| 1. |
Eiki Niwa, Maksymilian Kluczny, Hyo Young Kim, Jun Tae Song, Motonori Watanabe, Atsushi Takagaki, Tatsumi Ishihara, Proton conductivity in Yb-doped BaZrO3-based thin film prepared by pulsed laser deposition, SOLID STATE IONICS, 10.1016/j.ssi.2023.116240, 396, 2023.08.  |
| 2. |
Yuta Takaoka, Jun Tae Song, Atsushi Takagaki, Motonori Watanabe, Tatsumi Ishihara, Bi/UiO-66-derived electrocatalysts for high CO2-to-formate conversion rate, Applied Catalysis B: Environmental, 326, 122400, 2023.06. |
| 3. |
Nuttavut Kosem, Motonori Watanabe, Jun Tae Song, Atsushi Takagaki, Tatsumi Ishihara, A comprehensive study on the rational biocatalysts and individual components of photobiocatalytic H2 production system, Applied Catalysis A: General, 651, 1190195, 2023.02. |
| 4. |
Xiao-Feng Shen, Motonori Watanabe, Atsushi Takagaki, Jun Tae Song, Tatsuki Abe, Daisuke Kawaguchi, Keiji Tanaka, Tatsumi Ishihara, Pyridyl anchoring squaraine as a near-infrared dye sensitizer for effective sensitized hydrogen production over a titanium dioxide photocatalyst in water medium, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 10.1007/s00339-022-06281-7, 129, 1, 2023.01. |
| 5. |
Tatsumi Ishihara, Zhe Tan, Jun Tae Song, Atsushi Takagaki, Sequential-infiltration of Ce and Ni in NiO-YSZ fuel electrode for tubular type solid oxide reversible cells (SORC) using LaGaO3 electrolyte film, SOLID STATE IONICS, 10.1016/j.ssi.2022.115914, 379, 2022.06. |
| 6. |
Atsushi Takagaki, Shohei Nakamura, Shu Ashimura, Masaaki Yoshida, Jun Tae Song, Motonori Watanabe, Shigenobu Hayashi, Tatsumi Ishihara, Mixing nitrogen-containing compounds for synthesis of porous boron nitride for improved porosity, surface functionality, and solid base catalytic activity, APPLIED CATALYSIS A-GENERAL, 10.1016/j.apcata.2022.118635, 638, 2022.05. |
| 7. |
Maksymilian Kluczny, Jun Tae Song, Taner Akbay, Eiki Niwa, Atsushi Takagaki, Tatsumi Ishihara, Sillén–Aurivillius phase bismuth niobium oxychloride, Bi4NbO8Cl, as a new oxide-ion conductor, Journal of Materials Chemistry A, 10.1039/d1ta07335d, 10, 5, 2550-2558, 2022.03. |
| 8. |
Rauf Khan, Muhamad Affiq Bin Misran, Michitaka Ohtaki, Jun Tae Song, Tatsumi Ishihara, Reiji Hattori, Back-channel etched In-Ga-Zn-O Thin-film Transistor utilizing Selective Wet-Etching of Copper Source and Drain, Processes, 2021.12. |
| 9. |
Tatsumi Ishihara, Syuaibatul Islamiyah, Maksymilian Kluczny, Jun Tae Song, Atsushi Takagaki, PrBaCo2O5+δ-Sm0.5Sr0.5CoO3 Composite Oxide as Active Cathode for Intermediate-Temperature Solid Oxide Fuel Cells, ECS Transactions, 103, 1425, 2021.08. |
| 10. |
Osamu Iwanaga, Kazuki Fukuyama, Shigeki Mori, Jun Tae Song, Tatsumi Ishihara, Takaaki Miyazaki, Masatoshi Ishida, Hiroyuki Furuta, Ruthenium(iv) N-confused porphyrin μ-oxo-bridged dimers: acid-responsive molecular rotors, RSC Advances, 11, 24575, 2021.07. |
| 11. |
Zhe Tan, Jun Tae Song, Atsushi Takagaki, Tatsumi Ishihara, Infiltration of cerium into a NiO–YSZ tubular substrate for solid oxide reversible cells using a LSGM electrolyte film, Journal of Materials Chemistry A, 10.1039/d0ta08564b, 9, 3, 1530-1540, 2021.01. |
| 12. |
Yoonyoung Kim, Motonori Watanabe, Junko Matsuda, Jun Tae Song, Atsushi Takagaki, Aleksandar Staykov, Tatsumi Ishihara, Tensile strain for band engineering of SrTiO3 for increasing photocatalytic activity to water splitting, APPLIED CATALYSIS B-ENVIRONMENTAL, 10.1016/j.apcatb.2020.119292, 278, 2020.12, SrTiO3 is a well-known highly active photocatalyst with high energy conversion efficiency. In this study, we investigated the formation of oxygen vacancy by using the chemo-mechanical effect that was introduced by the dispersion of metal particles into grain and photocatalytic