https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/250 2026-04-04T08:31:23Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/211015 Title: Bypassing Pt(100)-O*OH* deactivation sites via superb ionomer network towards ultra-stable stationary fuel cells Authors: Choi, Hyunguk; Choi, Won Young; Choi, Seo Won; Park, Young Je; Lee, Nam Jin; Myung, Kwang Shik; Jung, Jae Young; Lee, Jong Min; Ko, Min Jae; Jung, Chi-Young Abstract: Understanding the voltage degradation under long-term continuous operation is essential for deploying highly stable polymer electrolyte fuel cell (PEFC) in stationary applications, e.g. artificial intelligence (AI) data centers. Here, we identify that Pt(100) surfaces, one of the dominant planes in polycrystalline Pt, are gradually covered by O*OH* species at E = 0.708 VRHE, based on chronoamperometry experiments coupled with density functional theory calculations. This coverage elevates the O*OH*→H2O barrier and significantly aggravates the oxygen reduction reaction (ORR) kinetics. Guided by this insight, the ORR electrode is constructed with a highly connected network of perfluorinated sulfonic acid ionomer, which is beneficial in bypassing O*OH* sites while maintaining sufficient porosity for O2 transport. Firstly, the short-side-chain ionomers with different ion exchange capacities (IECs) are mixed with Pt/C to reach the adsorbed ionomer-to-carbon ratios ranging from 0.034 to 0.076, then after the selective isolation of adsorbed ionomers, the desired amount of ionomer with higher IEC is added to create a highly connected network of non-adsorbed ionomers. Electrode slurries are characterized both qualitatively and quantitatively by using rheometer and thermogravimetric analyzer, respectively. The optimized membrane electrode assembly (MEA) results in a cell voltage higher than 0.71 V at 0.5 A·cm−2, with an unprecedented low decay rate of 10 µV·h−1 over 400 h, that is 4-fold lower than the state-of-the-art commercial MEA. Based on these findings, the rises of both electrode ionomer coverage and connectivity vitalize PEFC to offer a sustainable off-grid solution for ever-growing electricity demands in the current AI challenge. 2026-07-01T00:00:00Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/210923 Title: NiCe@SiO2 core-shell-structured catalyst for an enhanced thermal stability for dry reforming of CH4 with CO2 Authors: Kwon, Jae Hyeon; Lee, Sooin; Park, Kyung Soo; Soh, Byoung-Whan; Kim, Kyeounghak; Bae, Jong Wook Abstract: Dry reforming of methane with CO<inf>2</inf> (DRM) is an environmentally beneficial route to convert two major greenhouse gases into synthesis gas (syngas), contributing to an environmentally sustainable carbon cycle, which are generally suffered from significant catalyst deactivations through coke depositions and aggregations of active metal nanoparticles. To solve those intrinsic deactivation phenomena during the harsh DRM reaction conditions, a simple encapsulation strategy of typical Ni-CeO<inf>2</inf> core-side nanoparticles within inert silica shells at an optimal Ni/Ce ratio is proposed and it is found to be effective in preventing those aggregations of active metal nanoparticles with insignificant coke depositions. The stably preserved crystallite sizes of Ni nanoparticles even after a high-temperature DRM reaction, and oxygen vacant sites formed on the CeO<inf>2</inf> metal oxide promoter were responsible for an enhanced catalytic activity and stability by mitigating strong metal–support interactions with silica shells as well as by increasing CO<inf>2</inf> activation activity on the electron-rich Ni-CeO<inf>2</inf> interfaces as supported by DFT calculation results. The CeO<inf>2</inf>-promoted NiCe@SiO₂ catalyst at an optimal Ce/Ni molar ratio of 0.5 – 1.0 exhibited an improved DRM reaction activity and long-term stability, which were attributed to the highly dispersed active metallic Ni nanoparticles decorated with the CeO<inf>2</inf> metal oxides by enhancing CH<inf>4</inf> decomposition as well as successive CO<inf>2</inf> dissociation with the help of SiO<inf>2</inf> protective overlayers through effective suppression of coke formation and metal aggregation. 2026-06-01T00:00:00Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/211923 Title: Photo-induced crystallization of metal-organic chalcogenide films for large-area photodetector arrays Authors: Bae, Sang Woo; Jang, Eun-Ji; Nam, Sang Hyun; Chin, Sang-Hyun; Lee, Kyeong Ho; Kim, Min Ku; Yeom, Bongjun; Kim, Yongju; Jang, Jaeyoung; Yi, Yeonjin; Kim, Young-Hoon Abstract: Metal–organic chalcogenides have emerged as a promising class of semiconductors due to their tunable optoelectronic properties and solution processability. However, the formation of thin film and integration into optoelectronic devices remain challenging. Here, we report a photo-induced crystallization strategy for fabricating silver phenylselenolate (AgSePh) films directly from Ag and Ph2Se2 precursors under ultraviolet (UV) irradiation. In this process, surface oxidation of Ag and the homolytic cleavage of Ph2Se2, both are induced by UV irradiation, synergistically generate Ag+and PhSe-species, which subsequently couple to form uniform AgSePh thin film. Based on this thin film, we for the first time demonstrate AgSePh-based diode-type photodetectors exhibiting efficient photoresponse, achieving a detectivity of 3.58 × 1011Jones at 450 nm. Moreover, we fabricate a large-area (81 cm2) AgSePh thin film and demonstrate the passive-matrix image sensors comprising of 100 photodetector pixels. Our work provides a facile route for producing stable AgSePh films and demonstrate the potential of metal-organic chalcogenides in next-generation optoelectronic devices. 2026-05-01T00:00:00Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/211539 Title: Dynamic control of the three-phase boundary in hydrogel assisted TiO₂-Graphdiyne photocatalysts for Ammonia production Authors: Lee, Hyeran; Han, Yujin; Jo, Yeseul; Mjuli, Michael Boniface; Kim, Hyejeong; Jang, Youn Jeong Abstract: Producing NH3 via photocatalytic N2 reduction requires an ideal three-phase boundary (TPB) among N2 (gas), H2O (liquid), and a catalyst (solid). A promising strategy for developing TPB system involves photocatalyst passivation with temperature-responsive hydrogels that reversibly switch hydrophilic–hydrophobic characteristics. In this study, a self-controlling TPB system that combines a TiO2/graphdiyne photocatalyst with poly(N-isopropylacrylamide) (TiO2/GDY@PNIPAm) is explored. TiO2/GDY offers excellent solar absorption characteristics, efficient charge separation at the heterojunction, and abundant active sites for N2 reduction. Owing to a unique photothermal effect, TiO2/GDY generates a local temperature increase (39.5 °C) under irradiation. The temperature-responsive PNIPAm, utilized as an adaptive porous framework, enables dynamic regulation of interfacial wettability and gas transport within the TPB microenvironment through its hydrophilic–hydrophobic transition, thereby promoting selective N2 transport while inhibiting H2O transport. Under solar-light irradiation, the room temperature NH3 production rate of TiO2/GDY@PNIPAm (59.5 μmol/gh) exceeds that of TiO2 (0.46 μmol/gh). These findings provide valuable insights into photocatalyst design and local environment optimization using stimuli-responsive hydrogels toward green NH3 production. 2026-04-01T00:00:00Z