• 제목/요약/키워드: hydrothermal energy

검색결과 791건 처리시간 0.023초

Template-free preparation of TiO2 microspheres for the photocatalytic degradation of organic dyes

  • Al Ruqaishy, Mouza;Al Marzouqi, Faisal;Qi, Kezhen;Liu, Shu-yuan;Karthikeyan, Sreejith;Kim, Younghun;Al-Kindy, Salma Mohamed Zahran;Kuvarega, Alex Tawanda;Selvaraj, Rengaraj
    • Korean Journal of Chemical Engineering
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    • 제35권11호
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    • pp.2283-2289
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    • 2018
  • $TiO_2$ microspheres were successfully synthesised by simple solution phase method by using various amount of titanium butoxide as precursor. The prepared $TiO_2$ were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance absorption spectra (UV-DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XRD analysis revealed that the as-synthesized $TiO_2$ microsphere poses an anatase phase. The photocatalytic degradation experiments were carried out with three different dyes, such as methylene blue, brilliant black, reactive red-120 for four hours under UV light irradiation. The results show that $TiO_2$ morphology had great influence on photocatalytic degradation of organic dyes. The experimental results of dye mineralization indicated the concentration was reduced by a high portion of up to 99% within 4 hours. On the basis of various characterization of the photocatalysts, the reactions involved to explain the photocatalytic activity enhancement due to the concentration of titanium butoxide and morphology include a better separation of photogenerated charge carriers and improved oxygen reduction inducing a higher extent of degradation of aromatics.

Synergy study on charge transport dynamics in hybrid organic solar cell: Photocurrent mapping and performance analysis under local spectrum

  • Hong, Kai Jeat;Tan, Sin Tee;Chong, Kok-Keong;Lee, Hock Beng;Ginting, Riski Titian;Lim, Fang Sheng;Yap, Chi Chin;Tan, Chun Hui;Chang, Wei Sea;Jumali, Mohammad Hafizuddin Hj
    • Current Applied Physics
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    • 제18권12호
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    • pp.1564-1570
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    • 2018
  • Charge transport dynamics in ZnO based inverted organic solar cell (IOSC) has been characterized with transient photocurrent spectroscopy and localised photocurrent mapping-atomic force microscopy. The value of maximum exciton generation rate was found to vary from $2.6{\times}10^{27}m^{-3}s^{-1}$ ($J_{sat}=79.7A\;m^{-2}$) to $2.9{\times}10^{27}m^{-3}s^{-1}$ ($J_{sat}=90.8A\;m^{-2}$) for devices with power conversion efficiency ranging from 2.03 to 2.51%. These results suggest that nanorods served as an excellent electron transporting layer that provides efficient charge transport and enhances IOSC device performance. The photovoltaic performance of OSCs with various growth times of ZnO nanorods have been analysed for a comparison between AM1.5G spectrum and local solar spectrum. The simulated PCE of all devices operating under local spectrum exhibited extensive improvement with the gain of 13.3-3.7% in which the ZnO nanorods grown at 15 min possess the highest PCE under local solar with the value of 2.82%.

Electrochemical Synthesis of Metal-organic Framework (전기화학적 방법을 통한 금속 유기 골격체 합성)

  • Moon, Sanghyeon;Kim, Jiyoung;Choi, Hyun-Kuk;Kim, Moon-Gab;Lee, Young-Sei;Lee, Kiyoung
    • Applied Chemistry for Engineering
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    • 제32권3호
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    • pp.229-236
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    • 2021
  • During the last two decades, metal-organic frameworks (MOFs) have been drawn attention due to their high specific surface area, porosity, and catalytic activities that allow to use in many applications such as sensor, catalysis, energy storage, etc. To synthesize MOFs hydrothermal or solvothermal method were generally used. However, these methods require high-cost equipment and long time-spend for the synthesis with multi-step process. In contrast, electrochemical synthesis has been considered as a simple and easy process under the ambient conditions. In this review, we described the mechanism of electrochemical MOFs synthesis by the number of configured electrodes system, with the recent reports of various applications.

