• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.701-705
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• 2019

Oxygen-evolution reaction (OER) in alkaline media has been considered as a key process for various energy applications. Many types of catalysts have been developed to reduce high overpotential in OER, such as metal alloys, metal oxides, perovskite, or spinel. Nickel oxide (NiO) has high potential to increase OER activity according to volcano plots. The exact mechanisms for OER has not been discovered, but defects such as cation or anion vacancy typically act as an active site for diverse electrochemical reactions. In this study, nitrogen was doped into NiO by using ethylenediamine for formation of Ni vacancy, and the effects of N doping on OER activity and stability was studied.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.134-137
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• 2004

새로운 리튬 2차전지용 양극활물질인 Li[NiMnCo]O2를 간단히 합성할 수 있는 방법과 Si의 doping에 의해 그 특성을 향상하였다. 원하는 당량비의 Li, Ni, Co, Mn의 nitrate를 고순도의 에탄올에 용해하고 여기에 Si의 원료물질로서 poly(methyl phenyl siloxane)을 원하는 양(전체 전이금속 이온의 $2{\sim}10\;mol%$)만큼 첨가한 후 약 30분 정도 교반하였다. 이 용액을 약 $70{\sim}80^{\circ}C$ 정도의 온도에서 고점도의 진흙 상태가 될 정도로 가열하고 $450{\sim}500^{\circ}C$의 온도에서 약 5시간 정도 열처리 하여 유기물이 없는 상태의 전구체를 제조하였다. 이 전구체를 분말형태로 분쇄하고 $600{\sim}650^{\circ}C$ 정도의 온도에서 3시간, $900{\sim}950^{\circ}C$ 정도의 온도에서 5시간 연속적으로 열처리 하여 최종 활물질을 제조하였다. 이렇게 제조된 활물질은 175mAh/g 정도의 높은 비용량을 나타내었으며 4.5V 충전 조건에도 우수한 수명특성을 나타내었다. Si이 doping되지 않은 활물질에 비해 Si이 doping된 물질은 율특성, 수명특성에서 보다 우수한 특성을 나타내었는데 이것은 층상구조 활물질의 격자상수 증가와 impedance 증가 억제에 기인한 것으로 분석되었다.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4052-4058
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• 2012

The composite photocatalyst, N-$TiO_2$ loaded with $Ni_2O_3$, was prepared by $N_2$ plasma treatment. X-ray diffraction, X-ray fluorescence, $N_2$ adsorption, UV-vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared $TiO_2$ samples. The results indicated that the band gap energy was decreased obviously by nitrogen doping, whereas loading of $Ni_2O_3$ did not influence the band gap and visible light absorption. The photocatalytic activities were tested in the degradation of 2,4,6-trichlorophenol (TCP) under visible light. The photocatalytic activity and stability of composite photocatalyst were much higher than that of catalyst modified with nitrogen or $Ni_2O_3$ alone. The synergistic effect of doping nitrogen and $Ni_2O_3$ over $TiO_2$ was investigated.

• Bulletin of the Korean Chemical Society
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• v.27 no.6
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• pp.821-829
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• 2006

A series of catalysts, $NiO/La_2O_3-ZrO_2/WO_3$, for acid catalysis was prepared by the precipitation and impregnation methods. For the $NiO/La_2O_3-ZrO_2/WO_3$ samples, no diffraction lines of nickel oxide were observed, indicating good dispersion of nickel oxide on the catalyst surface. The catalyst was amorphous to X-ray diffraction up to 300 ${^{\circ}C}$ of calcination temperature, but the tetragonal phase of $ZrO_2$ and monoclinic phase of $WO_3$ by the calcination temperatures from 400 ${^{\circ}C}$ to 700 ${^{\circ}C}$ were observed. The role of $La_2O_3$ in the catalyst was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity. The high acid strength and high acidity were responsible for the W=O bond nature of complex formed by the modification of $ZrO_2$ with $WO_3$. For 2-propanol dehydration the catalyst calcined at 400 ${^{\circ}C}$ exhibited the highest catalytic activity, while for cumene dealkylation the catalyst calcined at 600 ${^{\circ}C}$ showed the highest catalytic activity. 25-$NiO/5-La_2O_3-ZrO_2/15-WO_3$ exhibited maximum catalytic activities for two reactions due to the effects of $WO_3$ modifying and $La_2O_3$ doping.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.208-208
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• 2013

