Unilamellar Nanosheet of Layered Manganese Cobalt Nickel Oxide and Its Heterolayered Film with Polycations

Oh, Eun-Jin,Kim, Tae Woo,Lee, Kyung Min,Song, Min-Sun,Jee, Ah-Young,Lim, Seung Tae,Ha, Hyung-Wook,Lee, Minyung,Choy, Jin-Ho,Hwang, Seong-Ju American Chemical Society 2010 ACS NANO Vol.4 No.8

<P>The exfoliation of layered Li[Mn<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>]O<SUB>2</SUB> into individual monolayers could be achieved through the intercalation of quaternary tetramethylammonium (TMA<SUP>+</SUP>) ions into protonated metal oxide. An effective exfoliation occurred when the TMA<SUP>+</SUP>/H<SUP>+</SUP> ratio was 0.5−50. Reactions outside this range produced no colloidal suspension, but all the manganese cobalt nickel oxides precipitated. Atomic force microscopy and transmission electron microscopy clearly demonstrated that exfoliated manganese cobalt nickel oxide nanosheets have a nanometer-level thickness, underscoring the formation of unilamellar nanosheets. The maintenance of the hexagonal atomic arrangement of the manganese cobalt nickel oxide layer upon the exfoliation was confirmed by selected area electron diffraction analysis. According to diffuse reflectance ultraviolet−visible spectroscopy, the exfoliated manganese cobalt nickel oxides displayed distinct absorption peaks at ∼354 and ∼480 nm corresponding to the d<I>−</I>d transitions of octahedral metal ions, which contrasted with the featureless spectrum of the pristine metal oxide. In the light of zeta potential data showing the negative surface charge of manganese cobalt nickel oxide nanosheets, a heterolayered film of manganese cobalt nickel oxide and conductive polymers could be prepared through the successive coating process with colloidal suspension and polycations. The UV−vis and X-ray diffraction studies verified the layer-by-layer ordered structure of the obtained heterolayered film, respectively.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-8/nn100286u/production/images/medium/nn-2010-00286u_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn100286u'>ACS Electronic Supporting Info</A></P>

Nickel-cobalt oxide/activated carbon composite electrodes for electrochemical capacitors

Sook-Keng Chang,Zulkarnain Zainal,Kar-Ban Tan,Nor Azah Yusof,Wan Mohamad Daud Wan Yusoff,S.R.S. Prabaharan 한국물리학회 2012 Current Applied Physics Vol.12 No.6

Nanostructured synthesis of nickelecobalt oxide/activated carbon composite by adapting a coprecipitation protocol was revealed by transmission electron microscopy. X-ray diffraction analysis confirmed that nickelecobalt oxide spinel phase was maintained in the pure and composite phases. Cyclic voltammetry, galvanostatic chargeedischarge tests and ac impedance spectroscopy were employed to elucidate the electrochemical properties of the composite electrodes in 1.0 M KCl. The specific capacitance which was the sum of double-layer capacitance of the activated carbon and pseudocapacitance of the metal oxide increased with the composition of nickelecobalt oxide before showing a decrement for heavily-loaded electrodes. Utilisation of nickelecobalt oxide component in the composite with 50 wt. % loading displayed a capacitance value of ~59 F g-1. The prepared composite electrodes exhibited good electrochemical stability. Nanostructured synthesis of nickelecobalt oxide/activated carbon composite by adapting a coprecipitation protocol was revealed by transmission electron microscopy. X-ray diffraction analysis confirmed that nickelecobalt oxide spinel phase was maintained in the pure and composite phases. Cyclic voltammetry, galvanostatic chargeedischarge tests and ac impedance spectroscopy were employed to elucidate the electrochemical properties of the composite electrodes in 1.0 M KCl. The specific capacitance which was the sum of double-layer capacitance of the activated carbon and pseudocapacitance of the metal oxide increased with the composition of nickelecobalt oxide before showing a decrement for heavily-loaded electrodes. Utilisation of nickelecobalt oxide component in the composite with 50 wt. % loading displayed a capacitance value of ~59 F g-1. The prepared composite electrodes exhibited good electrochemical stability.

Supercapacitive Properties of Co-Ni Mixed Oxide Electrode Adopting the Nickel Foam as a Current Collector

Hyeon Woo Cho,Ji Hyun Nam,박정호,KwangManKim,고장면 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.12

Three-dimensional porous nickel foam was used as a current collector to prepare a Co-Ni oxide/Ni foam electrode for a supercapacitor. The synthesized Co-Ni oxide was proven to consist of mixed oxide phases of Co3O4 and NiO. The Co-Ni oxide/Ni foam electrode prepared was characterized by morphological observation, crystalline property analysis, cyclic voltammetry, and impedance spectroscopy. Cyclic voltammetry for the electrode showed high specific capacitances, such as 936 F g−1 at 5 mV s−1 and 566 F g−1 at 200 mV s−1, and a comparatively good cycle performance. These improved results were mainly due to the dimensional stability of the nickel foam and its high electrical contact between the electrode material and the current collector substrate.

