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Fe???N/C catalysts with tunable mesoporous structures and carbon layer numbers reveal the role of interlayer O<sub>2</sub> activation
No full textA class of Fe,N-codoped carbon (Fe???N/C) electrocatalysts has made remarkable advances as highly promising non-Pt group metal catalysts for the oxygen reduction reaction (ORR). However, the design of Fe???N/C catalysts whose active site structure and O2 activation mode mimic those of an enzymatic ORR catalyst still remains a challenge. Herein, we report the preparation of mesoporous Fe???N/C catalysts with tunable tube- or rod-like frameworks and carbon layer numbers via solid-state nanocasting of mesoporous silica with an iron???phenanthroline complex. The tube-type Fe???N/C exhibited a larger surface area and active site density than the rod-type Fe???N/C. Unexpectedly, the rod-type Fe???N/C showed superior ORR activity to the tube-type Fe???N/C, with a smaller overpotential, greater turnover frequency (TOF), and lower Tafel slope. Temperature-programmed desorption studies revealed a weaker binding strength of the rod-type Fe???N/C with O2. The rod-type Fe???N/C consisting of multiple carbon layers is likely to activate O2 in the interlayer between the Fe???Nx-containing carbon layers, reminiscent of the enzymatic catalyst, whereas in the tube-type Fe???N/C with 3???4 carbon layers, O2 is mostly activated at a single Fe center on the external carbon layer. As a result, the TOF of the rod-type Fe???N/C exceeded those of reported catalysts. We envisage that our work can provide a new insight into the design of highly active Fe???N/C catalysts
Intermetallic Nanoarchitectures for Efficient Electrocatalysis
Get PDFIntermetallic structures whose regular atomic arrays of constituent elements present unique catalytic properties have attracted considerable attention as efficient electrocatalysts for energy conversion reactions. Further performance enhancement in intermetallic catalysts hinges on constructing catalytic surfaces possessing high activity, durability, and selectivity. In this Perspective, we introduce recent endeavors to boost the performance of intermetallic catalysts by generating nanoarchitectures, which have well-defined size, shape, and dimension. We discuss the beneficial effects of nanoarchitectures compared with simple nanoparticles in catalysis. We highlight that the nanoarchitectures have high intrinsic activity owing to their inherent structural factors, including controlled facets, surface defects, strained surfaces, nanoscale confinement effects, and a high density of active sites. We next present notable examples of intermetallic nanoarchitectures, namely, facet-controlled intermetallic nanocrystals and multidimensional nanomaterials. Finally, we suggest the future research directions of intermetallic nanoarchitectures
Spider silk-derived nanoporous activated carbon fiber for CO2 capture and CH4 and H2 storage
No full textHigh surface area porous carbon with fibrous microstructure offers a broader application potential than powder form. However, controlling the microstructure with high porosity is difficult, and if possible then through a complex and time-consuming synthesis method. Herein, the development of high surface area nanoporous activated carbon fiber by activating spider silk (natural biomaterials) using potassium hydroxide is being reported. The specific surface area (SSA) and total pore volume for the developed material were 2730 m(2)/g and 1.56 cc/g, respectively, and its surface contain high oxygen content. Its high SSA and oxygen-rich surface provide an enhanced CO2 capture and energy carrier gases (H-2 and CH4) storage capacity. The CO2 capture capacity at 0 ? and 25 ?, 25 bar, were estimated to be 23.6 and 15.4 mmol/g, respectively, among the highest reported values for porous carbon fiber. Moreover, the developed sample has shown the CH4 storage capacity of 8.6 mmol/g at 0 ?, 25 bar, and for H-2, it was 4.1 wt% at - 196 ?, 25 bar. In addition, the developed carbon material demonstrated an easy regeneration and almost negligible loss in uptake capacity, confirmed by adsorption-desorption cycles. The observation of high porosity and promising gas storage and recyclability in spider silk-derived activated carbon fiber indicates that the employed method can effectively convert biomaterials into high surface area activated carbon fibers for advanced energy and environmental applications
