• Title/Summary/Keyword: Oxygen desorption

Search Result 85, Processing Time 0.024 seconds

Heat-treatment effects on oxygen evolution reaction of nickel-cobalt layered double hydroxide

  • Lee, Jung-Il;Ko, Daehyeon;Mhin, Sungwook;Ryu, Jeong Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.31 no.3
    • /
    • pp.143-148
    • /
    • 2021
  • Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiency and green hydrogen production through electrochemical water splitting. Transition metal-based electrocatalysts have emerged as promising materials that can significantly reduce the hydrogen production costs. Among the available electrocatalysts, transition metal-based layered double hydroxides (LDHs) have demonstrated outstanding OER performance owing to the abundant active sites and favorable adsorption-desorption energies for OER intermediates. Currently, cobalt doped nickel LDHs (NiCo LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemical synergetic effects between Ni and Co. We report effects of heat-treatment of the as-grown NiCo LDH on electrocatalytic activities in a temperature range from 250 to 400℃. Electrocatalytic OER properties were analysed by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The heat-treatment temperature was found to play a crucial role in catalytic activity. The optimum heat-treatment temperature was discussed with respect to their OER performance.

Formation Fe2O3 Nanowalls through Solvent-Assisted Hydrothermal Process and Their Application for Titan Yellow GR Dye Degradation

  • Ahmed, Khalid Abdelazez Mohamed
    • Journal of the Korean Chemical Society
    • /
    • v.58 no.2
    • /
    • pp.205-209
    • /
    • 2014
  • Hematite iron oxide (${\alpha}$-$Fe_2O_3$) nanowalls were fabricated on aluminum substrate by a facile solvent-assisted hydrothermal oxidation process. The XRD and EDS patterns indicate that the sample has a rhombohedral phase of hematite $Fe_2O_3$. FE-SEM, TEM, HR-TEM, SA-ED were employed to characterize the resulting materials. $N_2$ adsorption-desorption isotherms was used to study a BET surface area. Their capability of catalytic degradation of titan yellow GR azo dye with air oxygen in aqueous solution over $Fe_2O_3$ catalysts was studied. The result indicates that the as-prepared product has a high catalytic activity, because it has a larger surface area. Langmuir and Freundlich isotherms of adsorption dye on the catalysts surface were investigated and the decomposition of titan yellow GR follows pseudo-first order kinetic.

Analysis of Electrical Property of Room Temperature-grown ZnO:Al Thin films Annealed in Hydrogen Ambient (수소 분위기에서 후열처리한 상온증착 ZnO:Al 박막의 전기적 특성 분석)

  • Jeong, Yun-Hwan;Chen, Hao;Jin, Hu-Jie;Park, Choon-Bae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.22 no.4
    • /
    • pp.318-322
    • /
    • 2009
  • In this paper, to establish growth technology of ZnO:Al thin films at low temperature applied to photoelectronic devices, ZnO:Al were prepared by RF magnetron sputtering on glass substrate at room temperature using different RF power with subsequent annealing process at different temperature in $H_2$ ambient. The resistivity of hydrogen-annealed ZnO:Al thin film at temperature of $300^{\circ}C$ was reduced to $8.32{\times}10^{-4}{\Omega}cm$ from $9.44{\times}10^{-4}{\Omega}cm$ which was optimal value for as-grown films. X-ray photoelectron spectroscopy(XPS) revealed that improved electrical properties are ascribed to desorption of the negatively charged oxygen species from the grain boundary surfaces by the hydrogen annealing process.

Catalytic Upgrading of Geodae-Uksae 1 over Mesoporous MCM-48 Catalysts

  • Jeon, Ki-Joon;Jin, Sung Ho;Park, Sung Hoon;Jeon, Jong-Ki;Jung, Sang-Chul;Ryu, Changkook;Park, Young-Kwon
    • Bulletin of the Korean Chemical Society
    • /
    • v.35 no.7
    • /
    • pp.1951-1955
    • /
    • 2014
  • Catalytic pyrolysis of Geodae-Uksae 1, a kind of miscanthus found in Korea, was carried out over mesoporous MCM-48 catalysts. For rapid product analysis and catalyst evaluation, pyrolysis-gas chromatography/mass spectrometry was used. X-ray diffraction, nitrogen sorption, pyridine adsorbed Fourier transform infrared, and NH3 temperature programmed desorption were utilized to analyze the properties of the catalysts. Compared to non-catalytic reaction, catalytic upgrading over mesoporous Al-MCM-48 catalysts produced a higher-quality bio-oil with a high stability and low oxygen content. Al-MCM-48 exhibited higher deoxygenation ability than Si-MCM-48 due to its higher acidity.