Supercapacitive Properties of Co-Ni Mixed Oxide Electrode Adopting the Nickel Foam as a Current Collector

Cho, Hyeon Woo,Nam, Ji Hyun,Park, Jeong Ho,Kim, Kwang Man,Ko, Jang Myoun Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.12

Three-dimensional porous nickel foam was used as a current collector to prepare a Co-Ni oxide/Ni foam electrode for a supercapacitor. The synthesized Co-Ni oxide was proven to consist of mixed oxide phases of $Co_3O_4$ and NiO. The Co-Ni oxide/Ni foam electrode prepared was characterized by morphological observation, crystalline property analysis, cyclic voltammetry, and impedance spectroscopy. Cyclic voltammetry for the electrode showed high specific capacitances, such as 936 F $g^{-1}$ at 5 mV $s^{-1}$ and 566 F $g^{-1}$ at 200 mV $s^{-1}$, and a comparatively good cycle performance. These improved results were mainly due to the dimensional stability of the nickel foam and its high electrical contact between the electrode material and the current collector substrate.

p-p Heterojunction of Nickel Oxide-Decorated Cobalt Oxide Nanorods for Enhanced Sensitivity and Selectivity toward Volatile Organic Compounds

Suh, Jun Min,Sohn, Woonbae,Shim, Young-Seok,Choi, Jang-Sik,Song, Young Geun,Kim, Taemin L.,Jeon, Jong-Myeong,Kwon, Ki Chang,Choi, Kyung Soon,Kang, Chong-Yun,Byun, Hyung-Gi,Jang, Ho Won American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.1

<P>The utilization of p-p isotype heterojunctions is an effective strategy to enhance the gas sensing properties of metal-oxide semiconductors, but most previous studies focused on p-n heterojunctions owing to their simple mechanism of formation of depletion layers. However, a proper choice of isotype semiconductors with appropriate energy bands can also contribute to the enhancement of the gas sensing performance. Herein, we report nickel oxide (NiO)-decorated cobalt oxide (Co<SUB>3</SUB>O<SUB>4</SUB>) nanorods (NRs) fabricated using the multiple-step glancing angle deposition method. The effective decoration of NiO on the entire surface of Co<SUB>3</SUB>O<SUB>4</SUB> NRs enabled the formation of numerous p-p heterojunctions, and they exhibited a 16.78 times higher gas response to 50 ppm of C<SUB>6</SUB>H<SUB>6</SUB> at 350 °C compared to that of bare Co<SUB>3</SUB>O<SUB>4</SUB> NRs with the calculated detection limit of approximately 13.91 ppb. Apart from the p-p heterojunctions, increased active sites owing to the changes in the orientation of the exposed lattice surface and the catalytic effects of NiO also contributed to the enhanced gas sensing properties. The advantages of p-p heterojunctions for gas sensing applications demonstrated in this work will provide a new perspective of heterostructured metal-oxide nanostructures for sensitive and selective gas sensing.</P> [FIG OMISSION]</BR>

Enhanced electrochemical performance of nickel-cobalt-oxide@reduced graphene oxide//activated carbon asymmetric supercapacitors by the addition of a redox-active electrolyte

Lamiel, Charmaine,Lee, Yong Rok,Cho, Moo Hwan,Tuma, Dirk,Shim, Jae-Jin Elsevier 2017 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.507 No.-

<P><B>Abstract</B></P> <P>Supercapacitors are an emerging energy-storage system with a wide range of potential applications. In this study, highly porous nickel-cobalt-oxide@reduced graphene oxide (Ni-Co-O@RGO-s) nanosheets were synthesized as an active material for supercapacitors using a surfactant-assisted microwave irradiation technique. The RGO-modified nanocomposite showed a larger specific area, better conductivity, and lower resistivity than the unmodified nanocomposite because the RGO facilitated faster ion diffusion/transport for improved redox activity. The synergistic effect of Ni-Co-O@RGO-s resulted in a high capacitance of 1903Fg<SUP>−1</SUP> (at 0.8Ag<SUP>−1</SUP>) in a mixed KOH/redox active K<SUB>3</SUB>Fe(CN)<SUB>6</SUB> electrolyte. The asymmetric Ni-Co-O@RGO-s//AC supercapacitor device yielded a high energy density and power density of 39Whkg<SUP>−1</SUP> and 7500Wkg<SUP>−1</SUP>, respectively. The porous structure and combination of redox couples from both the electrode and electrolyte provided a highly synergistic effect, which improved the performance of the supercapacitor device.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrochemical properties of Ir doped NiCoOx nano structure catalyst for Enhanced Oxygen Evolution in alkaline media