Asymmetric ElasticMetasurface forWave Manipulation Between Different Media
No full textThis paper mainly studies the problem of metasurfaces between different mediums. Despite recent advances on metasurfaces, there has been a critical limitation that wave manipulation between two different mediums is theoretically impossible with general approaches since full transmission and desired phase shift cannot be achieved simultaneously. In order to get over this theoretical issue, we propose an asymmetric metasurface that can manipulate waves between two different mediums. By introducing the asymmetry, achieving both full transmission and desired phase shift simultaneously is theoretically enabled. From theoretical approaches, an actual continuum metasurface is designed and applied to various wave manipulations between two different mediums. We expect that the proposed metasurface can be applied to various applications in the area of ultrasonics and vibrations
Tunable Multilevel Gate Oxide Capacitance and Flat-Band Voltage Shift Characteristics by Filament Formation in Double-Floating-Gate Metal-Oxide-Semiconductor Capacitors
No full textTunable multilevel gate oxide capacitance and flat-band voltage shift characteristics in double-floating-gate metal-oxide-semiconductor (DFG-MOS) capacitors are investigated for non-volatile memory and programmable logic device applications. The DFG-MOS capacitor with the structure of Ag(control gate)/CeO2(upper control oxide)/Al(upper FG)/CeO2(lower control oxide)/Pt(lower FG)/HfO2(tunneling oxide) on n-Si substrate, that is Ag/CeO2/Al/CeO2/Pt/HfO2/n-Si, exhibits three capacitance states as a result of reversible formation and rupture of conducting filaments at serially stacked Ag/CeO2/Al and Al/CeO2/Pt capacitors upon applying positive and negative gate voltages, respectively. In contrast, the DFG-MOS capacitor with Ag/CeO2/Pt/HfO2/Pt/HfO2/n-Si employing inert Pt upper and lower FGs exhibits two capacitance states via the formation and rupture of filament only at the upper Ag/CeO2/Pt stack. Instead, it accompanies a flat-band voltage shift by electrical charging at the lower FG of Pt. The proposed devices operate with tunable multilevel gate oxide capacitance and flat-band voltage shift associated with filament formation inside gate stacks and electrical charging with respect to the constituent materials of the FGs. These results pave the way for potential application to non-volatile memory and programmable MOSFET logic device with tunable gate oxide capacitance, without relying solely on the electrical charging used in the current flash-type memory
Connectivity, sport events, and tourism development of Mandalika's special economic zone: A perspective from big data cognitive analytics
No full textThis study examines the interplay of air connectivity, sports events, infrastructures, and fiscal support during the period 2017 and 2022 in a designated area called Special Economic Zone in Mandalika, Lombok Island, West Nusa Tenggara to boost tourism development in Indonesia by utilizing big data cognitive analytics. We examine the tourism development impacted by the MotoGP event in 2022 and air connectivity. Further, this paper discusses the network connectivity of flights at Zainuddin Abdul Madjid International Airport during the COVID-19 Pandemic and the new normal. We found that the combination of an international airport, globally recognized sports events, and government support has directly and positively improved the tourism industry???s performance in the country and especially within Lombok Island. We suggest policy recommendations to support economic activities in Mandalika???s Special Economic Zone and its hinterland to maintain business sustainability and utilize the existing infrastructures at the optimum level. Lessons learned from the Indonesian experience could help other developing countries that are devising policies and strategies to develop the tourism industry by employing proper instruments such as infrastructure, events, and fiscal policies
The "Cins" of Our Fathers: Rejuvenated Interest in Colicins to Combat Drug Resistance
