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53. Advanced electrocatalysts with unusual active sites for electrochemical water splitting.

Author

Sun, Hainan, Xu, Xiaomin, Kim, Hyunseung, Shao, Zongping, and Jung, WooChul

Subjects
ELECTROCATALYSTS, HYDROGEN evolution reactions, STRUCTURE-activity relationships, TRANSITION metals, HYDROGEN production
Abstract

Electrochemical water splitting represents a promising technology for green hydrogen production. To design advanced electrocatalysts, it is crucial to identify their active sites and interpret the relationship between their structures and performance. Materials extensively studied as electrocatalysts include noble‐metal‐based (e.g., Ru, Ir, and Pt) and non‐noble‐metal‐based (e.g., 3d transition metals) compounds. Recently, advancements in characterization techniques and theoretical calculations have revealed novel and unusual active sites. The present review highlights the latest achievements in the discovery and identification of various unconventional active sites for electrochemical water splitting, with a focus on state‐of‐the‐art strategies for determining true active sites and establishing structure–activity relationships. Furthermore, we discuss the remaining challenges and future perspectives for the development of next‐generation electrocatalysts with unusual active sites. By presenting a fresh perspective on the unconventional reaction sites involved in electrochemical water splitting, this review aims to provide valuable guidance for the future study of electrocatalysts in industrial applications. [ABSTRACT FROM AUTHOR]

Published
2024
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54. Simultaneous Performance and Stability Enhancement in Intermediate Temperature Solid Oxide Fuel Cells by Powder‐Atomic Layer Deposited LSCF@ZrO2 Cathodes.

Author

Jo, Sung Eun, Jeon, SungHyun, Kim, Hyong June, Yang, Byung Chan, Ju, Kyoungjae, Gür, Turgut M., Jung, WooChul, and An, Jihwan

Subjects
SOLID oxide fuel cells, SOLID oxide fuel cell electrodes, POROUS electrodes, CATHODES, ATOMIC layer deposition, ENERGY conversion
Abstract

Employing porous structures is essential in high‐performance electrochemical energy devices. However, obtaining uniform functional coatings on high‐tortuosity structures can be challenging, even with specialized processes such as atomic layer deposition (ALD). Herein, a novel method for achieving a porous composite electrode for solid oxide fuel cells by coating La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) powders with ZrO2 using a powder ALD process is presented. Unlike conventional ALD, powder ALD can be used to fabricate extremely uniform coatings on porous electrodes with a thickness of tens of micrometers. The powder ALD ZrO2 coating is found to effectively suppress chemical degradation of the LSCF electrodes. The cell with the powder ALD coated cathode shows a 2.2 times higher maximum power density and 60% lower thermal degradation in activation resistance than the bare LSCF cathode cell at 700–750 °C. The result demonstrated in this study is expected to have significant implications for high‐performance and durable electrodes in energy conversion/storage devices. [ABSTRACT FROM AUTHOR]

Published
2024
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56. Imparting Metal Oxides with High Sensitivity Toward Light‐Activated NO2 Detection Via Tailored Interfacial Chemistry (Adv. Funct. Mater. 17/2023)

Author

Park, Seyeon, primary, Jeon, SungHyun, additional, Kim, Honghui, additional, Philips, James, additional, Oh, DongHwan, additional, Ahn, Jaewan, additional, Kim, Minhyun, additional, Park, Chungseong, additional, Hong, Seungbum, additional, Kim, Jihan, additional, Jung, WooChul, additional, and Kim, Il‐Doo, additional

Published
2023
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61. Advances in Materials and Interface Understanding in Protonic Ceramic Fuel Cells.

