• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.146-152
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• 2016

A combined system with PEMFC and reformer is introduced and optimized for the real use of this kind of system in the future. The hydrogen source to operate the PEMFC system is methanol, which needs two parts of methanol reforming reaction and preferential oxidation (PROX) for the hydrogen fuel process in the combined operation PEMFC system. With the optimized methanol steam reforming condition, we tested PROX reactions in various operation temperature from 170 to 270 ℃ to investigate CO concentration data in the reformed gases. Using these different CO concentration, PEMFC performances are achieved at the combined system. Pt/C and Ru promoted Pt/C were catalysts were used for the anode to compare the stability in CO contained gases. The alloy catalyst of PtRu/C shows higher performance and better resistance to CO than the Pt/C at even high CO amount of 200 ppm, indicating a promotion not only to the activity but also to the CO tolerance. Furthermore, in a system point of view, there is a fluctuation in the PEMFC operation due to the unstable fuel supply. Therefore, we also modified the methanol reforming by a scaled up reactor and pressurization to produce steady operation of PEMFC. The optimized system with the methanol reformer and PEMFC shows a stable performance for a long time, which is providing a valuable data for the PEMFC commercialization.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.223-228
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• 2006

Pore-size controlled porous carbons for the catalyst supports of the direct methanol fuel cell were prepared from the mesophase pitch by using the silica spheres with different sizes. Pitch solution in THF and spheres were mixed, carbonized and etched by 5 M NaOH to make porous carbon. Specific surface area of the porous carbons was $14.7{\sim}87.7m^2/g$ and average pore diameter was 50~550 nm which were dependent on the size of silica spheres. Aqueous reduction method was used to load 60 wt% PtRu on the prepared porous carbon supports. The electro-oxidation activity of the supported 60 wt% Pt-Ru catalysts was measured by cyclic voltammetry and unit cell test. For the 60 wt% Pt-Ru/porous carbon synthesized by 50 nm silica, current density value in the cyclic voltammetry test was $123mA/cm^2$ at 0.4 V and peak power density in the unit cell test were 105 and $162mW/cm^2$ under oxygen at 60 and $80^{\circ}C$, respectively.

• Resources Recycling
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• v.21 no.3
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• pp.15-20
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• 2012

In this paper, we carried out separation of membrane and leaching of Pt and Ru using hydrochloric acid from MEA(membrane-electrode assembly) of fuel cell. In this method, these were separated from MEA of fuel cell using the distilled water, 10 vol.% butanol solution and 15 vol.% cationic surfactant(Koremul-LN-7) by dipping method without the dispersion of catalyst particles. And the leaching of Pt and Ru containing in the separated carbon paper catalysts has been studied by hydrochloric acid using $HNO_3$ or $H_2O_2$ as a oxidant. The leaching ratio of Pt and Ru were higher when $H_2O_2$ was used as a oxidant and the optimum conditions were obtained in 8M HCl, the amount of $H_2O_2$ 5M and 6 hours of leaching time at $90^{\circ}C$. In this condition, extraction of Pt and Ru were 98% and 71.5%, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.132-132
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• 2013

Colloidal synthesis of nanoparticles with well-controlled size, shape, and composition, together with development of in situ surface science characterization tools, such as ambient pressure X-ray photoelectron spectroscopy (APXPS), has brought new opportunities to unravel the surface structure of working catalysts. Recent studies suggest that surface oxides on transition metal nanoparticles play an important role in determining the catalytic activity of CO oxidation. In this talk, I will outline the recent studies on the influence of surface oxides on Rh, Pt, Ru and Co nanoparticles on the catalytic activity of CO oxidation [1-3]. Transition metal nanoparticle model catalysts were synthesized in the presence of poly(vinyl pyrrolidone) polymer capping agent and deposited onto a flat Si support as two-dimensional arrays using the Langmuir-Blodgett deposition technique. APXPS studies exhibited the reversible formation of surface oxides during oxidizing, reducing, and CO oxidation reaction [4]. General trend is that the smaller nanoparticles exhibit the thicker surface oxides, while the bigger ones have the thin oxide layers. Combined with the nature of surface oxides, this trend leads to the different size dependences of catalytic activity. Such in situ observations of metal nanoparticles are useful in identifying the active state of the catalysts during use and, hence, may allow for rational catalyst designs for practical applications. I will also show that the surface oxide can be engineered by using the simple surface treatment such as UV-ozone techniques, which results in changing the catalytic activity [5]. The results suggest an intriguing way to tune catalytic activity via engineering of the nanoscale surface oxide.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1865-1872
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• 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 $^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.601-607
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• 2019