activity to water splitting. Au dispersion on SrTiO3 followed by sintering treatment was studied for introduction of chemo-mechanical strain because of a different thermal expansion coefficient; the introduced chemo-mechanical strain generated oxygen vacancy in SrTiO3. Thus, induced chemo-mechanical strain shows change in electronic band structure resulting in increasing lowest unoccupied molecular orbital (LUMO) level with increasing Au content. Since photoluminescence was significantly decreased by sintering after Au dispersion, the introduced strain effects may work for increasing a charge separation efficiency and adsorption site in water splitting. Therefore, the photocatalytic activity was much increased by sintering treatment after Au dispersion on SrTiO3.. |
| 13. |
Hakhyeon Song, Jun Tae Song, Beomil Kim, Ying Chuan Tan, Jihun Oh, Activation of C2H4 reaction pathways in electrochemical CO2 reduction under low CO2 partial pressure, APPLIED CATALYSIS B-ENVIRONMENTAL, 10.1016/j.apcatb.2020.119049, 272, 2020.09, Selective conversion of CO2 to fuels and chemicals has been considered one of the key challenges in the electrochemical CO2 reduction reaction (CO2RR). Here, we demonstrate the reaction pathways for CO and C2H4 formation on Cu can be regulated by supplying different CO2 partial pressures. Although it is believed high concentration of surface bound CO is required for C2H4 formation, we show excessive supply of CO2 interferes with C-C coupling and suppress C2H4 reaction pathways. This indicates C2H4 reaction pathways are limited by the surface recombination of surface bound CO and hydrogen, and the kinetics is affected by adsorbate-adsorbate interactions and/or by physical blocking of active sites on Cu with excess CO2. Through systematic study, we demonstrate a dilute CO2 stream selectively activates C2H4 formation with significant reduction of the overpotentials (similar to 400 mV) to achieve similar to 50% C2H4 Faradaic efficiency and enhancement in the C2H4 current density (similar to 50 mA cm(-2)).. |
| 14. |
Jaehoon Kim, Jun Tae Song, Jihun Oh, Facile electrochemical synthesis of dilute AuCu alloy nanostructures for selective and long-term stable CO2 electrolysis, JOURNAL OF CHEMICAL PHYSICS, 10.1063/5.0009340, 153, 5, 2020.08, Electrochemical CO production from CO2 electrolysis has been considered the most economically viable approach among various candidate products. AuCu bimetallic alloys are currently receiving attention for their potential to tailor catalytic activity. Here, we synthesized a dilute AuCu alloy nanostructure with an AuCu atomic composition ratio of 3% by using a simple electrochemical treatment method on a 200 nm-thick Au thin film. The dilute AuCu alloy catalyst shows an exceptional CO2 reduction activity in terms of selectivity and overpotential for CO production. In addition, the stability property is more significantly enhanced as compared to pure Au nanostructures. In addition, we describe an in situ tailoring method of catalytic activity for Au nanostructures by repeating an electrochemical treatment process that is performed for forming the Au nanostructure. This approach will be a promising and facile strategy not only for reactive Au catalysts but also to increase the stability activity simultaneously by utilizing Cu impurities existing in an aqueous electrolyte for CO2 reduction.. |
| 15. |