Synthesis and Characterization of LSCF/CGO Composite Used as SOFC Cathode Materials (SOFC 용 LSCF/CGO 공기극의 제조 및 특성연구)

  • Park, Jae-Layng;Lim, Tak-Hyoung;Lee, Seung-Bok;Park, Seok-Joo;Shin, Dong-Ryul;Song, Rak-Hyun
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2009.11a
    • /
    • pp.184-186
    • /
    • 2009
  • Composites of LSCF($La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ and CGO(gadolinium doped ceria) is an efficient candidate cathode material with CGO electrolytes. In this study, LSCF with exact perovskite structure was synthesized by using solid state reaction(SSR) method. The optimized temperature to synthesize $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ with rhombohedral structure. was $1100^{\circ}C$. The polarization resistance of the LSCF/CGO(50:50 wt.%) was smaller than those of other composite cathodes. The analysis of the EIS data of LSCF/CGO suggests that the diffusion and adsorption-desorption of oxygen can be the key process in the cathodic reaction of SOFC using LSCF/CGO as cathode material.

  • PDF

The Studies on the Simultaneous Removals of NOx and SOx from Stationary Sources by using Perovskite type Catalysts (페로브스카이트형 촉매계를 이용한 고정원 배가스로부터의 NOx 와 SOx의 동시제거 기술에 관한 연구)

  • Lee, Byong-Yong;Choung, Suk-Jin
    • Proceedings of the KIEE Conference
    • /
    • 1996.11a
    • /
    • pp.475-479
    • /
    • 1996
  • At present studies, we are going to suggest the new type of Perovskite derived catalysts which modify the defects of transition metals impregnated. Perovskite type catalyst is a typical mixed metal oxides, and there are "defect"s (from like that oxygen, cation, crystallic structure) were made by difference from composition, preparing method and so forth. And because this, its electro-magnetic character could be much changed. By using this phenomena, it could utilize the modification of adsorption/desorption characters as well as the catalytic activities in NOx reduction. Because perovskite type catalyst can exchange the metal of the each lattice site freely and it is possible to represent the peculiar.

  • PDF

Chemisorption and Oxidation of Methanol over V2O5 Catalyst - I. Chemisorptive Behaviors of CO and CH3OH - (V2O5 촉매상에서의 메탄올 흡탈착 및 산화반응 - I. CO와 CH3OH의 화학흡착 특성 -)

  • Kim, Eul-San;Choi, Ki-Hyouk;Lee, Ho-In
    • Applied Chemistry for Engineering
    • /
    • v.5 no.2
    • /
    • pp.189-198
    • /
    • 1994
  • The adsorptive behaviors of carbon monoxide and methanol over $V_2O_5$catalyst were studied by means of thermal desorptlon spectroscopy (TDS) under ultrahigh vacuum conditions. Carbon monoxide adsorbed on oxygen-deficient V sites as well as on V=O groups of the $V_2O_5$ surface. CO adsorbed on the V sites desorbed at 380 K while CO adsorbed on the V=O groups formed carbonate species with surface oxygen of $V_2O_5$ and desorbed as $CO_2$ resulting in the reduction of the surface of she $V_2O_5$catalyst. The amount of CO adsorbed in the form of carbonate species increased by both the pre- and post-adsorbed oxygen. The adsorptive behavior of methanol over the catalyst was studied by thermal desorption experiments of $CH_3OH$, HCHO, CO, and $H_2$ upon methanol adsorption at 298 K. The results showed that methanol was adsorbed dissociatively on the $V_2O_5$catalyst as methoxy and hydroxyl groups at 298K.

  • PDF

Study on Catalytic Activity of the Selective CO Oxidation and Characterization Using $La_{0.5}Ce_{0.5}Co_{1-x}Cu_xO_{3-{\alpha}}$ Perovskite Catalysts ($La_{0.5}Ce_{0.5}Co_{1-x}Cu_xO_{3-{\alpha}}$ Perovskite촉매의 선택적 CO 산화반응 및 특성 분석에 관한 연구)

