• Korean Chemical Engineering Research
• /
• v.46 no.2
• /
• pp.286-290
• /
• 2008

Small amounts of CO in reformate fuel gas effectively block platinum catalysts by strong adsorption on the platinum surface at the operation temperature of $60{\sim}80^{\circ}C$ in PEMFC. To oxidate CO, Ru/C layer (CO filter) was placed between Pt/C layer and GDL (gas diffusion layer) in this study. Ru/C filter provided good CO-tolerant PEMFC anode, but decreased the performance of unit cell about 10% at 0.6 V due to mass transfer resistance from Ru/C filter thickness and increase of charge transfer resistance. Membrane degradation is one of the most important factors limiting the life-time of PEMFCs. Membrane durability would be dependent on the electrode catalyst type. It seemed that Ru catalyst layer would shorten the life time of PEMFC as enhanced the fluoride emission rate of membrane in acceleration test.

• Korean Journal of Materials Research
• /
• v.27 no.2
• /
• pp.94-99
• /
• 2017

Dinickel-silicide $(Ni_2Si)/glass$ was employed as a counter electrode for a dye-sensitized solar cell (DSSC) device. $Ni_2Si$ was formed by rapid thermal annealing (RTA) at $700^{\circ}C$ for 15 seconds of a 50 nm-Ni/50 nm-Si/glass structure. For comparison, $Ni_2Si$ on quartz was also prepared through conventional electric furnace annealing (CEA) at $800^{\circ}C$ for 30 minutes. XRD, XPS, and EDS line scanning of TEM were used to confirm the formation of $Ni_2Si$. TEM and CV were employed to confirm the microstructure and catalytic activity. Photovoltaic properties were examined using a solar simulator and potentiostat. XRD, XPS, and EDS line scanning results showed that both CEA and RTA successfully led to tne formation of nano $thick-Ni_2Si$ phase. The catalytic activity of $CEA-Ni_2Si$ and $RTA-Ni_2Si$ with respect to Pt were 68 % and 56 %. Energy conversion efficiencies (ECEs) of DSSCs with $CEA-Ni_2Si$ and $RTA-Ni_2Si$catalysts were 3.66 % and 3.16 %, respectively. Our results imply that nano-thick $Ni_2Si$ may be used to replace Pt as a reduction catalytic layer for a DSSCs. Moreover, we show that nano-thick $Ni_2Si$ can be made available on a low-cost glass substrate via the RTA process.

• Journal of Sensor Science and Technology
• /
• v.29 no.6
• /
• pp.407-411
• /
• 2020

In this study, we propose an array-type gas sensor with high selectivity and response using multiple oxide semiconductors. The sensor array was composed of SnO₂ and In₂O₃, and the detection characteristics were improved by using Pt, Au, and Pd catalysts. All samples were deposited directly on the Pt interdigitated electrode (IDE) through the e-beam evaporator glancing angle deposition (GAD) method. They grew in the form of well-aligned nanorods at off-axis angles. The prepared SnO₂ and In₂O₃ nanorod samples were exposed to CH₃COCH₃, C₇H₈, and NO₂ gases in a 300℃ dry condition. Au-decorated SnO₂, Au-decorated In₂O₃, and Pd-decorated In₂O₃ exhibited high selectivity for CH₃COCH₃, C₇H₈, and NO₂, respectively. They demonstrated a high detection limit of the sub ppb level computationally. In addition, measurements from each sensor were executed in the 40% relative humidity condition. Although there was a slight reduction in detection response, high selectivity and distinguishable detection characteristics were confirmed.

