🏛️國立陽明交通大學機構典藏

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Activating basal-plane catalytic activity of two-dimensional MoS2 monolayer with remote hydrogen plasma
(2016-12)
Cheng, Chia-Chin
;
Lu, Ang-Yu
;
Tseng, Chien-Chih
;
Yang, Xiulin
;
Hedhili, Mohamed Nejib
Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disufide (MoS2) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS2 monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS2 for enhancing their HER activity. Here, we report a simple and efficient approach using a remote hydrogen-plasma process to creating S-vacancies on the basal plane of monolayer crystalline MoS2; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS2 monolayer. The density of S-vacancies (defects) on MoS2 monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. The H-2-plasma treated MoS2 also provides an excellent platform for systematic and fundamental study of defect-property relationships in TMDs, which provides insights for future applications including electrical, optical and magnetic devices. (C) 2016 Elsevier Ltd. All rights reserved.
Fabrication of Ni nanowires for hydrogen evolution reaction in a neutral electrolyte
(2009-08-01)
Chen, Po-Chun
;
Chang, Yun-Min
;
Wu, Pu-Wei
;
Chiu, Yu-Fan
;
材料科學與工程學系
Hydrogen evolution reaction in 1 M Na(2)SO(4) was investigated using Ni nanowires in diameter of 250 nm with exposed lengths of 20, 35, and 45 mu m, respectively. The Ni nanowires were fabricated by a direct-current pulse electrodeposition technique using an anodic aluminum oxide template, followed by selective removal of the supporting pore walls. Scanning Electron Microscope images revealed structural stabilities and X-ray diffraction pattern indicated a polycrystalline fcc phase. In current-potential (i-V) polarizations, the Ni nanowires with longer exposed lengths demonstrated larger current responses. Analysis from impedance spectroscopy confirmed increasing double-layer capacitances with longer Ni nanowires. in galvanostatic lifetime experiments, the freestanding Ni nanowires exhibited a reduced overpotential over that of supported ones. Similar procedures were performed for the oxygen evolution reaction in both i-V and lifetime measurements. For the Ni nanowires of 45 pm length, we estimated the energy cost for hydrogen production was 5.24 x 10(5) J/mole. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
Enhancing the electrocatalytic water splitting efficiency for amorphous MoSx
(2014-03-26)
Hsu, Chang-Lung
;
Chang, Yung-Huang
;
Chen, Tzu-Yin
;
Tseng, Chien-Chih
;
Wei, Kung-Hwa
Amorphous molybdenum sulfide (MoSx) materials have been considered as cheap and promising catalysts for hydrogen evolution reaction (HER). In this contribution, we report that the amorphous MoSx catalysts prepared by the low temperature thermolysis of the (NH4)(2)MoS4 precursors on carbon clothes (catalyst loading: 3.2 mg/cm(2)) exhibit a Tefal slope of 50.5 mV/dec and a high exchange current density of 1.5 x 10(-3) mA/cm(2) in 0.5 M H2SO4 solutions. Spectroscopic studies of the amorphous MoSx catalysts show that the increase of HER efficiency is positively correlated to the concentration of S-2(2-) species, providing strong evidence to support the argument that S-2(2-) is an active species for electrocatalytic HER. Additionally, the method for preparing catalysts is simple, scalable and applicable for large-scale production. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Comparative study on MoS2 and WS2 for electrocatalytic water splitting
(2013-09-19)
Chen, Tzu-Yin
;
Chang, Yung-Huang
;
Hsu, Chang-Lung
;
Wei, Kung-Hwa
;
Chiang, Chia-Ying
Replacing Pt by earth abundant catalysts is one of the most important tasks toward potential large-scale HER applications. Among many potential candidates, low cost and earth abundant transition metal dichalcogenides such as MoS2 and WS2 have been promising as good H-2 evolution electrocatalysts when they are engineered into the structures with active sites. In this work, we have performed systematic studies on the catalytic reactivity of both MoS2 and WS2 materials produced by one-step and scalable thermolysis from (NH4)(2)WS4 and (NH4)(2)MoS4 precursors respectively. Structural analysis shows that these materials prepared at a higher thermolysis temperature exhibit higher crystallinity. The H-2 evolution electrocatalysts efficiency for the MoS2 prepared at a lower temperature is higher than those at higher temperatures, where amorphous MoS2 or S-2(2-) species instead of crystalline MoS2 is the main active site. By contrast, crystalline WS2 prepared at high temperature is identified to be the key reaction site. Both catalysts display excellent efficiency and durability as an electrocatalyst operating in acidic electrolytes. This work provides fundamental insights for further design and preparation of emergent metal dichalcogenide catalysts, beneficial for the development in clean energy. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

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