Siman Fang, Atsushi Takagaki, Motonori Watanabe, Jun Tae Song, Tatsumi Ishihara, Scandium and copper co-doping effect on stability and activity to the NO direct decomposition of Ba3Y4O9, APPLIED CATALYSIS A-GENERAL, 10.1016/j.apcata.2020.117743, 602, 2020.07, Direct decomposition of NO on Ba3Y4O9 doped with Cu and Sc was studied and it was found that co-doping of Sc and Cu into Ba3Y4O9 was effective for increasing both lattice stability and NO decomposition activity. In particular, Ba3Y3Sc0.6Cu0.4O9 (10 % Cu and 15 % Sc doping) catalyst showed N-2 and O-2 yield of 90 % and 99 %, respectively, in NO decomposition reaction at 700 degrees C. Comparing with the pristine and single-metal doped system, the optimized catalyst showed superior long-term stability and increased activity under O-2, and water vapor co-existence conditions because of the increased stability of crystal structure, improved lattice oxygen mobility and weakened oxygen adsorption on the surface. TPD and in-situ FT-IR results suggested that the co-doping effect was assigned to the easier removal of surface NO2- or NO3- species which blocks the active site to NO decomposition.. |
| 16. |
Xiao-Feng Shen, Motonori Watanabe, Atsushi Takagaki, Jun Tae Song, Tatsumi Ishihara, Pyridyl-Anchored Type BODIPY Sensitizer-TiO2 Photocatalyst for Enhanced Visible Light-Driven Photocatalytic Hydrogen Production, CATALYSTS, 10.3390/catal10050535, 10, 5, 2020.05, Dye-sensitized photocatalytic hydrogen production using a boron-dipyrromethene (BODIPY) organic material having a pyridyl group at the anchor site was investigated. Phenyl, carbazole, and phenothiazine derivatives were introduced into BODIPY dyes, and their photocatalytic activities were examined. Identification was performed by nuclear magnetic resonance (NMR), infrared (IR), mass (MS) spectra, and absorption spectra, and catalyst evaluation was performed by using visible-light irradiation and photocatalytic hydrogen production and photocurrent. These dyes have strong absorption at 600-700 nm, suggesting that they are promising as photosensitizers. When the photocatalytic activity was examined, stable catalytic performance was demonstrated, and the activity of the Pt-TiO(2)photocatalyst carrying a dye having a carbazole group was 249 mu mol/g(cat)center dot h. Photocurrent measurements suggest that dye-sensitized photocatalytic activity is occurring. This result suggests that BODIPY organic materials with pyridyl groups as anchor sites are useful as novel dye-sensitized photocatalysts.. |
| 17. |
Chitiphon Chuaicham, Sekar Karthikeyan, Radheshyam R. Pawar, Yihuang Xiong, Ismaila Dabo, Bunsho Ohtani, Yoonyoung Kim, Jun Tae Song, Tatsumi Ishihara, Keiko Sasaki, Energy-resolved distribution of electron traps for O/S-doped carbon nitrides by reversed double-beam photoacoustic spectroscopy and the photocatalytic reduction of Cr(vi), CHEMICAL COMMUNICATIONS, 10.1039/c9cc09988c, 56, 26, 3793-3796, 2020.04, We report for the first time to our knowledge the identification of heteroatom-doped and undoped C3N4 with the energy-resolved distribution of electron traps (ERDT) near the conduction band bottom position (CBB) using reversed double-beam photoacoustic spectroscopy. The ERDT/CBB pattern is used to classify the type of elemental doping in C3N4, related to photocatalytic efficiency.. |
| 18. |
Gayea Hyun, Jun Tae Song, Changui Ahn, Youngjin Ham, Donghwi Cho, Jihun Oh, Seokwoo Jeon, Hierarchically porous Au nanostructures with interconnected channels for efficient mass transport in electrocatalytic CO2 reduction, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 10.1073/pnas.1918837117, 117, 11, 5680-5685, 2020.03, Electrocatalytic CO2 reduction is a promising way to provide renewable energy from gaseous CO2. The development of nanostructures improves energy efficiency and selectivity for value-added chemicals, but complex nanostructures limit the CO2 conversion rates due to poor mass transport during vigorous electrolysis. Herein, we propose a three-dimensional (3D) hierarchically