Asymmetric Supercapacitors Based on Co3O4@MnO2@PPy Porous Pattern Core-Shell Structure Cathode Materials

  • Wang, Zihan;Pan, Shuang;Wang, Bing;Qi, Jingang;Tang, Lidan;Liu, Liang
    • Journal of Electrochemical Science and Technology
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    • 제12권3호
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    • pp.346-357
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    • 2021
  • In recent years, supercapacitors have been developed rapidly as a rechargeable energy storage device. And the performance of supercapacitors is depending on electrode materials, the preparation method and performance of electrode materials have become the primary goal of scientific development. This study synthesizes Co3O4@MnO2@PPy cathode material with porous pattern core-shell structure by hydrothermal method and electrodeposition. The result samples are characterized by X-ray diffraction transmission/scanning electron microscope, and X-ray photoelectron spectroscopy. Electrochemical evaluation reveals that electrochemical performance is significantly enhanced by PPy depositing. The specific capacitance of Co3O4@MnO2@PPy is 977 F g-1 at 1 A g-1, the capacitance retention rate of 105%. Furthermore, the electrochemical performance of Co3O4@MnO2@PPy//AC asymmetric supercapacitor assembles with AC as the negative electrode material is significantly better than that of MnO2//AC and Co3O4@MnO2//AC. The capacity of Co3O4@MnO2@PPy//AC is 102.78 F g-1. The capacity retention rate is still 120% for 5000 charge-discharge cycles.

Facile Synthesis of g-C3N4 Modified Bi2MoO6 Nanocomposite with Improved Photoelectronic Behaviors

  • Zhu, Lei;Tang, Jia-Yao;Fan, Jia-Yi;Sun, Chen;Meng, Ze-Da;Oh, Won-Chun
    • Korean Journal of Materials Research
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    • 제31권11호
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    • pp.593-600
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    • 2021
  • Herein, a series of g-C3N4 modified Bi2MoO6 nanocomposites using Bi2MoO6 and melamine as original materials are fabricated via sintering process. For presynthesis of Bi2MoO6 an ultrasonic-assisted hydrothermal technique is researched. The structure and composition of the nanocomposites are characterized by Raman spectroscopy, X-ray diffraction (XRD), and high-resolution field emission scanning electron microscopy (SEM). The improved photoelectrochemical properties are studied by photocurrent density, EIS, and amperometric i-t curve analysis. It is found that the structure of Bi2MoO6 nanoparticles remains intact, with good dispersion status. The as-prepared g-C3N4/Bi2MoO6 nanocomposites (BMC 5-9) are selected and investigated by SEM analysis, which inhibits special morphology consisting of Bi2MoO6 nanoparticles and some g-C3N4 nanosheets. The introduction of small sized g-C3N4 nanosheets in sample BMC 9 is effective to improve the charge separation and transfer efficiency, resulting in enhancing of the photoelectric behavior of Bi2MoO6. The improved photoelectronic behavior of g-C3N4/Bi2MoO6 may be attributed to enhanced charge separation efficiency, photocurrent stability, and fast electron transport pathways for some energy applications.

Synergistically Enhanced Oxygen Evolution Catalysis with Surface Modified Halloysite Nanotube

