Enhanced cycle stability of iron(II, III) oxide nanoparticles encapsulated with nitrogen-doped carbon and graphene frameworks for lithium battery anodes

Pham-Cong, De,Kim, Su Jae,Jeong, Se Young,Kim, Jong-Pil,Kim, Hyun Gyu,Braun, Paul V.,Cho, Chae-Ryong Elsevier 2018 Carbon Vol.129 No.-

<P><B>Abstract</B></P> <P>Nitrogen-doped carbon-coated and graphene oxide-wrapped Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles were prepared using the electrostatic force between polyethyleneimine-functionalized Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles and graphene oxide layers, followed by annealing in an N<SUB>2</SUB> atmosphere (Fe<SUB>3</SUB>O<SUB>4</SUB>@NCG). The electrochemical performance of Fe<SUB>3</SUB>O<SUB>4</SUB>@NCG was superior to that of graphene oxide- or reduced graphene oxide-wrapped Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles and carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles. Fe<SUB>3</SUB>O<SUB>4</SUB>@NCG exhibited stable specific capacity of ∼895 mAh g<SUP>−1</SUP> after 350 cycles over the voltage range 0.001–3.0 V vs. Li/Li<SUP>+</SUP>. The superior performance of Fe<SUB>3</SUB>O<SUB>4</SUB>@NCG was attributed to the presence of a nitrogen-doped carbon layer and networks of reduced graphene oxide. The chemical route-derived Fe<SUB>3</SUB>O<SUB>4</SUB>@NCG may be a promising anode material for high-performance lithium-ion batteries.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced cycle stability of polypyrrole-derived nitrogen-doped carbon-coated tin oxide hollow nanofibers for lithium battery anodes

Pham-Cong, De,Park, Jung Soo,Kim, Jae Hyun,Kim, Jinwoo,Braun, Paul V.,Choi, Jun Hee,Kim, Su Jae,Jeong, Se Young,Cho, Chae Ryong Elsevier 2017 Carbon Vol.111 No.-

<P>SnO2 hollow nanofibers (SnO2 hNFs) are prepared through electrospinning and annealing processes. The polypyrrole layers coated onto the surface of the SnO2 hNFs are annealed in a nitrogen atmosphere. The nitrogen-doped carbon-coated SnO2 hNFs (SnO2/NC hNFs) are composed of SnO2 hNFs with a wall thickness of 60-80 nm and a nitrogen-doped carbon layer similar to 10 nm thick. The nitrogen content in the carbon layer is approximately 7.95%. Owing to the nitrogen-doped carbon shell layers, the specific reversible capacity of SnO2/NC hNFs at a current density of 0.2 A g(-1) after 100 cycles is 1648 mAh g(-1) which is 427% higher than that of (386 mAh g(-1)) SnO2 hNFs. This strategy may open new avenues for the design of other composite architectures as electrode materials in order to achieve high-performance lithium ion batteries. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Effect of Reactive Gases in an Atmospheric-pressure Plasma for Dye Adsorption on ZnO Nanorods

De Pham-Cong,안균,김종만,정세영,조채용,김종필,김현규,안형수,김홍승 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.7

In this study, ZnO nanorods (NRs) were grown on F-doped SnO2 (FTO)/glass substrate by using a chemical bath deposition (CBD) method. The NRs were crystallized well. The surfaces of the NRs were modified using an atmospheric-pressure (AP) plasma containing reactive gases such as O2, H2, and N2. In the case of the Ar/O2 and Ar/N2 plasma-treated ZnO NRs, chemical bonding states and the dye adsorption on the surface of the ZnO layer increased because of -O and -OH radicals. We present the efficiencies of ZnO-NR-based dye-sensitized solar cells (DSSCs) treated with AP plasmas containing reactive gases.

Synergistically Enhanced Electrochemical Performance of Hierarchical MoS₂/TiNb₂O₇ Hetero-nanostructures as Anode Materials for Li-Ion Batteries

Pham-Cong, De,Choi, Jun Hee,Yun, Jeongsik,Bandarenka, Aliaksandr S.,Kim, Jinwoo,Braun, Paul V.,Jeong, Se Young,Cho, Chae Ryong American Chemical Society 2017 ACS NANO Vol.11 No.1

<P>As potential high-performance anodes for Li-ion batteries (LIBs), hierarchical heteronanostructures consisting of TiNb2O7 nanofibers and ultrathin MoS2 nanosheets (TNO@MS HRs) were synthesized by simple electrospinning/hydrothermal processes. With their growth mechanism revealed, the TNO@MS HRs exhibited an entangled structure both for their ionic and electronic conducting pathways, which enabled the synergetic combination of one-and two-dimensional structures to be realized. In the potential range of 0.001-3 V vs Li/Li+, the TNO@MS HR-based LIBs exhibited high capacities of 872 and 740 mAh g(-1) after 42 and 200 cycles at a current density of 1 A g(-1), respectively, and excellent rate performance of 611 mAh g(-1) at 4 A g(-1). We believe that the fabrication route of TNO@MS HRs will find visibility for the use of anode electrodes for high capacity LIBs at low cost.</P>

