element carbon plays a key role in the 21st century. “The new carbon age” is associated with the global warming due to increasing carbon dioxide emissions. The latter are a major consequence of the continued combustion of fossil fuels for energy generation. However, carbon is also one key component to overcome these problems. Especially porous carbon materials are highly attractive for many environmentally relevant applications. These materials provide high specific surface area, high pore volume, thermal/chemical stability, and high electrical conductivity. They are promising candidates for the removal of carbon dioxide or other environmentally relevant gases from exhaust gas mixtures. Furthermore, porous carbons are used in electrochemical energy storage devices (e.g. batteries or electrochemical capacitors). The performance of the materials in these applications depends on their pore structure. Hence, precise control over the pore size and the pore geometry is important to achieve. Besides a high specific surface area (SSA) and a well-defined pore size, pore accessibility must be ensured because the surface must be completely available. If the porous carbons exhibit ink-bottle pores, the high surface area is useless because the guest species do not reach the pore interior. Therefore, carbon materials with hierarchical pore structure are attractive. They combine at least two different pore systems of different size which contribute with their individual advantages. While smaller pores provide large specific surface area, larger pores ensure efficient mass transport. Numerous methods for the targeted synthesis of carbide-derived carbon materials (CDCs) with hierarchical pore architectures were developed within this thesis (Figure 1). CDCs are produced by the extraction of metal- or semi-metal atoms from carbide precursors leading to the formation of a microporous carbon network with high specific surface area. PolyHIPE-CDCs with porosity on three hierarchy levels and total pore volumes as high as 8.5 cm3/g were prepared by a high internal phase emulsion technique. CO2 activation increases the SSA to values above 3100 m2/g. These materials are promising for the filtration of non-polar organic compounds from gas mixtures. CDC nanospheres with diameters below 200 nm were obtained from polycarbosilane-based miniemulsions. They show high capacitance of up to 175 F/g in symmetrical EDLCs in 1 M H2SO4 aqueous electrolyte. Besides such emulsion techniques, the hard-templating concept (also referred to as nanocasting) was presented as an efficient approach for the synthesis of CDC mesofoam powders and meso-macroporous CDC monoliths starting from silica templates and polycarbosilane precursors. As a wide range of pore sizes is approachable, the resulting materials are highly versatile in terms of application. Due to their high nanopore volume, well-defined mesopores and large SSA, they show outstanding properties as electrode materials in EDLCs or in Li-S batteries as well as high and rapid uptake in gas adsorption processes. CDC aerogels were produced by pyrolysis and high-temperature chlorine treatment of cross-linked polycarbosilane aerogels. These materials can be tailored for efficient CO2 adsorption and show outstanding performance in EDLC electrodes at high current densities of up to 100 A/g due to the very short electron diffusion pathways within the aerogel-type pore system. It was further shown that CDCs can be combined with mesopores by the sacrificial template method starting from PMMA particles as the pore-forming material. The use of highly toxic hydrofluoric acid for template removal and large amounts of organic solvents as typical for hard- and soft-templating approaches can be overcome. SSAs and total pore volumes of 2434 m2/g and 2.64 cm3/g are achieved ensuring good performance of PMMA-CDCs in Li-S batteries cathodes. Besides the characterization of CDCs in real energy storage devices and adsorption processes, their use as model substances in energy- and environmentally relevant applications was part of this thesis. The questions “How does it work?” and “What do we need?” must be clearly answered before any material can be tailored under the consideration of economic and ecological perspectives. The high potential of CDCs for this purpose was shown in this thesis. These carbons were used as model substances in combination with nuclear magnetic resonance (NMR) techniques to get a detailed understanding of the adsorption processes on porous carbon surfaces. However, such investigations require the use of model substances with a tailored and well-defined pore structure to clearly differentiate physical states of adsorbed species and to understand fundamental mechanisms. The characterization of the interaction of electrolyte molecules with the carbon surface was performed with solid-state NMR experiments. The materials were also studied in the high-pressure adsorption of 129Xe using an in-situ NMR technique. Both NMR studies enable the analysis of ions or gas atoms adsorbed on the carbon surface on an atomic level and experimentally demonstrate different strength of interaction with pores of variable size and connectivity. In addition, the novel InfraSORP technology was used for the investigation of the thermal response of CDCs and templated carbon and carbide materials during n-butane adsorption. These model systems lead to a more profound understanding of this technique for the rapid characterization of porous materials. The Kroll-Carbon (KC) concept is a highly attractive alternative for the synthesis of well-defined carbons on the large scale. In this technique, the porous materials are produced by the reductive carbochlorination reaction between oxidic nanoparticles and a surrounding carbon matrix. First KC materials were produced with high SSA close to 2000 m2/g and total pore volumes exceeding 3 cm3/g. This method was established with template particles of various dimensions as well as by using various types of oxides (silica, alumina, titania). Hence, porous carbon materials with various textural parameters are approachable. The first generation of KCs is promising for the use in Li-S battery cathodes and as electrode materials in EDLCs

The functional chameleon of materials chemistry—combining carbon structures into all-carbon hybrid nanomaterials with intrinsic porosity to overcome the “functionality-conductivity-dilemma” in electrochemical energy storage and electrocatalysis