  • Hyeongwon Jeong;Bharat Sharma;Jae-ha Myung
    • Journal of Electrochemical Science and Technology
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    • 제14권1호
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    • pp.96-104
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    • 2023
  • Synergistically increased oxygen evolution reaction (OER) of manganese oxide (MnO2) catalyst is introduced with surface-modified halloysite nanotube (Fe3O4-HNTs) structure. The flake shaped MnO2 catalyst is attached on the nanotube template (Fe3O4-HNTs) by series of wet chemical and hydrothermal method. The strong interaction between MnO2 and Fe3O4-HNTs maximized active surface area and inter-connectivity for festinate charge transfer reaction for OER. The synergistical effect between Fe3O4 layer and MnO2 catalyst enhance the Mn3+/Mn4+ ratio by partial replacement of Mn ions with Fe. The relatively increased Mn3+/Mn4+ ratio on MnO2@FHNTs induced 𝜎* orbital (eg) occupation close to single electron, improving the OER performances. The MnO2@FHNTs catalyst exhibited the reduced overpotential of 0.42 V (E vs. RHE) at 10 mA/cm2 and Tafel slope of (99 mV/dec), compared with that of MnO2 with unmodified HNTs (0.65 V, 219 mV/dec) and pristine MnO2 (0.53 V, 205 mV/dec). The present study provides simple and innovative method to fabricate nano fiberized OER catalyst for a broad application of energy conversion and storage systems.

Generation of Hydrogen Peroxide by Single-Atom Clusters Pd Anchored on t-BaTiO3 for Piezoelectric Degradation of Tetracycline

  • Xin Ni;Yuan Liang;Quanzi Pan;Hengjie Guo;Kai Chen;Bo Zhang;Shaocong Ni;Bin Sheng;Zeda Meng;Shouqing Liu;Won-Chun Oh
    • Korean Journal of Materials Research
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    • 제33권11호
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    • pp.447-457
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    • 2023
  • Single-atom Pd clusters anchored on t-BaTiO3 material was synthesized using hydrothermal and ultrasonic methods for the effective piezoelectric catalytic degradation of pollutants using vibration energy. XRD patterns of BaTiO3 loaded with monoatomic Pd were obtained before and after calcining, and showed typical cubic-phase BTO. TEM and HAADF-STEM images indicated single-atom Pd clusters were successfully introduced into the BaTiO3. The piezoelectric current density of the prepared Pd-BaTiO3 binary composite was significantly higher than that of the pristine BaTiO3. Under mechanical vibration, the nanomaterial exhibited a tetracycline decomposition rate of ~95 % within 7 h, which is much higher than the degradation rate of 56.7 % observed with pure BaTiO3. Many of the piezo-induced electrons escaped to the Pd-doped BaTiO3 interface because of Pd's excellent conductivity. Single-atom Pd clusters help promote the separation of the piezo-induced electrons, thereby achieving synergistic catalysis. This work demonstrates the feasibility of combining ultrasonic technology with the piezoelectric effect and provides a promising strategy for the development of ultrasonic and piezoelectric materials.

MOF-Derived FeCo-Based Layered Double Hydroxides for Oxygen Evolution Reaction

  • Fang Zheng;Mayur A. Gaikwad;Jin Hyeok Kim
    • Korean Journal of Materials Research
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    • 제33권10호
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    • pp.377-384
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    • 2023
  • Exploring earth-abundant, highly effective and stable electrocatalysts for electrochemical water splitting is urgent and essential to the development of hydrogen (H2) energy technology. Iron-cobalt layered double hydroxide (FeCo-LDH) has been widely used as an electrocatalystfor OER due to its facile synthesis, tunable components, and low cost. However, LDH synthesized by the traditional hydrothermal method tends to easily agglomerate, resulting in an unstable structure that can change or dissolve in an alkaline solution. Therefore, studying the real active phase is highly significant in the design of electrochemical electrode materials. Here, metal-organic frameworks (MOFs) are used as template precursors to derive FeCo-LDH from different iron sources. Iron salts with different anions have a significant impact on the morphology and charge transfer properties of the resulting materials. FeCo-LDH synthesized from iron sulfate solution (FeCo-LDH-SO4) exhibits a hybrid structure of nanosheets and nanowires, quite different from other electrocatalysts that were synthesized from iron chloride and iron nitrate solutions. The final FeCo-LDH-SO4 had an overpotential of 247 mV with a low Tafel-slope of 60.6 mV dec-1 at a current density of 10 mA cm-2 and delivered a long-term stability of 40 h for the OER. This work provides an innovative and feasible strategy to construct efficient electrocatalysts.