No full textWith the growing threat of antibiotic resistance, researchers around the globe are seeking alternatives to stem bacterial pathogenesis. One such alternative is bacteriocins, proteins produced by bacterial species to inhibit the growth and viability of related bacterial species. With their diverse mechanisms, which include pore formation and nuclease activities, and narrow spectrum of activities, which limit their impact to only certain bacterial species, unlike many chemical antibiotics, bacteriocins offer intriguing possibilities to selectively control individual bacterial populations. Within this review, therefore, we highlight current research exploring the application of colicins and microcins, a subset of bacteriocins, with an emphasis on their activities against drug-resistant pathogens, both in in vitro and in vivo settings
Enabling On-Demand Conformal Zn-Ion Batteries on Non-Developable Surfaces
No full textConventional power sources encounter difficulties in achieving structural unitization with complex-shaped electronic devices because of their fixed form factors. Here, it is realized that an on-demand conformal Zn-ion battery (ZIB) on non-developable surfaces uses direct ink writing (DIW)-based nonplanar 3D printing. First, ZIB component (manganese oxide-based cathode, Zn powder-based anode, and UV-curable gel composite electrolyte) inks are designed to regulate their colloidal interactions to fulfill the rheological requirements of nonplanar 3D printing, and establish bi-percolating ion/electron conduction pathways, thereby enabling geometrical synchronization with non-developable surfaces, and ensuring reliable electrochemical performance. The ZIB component inks are conformally printed on arbitrary curvilinear substrates to produce embodied ZIBs that can be seamlessly integrated with complicated 3D objects (including human ears). The conformal ZIB exhibits a high fill factor (i.e., areal coverage of cells on underlying substrates, approximate to 100%) that ensures high volumetric energy density (50.5 mWh cm(cell)(-3)), which exceeds those of previously-reported shape-adaptable power sources
Non-Abelian Chern-Simons-Higgs system with indefinite functional
No full textIn this paper, we are concerned with the general non-Abelian Chern-Simons-Higgs models of rank two. The corresponding self-dual equations can be reduced to a nonlinear elliptic system, and the form is determined by a non-degenerate matrix K. One of the major questions is how the matrix K affects the structure of the solutions to the self-dual equations. There have been some existence results of the solutions to the self-dual equations when det(K)> 0. However, the solvability for the case det(K)< 0 < 0 is not fully understood in spite of its physical importance. In contrast to det(K)> 0, one major difficulty for the case det(K)< 0 is that the energy functional associated with the elliptic system is usually indefinite. The direct variational method thus fails. We overcome this obstacle and obtain a partially positive answer for the solvability when det(K)< 0 by controlling the indefinite functional with a suitable constraint
Preliminary Results of the GMAP/SIJAQ Campaign: Remote Sensing Measurements of Air Pollution over Korea
No full textGEMS (Geostationary Environmental Monitoring Spectrometer), the world???s first geostationary environmental satellite was successfully launched in February 2020 and keeps monitoring the trace gases around East Asia. For improving the GEMS retrieval algorithms and validation of the products, NIER (National Institute of Environmental Research) organized two international field campaigns in Korea: GMAP2021 (GEMS MAP of Air Pollution) and SIJAQ2022 (Satellite Integrated Joint monitoring of Air Quality), respectively in winter and summer season. In the framework of these campaigns, to fill the gap of the reference ground remote sensing observation network, additional Pandora and MAX-DOAS instruments were installed in SMA (Seoul Metropolitan Area), Ulsan, and Busan. In addition, we operated Car-DOAS and GCAS (GeoCAPE Airborne Simulator) flight measurements around the SMA and the Southeastern region to catch the detailed distribution of emission sources. Preliminary results indicate different diurnal variation patterns of NO2 columns in SMA and the Southeastern region, visible both in ground-based and GEMS data. Car-DOAS measurements show a detailed distribution of trace gases at city level and for a few days during the summer season (SIJAQ2022), Car-DOAS even caught some well-synchronized high SO2 and HCHO signals with NO2, which can be related to anthropogenic emissions around the industrial area and in the case of the SMA emission estimation measurement, nice plumes were observed along the wind direction on good meteorological condition days