Nanoporous carbon materials can cover a remarkably wide range of physicochemical properties. They are widely applied in electrochemical energy storage and electrocatalysis. As a matter of fact, all these applications combine a chemical process at the electrode–electrolyte interface with the transport (and possibly the transfer) of electrons. This leads to multiple requirements which can hardly be fulfilled by one and the same material. This “functionality‐conductivity‐dilemma” can be minimized when multiple carbon‐based compounds are combined into porous all‐carbon hybrid nanomaterials. This article is giving a broad and general perspective on this approach from the viewpoint of materials chemists. The problem and existing solutions are first summarized. This is followed by an overview of the most important design principles for such porous materials, a chapter discussing recent examples from different fields where the formation of comparable structures has already been successfully applied, and an outlook over the future development of this field that is foreseen

Who are the ‘dark’ politicians? Insights from self-reports of German state parliament candidates

A growing body of studies is focusing on politicians' personalities, as the personality of political elites has been shown to affect their behavior. Whereas most research uses the big five framework or HEXACO, only a few studies have been able to capture more "aversive," "dark" - yet non-pathological - personality traits of politicians. However, these studies refer to top politicians; information on the distribution and the correlates of dark personality traits in the broad mass of politicians is still lacking. Moreover, information on dark personality traits in politicians is usually based on expert ratings; data using self-placement is missing. Based on data from six surveys with candidates running for German state elections in 2021 and 2022 (N[pooled data set] = 1,632), we, to the best of our knowledge, offer, for the first time, insights into politicians’ self-reported socially aversive personality traits. "Dark" personality traits are measured by the political elites aversive personality scale (PEAPS). Results show that German politicians exhibit moderate levels of aversive personality traits. In addition, the extent of candidates' dark personalities is strongly negatively correlated with honesty-humility, agreeableness vs. anger, and extraversion, while associations with other basic personality traits are much weaker or insignificant. We also find that younger, more right-leaning, and more ideologically extreme candidates report higher levels of aversive personality

Are candidates rational when it comes to negative campaigning? Empirical evidence from two German candidate surveys

This article tests the assumption that candidates’ attack behavior is a result of their rational consideration of potential benefits and likely risks. Based on candidate surveys from three German state elections, we demonstrate that (i) attacks are an important strategy; (ii) on balance, candidates regard attacking opponents as a costly instead of a beneficial strategy; (iii) the differential between benefits and costs is positively associated with attack behavior; nevertheless, most candidates attack at least sometimes even when costs exceed benefits; (iv) candidate characteristics and the electoral context are rarely reflected in benefit-cost calculations; and (v) the theoretically assumed mediating role of the benefit-cost differential on attack behavior applies only to some explanatory factors. While the findings provide some evidence for rational choice explanations of negative campaigning, they also challenge some central assumptions. As such, they demonstrate the need for more comprehensive theoretical explanations and measurements of negative campaigning.<br/

Studie zu Verbindungstechniken für automatisierte Montagen mehrgeschossiger Stahlbeton-Skelettbauwerke

In vielen Branchen werden bzw. sind die verschiedensten Arbeitsgänge automatisiert. Speziell im Bauwesen ist auch dieser Trend in den letzten Jahren zu erkennen. Viele Arbeitsprozesse wie Vorfertigung und Montage laufen schon mechanisch ab. Durch die Weiterentwicklung der Mikroelektronik und der Robotertechnik können bald sämtliche Prozesse vollautomatisch ablaufen. Bereits in Japan wurde durch das so genannte Smart-System ein Stahlskelettbau automatisch hergestellt. In dieser Arbeit soll eine Zusammenfassung aktueller Verbindungstechniken sowie Grundkenntnisse zu Fertigteilen und statischen Systemen im Stahlbeton-Skelettbau vermittelt werden. Aufbauend auf den grundsätzlichen Untersuchungen von Frau Anne Lauterbach, sollen die bautechnischen Voraussetzungen vertieft werden, die es gestatten, Baustellenmontagen vollständig zu mechanisieren und weitgehend zu automatisieren. Hauptziel ist, am Beispiel mehrgeschossiger Stahlbeton-Skelettbauwerke den aktuellen Stand der Verbindungstechnik im Stahlbeton-Fertigteilbau darzustellen und neue Möglichkeiten und Entwicklungstrends aufzuzeigen und durch statisch-konstruktive sowie technologische Betrachtungen zu untermauern. Weiterhin sind die Entwürfe zu den neuen Verbindungstechniken auf die Realisierbarkeit im statischen System zu untersuchen und auf Tauglichkeit für automatisierte Montagen zu bewerten

Raum für Krisenbewältigung: Identifizierung essenzieller Ausstattung in psychiatrischen Krisenbereichen

Patient:innen psychiatrischer Einrichtungen können durch übermäßiges, häufig situativ bedingtes Aggressions- oder Suizidpotential sowie Rauscherscheinungen in akute Notsituationen verfallen. Häufig überschreiten diese Extremfälle den Handlungsrahmen der Station, weshalb die Patient:innen eine Versorgung im kleineren Rahmen sowie durch spezialisiertes Personal benötigen. Aus diesem Grund verfügen manche Stationen bereits über einen externen Krisenbereich, welcher innerhalb der allgemeinen Station liegt. Dieser ist im Sinne der Patient:innen abgegrenzt, und ermöglicht besondere Schutzmaßnahmen sowie eine intensivere Überwachung durch das Personal. [... aus dem Text