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991.
Efficient Hydrogen Evolution Reaction Catalysis in Alkaline Media by All‐in‐One MoS2 with Multifunctional Active Sites
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Mohsin Ali Raza Anjum Hu Young Jeong Min Hee Lee Hyeon Suk Shin Jae Sung Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(20)
MoS2 becomes an efficient and durable nonprecious‐metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T‐phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2‐based catalysts targeting only a single or few of these characteristics, the all‐in‐one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A‐MoS2) that predominantly comprises 1T‐MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A‐MoS2 results in the removal of intercalated NH3 and H2S to form an all‐in‐one MoS2 with multifunctional active sites mentioned above (R‐MoS2) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2‐based electrocatalysts. In particular, a hybrid MoS2/nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high‐current region (>25 mA cm?2), demonstrating that R‐MoS2‐based materials can potentially replace Pt catalysts in practical alkaline HER systems. 相似文献
992.
Jian Guo Yuan Liu Yue Ma Enbo Zhu Shannon Lee Zixuan Lu Zipeng Zhao Changhao Xu Sung‐Joon Lee Hao Wu Kirill Kovnir Yu Huang Xiangfeng Duan 《Advanced materials (Deerfield Beach, Fla.)》2018,30(21)
The family of 2D semiconductors (2DSCs) has grown rapidly since the first isolation of graphene. The emergence of each 2DSC material brings considerable excitement for its unique electrical, optical, and mechanical properties, which are often highly distinct from their 3D counterparts. To date, studies of 2DSC are majorly focused on group IV (e.g., graphene, silicene), group V (e.g., phosphorene), or group VIB compounds (transition metal dichalcogenides, TMD), and have inspired considerable effort in searching for novel 2DSCs. Here, the first electrical characterization of group IV–V compounds is presented by investigating few‐layer GeAs field‐effect transistors. With back‐gate device geometry, p‐type behaviors are observed at room temperature. Importantly, the hole carrier mobility is found to approach 100 cm2 V?1 s?1 with ON–OFF ratio over 105, comparable well with state‐of‐the‐art TMD devices. With the unique crystal structure the few‐layer GeAs show highly anisotropic optical and electronic properties (anisotropic mobility ratio of 4.8). Furthermore, GeAs based transistor shows prominent and rapid photoresponse to 1.6 µm radiation with a photoresponsivity of 6 A W?1 and a rise and fall time of ≈3 ms. This study of group IV–V 2DSC materials greatly expands the 2D family, and can enable new opportunities in functional electronics and optoelectronics based on 2DSCs. 相似文献
993.
994.
Dong Wook Lee Jue‐Hyuk Jang Injoon Jang Yun Sik Kang Seguen Jang Kwan Young Lee Jong Hyun Jang Hyung‐Juhn Kim Sung Jong Yoo 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(36)
Recently, nonnoble‐metal catalysts such as a metal coordinated to nitrogen doped in a carbon matrix have been reported to exhibit superior oxygen reduction reaction (ORR) activity in alkaline media. In this work, Co2P nanoparticles supported on heteroatom‐doped carbon catalysts (NBSCP) are developed with an eco‐friendly synthesis method using bean sprouts. NBSCP can be easily synthesized through metal precursor absorption and carbonization at a high temperature. It shows a very large specific surface area with various dopants such as nitrogen, phosphorus, and sulfur derived from small organic molecules. The catalyst can exhibit activity in various electrochemical reactions. In particular, excellent performance is noted for the ORR. Compared to the commercial Pt/C, NBSCP exhibits a lower onset potential, higher current density, and superior durability. This excellent ORR activity and durability is attributable to the synergistic effect between Co2P nanoparticles and nitrogen‐doped carbon. In addition, superior performance is noted on applying NBSCP to a practical anion exchange membrane fuel cell system. Through this work, the possibility of applying an easily obtained bio‐derived material to energy conversion and storage systems is demonstrated. 相似文献
995.
Miniaturized,Battery‐Free Optofluidic Systems with Potential for Wireless Pharmacology and Optogenetics
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Kyung Nim Noh Sung Il Park Raza Qazi Zhanan Zou Aaron D. Mickle Jose G. Grajales‐Reyes Kyung‐In Jang Robert W. Gereau IV Jianliang Xiao John A. Rogers Jae‐Woong Jeong 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(4)
Combination of optogenetics and pharmacology represents a unique approach to dissect neural circuitry with high specificity and versatility. However, conventional tools available to perform these experiments, such as optical fibers and metal cannula, are limited due to their tethered operation and lack of biomechanical compatibility. To address these issues, a miniaturized, battery‐free, soft optofluidic system that can provide wireless drug delivery and optical stimulation for spatiotemporal control of the targeted neural circuit in freely behaving animals is reported. The device integrates microscale inorganic light‐emitting diodes and microfluidic drug delivery systems with a tiny stretchable multichannel radiofrequency antenna, which not only eliminates the need for bulky batteries but also offers fully wireless, independent control of light and fluid delivery. This design enables a miniature (125 mm3), lightweight (220 mg), soft, and flexible platform, thus facilitating seamless implantation and operation in the body without causing disturbance of naturalistic behavior. The proof‐of‐principle experiments and analytical studies validate the feasibility and reliability of the fully implantable optofluidic systems for use in freely moving animals, demonstrating its potential for wireless in vivo pharmacology and optogenetics. 相似文献
996.
