學術出版;;Publications

Permanent URI for this communityhdl:11536/1

收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

Browse

🏛️國立陽明交通大學機構典藏

Search Results

Now showing 1 - 5 of 5

Improved lithium storage capacity and high rate capability of nitrogen-doped graphite-like electrode materials prepared from thermal pyrolysis of graphene quantum dots
(2020-09-10)
Gu, Siyong
;
Christensen, Tommiejean
;
Hsieh, Chien-Te
;
Mallick, Bikash Chandra
;
Gandomi, Yasser Ashraf
Adopting a solid-phase microwave-assisted technique followed by thermal pyrolysis of N-functionalized graphene quantum dots, novel nitrogen-doped graphite-like (NGL) electrode materials were synthesized and served as the anode for Li-ion batteries. The NGL anode demonstrated reversible capacity of 530 mAh g(-1) at 0.1C, superior rate capability at high C rate operation (420 mAh g(-1) at 5C), remarkable initial coulombic efficiency (>95.7%), and excellent cyclic stability along with high efficiency (>99.1%) during entire cycling. The NGL anode nanostructure enables improved lithium ion mobility and reversible Li+ storage during cycling. The analysis of the Ragone plots revealed that the specific energy of NGL anode reaches to ca. 840 Wh kg(-1) at the power density of 4200 W kg(-1). The diffusion coefficient of Li ions was measured as 1.69 x 10(-9) cm(2) s(-1) for the NGL anode material, substantially improving over commonly used graphite electrodes (15-26 times higher Li+ diffusivity). The high-rate cyclability as well as the cyclic stability of the NGL anodes were also confirmed via long-term cycling of full pouch cells assembled with ternary cathode and NGL anode. The robust design of the NGL anode materials introduced in this work, paves the way for designing next-generation lithium-ion batteries operating at ultrahigh C rates. (C) 2020 Elsevier Ltd. All rights reserved.
NiCo2O4/graphene quantum dots (GQDs) for use in e fficient electrochemical energy devices: An electrochemical and X-ray absorption spectroscopic investigation
(2020-05-15)
Chang, Han-Wei
;
Fu, Ji-Xuan
;
Huang, Yu-Cheng
;
Lu, Ying-Rui
;
Kuo, Chun-Hong
NiCo2O4/graphene quantum dots (GQDs) were synthesized by the incorporation of GQDs into NiCo2O4 as electrode materials for use in electrochemical energy devices. The electronic structure and the electrochemical performance of NiCo2O4/GQDs were investigated by X-ray absorption spectroscopy (XAS) and electrochemical measurements. The rich redox active sites were revealed on the NiCo2O4/GQDs, which were formed by the strong CeOeNi/Co interaction between NiCo2O4 and GQDs. The synergetic double-layer capacitive and pseudocapacitive properties were suggested to provide favorable electrochemical characteristics. In/ex situ XAS elucidates local electronic and chemical environments and provides insights into the energy storage/conversion mechanisms. Analytical results demonstrate that the NiCo2O4/GQDs have strong oxygen-carbon bridges and have more Ni active sites than does NiCo2O4, favoring metal-to-ligand charge transfer at the interface between NiCo2O4 and GQDs, critically influencing electrochemical performance. This work contributes importantly to the field by elucidating an energy storage/conversion mechanism for electrochemical energy devices.
Fluorescence of functionalized graphene quantum dots prepared from infrared-assisted pyrolysis of citric acid and urea
(2020-01-01)
Gu, Siyong
;
Hsieh, Chien-Te
;
Yuan, Chun-Yao
;
Gandomi, Yasser Ashraf
;
Chang, Jeng-Kuei
This paper reports an efficient fabrication of N-doped graphene quantum dots (GQDs) showing controllable chemical and fluorescence (FL) properties through infrared carbonization (IRC) of citric acid and urea. The GQDs prefer to form an equilibrium shapes of circle with an average particle size ranged from 5 to 10 nm. The N/C atomic ratio in GQDs can be precisely tailored in a range from 21.6 to 49.6 at.