Browsing by Author "Tseng, Chung-Jen"

Now showing 1 - 7 of 7

Effects of TiO2 and SDC addition on the properties of YSZ electrolyte
(2019-11-12)
Shen, Chin-Tien
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Lee, Kan-Rong
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Hsieh, Yu-Pin
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Lee, Sheng-Wei
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Chang, Jeng-Kuei
In this study, we investigate the effects of adding titanium dioxide (TiO2) and samarium doped cerium oxide (SDC) on the properties of yttrium-stabilized zirconia (YSZ) electrolyte. The microstructure, mechanical, and electrochemical properties of the electrolyte are investigated. The performance in CO2 electrolysis is measured by supplying carbon dioxide to Ni-YSZ electrode and nitrogen to LSM electrode. Results show that TiO2 and SDC addition can reduce the sintering temperature and increase grain size. The ionic conductivity is 0.123 S cm(-1) at 1000 degrees C. In addition, the thermal expansion coefficient at 1000 degrees C is 8.25 x 10(-6)K(-1). The current density of the cell is 439 mA cm(-2) at 1.3 V and 1000 degrees C in solid oxide electrolysis cell. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Fabrication of anode-supported thin BCZY electrolyte protonic fuel cells using NiO sintering aid
(2019-09-03)
Lee, Kan-Rong
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Tseng, Chung-Jen
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Jang, Shian-Ching
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Lin, Jing-Chie
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Wang, Kuan-Wen
A thin and fully dense BaCe0.6Zr0.2Y0.2O3-delta(BCZY) electrolyte for the use of anode-supported protonic fuel cells has been successfully prepared by spin coating using NiO sintering aid. The effects of NiO addition on the electrolyte microstructures and fuel cell performances are also investigated. An appropriate NiO addition has a significant positive contribution to the densification and grain growth of thin BCZY electrolytes. However, too much NiO addition gives rise to NiO aggregation in BCZY electrolyte and deteriorates the cell performance. The enhanced sintering mechanism can be mainly attributed to the oxygen vacancies generated from the NiO decomposition and bulk diffusion of Ni into BCZY perovskites. The fuel cell with a BCZY-3%NiO electrolyte exhibits the highest maximum power density of similar to 106.6 mW/cm(2) at 800 degrees C among all fuel cells in this study. The electrochemical impedance characteristics of thin BCZY electrolyte fuel cells are further discussed under open circuit conditions. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Highly concentrated carbonate electrolyte for Li-ion batteries with lithium metal and graphite anodes
(2020-02-29)
Xie, Jian-De
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Patra, Jagabandhu
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Rath, Purna Chandra
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Liu, Weng-Jing
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Su, Ching-Yuan
Highly concentrated lithium bis(fluorosulfonyflimide (LiFSI) salt dissolved in carbonate solvent is employed as a high-performance and robust organic electrolyte for Li-ion batteries. The influences of Li salt type, concentration, and solvent type (such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethylene carbonate (EC)) on the electrochemical properties of Li metal and graphite anodes are systematically assessed. A superior electrolyte composition of 5.5 M LiFSI-DMC/EC is achieved, enhancing the anti-flammability, coulombic efficiency, and high rate capability. The optimal efficiency values of Li electrodeposition/stripping utilizing 5.5 M LiFSI-DMC/EC are 97.0% and 94.5% at 0.4 and 6 mA cm(-2), respectively. Such an enhanced performance is due to the formation of a three-dimensional ion network, composed of contact ion pairs (CIPs) and ion aggregates (AGGs) in the highly concentrated LiFSI electrolyte, which effectively decreases the number of free solvent molecules and inhibits the formation of undesired dendritic Li structures. Raman spectroscopy is employed to confirm the formation of CIP and AGG compounds within the electrolyte. The electrochemical data of the 5.5 M LiFSI-DMC/EC electrolyte cell demonstrates a remarkable improvement in the specific capacity and rate capability of a graphite anode.
Manipulation of Heteroatom Substitution on Nitrogen and Phosphorus Co-Doped Graphene as a High Active Catalyst for Hydrogen Evolution Reaction
(2019-09-12)
Hung, Yu-Han
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Dutta, Dipak
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Tseng, Chung-Jen
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Chang, Jeng-Kuei
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Bhattacharyya, Aninda J.