porous Au comprising interconnected macroporous channels (200-300 nm) and nanopores (similar to 10 nm) fabricated via proximity-field nanopatterning. The interconnected macropores and nanopores enable efficient mass transport and large active areas, respectively. The roles of each pore network are investigated using reliable 3D nanostructures possessing controlled pore distribution and size. The hierarchical nanostructured electrodes show a high CO selectivity of 85.8% at a low overpotential of 0.264 V and efficient mass activity that is maximum 3.96 times higher than that of dealloyed nanoporous Au. Hence, the systematic model study shows the proposed hierarchical nanostructures have important value in increasing the efficiency of expensive Au.. |
| 19. |
Beomil Kim, Hoeun Seong, Jun Tae Song, Kyuju Kwak, Hakhyeon Song, Ying Chuan Tan, Gibeom Park, Dongil Lee, Jihun Oh, Over a 15.9% Solar-to-CO Conversion from Dilute CO2 Streams Catalyzed by Gold Nanoclusters Exhibiting a High CO2 Binding Affinity, ACS ENERGY LETTERS, 10.1021/acsenergylett.9b02511, 5, 3, 749-757, 2020.03, Development of efficient and selective electro-catalysts is a key challenge to achieve an industry-relevant electrochemical CO2 reduction reaction (CO2RR) to produce commodity chemicals. Here, we report that Au-25 clusters with Authiolate staple motifs can initiate electrocatalytic reduction of CO2 to CO with nearly zero energy loss and achieve a high CO2RR current density of 540 mA cm(-2) in a gas-phase reactor. Electrochemical kinetic investigations revealed that the high CO2RR activity of the Au-25 originates from the strong CO2 binding affinity, leading to high CO2 electrolysis performance in both concentrated and dilute CO2 streams. Finally, we demonstrated an 18.0% solar-to-CO conversion efficiency using a Au-25 electrolyzer powered by a Ga0.5In0.5P/GaAs photovoltaic cell. The electrolyzer also showed 15.9% efficiency and a 5.2% solar-driven single-path CO2 conversion rate in a 10% CO2 gas stream, the CO2 concentration in a typical flue gas.. |
| 20. |
Chitiphon Chuaicham, Sekar Karthikeyan, Jun Tae Song, Tatsumi Ishihara, Bunsho Ohtani, Keiko Sasaki, Importance of ZnTiO3 Phase in ZnTi-Mixed Metal Oxide Photocatalysts Derived from Layered Double Hydroxide, ACS APPLIED MATERIALS & INTERFACES, 10.1021/acsami.9b18785, 12, 8, 9169-9180, 2020.02, In this study, ZnTi-mixed metal oxides (ZTM), such as ZnTiO3, were synthesized from ZnTi layered double hydroxides by varying the molar ratio of Zn/Ti, calcination temperatures, and synthesis methods (hydrothermal or reflux). The surface electronic characteristics of ZTM were investigated by the energy-resolved distribution of electron traps (ERDTs) using reversed double-beam photoacoustic spectroscopy. The ZTM samples obtained by conducting hydrothermal synthesis at 500 degrees C showed similar ERDT patterns independent of the molar ratio of Zn/Ti, although ZnTiO3 phase was not observed in the X-ray diffraction pattern, when the Zn/Ti ratio was high. When the ERDT patterns demonstrated a high electron accumulation level near the conduction band bottom in hydrothermal products at 500 degrees C, a higher photocatalytic phenol degradation efficiency was observed due to the formation of ZnTiO3 phase. This suggested that the product with the high Zn/Ti molar ratio (Zn/Ti = 6) constituted amorphous ZnTiO3.The enhanced photocatalytic performance of ZTM could be attributed to the heterojunction of electrons among ZnO, TiO2, and ZnTiO3, which enabled electron transfer in the composites, prevented charge recombination, and promoted a wider visible light adsorption by ZnTiO3 phase irrespective of its crystallinity.. |
| 21. |