A Study of Feasibility of Dipole-dipole Electric Method to Metallic Ore-deposit Exploration in Korea (국내 금속광 탐사를 위한 쌍극자-쌍극자 전기탐사의 적용성 연구)

  • Min, Dong-Joo;Jung, Hyun-Key;Park, Sam-Gyu;Chon, Hyo-Taek;Kwak, Na-Eun
    • Geophysics and Geophysical Exploration
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    • 제11권3호
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    • pp.250-262
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    • 2008
  • In order to assess the feasibility of the dipole-dipole electric method to the investigation of metallic ore deposit, both field data simulation and inversion are carried out for several simplified ore deposit models. Our interest is in a vein-type model, because most of the ore deposits (more than 70%) exist in a vein type in Korea. Based on the fact that the width of the vein-type ore deposits ranges from tens of centimeters to 2m, we change the width and the material property of the vein, and we use 40m-electrode spacing for our test. For the vein-type model with too small width, the low resistivity zone is not detected, even though the resistivity of the vein amounts to 1/300 of that of the surrounding rock. Considering a wide electrode interval and cell size used in the inversion, it is natural that the size of the low resistivity zone is overestimated. We also perform field data simulation and inversion for a vein-type model with surrounding hydrothermal alteration zones, which is a typical structure in an epithermal ore deposits. In the model, the material properties are assumed on the basis of resistivity values directly observed in a mine originated from an epithermal ore deposits. From this simulation, we can also note that the high resistivity value of the vein does not affect the results when the width of the vein is narrow. This indicates that our main target should be surrounding hydrothermal alteration zones rather than veins in field survey. From these results, we can summarize that when the vein is placed at the deep part and the difference of resistivity values between the vein and the surrounding rock is not large enough, we cannot detect low resistivity zone and interpret the subsurface structures incorrectly using the electric method performed at the surface. Although this work is a little simple, it can be used as references for field survey design and field data Interpretation. If we perform field data simulation and inversion for a number of models and provide some references, they will be helpful in real field survey and interpretation.

Electrochemical Characteristics of LiMn2O4 Cathodes Synthesized from Various Precursors of Manganese Oxide and Manganese Hydroxide (다양한 형태 및 구조의 망간산화물 및 망간수산화물 전구체로부터 합성한 LiMn2O4양극의 전기화학적 특성 연구)

  • Lee, Jong-Moon;Kim, Joo-Seong;Hong, Soon-Kie;Lee, Jeong-Jin;Ahn, Han-Cheol;Cho, Won-Il;Mho, Sun-Il
    • Journal of the Korean Electrochemical Society
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    • 제15권3호
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    • pp.172-180
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    • 2012
  • The $LiMn_2O_4$ cathodes for lithium ion battery were synthesized from various precursors of manganese oxides and manganese hydroxides. As the first step, nanosized precursors such as ${\alpha}-MnO_2$ (nano-sticks), ${\beta}-MnO_2$ (nano-rods), $Mn_3O_4$ (nano-octahedra), amorphous $MnO_2$(nano-spheres), and $Mn(OH)_2$ (nano-plates) were prepared by a hydrothermal or a precipitation method. Spinel $LiMn_2O_4$ with various sizes and shapes were finally synthesized by a solid-state reaction method from the manganese precursors and LiOH. Nano-sized (500 nm) octahedron $LiMn_2O_4$ showed high capacities of 107 mAh $g^{-1}$ and 99 mAh $g^{-1}$ at 1 C- and 50 C-rate, respectively. Three dimensional octahedral crystallites exhibit superior electrochemical characteristics to the other one-dimensional and two-dimensional shaped $LiMn_2O_4$ nanoparticles. After 500 consecutive charge discharge battery cycles at 10 C-rate with the nano-octahedron $LiMn_2O_4$ cathode, the capacity retention of 95% was observed, which is far better than any other morphologies studied in this work.