Author

Tsvetkov, Nikolai, Kim, Dongyeon, Jeong, Incheol, Kim, Jun Hyuk, Ahn, Sejong, Lee, Kang Taek, and Jung, WooChul

Subjects
ENERGY conversion, CERAMIC materials, SOLID oxide fuel cells, CHARGE exchange, ELECTRODES
Abstract

Protonic ceramic fuel cells (PCFCs) are promising eco‐energy electrochemical energy conversion systems that can efficiently operate in intermediate (500–700 °C) to low (500 °C) temperature ranges. In this review the most recent advances in materials research for the ceramic components of PCFCs (i.e., electrolyte, cathode, and anode) and their interface engineering are introduced. Recent approaches to improve the protonic of conductivity, and activity and stability of electrolyte and electrode materials are first presented. In addition, new attempts to stabilize/activate electrode/electrolyte interfaces and electrode surfaces are also discussed. Details of the theoretical background behind the electron and ion transfer processes at electrodes are also discussed. Finally, the challenges and perspectives of PCFC development are suggested from the point of view of materials engineering. [ABSTRACT FROM AUTHOR]

Published
2023
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81. An Event Detection Service for Spatio-temporal Applications

Author

Jung, WooChul, Lee, DaeRyung, Lee, WonIl, Mitchell, Stella, Munson, Jonathan, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Carswell, James D., editor, and Tezuka, Taro, editor

Published
2006
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87. Hierarchical Structure of CuO Nanowires Decorated with Ni(OH)2 Supported on Cu Foam for Hydrogen Production via Urea Electrocatalysis

Author

Sun, Hainan, Liu, Jiapeng, Chen, Gao, Kim, Hyunseung, Kim, Sangwoo, Hu, Zhiwei, Chen, Jin‐Ming, Haw, Shu‐Chih, Ciucci, Francesco, Jung, WooChul, Sun, Hainan, Liu, Jiapeng, Chen, Gao, Kim, Hyunseung, Kim, Sangwoo, Hu, Zhiwei, Chen, Jin‐Ming, Haw, Shu‐Chih, Ciucci, Francesco, and Jung, WooChul

Abstract

Owing to the low theoretical potential of the urea oxidation reaction (UOR), urea electrolysis is an energy-saving technique for the generation of hydrogen. Herein, a hierarchical structure of CuO nanowires decorated with nickel hydroxide supported on 3D Cu foam is constructed. Combined theoretical and experimental analyses demonstrate the high reactivity and selectivity of CuO and Ni(OH)2 toward the UOR instead of the oxygen evolution reaction. The hierarchical structure creates a synergistic effect between the two highly active sites, enabling an exceptional UOR activity with a record low potential of 1.334 V (vs the reversible hydrogen electrode) to reach 100 mA cm−2 and a low Tafel slope of 14 mV dec−1 in 1 m KOH and 0.5 m urea electrolyte. Assembling full urea electrolysis driven by this developed UOR electrocatalyst as the anode and a commercial Pt/C electrocatalyst as the cathode provides a current density of 20 mA cm−2 at a cell voltage of ≈1.36 V with promising operational stability for at least 150 h. This work not only enriches the UOR material family but also significantly advances energy-saving hydrogen production.

Published
2022

88. Ni-Doped CuO Nanoarrays Activate Urea Adsorption and Stabilizes Reaction Intermediates to Achieve High-Performance Urea Oxidation Catalysts

Author

Sun, Hainan, Liu, Jiapeng, Kim, Hyunseung, Song, Sanzhao, Fei, Liangshuang, Hu, Zhiwei, Lin, Hong-Ji, Chen, Chien-Te, Ciucci, Francesco, Jung, WooChul, Sun, Hainan, Liu, Jiapeng, Kim, Hyunseung, Song, Sanzhao, Fei, Liangshuang, Hu, Zhiwei, Lin, Hong-Ji, Chen, Chien-Te, Ciucci, Francesco, and Jung, WooChul

Abstract

Urea oxidation reaction (UOR) with a low equilibrium potential offers a promising route to replace the oxygen evolution reaction for energy-saving hydrogen generation. However, the overpotential of the UOR is still high due to the complicated 6e− transfer process and adsorption/desorption of intermediate products. Herein, utilizing a cation exchange strategy, Ni-doped CuO nanoarrays grown on 3D Cu foam are synthesized. Notably, Ni-CuO NAs/CF requires a low potential of 1.366 V versus a reversible hydrogen electrode to drive a current density of 100 mA cm−2, outperforming various benchmark electrocatalysts and maintaining robust stability in alkaline media. Theoretical and experimental studies reveal that Ni as the driving force center can effectively enhance the urea adsorption and stabilize CO*/NH* intermediates toward the UOR. These findings suggest a new direction for constructing nanostructures and modulating electronic structures, ultimately developing promising Cu-based electrode catalysts.