  • Sohn, Jung-Min
    • Transactions of the Korean hydrogen and new energy society
    • /
    • v.18 no.2
    • /
    • pp.116-123
    • /
    • 2007
  • [ $La_{0.5}Ce_{0.5}Co_{1-x}Cu_xO_{3-{\alpha}}$ ](X=0, 0.1, 0.3, 0.5) perovskites were prepared by coprecipitation method at pH 7 or pH 11 and its catalytic activity of selective CO oxidation was investigated. The characteristics of these catalysts were analyzed by $N_2$ adsorption, X-ray diffraction(XRD), SEM, $O_2$-temperature programmed desorption(TPD). The pH value at a preparation step made effect on particle morphology. The smaller particle was obtained with a condition of pH 7. The better catalytic activity was observed using catalysts prepared at pH 7 than pH 11. The maximum CO conversion of 98% was observed over $La_{0.5}Ce_{0.5}Co_{0.7}Cu_{0.3}O_{3-{\alpha}}$ at $320^{\circ}C$. Below $200^{\circ}C$, the most active catalyst was $La_{0.5}Ce_{0.5}Co_{0.9}Cu_{0.1}O_{3-{\alpha}}$, of which conversion was 92% at $200^{\circ}C$. By the substitution of Cu, the evolution of ${\alpha}$-oxygen was remarkably enhanced regardless of pH value at preparation step according to $O_2$-TPD. Among the different ${\alpha}$-oxygen species, the oxygen species evolved between $400^{\circ}C$ and $500^{\circ}C$, gave the better catalytic performance for selective CO oxidation including $La_{0.5}Ce_{0.5}CoO_3$ in which Cu was absent.

Oxidation Characteristics of Low Concentration CO Gas by the Natural Manganese Dioxide(NMD) in a Fixed Bed (고정층 반응기에서 망간광석(NMD)을 이용한 저농도 일산화탄소 산화특성)

  • Lee, Young Soon;Park, Jong Soo;Oh, Kwang Joong
    • Clean Technology
    • /
    • v.2 no.1
    • /
    • pp.60-68
    • /
    • 1996
  • The oxidation of carbon monoxide of low concentration on the natural manganese dioxide (NMD) has been investigated in a fixed bed reactor. The experimental variables were concentration of oxygen (500ppm~99.8%) and carbon monoxide (500ppm~10000ppm) and catalyst temperature ($50{\sim}750^{\circ}C$). The NMD(Natural Manganese Dioxide) has been characterized by temperature - program reduction(TPR) using 2.4% $CO/H_2$ as a reducing agent, thermogravimetric analysis (TGA), and reduction of NMD by 2.4% $CO/H_2$. It was found that the NMD catalyst activity on the unit area was greater than the $MnO_2$ catalyst for oxidation of CO at the same temperature. The thermal stability of oxidation activity was considered to be maintained when the NMD was heated to $750^{\circ}C$. The TGA, reduction by CO, and TPR of the NMD showed that the NMD had active lattice oxygen which was easily liberated on heating in the absence and low concentration of oxygen. The reaction order in CO is 0.701 between 500~3500ppm and almost zero between 3500~10000ppm of CO.

  • PDF

Effect of Iron Species in Mesoporous Fe-N/C Catalysts with Different Shapes on Activity Towards Oxygen Reduction Reaction

  • Kang, Taehong;Lee, Jiyeon;Kim, Jong Gyeong;Pak, Chanho
    • Journal of Electrochemical Science and Technology
    • /
    • v.12 no.1
    • /
    • pp.137-145
    • /
    • 2021
  • Among the non-precious metal catalysts, iron-nitrogen doped carbon (Fe-N/C) catalysts have been recognized as the most promising candidates for an alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) under alkaline and acidic conditions. In this study, the nano replication method using mesoporous silica, which features tunable primary particle sizes and shape, is employed to prepare the mesoporous Fe-N/C catalysts with different shapes. Platelet SBA-15, irregular KIT-6, and spherical silica particle (SSP) were selected as a template to generate three different kinds of shapes of the mesoporous Fe-N/C catalyst. Physicochemical properties of mesoporous Fe-N/C catalysts are characterized by using small-angle X-ray diffraction, nitrogen adsorption-desorption isotherms, and scanning electron microscopy images. According to the electrochemical evaluation, there is no morphological preference of mesoporous Fe-N/C catalysts toward the ORR activity with half-cell configuration under alkaline electrolyte. By implementing X-ray photoelectron spectroscopy analysis of Fe and N atoms in the mesoporous Fe-N/C catalysts, it is possible to verify that the activity towards ORR highly depends on the portions of "Fe-N" species in the catalysts regardless of the shape of catalysts. It was suggested that active site distribution in the Fe-N/C is one important factor towards ORR activity.