Graphene doped with heteroatoms is known to create a unique electronic structure with comparatively much higher active sites by the synergistic coupling effect. However, in the earlier attempts, the atomic structure of such co-doped graphene could not be altered; thus, there is a lack of reports discussing the influence of the atomic arrangement in the catalytic performance of the co-doped graphene. Here, by co-doping P and N atoms in graphene as a model system, we present a facile and two-step process wherein the sequence of doping helps in manipulating the heteroatom substitution, which is of great importance in defining better crystallinity and conductivity and favorable elemental functionalities and hence improving catalytic performance. The present method provides a clean, flexible, binder-free, and readily available electrocatalyst that avoids tedious conventional synthesis and device fabrication steps. The highest P-doping percentage (6 at. %) in the present work is superior to previous reports (3 at. %). By altering the sequence of N- and P-doping, the co-doped graphene electrode displayed excellent performance, with an increment of 148% in the sp(2) domain size and enormous lowering in overpotential and Tafel slope (78%). Further, the efficiency of the hydrogen evolution reaction catalyst sustains >98% for 20 h, which is significantly higher than the well-known MoSx (63%). Although here the P-N co-doped system was utilized as a proof of concept, this method could be adapted for other versatile co-doped graphene. This work may pave the way for the development of co-doped graphene-based devices where manipulation of atomic arrangement can result in a structure with properties desirable for catalytic or electronics applications.
Microstructures and electrical properties of zirconium doped barium cerate perovskite proton conductors
(2019-08-09)
Jhuang, Jhe-Wei
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Lee, Kan-Rong
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Lee, Sheng-Wei
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Chang, Jeng-Kuei
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Jang, Shian-Ching
In this work, we vary the Zr to Ce ratio to investigate the microstructures and electrical properties of zirconium doped barium cerates. The solid state reaction is used in synthesizing the BaCe0.8-xZrxY0.2O3 (X = 0.1-0.5). The electron backscatter diffraction (EBSD) is successfully applied to identify the crystal structure of the barium cerates. EBSD results indicate that all samples have the orthorhombic structure. Conductivity measurement results show that for temperatures below 700 degrees C, Zr-doped barium cerates have higher protonic conductivities than oxygen-ion/electron-hole conductivities. The protonic conductivity increases with the Zr content initially, but decreases after the Zr content is higher than 0.3. The protonic conductivity of BCZY0.3 reaches 8.8 mS/cm at 700 degrees C in dry hydrogen atmosphere. Stability test results show that, for stable operation in CO2 atmosphere, the Zr content in barium cerates should be greater than 0.2. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Nano-fibrous SrCe0.8Y0.2O3-delta-Ni anode functional layer for proton-conducting solid oxide fuel cells
(2019-10-01)
Lee, Kan-Rong
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Tseng, Chung-Jen
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Chang, Jeng-Kuei
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Wang, Kuan-Wen
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Huang, Yu-Shuo
This study presents a nanofiber-derived functional anode consisting of proton-conducting SrCe0.8Y0.2O3-delta nanofibers and electro-catalytic Ni for proton-conducting solid oxide fuel cells. Fuel cell testing with the nano fibrous SrCe0.8Y0.2O3-delta-Ni anode exhibits a maximum power density of 201.0 mW/cm(2) at 800 degrees C, which is significantly higher than those of cells with a powder-derived Ba0.8Sr0.2Ce0.6Zr0.2Y0.2O3-delta-Ni anode or a nano fibrous SrCe0.8Y0.2O3-delta anode. Its relatively lower ohmic resistance can be explained in terms of protonic and electronic "highways" throughout the nano-fibrous SrCe0.8Y0.2O3-delta-Ni anode. The significantly lower polarization resistance elements, R-1 and R-2, further indicate that the nano-fibrous SrCe0.8Y0.2O3-delta-Ni anode has superior catalytic activity for the hydrogen oxidation reaction and thus generates more protons that can participate in the cathode reactions. The results show that the performance enhancement in the fuel cell with the nano-fibrous SrCe0.8Y0.2O3-delta-Ni anode can be attributed to its low ohmic resistance, excellent electrode catalytic activity, and good gas transport property.
Nanomechanical Properties and Fracture Behaviors of Ba1-xKxCe0.6Zr0.2Y0.2O3-delta Electrolytes by Nanoindentation
(2014-08-01)
Jian, Sheng-Rui
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Lee, Sheng-Wei
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Chang, Jeng-Kuei
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Tseng, Chung-Jen
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Juang, Jenh-Yih
The nanomechanical characteristics and fracture behaviors of the Ba1-xKxCe0.6Zr0.2Y0.2O3-delta (K-doped BCZY, 0.0 <= x <= 0.15) oxides were investigated by using nanoindentation techniques. The BKCZY samples were prepared by the citrate-ethylenediaminetetraacetic acid (EDTA) complexing sol-gel process, followed by uniaxial pressure pressing and sintering at 1600 degrees C for 4 h. The XRD results indicated that the BKCZY samples occurred predominantly in perovskite-type cubic structures. The hardness and Young\'s modulus of BKCZY samples were measured by a Berkovich nanoindenter operated in continuous contact stiffness measurements (CSM) mode. Results indicated that the hardness and Young\'s modulus of BKCZY sample decreased substantially with increasing the K doping concentration, presumably due to doping-enhanced grain growth. Furthermore, the SEM observations indicated that Berkovich nanoindentation-induced fracture mode was mostly transgranular and the fracture toughness exhibited a similar doping dependence as that of the hardness and Young\'s modulus.