• Korean Journal of Materials Research
• /
• v.28 no.11
• /
• pp.633-639
• /
• 2018

In anion exchange membrane fuel cells, Pd nanoparticles are extensively studied as promising non-Pt catalysts due to their electronic structure similar to Pt. In this study, to fabricate Pd nanoparticles well dispersed on carbon support materials, we propose a synthetic strategy using mixed organic ligands with different chemical structures and functions. Simultaneously to control the Pd particle size and dispersion, a ligand mixture composed of oleylamine(OA) and trioctylphosphine(TOP) is utilized during thermal decomposition of Pd precursors. In the ligand mixture, OA serves mainly as a reducing agent rather than a stabilizer since TOP, which has a bulky structure, more strongly interacts with the Pd metal surface as a stabilizer compared to OA. The specific roles of OA and TOP in the Pd nanoparticle synthesis are studied according to the mixture composition, and the oxygen reduction reaction(ORR) activity and durability of highly-dispersed Pd nanocatalysts with different particles sizes are investigated. The results of this study confirm that the Pd nanocatalyst with large particles has high durability compared to the nanocatalyst with small Pd nanoparticles during the accelerated degradation tests although they initially indicated similar ORR performance.

• Korean Chemical Engineering Research
• /
• v.61 no.4
• /
• pp.505-516
• /
• 2023

Plastic's ease of processing drives its growing production, resulting in a surge of plastic waste. Addressing this issue, catalytic upcycling emerges as a promising remedy. Various metals (Ru, Pt, etc.) and supports (TiO₂, CeO₂, etc.) have been employed for the chemical recycling of polyolefin plastics. Strategies to enhance liquid fuel selectivity and minimize methane include manipulating particle size, introducing heterogeneous metals, and tuning support characteristics. Simultaneously, endeavors to optimize catalysts by reducing precious metal usage were pursued. This study explores enhancing economic viability in hydrogenolysis and hydrocracking reactions, underscoring the potential of catalystdriven upcycling to tackle plastic waste.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.9
• /
• pp.2830-2844
• /
• 2012

This review covers recent developments in our group regarding the synthesis, characterization and applications of single-crystalline one-dimensional nanostructures based on a wide range of material systems including noble metals, metal silicides and metal germanides. For the single-crystalline one-dimensional nanostructures growth, we have employed chemical vapor transport approach without using any catalysts, capping reagents, and templates because of its simplicity and wide applicability. Au, Pd, and Pt nanowires are epitaxially grown on various substrates, in which the nanowires grow from seed crystals by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. We also present the synthesis of numerous metal silicide and germanide 1D nanostructures. By simply varying reaction conditions, furthermore, nanowires of metastable phase, such as $Fe_5Si_3$ and $Co_3Si$, and composition tuned cobalt silicides (CoSi, $Co_2Si$, $Co_3Si$) and iron germanides ($Fe_{1.3}Ge$ and $Fe_3Ge$) nanowires are synthesized. Such developments can be utilized as advanced platforms or building blocks for a wide range of applications such as plasmonics, sensings, nanoelectronics, and spintronics.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.8
• /
• pp.2539-2545
• /
• 2012

In the present study, we suggest a new way to reactivate performance of direct formic acid fuel cell (DFAFC) and explain its mechanism by employing electrochemical analyses like chronoamperometry (CA) and cyclic voltammogram (CV). For the evaluation of DFAFC performance, palladium (Pd) and platinum (Pt) are used as anode and cathode catalysts, respectively, and are applied to a Nafion membrane by catalyst-coated membrane spraying. After long DFAFC operation performed at 0.2 and 0.4 V and then CV test, DFAFC performance is better than its initial performance. It is attributed to dissolution of anode Pd into $Pd^{2+}$. By characterizations like TEM, Z-potential, CV and electrochemical impedance spectroscopy, it is evaluated that such dissolved $Pd^{2+}$ ions lead to (1) increase in the electrochemically active surface by reduction in Pd particle size and its improved redistribution and (2) increment in the total oxidation charge by fast reaction rate of the Pd dissolution reaction.