이학주,박경원,박덕혜,이슬기,이우준 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

전 세계적으로 화석연료를 대체할 수 있는 친환경 에너지원으로 수소에 주목을 하고 있다. 이에 따라 전기를 사용해 물을 분해하여 수소를 발생시키는 친환경 수전해 방법이 각광받고 있다. 그 중에서도 저온에서 운용되며 수소생산속도가 빠른 Alkaline 수전해가 주목을 받고 있다. 특히 수전해의 효율을 증가시키기 위해 복잡한 매커니즘을 가지며 에너지 손실이 많이 발생하는 OER(Oxygen Evolution Reaction)에 관해 연구가 많이 진행되고 있다. 수전해의 Anode에서 주로 귀금속 산화물이 많이 사용되는데 매장량과 가격에서 문제점을 가지고 있다. 이 문제점을 극복하기 위해서 매장량이 풍부하고 가격이 저렴한 전이금속 산화물인 Cobalt와 Nickel에 관한 연구가 많이 진행되고 있다. 본 연구에서는 각각의 mono metal oxide보다 전기전도도, 촉매적 활성이 더 좋은 binary metal oxide에 Iridium 을 도핑하는 연구를 진행하였다. Hydrothermal method를 이용한 합성과정에서 nano size의 비표면적이 높은 촉매를 합성하고 alkaline 환경에서 전기화학 평가를 진행하였다.

Additive effect of Ce, Mo and K to nickel-cobalt aluminate supported solid oxide fuel cell for direct internal reforming of methane

Bu Ho Kwak,정종식,Jungdeok Park,Heechul Yoon,Hyeon Hui Kim,Lim Kim 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.1

Direct internal reforming of methane (steam/carbon=0.031, 850 oC) is tested using button cells of Ni-YSZ/YSZ/LSM in which the anode layer is supported either on Ni-YSZ or on Ni-CoAl2O4. The Ni-CoAl2O4 supported cell shows little degradation with operating time, as a result of higher resistance against carbon deposition, whereas the Ni-YSZ supported cell deactivates quickly and suffers fracture in 50 h. Upon incorporation of additives such as K,Ce, or Mo into the Ni-CoAl2O4 support, cells with 0.5 wt% CeO2 exhibit the best stable performance as a result of reduced coke formation. Cells with 0.5 wt% Mo exhibit the lowest performance. Although no carbon deposit is detected in the cells with K2CO3 additives, their performance is worse than that in the CeO2 case, and, in constant-current mode,there is a sudden voltage drop to zero after a certain period of time; this time becomes shorter with increasing K content. The injection of potassium into the anode side facilitates the generation of OH− and CO32− in the anode and promotes the diffusion of these ions to the cathode. Increased polarization resistance at the cathode and increased electrolyte resistance result in such a sudden failure.

테일러-쿠에트 유동에 의한 Nickel/Cobalt/Manganese oxide 입자 성장 수치 해석

윤성호(Sung-Ho Yoon),임장균(Jang Gyun Lim),최재붕(Jae-Boong Choi),김문기(Moon Ki Kim),이태린(Tae-Rin Lee) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

Porous interconnected NiCo₂O₄ nanosheets and nitrogen- and sulfur-codoped reduced graphene oxides for high-performance hybrid supercapacitors

Sivakumar, Periyasamy,Jana, Milan,Kota, Manikantan,Lee, Hyun Sun,Park, Ho Seok Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.781 No.-

<P><B>Abstract</B></P> <P>We demonstrate a facile hydrothermal synthesis of the interconnected porous NiCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets for hybrid supercapacitor applications. The as-synthesized NiCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets show a high specific capacitance of 3137 F g<SUP>−1</SUP> at a current density of 2 A g<SUP>−1</SUP>, which is much greater than 1916 and 1251 F g<SUP>−1</SUP> of Co<SUB>3</SUB>O<SUB>4</SUB> and NiO, respectively. Interestingly, the total specific capacitance of the NiCo<SUB>2</SUB>O<SUB>4</SUB> is almost close to the sum of the specific capacitance of the NiO and Co<SUB>3</SUB>O<SUB>4</SUB>. Furthermore, a hybrid supercapacitor is configured with the NiCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets and the nitrogen- and sulfur-codoped reduced graphene oxide as the positive and negative electrodes, respectively. This hybrid supercapacitor delivers a maximum energy density of 33.64 W h kg<SUP>−1</SUP> at a power density of 1196 W kg<SUP>−1</SUP> and excellent long-term cyclic stability over 12,000 charge/discharge cycles at the enlarged voltage window of 1.5 V. The remarkable supercapacitive performances of the hybrid device are attributed to the interconnected porous structure of NiCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets and three-dimensional continuous macropores of codoped reduced graphene oxides.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The interconnected porous NiCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets are synthesized. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB> shows high capacitances of 3137 and 2420 F g<SUP>−1</SUP> at 2 and 20 A g<SUP>−1</SUP>. </LI> <LI> The HSC consists of NiCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets and 3D N,S-rGO. </LI> <LI> The HSC delivers a maximum energy density of 33.64 W h kg<SUP>−1</SUP>. </LI> <LI> The HSC exhibits the outstanding cyclic stability and Coulombic efficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>