Publications by authors named "Young-Jun Sohn"

3 Publications

  • Page 1 of 1

Molecular dynamics simulation study on the effect of perfluorosulfonic acid side chains on oxygen permeation in hydrated ionomers of PEMFCs.

Sci Rep 2021 Apr 22;11(1):8702. Epub 2021 Apr 22.

School of Chemical Engineering, Pusan National University, 2, Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan, 46241, Republic of Korea.

We prepared two types of perfluorosulfonic acid (PFSA) ionomers with Aquivion (short side chain) and Nafion (long side chain) on a Pt surface and varied their water contents (2.92 ≤ λ ≤ 13.83) to calculate the solubility and permeability of O in hydrated PFSA ionomers on a Pt surface using full atomistic molecular dynamics (MD) simulations. The solubility and permeability of O molecules in hydrated Nafion ionomers were greater than those of O molecules in hydrated Aquivion ionomers at the same water content, indicating that the permeation of O molecules in the ionomers is affected not only by the diffusion coefficient of O but also by the solubility of O. Notably, O molecules are more densely distributed in regions where water and hydronium ions have a lower density in hydrated Pt/PFSA ionomers. Radial distribution function (RDF) analysis was performed to investigate where O molecules preferentially dissolve in PFSA ionomers on a Pt surface. The results showed that O molecules preferentially dissolved between hydrophilic and hydrophobic regions in a hydrated ionomer. The RDF analysis was performed to provide details of the O location in hydrated PFSA ionomers on a Pt surface to evaluate the influence of O solubility in ionomers with side chains of different lengths. The coordination number of C(center)-O(O) and O(side chain)-O(O) pairs in hydrated Nafion ionomers was higher than that of the same pairs in hydrated Aquivion ionomers with the same water content. Our investigation provides detailed information about the properties of O molecules in different PFSA ionomers on a Pt surface and with various water contents, potentially enabling the design of better-performing PFSA ionomers for use in polymer electrolyte membrane fuel cells.
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http://dx.doi.org/10.1038/s41598-021-87570-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8062474PMC
April 2021

Highly Platinum-Loaded Magnéli Phase Titanium Oxides as a High Voltage Tolerant Electrocatalyst for Polymer Electrolyte Fuel Cells.

J Nanosci Nanotechnol 2015 Sep;15(9):6988-94

Magnéli phase titanium oxides (MPTOs), possess high electrical conductivity and chemical stability, are promising support materials for the development of novel electrocatalyst in polymer electrolyte fuel cells (PEFCs). Despite MPTO's extremely low specific surface area (1 m2/g or less), high Pt loading (40 wt%) and excellent Pt particle-size distribution were obtained by the modified borohydride method. The reasons were discussed and compared with polyol method. Membrane electrode assembly (MEA) performance of those Pt/MPTO catalysts were found to be 169.7 and 366.2 mA/cm2 at 0.7 V for H2/air and H2/O2, respectively. The accelerated stress tests (ASTs) showed superior durability of the Pt/MPTO catalyst as a cathode electrode. After 10,000 cycles of high-voltage cycling test from 0.9 V and 1.3 V RHE, no significant performance degradation of the Pt/MPTO electrode was observed comparing with Pt/C. Thus, MPTOs can be considered as a good substitute of carbon supports in fuel cells.
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http://dx.doi.org/10.1166/jnn.2015.10549DOI Listing
September 2015

Imaging findings of desmoplastic fibroma rarely involving the clavicle: case report.

Korean J Radiol 2014 Jan-Feb;15(1):130-3. Epub 2014 Jan 8.

Department of Pathology, Wonkwang University School of Medicine & Hospital, Iksan 570-749, Korea.

Desmoplastic fibroma of bone is a rare locally aggressive, but non-metastatic tumor. In this case report, we present a desmoplastic fibroma in an unusual location, the clavicle. Desmoplastic fibroma involving the clavicle is extremely rare, with only 2 reported cases before 1985. We report the imaging findings of a desmoplastic fibroma of the clavicle with a review of the relevant literature.
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http://dx.doi.org/10.3348/kjr.2014.15.1.130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3909845PMC
April 2014
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