Ammonia would be formed in natural gas containing small amount of nitrogen reforming process in the process natural gas, which might damage the Pt catalyst and Prox catalyst. In the article, the effect of nitrogen contents on the formation of ammonia in the reforming process has been studied. In the experiments, Ru based and Ni based catalysts were used and the concentration of ammonia in the reformate gas at various gas hourly space velocity was measured. Experimental result shows that relatively higher ammonia concentration was measured with Ru based catalyst than with Ni based catalyst. It also shows that the concentration of ammonia increased rapidly after most of the methane converted into hydrogen. Based on the experimental results to reduce ammonia concentration it might be better to finish methane conversion at the exit position of the reforming reactor to minimize the contact time of catalyst and nitrogen with high concentration of hydrogen.

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

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.11-15
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• 2008

The composite membrane for direct methanol fuel cell (DMFC) was developed using $H_3O^+-{\beta}"-Al_2O_3$ powder and perfluorosulfonylfluroride copolymer (Nafion) resin. The perfluorosulfonylfluroride copolymer (Nafion) resin was mixed with $H_3O^+-{\beta}"-Al_2O_3$ powder and it was made to sheet form by hot pressing. The electrodes were prepared with 60 wt% PtRu/C and 60wt% Pt/C catalysts for anode and cathode, respectively. The morphology and the chemical composition of the composite membrane have been investigated by using SEM and EDXA, respectively. The composite membrane and $H_3O^+-{\beta}"-Al_2O_3$ were analyzed by using FT-IR and XRD. The methanol permeability of the composite membranes was also measured by gas chromatography (GC). The performance of the MEA containing the composite membrane (2wt% $H_3O^+-{\beta}"-Al_2O_3$) was higher than that of normal pure Nafion membrane at high operating temperature (e.g. $110^{\circ}C$), due to the homogenous distribution of $H_3O^+-{\beta}"-Al_2O_3$, which decreased the methanol permeability through the membrane and enhanced the water contents in the composite membrane.

• Journal of the Korean Electrochemical Society
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• v.25 no.4
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• pp.154-161
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• 2022

The carbon-neutrality induced by the global warming is important for the modern society. Hydrogen has been received the attention as a new energy source to replace the fossil fuels. Polymer electrolyte membrane fuel cells, which convert the chemical reaction energy of hydrogen into electric power directly, are a type of eco-friendly power for future vehicles. Due to the sluggish oxygen reduction reaction and costly Pt catalyst in the cathode, the research related to the replacement of Pt-based catalysts has been vitally carried out. In this case, however, the performance is significantly different from each other and a variety of factors have existed. In this review paper, we rearrange and summarize relevant papers published within 5 years approximately. The selection of precursors, synthesis method, and co-catalyst are represented as a core factor, while the necessity of research for the further enhancement of activity may be raised. It can be anticipated to contribute to the replacement of precious metal catalysts in the various fields of study. The final objective of the future research is depicted in detail.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1079-1085
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• 1999

An investigation was made of the effect of various transition metal catalysts, ligands, and a promoter on the synthesis of N,N'-diphenylurea(DPU) from nitrobenzene, aniline, and carbon monoxide. Homogeneous Pd and Ni catalysts were found to be highly efficient, giving almost quantitative isolated DPU yields at 100% nitrobenzene conversion. Bidentate ligand, 1,3-bis(diphenylphosphino)proane(dppp) showed much improved activity and significantly different reactivity relative to the usual monodentate $PPh_3$ ligand in the presence of Ni and Pd catalysts. These results were inferred to the effect of the cis coordination of bidentate dppp ligand on the metal. The use of a promoter $Et_4NCl$ was indispensable in the case of $PPh_3$, yet inhibited the reaction if used with dppp. It was possible to reuse the Pd-dppp catalyst system, although the catalytic activity was reduced slowly.