Electrochemical behavior of interconnected Ti₂Nb₁₀O₂₉ nanoparticles for high-power Li-ion battery anodes

Pham-Cong, De,Kim, Jinwoo,Tran, Van Tan,Kim, Su Jae,Jeong, Se-Young,Choi, Jun-Hee,Cho, Chae Ryong Elsevier 2017 ELECTROCHIMICA ACTA Vol.236 No.-

<P><B>Abstract</B></P> <P>We synthesized polycrystalline Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> nanofibers (NFs) via a simple post-annealing process of as-electrospun polymeric NFs as an anode material for Li-ion batteries (LIBs). During the first discharge/charge process, the Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> NFs annealed at 900°C exhibited insertion/extraction capacities of up to 344 and 304mAhg<SUP>−1</SUP>, corresponding to 19.1 and 16.7mol Li<SUP>+</SUP> per formula unit, respectively. This material exhibited excellent rate capability (93mAhg<SUP>−1</SUP> at 15Ag<SUP>−1</SUP>) and a higher average diffusion coefficient (D<SUB>Li</SUB> =∼1.5×10<SUP>−12</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>) than Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> powder (∼6.9×10<SUP>−13</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>). This performance can be attributed to the unique nanostructure of firmly interconnected, highly crystalline Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> nano-grains, which facilitates the Li<SUP>+</SUP> and electron transport. The kinetics obtained from current-voltage curves indicate a mixture of diffusion-limited and capacitive processes. The suggested electro-spinning/post annealing approach can effectively provide a simple route towards high-quality Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> NF-based anodes for high-performance LIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> nanofibers and powders are fabricated by electrospinning and solid-state reaction process. </LI> <LI> Linearly connected single crystal nanofibers are formed. </LI> <LI> Rate capability and cycle stability of the nanofibers are enhanced compared to the powders. </LI> <LI> Diffusion behaviors of Li ion through the Ti<SUB>2</SUB>Nb<SUB>10</SUB>O<SUB>29</SUB> single crystallite are better than other samples. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Bandgap-designed TiO2/SnO2 hollow hierarchical nanofibers: Synthesis, properties, and their photocatalytic mechanism

Kyun Ahn,De Pham-Cong,Hun Seok Choi,Se-Young Jeong,Jin Hyuk Cho,Jinwoo Kim,Jong-Pil Kim,Jong Seong Bae,Chae-Ryong Cho 한국물리학회 2016 Current Applied Physics Vol.16 No.3

In this work, TiO2/SnO2 hollow hierarchical nanofibers (TiO2/SnO2 hHNFs) are prepared by first synthesizing SnO2 hollow nanofibers by electrospinning and annealing, then using them as substrates to grow TiO2 nanorods using a hydrothermal process. The samples are tested under UV irradiation for their photocatalytic activity toward Reactive Black 5 (RB5) and Rhodamine B dyes. The TiO2/SnO2 hHNFs show excellent photocatalytic activity toward the RB5 dye, and perform at level 73 times higher than that of SnO2 nanofibers and comparable with that of commercially available TiO2 nanoparticles. The repeatability of the photocatalytic performance of the TiO2/SnO2 hHNFs is quite high; the decolorization capacity decrease to 80.6% of the initial value after 20 cycles. These significant performance improvements are attributed to the increased specific surface area and advantageous energy-band heterostructure of the TiO2/SnO2 hHNFs, which enable effective electron/hole transport and suppresses the recombination of photogenerated electron/hole pairs.

성장 온도에 따른 Cu(In,Ga)Se₂광흡수층의 물리적 특성 및 깊이 조성 분석

안균,정용민,강윤희,Pham Cong De,조채용,안형수,이삼녕 한국물리학회 2011 새물리 Vol.61 No.5

This paper presents the results obtained from glow discharge optical emission spectrometry (GD-OES) depth profiling of Cu(In,Ga)Se₂(CIGS) thin films prepared at various substrate temperatures. The CIGS thin films were grown on molybdenum-coated soda-lime glass substrats by using a three-stage process with a co-evaporator system. For the substrate temperature T_(sub) of the second stage. the CIGS thin films showed a (220)/(204)-preferred orientation at temperatures below 450℃ and a (112)-preferred orientation at temperatures above 500℃. The grain size of the CIGS films increased with increasing T_(sub). The GD-OES depth profiling of the CIGS thin films prepared at various T_(sub)'s showed uniform distributions of all the elements through the CIGS film. These results were compared with the SIMS depth profiles for the CIGS thin films. A solar cell using a CIGS absorber layer prepared at the optimized T_(sub) showed a conversion efficiency of about 8%. 본 연구는 다양한 성장 온도에 따라 증착된 Cu(In,Ga)Se₂(이하,CIGS) 박막의 특성과 글로우방전분광기(GD-OES; glow discharge optical emission spectrometry)를 이용하여 박막의 깊이에 따른 원소분포 분석결과를 조사하였다. CIGS 박막은 동시증발장비를 이용하여 3단계공정으로 Mo/유리 기판 위에 증착되었다. 2단계 과정에서, 성장기판온도에 따른 CIGS 박막의 결정성은 450℃이하에서는(220)/(204) 방향으로, 500℃ 이상에서는 (112) 방향으로 우선성장하였다. 또한, 성장 기판 온도가 증가함에 따라 CIGS 박막의 결정립크기는 증가하였다. 수십 ㎛의 깊이, 짧은 시간, 극미량원소분석이가능한 GD-OES를 CIGS 박막분석에 활용하고자 하였으며, 기존 미량분석에사용되는 이차이온질량분광기(SIMS) 깊이 조성 분석 결과와 비교하였다. GD-OES를 이용하여 CIGS 박막의 깊이 조성을 조사한 결과, Cu, In, Ga 및Se 원소가 균일하게 분포하고 있음을 확인하였다. 1단계 450℃와2단계 550℃의 성장온도에서 증착된 CIGS 박막으로 제조된태양전지는 약 8.12%의 에너지 변환 효율을 보였다.