Published
2022

89. Understanding and mitigating A-site surface enrichment in Ba-containing perovskites: a combined computational and experimental study of BaFeO3

Author

Liu, Jiapeng, Kim, Jun Kyu, Wang, Yuhao, Kim, Hyunseung, Belotti, Alessio, Koo, Bonjae, Wang, Zheng, Jung, WooChul, Ciucci, Francesco, Liu, Jiapeng, Kim, Jun Kyu, Wang, Yuhao, Kim, Hyunseung, Belotti, Alessio, Koo, Bonjae, Wang, Zheng, Jung, WooChul, and Ciucci, Francesco

Abstract

BaFeO3-Based perovskites are promising cathode materials for intermediate-temperature solid oxide fuel cells and protonic ceramic fuel cells due to their high electrocatalytic activity. However, during operation Ba has been observed to segregate towards the surface of these materials, deteriorating the activity. Herein, the surface of BaFeO3-based materials is studied using both density functional theory and strain-controlled epitaxial thin films. The results suggest that the surface Ba concentration can be controlled by tensile strain or by substituting Fe with a larger cation. Specifically, first-principles calculations suggest that the surface with low Ba content (i.e. (110)BaFeO), stabilizes when a biaxial tensile strain is applied, in agreement with the decreased surface Ba concentration observed in tensilely strained Ba0.95La0.05FeO3-delta thin films. As verified by simulations and experiments, substituting the Fe with the larger Zr cations also strains the material tensilely, thereby lowering Ba surface concentration. Further analysis suggests that stretching the Ba-O bond can strengthen the interaction between Ba and O and increase the energy required to form Ba vacancies in bulk, thereby reducing surface enrichment. Electrical conductivity relaxation and electrochemical impedance spectroscopy tests demonstrated that surface oxygen exchange kinetics is enhanced by introducing Zr into Ba0.95La0.05FeO3-delta. Zr-Substituted Ba0.95La0.05FeO3-delta is also shown to work effectively as a cathode for full solid oxide and proton ceramic fuel cells achieving high performance in the 600 to 850 degrees C range. This work explains how the surface composition of BaFeO3-based perovskites can be adjusted by lattice strain and cationic substitution, paving the way for the rational design of ceramic fuel cell cathode materials with enhanced performance.

Published
2022

90. Imparting Metal Oxides with High Sensitivity Toward Light‐Activated NO2 Detection Via Tailored Interfacial Chemistry.

Author

Park, Seyeon, Jeon, SungHyun, Kim, Honghui, Philips, James, Oh, DongHwan, Ahn, Jaewan, Kim, Minhyun, Park, Chungseong, Hong, Seungbum, Kim, Jihan, Jung, WooChul, and Kim, Il‐Doo

Subjects
GAS detectors, SURFACE chemistry, CHEMICAL reactions, METALLIC surfaces, METAL activation, LIGHT metals, METALLIC oxides
Abstract

Activation of metal oxides by light is a robust yet facile approach to manipulating their surface chemistry for favorable reactions with target molecules in heterogeneous catalysis and gas sensors. However, a limited understanding of interface chemistry and the involved mechanism impedes the development of a rational design of oxide interfaces for light‐activated gas sensing. Herein, the TiOx‐assisted photosensitization of In2O3 toward NO2 sensing is investigated as a case study to elucidate the detailed mechanism of light‐activated surface chemistry at the metal/gas interface. The resultant heterogeneous oxides exhibit outstanding NO2 sensing performance under light irradiation thanks to abundant photoexcited electrons and holes that serve as adsorption and desorption sites, respectively, to accelerate both surface reactions. Furthermore, the facile transfer of electrons and holes across the TiOx‐In2O3 interface contributes to improving the reversibility of sensing kinetics. Through this study, the mechanistic understanding is established of how the surface chemistry of metal oxide surfaces can be tuned by light activation providing an effective route to the design fabrication of high‐performance gas sensors. [ABSTRACT FROM AUTHOR]

Published
2023
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