Graphene has emerged as a fascinating material for next-generation nanoelectronics due to its outstanding electronic properties. In particular, graphene-based field effect transistors (GFETs) have been a promising research subject due to their superior response times, which are due to extremely high electron mobility at room temperature. The biggest challenges in GFET applications are control of carrier concentration and opening the bandgap of graphene. To overcome these problems, three approaches to doping graphene have been developed. Here we demonstrate the decoration of Ni nanoparticles (NPs) on graphene films by simple annealing for p-type doping of graphene. Ni NPs/graphene films were fabricated by coating a $NiCl2{\cdot}6H2O$ solution onto graphene followedby annealing. Scanning electron microscopy and atomic force microscopy revealed that high-density, uniformly sized Ni NPs were formed on the graphene films and the density of the Ni NPs increased gradually with increasing $NiCl2{\cdot}6H2O$ concentration. The formation of Ni NPs on graphene films was explained by heat-driven dechlorination and subsequent particlization, as investigated by X-ray photoelectron spectroscopy. The doping effect of Ni NPs onto graphene films was verified by Raman spectroscopy and electrical transport measurements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.407-411
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• 2022

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.1-8
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• 1996

We investigated the effects of doping elements on the Bi-Sr-Ca-Cu-O ceramics. The doping elements can be classified into four groups depending on their supeconducting characteristics in the Bi-Sr-Ca-Cu-O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase. The third group of doping elements(P and K) have a tendency to decompose the superconducting phase and reduce the optimal sintering temperature. The fourth group of doping elements(B, Si, Sn and Ba) almost unaffected the superconductivity of the 2223 and 2212 phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.941-948
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• 2009

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed more than $100^{\circ}C$ lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of $Zn_7Sb_2O_{12}$ spinel ($\alpha$ and $\beta$), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than $Sb/Bi{\geq}1.0$ composed of $\beta$-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient $\alpha\;=\;6{\sim}11$) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form ${V_0}^{\cdot}$ (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.210-215
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• 2022

Extensive research is being carried out on Ni-rich Li(Ni_xCo_yMn_1-x-y)O₂ (NCM) due to the growing demand for electric vehicles and reduced cost. In particular, Ni-rich Li(Ni_xCo_yMn_1-x-y-zAl_z)O₂ (NCMA) is attracting great attention as a promising candidate for the rapid development of Co-free but electrochemically more stable cathodes. Al, an inactive element in the structure, helps to improve structural stability and is also used as a doping element to improve cycle capability in Ni-rich NCM. In this study, NCMA was successfully synthesized with the desired composition by direct coprecipitation. Boron and tin were also used as dopants to improve the battery performance. Macro- and microstructures in the cathodes were examined by microscopy and X-ray diffraction. While Sn was not successfully doped into NCMA, boron could be doped into NCMA, leading to changes in its physicochemical properties. NCMA doped with boron revealed substantially improved electrochemical properties in terms of capacity retention and rate capability compared to the undoped NCMA.

• Environmental Engineering Research
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• v.20 no.4
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• pp.329-335
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• 2015

The effects of ion-doping on $TiO_2$ nanotubes were investigated to obtain the optimal catalyst for the effective decomposition of Rhodamine B (RB) through UV photocatalytic oxidation process. Changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the BET surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on RB removal increased when $Ag^+$, $Al^{3+}$ and $Zn^{2+}$ were doped into the $TiO_2$ nanotubes, whereas such activities decreased as a result of $Mn^{2+}$ or $Ni^{2+}$ doping. In the presence of $Zn^{2+}$-doped $TiO_2$ nanotubes calcined at $550^{\circ}C$, the removal efficiency of RB within 50 min was 98.7%.