% by simply controlling the weight ratio of citric acid to urea. With increasing the urea content, the GQDs not only contain N-doped graphene but also incorporate with crystalline cyanuric acid, forming a binary crystallinity. The quantum yield of 22.2% is achieved by N-doped GQDs, prepared from the IRC synthesis of chemical precursor at the citric acid/urea at 3:1. Excessive N and cyanuric acid can lead to FL quenching, red shift and wide spectral distribution. The design of GQDs possesses a multiple chromophoric band-gap structure, originated from the presence of cyanuric acid, defect-related emissive traps, and functional group distributions. This work offers an effective and inspiring approach to engineering both chemical compositions and unique crystalline structures of GQDs, and will therefore facilitate their fundamental research and applications to optical, sensing, energy and biological fields.
A critical review on two-dimensional quantum dots (2D QDs): From synthesis toward applications in energy and optoelectronics
(2019-11-01)
Manikandan, Arumugam
;
Chen, Yu-Ze
;
Shen, Chih-Chiang
;
Sher, Chin-Wei
;
Kuo, Hao-Chung
Recent advances in the development of quantum dots (QDs) have offered new possibilities for the exploration of sensors, bio imaging, batteries, electrochemical water splitting and optoelectronic applications because of their intriguing optical, electrical, catalytic and electrochemical properties. Among QDs, atomically thin two-dimensional quantum dots (2D QDs) derived from graphene sheets, transition metal dichalcogenide (TMD) layers and phosphorene have been of considerable interest for the past few years. There have been several intensive studies of carbon QDs, but TMD QDs and heterostructures based on 2D QDs are rapidly advancing. Herein, the synthesis and properties of 2D QDs, particularly carbon and TMD QDs, are reviewed for the recent progress in their application toward electrochemical water splitting, photocatalytic wastewater treatment, supercapacitors, batteries and photodetectors. Moreover, the assembly of such 2D QDs to achieve industrial-scale production and boost their performance in widespread applications is emphasized.
Graphene quantum dots mediated charge transfer of CdSe nanocrystals for enhancing photoelectrochemical hydrogen production
(2015-03-01)
Tsai, Kai-An
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated the use of CdSe/graphene quantum dot (QD) nanoheterostructures as the photoanode for remarkable photoelectrochemical hydrogen production. By employing a delicate hydrothermal cutting approach, reduced graphene oxide (RGO) sheets with the lateral size in a desirable range can be obtained, from micrometer size (micro-RGO), to 30-100 nm (nano-RGO), and to 2-4 nm (QD-RGO). Because of the significant zigzag edge effect, nano-RGO and QD-RGO possessed well-defined band structure which enabled efficient light absorption and distinctive photoluminescence emission. Time-resolved photoluminescence spectra showed that nano-RGO and QD-RGO surpassed micro-RGO in enhancing the charge separation efficiency of CdSe. According to the cyclic voltammetry data, a type-II vectorial charge transfer model was considered for CdSe/nano-RGO and CdSe/QD-RGO nanoheterostructures, fundamentally different from the unidirectional electron transfer mechanism of CdSe/micro-RGO. Among the three CdSe/RGO samples tested, CdSe/QD-RGO achieved the highest photocurrent generation in the photoelectrochemical cell, which exceeded 5 times the value of CdSe. The incident photon-to-electron conversion efficiency (IPCE) spectra suggested that the significantly enhanced photoactivity of CdSe/QD-RGO originated from the type-II vectorial charge transfer feature, which not only promoted charge carrier separation but also improved the overall light harvesting. Furthermore, no appreciable decay of photocurrent was found for CdSe/QD-RGO after continuously used in the photoelectrochemical cell for over 2 h, revealing its substantially high stability during the water reduction process. The demonstrations from this work may facilitate the use of graphene QDs in semiconductor-based photocatalysis, in which the efficient light harvesting and high chemical inertness of graphene QDs can be well employed. (C) 2014 Elsevier B.V. All rights reserved.

學術出版;;Publications

Browse

Filters

Settings

Sort By

Results per page

🏛️國立陽明交通大學機構典藏

Search Results