Super‐Absorbent Polymer Valves and Colorimetric Chemistries for Time‐Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin‐Mounted Soft Microfluidics
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Sung Bong Kim Yi Zhang Sang Min Won Amay J. Bandodkar Yurina Sekine Yeguang Xue Jahyun Koo Sean W. Harshman Jennifer A. Martin Jeong Min Park Tyler R. Ray Kaitlyn E. Crawford Kyu‐Tae Lee Jungil Choi Rhonda L. Pitsch Claude C. Grigsby Adam J. Strang Yu‐Yu Chen Shuai Xu Jeonghyun Kim Ahyeon Koh Jeong Sook Ha Yonggang Huang Seung Wook Kim John A. Rogers 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(12)
This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin‐mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well‐defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances. 相似文献
997.
Gi Dae Park Sung Jin Yang Jong‐Heun Lee Yun Chan Kang 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(51)
Highly efficient anode materials with novel compositions for Li‐ion batteries are actively being researched. Multicomponent metal selenite is a promising candidate, capable of improving their electrochemical performance through the formation of metal oxide and selenide heterostructure nanocrystals during the first cycle. Here, the binary nickel–cobalt selenite derived from Ni–Co Prussian blue analogs (PBA) is chosen as the first target material: the Ni–Co PBA are selenized and partially oxidized in sequence, yielding (NiCo)SeO3 phase with a small amount of metal selenate. The conversion mechanism of (NiCo)SeO3 for Li‐ion storage is studied by cyclic voltammetry, in situ X‐ray diffraction, ex situ X‐ray photoelectron spectroscopy, in situ electrochemical impedance spectroscopy, and ex situ transmission electron microscopy. The reversible reaction mechanism of (NiCo)SeO3 with the Li ions is described by the reaction: NiO + CoO + xSeO2 + (1 ‐ x)Se + (4x + 6)Li+ + (4x + 6)e? ? Ni + Co + (2x + 2)Li2O + Li2Se. To enhance electrochemical properties, polydopamine‐derived carbon is uniformly coated on (NiCo)SeO3, resulting in excellent cycling and rate performances for Li‐ion storage. The discharge capacity of C‐coated (NiCo)SeO3 is 680 mAh g?1 for the 1500th cycle when cycled at a current density of 5 A g?1. 相似文献
998.
Lee Jin Hee Lee Hack-Keun Chun Dong Hyun Choi Hyunkyung Rhim Geun Bae Youn Min Hye Jeong Heondo Kang Shin Wook Yang Jung-Il Jung Heon Kim Chul Sung Park Ji Chan 《Nano Research》2019,12(10):2568-2575
Nano Research - Iron-based nanoparticles with uniform and high particle dispersion, which are supported on carbon structures, have been used for various applications. However, their preparation... 相似文献
999.
Jaeyong Lee Soonjae Pyo Dae‐Sung Kwon Eunhwan Jo Wondo Kim Jongbaeg Kim 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(12)
Although there have been remarkable improvements in stretchable strain sensors, the development of strain sensors with scalable fabrication techniques and which both high sensitivity and stretchability simultaneously is still challenging. In this work, a stretchable strain sensor based on overlapped carbon nanotube (CNT) bundles coupled with a silicone elastomer is presented. The strain sensor with overlapped CNTs is prepared by synthesizing line‐patterned vertically aligned CNT bundles and rolling and transferring them to the silicone elastomer. With the sliding and disconnection of the overlapped CNTs, the strain sensor performs excellently with a broad sensing range (≥145% strain), ultrahigh sensitivity (gauge factor of 42 300 at a strain of 125–145%), high repeatability, and durability. The performance of the sensor is also tunable by controlling the overlapped area of CNT bundles. Detailed mechanisms of the sensor and its applications in human motion detection are also further investigated. With the novel structure and mechanism, the sensor can detect a wide range of strains with high sensitivity, demonstrating the potential for numerous applications including wearable healthcare devices. 相似文献
1000.
Sung Bo Lee Seung-Yong Lee Miyoung Kim Heung Nam Han 《Journal of Materials Science》2018,53(4):2383-2388
When subjected to electron-beam irradiation in a transmission electron microscope, the grain boundary in an α-Al2O3 bicrystal is observed to migrate even at room temperature. The bicrystal is composed of grains with the same normal direction, and thus the difference in strain energy or surface energy between the two grains cannot explain the observed migration. We attribute this phenomenon to an increase in grain boundary mobility by electron-beam irradiation, especially by radiolysis effects. 相似文献