4,365 research outputs found
The functional chameleon of materials chemistryâcombining carbon structures into all-carbon hybrid nanomaterials with intrinsic porosity to overcome the âfunctionality-conductivity-dilemmaâ 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 electrodeâelectrolyte 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 âfunctionalityâconductivityâdilemmaâ can be minimized when multiple carbonâbased compounds are combined into porous allâcarbon 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
Caffeine-derived noble carbons as ball milling-resistant cathode materials for lithium-ion capacitors
Energy consumption is a growing phenomenon in our society causing many negative effects such as global warming. There is a need for the development of new sustainable materials for energy storage. Carbons are materials derivable from biowaste that can rather easily store energy due to their high conductivity and surface area. However, their large-scale processing is challenging as derived materials can be rather heterogeneous and homogenization requires ball milling, a process that can damage carbons in the process of oxidation. Herein, we have prepared caffeine-derived noble nitrogen-doped carbon that withstands the ball milling process without significant oxidation. Additionally, it performs extraordinarily as a cathode material for lithium-ion capacitors, making it an attractive biowaste-derived alternative to commercial heavy metal cathodes
The intrinsic Baldwin effect in broad Balmer lines of six long-term monitored AGNs
We investigate the intrinsic Baldwin effect (Beff) of the broad H and
H emission lines for six Type 1 active galactic nuclei (AGNs) with
different broad line characteristics: two Seyfert 1 (NGC 4151 and NGC 5548),
two AGNs with double-peaked broad line profiles (3C 390.3 and Arp 102B), one
narrow line Seyfert 1 (Ark 564), and one high-luminosity quasar with highly red
asymmetric broad line profiles (E1821+643). We found that a significant
intrinsic Beff was present in all Type 1 AGNs in our sample. Moreover, we do
not see strong difference in intrinsic Beff slopes in different types of AGNs
which probably have different physical properties, such as inclination, broad
line region geometry, or accretion rate. Additionally, we found that the
intrinsic Beff was not connected with the global one, which, instead, could not
be detected in the broad H or H emission lines. In the case of
NGC 4151, the detected variation of the Beff slope could be due to the change
in the site of line formation in the BLR. Finally, the intrinsic Beff might be
caused by the additional optical continuum component that is not part of the
ionization continuum.Comment: 12 pages, 8 figures, Accepted for publication in A&
Spectral monitoring of AGNs: Preliminary results for Ark 564 and Arp 102B
We present preliminary results of the long term spectral monitoring of two
active galactic nuclei with different broad line shapes: Ark 564 and Arp 102B.
Ark 564 is a bright nearby narrow line Syfert 1 (NLS1) galaxy with relatively
narrow permitted optical emission lines and a high FeII/H ratio, while
Arp 102B is a nearby broad-line radio galaxy with broad double-peaked Balmer
emission lines. The spectra of Ark 564 were observed during 11-year period
(1999-2009) and the spectra of Arp 102B in the 12-year period (1998-2009), with
SAO 6-m and 1-m telescopes (Russia) and the GHAO 2.1-m telescope (Cananea,
Mexico).Comment: Presented on "8th Serbian Conference on Spectral Line Shapes in
Astrophysics". In revised version minor changes in the tex
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