Enhanced electrochemical performance of template-free carbon-coated iron(II, III) oxide hollow nanofibers as anode material for lithium-ion batteries

Im, Mi Eun,Pham-Cong, De,Kim, Ji Yoon,Choi, Hun Seok,Kim, Jae Hyun,Kim, Jong Pil,Kim, Jinwoo,Jeong, Se Young,Cho, Chae Ryong Elsevier 2015 Journal of Power Sources Vol.284 No.-

<P><B>Abstract</B></P> <P>Carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> hollow nanofibers (Fe<SUB>3</SUB>O<SUB>4</SUB>/C hNFs) as a lithium ion battery anode material are prepared through electrospinning, annealing, and hydrothermal processing. At a high current density of 1000 mAg<SUP>−1</SUP>, the template-free Fe<SUB>3</SUB>O<SUB>4</SUB>/C hNFs exhibit high 1st- and 150th-cycle specific capacities of ∼963 and 978 mAhg<SUP>−1</SUP>, respectively. Moreover, Fe<SUB>3</SUB>O<SUB>4</SUB>/C hNFs have excellent and stable rate capability, compared to that of the Fe<SUB>3</SUB>O<SUB>4</SUB> hNFs, and a capacity of 704 mAhg<SUP>−1</SUP> at a current density of 2000 mAg<SUP>−1</SUP>. Owing to the carbon layer, the Li-ion diffusion coefficient of the Fe<SUB>3</SUB>O<SUB>4</SUB>/C hNFs, 8.10 × 10<SUP>−14</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>, is 60 times higher than that (1.33 × 10<SUP>−15</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>) of the Fe<SUB>3</SUB>O<SUB>4</SUB> hNFs. These results indicate that Fe<SUB>3</SUB>O<SUB>4</SUB>/C hNFs may have important implications for developing high performance anodes for next-generation lithium ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe<SUB>3</SUB>O<SUB>4</SUB> hollow nanofibers are fabricated by electrospinning and annealing process. </LI> <LI> Carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> hollow nanofibers are formed by using hydrothermal process. </LI> <LI> Physical and electrochemical properties of the samples are investigated in detail. </LI> <LI> Carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> hollow nanofibers are showing better electrochemical performance. </LI> </UL> </P>

TiO₂ nanofiber/nanoparticles composite photoelectrodes with improved light harvesting ability for dye-sensitized solar cells

Vu, Hong Ha Thi,Atabaev, Timur Sh.,Pham-Cong, De,Hossain, Md Ashraf,Lee, Dongyun,Dinh, Nguyen Nang,Cho, Chae-Ryong,Kim, Hyung-Kook,Hwang, Yoon-Hwae Elsevier 2016 ELECTROCHIMICA ACTA Vol.193 No.-

<P><B>Abstract</B></P> <P>In this study, a TiO<SUB>2</SUB> nanofiber/nanoparticles composite photoelectrode was combined with spectral convertors to improve the overall efficiency of dye-sensitized solar cells (DSSCs). In a typical preparation process, several photoelectrodes (PE) with equal thickness but different compositions were prepared. The DSSC composed of TiO<SUB>2</SUB> nanofiber/nanoparticles incorporated with 15wt.% spectral convertors showed an optimal light-to-electric energy conversion efficiency of 8.94%. This light-to-electricity conversion efficiency was 38.6% higher than that of the bare DSSC with TiO<SUB>2</SUB> nanoparticles only. The significantly enhanced efficiency of the DSSC was attributed to the highly favored scattering effect from the TiO<SUB>2</SUB> nanofibers in combination with enhanced incident light harvesting from spectral convertors.</P>

A Study on the Synthesis and Electrochemical Characteristics of Carbonized Coffee Powder for Use as a Lithium-Ion Battery Anode

KIM, Tae Gyun,CHO, Jin Hyuk,PHAM-CONG, De,JEON, Injun,HWANG, Jin Hyun,KIM, Kyoung Hwa,CHO*, Chae Ryong Korean Physical Society 2018 New Physics: Sae Mulli Vol.68 No.12