• Journal of Energy Engineering
• /
• v.8 no.1
• /
• pp.34-47
• /
• 1999

본 연구에서는 촉매상에서 메탄의 산화시 발생되는 반응열을 이용하고 반응생성물과 미반응 메탄과의 개질반응에 의해 합성가스의 수율을 증대시키기 위하여 연소촉매와 개질촉매를 연속적으로 배치한 hybrid 촉매상에서 개질촉매에 따른 메탄의 부분산화반응의 반응 특성과 합성가스 수율에 미치는 영향을 관찰하였다. 메탄의 산화를 위해서 Pt-Rh/cordierite 촉매를 사용하였으며, 개질촉매로는 상업용 개질촉매인 R67, ICI46-1, 수성가스 전환반응촉매인 LX821 촉매와 6 wt% Ni/cordierite 촉매를 사용하였다. 실험결과 연소촉매와 개질촉매를 연속적으로 사용한 경우 메탄의 산화 과정에서 생성된 CO2 및 H2O가 미반응 메탄과의 개질반응 촉진으로 인하여 합성가스이 수율이 증가됨을 확인할 수 있었다. 이때 생성되는 합성가스의 H2/CO 몰비는 온도에 따라 감소하는 것으로 나타났으며, 80$0^{\circ}C$에서 촉매에 따라 2.2~2.8의 값을 가짐을 알 수 있었다. 개질촉매로 R67 및 Ni/cordierite 촉매를 사용하였을 경우 가장 높은 합성가스의 수율을 얻을 수 있었으며, 연소촉매와 개질촉매의 질량비는 1:1~1:2에서 가장 높은 수율의 합성가스를 얻을 수 있었다. 메탄과 산소의 몰비가 2:2에서 메탄의 전환율과 수소 수율이 가장 높게 나타났으며 메탄의 몰비 증가에 따라 감소되는 경향을 보였다.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.6
• /
• pp.1865-1872
• /
• 2011

This study investigates the sensitivity of a gas sensor to volatile organic compounds (VOCs) at various operating temperatures and catalysts. Nano-sized powdered $WO_3$ prepared by sol-gel and chemical precipitation methods was mixed with various metal oxides. Next, transition metals (Pt, Ru, Pd, and In) were doped on the surface of the mixture. Metal-$WO_3$ thick films were prepared using the screen-printing method. The physical and chemical properties of the films were studied by SEM/EDS, XRD, and BET techniques. The measured sensitivity to VOCs is defined as the ratio ($R_a/R_g$) of resistance ($R_{air}$) of $WO_3$ film in the air to resistance ($R_{gas}$) of $WO_3$ film in a VOCs test gas. The sensitivity and selectivity of the films were tested with various VOCs such as acetaldehyde, formaldehyde, methyl alcohol, and BTEX. The thick $WO_3$ film containing 1 wt % of Ru and 5 wt % of $SnO_2$ showed the best sensitivity and selectivity to acetaldehyde gas at an operating temperature of 300 $^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.204.2-204.2
• /
• 2014

Among various metal oxides, ZrO2 is of particular interests and has received widespread attention thanks to its ideal mechanical and chemical stability. As a cheap metal, Ag nanoparticles are also widely used as catalysts in ethylene epoxidation and methanol oxidation. However, the nature of Ag-ZrO2 interfaces is still unknown. In this work, the growth, interfacial interaction and thermal stability of Ag nanoparticles on ZrO2(111) film surfaces were studied by low-energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES), and X-ray photoelectron spectroscopy (XPS). The ZrO2(111) films were epitaxially grown on Pt(111). Three-dimensional (3D) growth model of Ag on the ZrO2(111) surface at 300 K was observed with a density of ${\sim}2.0{\times}1012particles/cm2$. The binding energy of Ag 3d shifts to low BE from very low to high Ag coverages by 0.5 eV. The Auger parameters shows the primary contribution to the Ag core level BE shift is final state effect, indicating a very weak interaction between Ag clusters and ZrO2(111) film. Thermal stability experiments demonstrate that Ag particles underwent serious sintering before they desorb from the zirconia film surface. In addition, large Ag particles have stronger ability of inhibiting sintering.