Jun Tae Song, Hakhyeon Song, Beomil Kim, Jihun Oh, Towards Higher Rate Electrochemical CO2 Conversion: From Liquid-Phase to Gas-Phase Systems, CATALYSTS, 10.3390/catal9030224, 9, 3, 2019.03, Electrochemical CO2 conversion offers a promising route for value-added products such as formate, carbon monoxide, and hydrocarbons. As a result of the highly required overpotential for CO2 reduction, researchers have extensively studied the development of catalyst materials in a typical H-type cell, utilizing a dissolved CO2 reactant in the liquid phase. However, the low CO2 solubility in an aqueous solution has critically limited productivity, thereby hindering its practical application. In efforts to realize commercially available CO2 conversion, gas-phase reactor systems have recently attracted considerable attention. Although the achieved performance to date reflects a high feasibility, further development is still required in order for a well-established technology. Accordingly, this review aims to promote the further study of gas-phase systems for CO2 reduction, by generally examining some previous approaches from liquid-phase to gas-phase systems. Finally, we outline major challenges, with significant lessons for practical CO2 conversion systems.. |
| 22. |
Sangwoo Ryu, Hyung Cheoul Shim, Jun Tae Song, Ilhwan Kim, Hyewon Ryoo, Seungmin Hyun, Jihun Oh, High-Pressure Evaporation-Based Nanoporous Black Sn for Enhanced Performance of Lithium-Ion Battery Anodes, PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, 10.1002/ppsc.201800331, 36, 1, 2019.01, Increasing the surface area to improve chemical activity is an unending task from conventional catalysis to recently emerging electrochemical energy conversion and storage. Here, a simple, vacuum-deposition-based method to form nanoporous structures of metals is reported. By utilizing thermal evaporation at a high pressure, fractal-like nanoporous structures of Sn with porosity exceeding 98% are synthesized. The obtained nanostructure consists of nanoparticle aggregates, and the morphology can be controlled by adjusting the working pressure. The formation of the nanoporous structure is explained by homogeneous nucleation and diffusion-limited aggregation, where nanoparticles produced by the repeated collisions of evaporated atoms adhere to the substrate without diffusion, forming porous aggregates. Due to the easy oxidation of Sn, the constituent nanoparticles are covered with amorphous SnOx and crystalline SnO phases. When the nanoporous Sn/SnOx aggregates are applied to a lithium-ion battery anode through direct deposition on a Cu foil current collector without binders or conducting additives, the nanoporous Sn/SnOx anode shows greatly enhanced cyclability and exceptional rate performance compared to those of a dense Sn thin film anode. The approach investigated in this work is expected to provide a new platform to other fields that require highly porous structures.. |
| 23. |
Seungtaeg Oh, Soonyoung Jung, Yong Hwan Lee, Jun Tae Song, Tae Hyun Kim, Dip K. Nandi, Soo-Hyun Kim, Jihun Oh, Hole-Selective CoOx/SiOx/Si Heterojunctions for Photoelectrochemical Water Splitting, ACS CATALYSIS, 10.1021/acscatal.8b03520, 8, 10, 9755-9764, 2018.10, Cobalt oxide (CoOx), an earth-abundant and low-cost oxygen evolving catalyst (OEC), has notable advantages as a top protection layer of photoanodes for solar-driven water oxidation because of its desirable durability. However, cobalt oxides exist as various phases, such as Co(II)O, Co2(III)O3, Co3(II,III)O4, and the (photo)electrochemical properties of CoOx are significantly governed by its phase. Atomic layer deposition (ALD) is a suitable method to form a multifunctional layer for photoelectrochemical (PEC) water splitting because it allows direct growth of a conformal high-quality film on various substrates as well as facile control over its chemical phases by adjusting the deposition conditions. Here, a well-controlled CoOx/SiOx/n-Si heterojunction prepared by ALD is demonstrated for solar-driven water splitting. The phase of the ALD CoOx films can be easily controlled from CoO to Co3O4 by varying the deposition temperature. In addition, this systematic study reveals that its energetic as well as electrochemical properties are changed significantly with the phase. Whereas CoO grown at 150 degrees C produces high photovoltage by building desirable hole-selective heterojunctions with n-Si, Co3O4 formed at 300 degrees C has a better catalytic property for water oxidation. To address this competitive correlation, we developed a double-layered (DL) ALD CoO, film that has advantages of both CoO and Co3O4. The DL ALD CoOx/SiOx/Si heterojunction photoanode produces a photocurrent density of 3.5 mA/cm(2) without a buried junction and maintains a saturating current density of 32.5 mA/cm(2) without noticeable degradation during 12 h in 1 M KOH under a simulated 1 sun illumination.. |
| 24. |
Hakhyeon Song, Mintaek Im, Jun Tae Song, Jung-Ae Lim, Beom-Sik Kim, Youngkook Kwon, Sangwoo Ryu, Jihun Oh, Effect of mass transfer and kinetics in ordered Cu-mesostructures for electrochemical CO2 reduction, APPLIED CATALYSIS B-ENVIRONMENTAL, 10.1016/j.apcatb.2018.03.071, 232, 391-396, 2018.09, Mass transfer, kinetics, and mechanism of electrochemical CO2 reduction have been explored on a model mesostructure of highly-ordered copper inverse opal (Cu-IO), which was fabricated by Cu electrodeposition in a hexagonally-closed packed polystyrene template. As the number of Cu-IO layers increases, the formation of C-2 products such as C2H4 and C2H5OH was significantly enhanced at reduced overpotentials (similar to 200 mV) compared to a planar Cu electrode. At the thickest layer, we observe for the first time the formation of acetylene (C2H2), which can be generated through a kinetically slow reaction pathway and be a key descriptor in the unveiling of the C-C coupling reaction mechanism. Based on our experimental observation, a plausible reaction pathway in Cu mesostructures is rationalized.. |
| 25. |
Jaehoon Kim, Jun Tae Song, Hyewon Ryoo, Jin-Gyu Kim, Sung-Yoon Chung, Jihun Oh, Morphology-controlled Au nanostructures for efficient and selective electrochemical CO2 reduction, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/c8ta01010b, 6, 12, 5119-5128, 2018.03, Electrochemical conversion of CO2 has been considered as a promising method for producing value-added chemicals. Here, we report a systematic study on the formation of Au nanostructures via electroreduction of anodic Au(OH)(3) for selective CO production by an electrochemical CO2 reduction reaction (CO2RR). First, we demonstrate the influence of electrochemical process parameters on the formation of Au nanostructures and Au(OH)(3). The Au nanostructure morphologies can be tuned into either pore-like or pillar-like structures by controlling the anodic potential and/or reduction current density. This distinctive morphology is associated with the electric-field-assisted transport of Au3+ at/near the Au(OH)(3)/Au interface. Additionally, we report the catalytic activity of the morphology-controlled Au nanostructures in the CO2RR. Both Au nanostructures exhibit significantly higher CO selectivity at a low overpotential than the untreated Au film due to the high density of grain boundaries which can assist with faster stabilization of the CO2- intermediate. In particular, the pore-like structures have a higher CO selectivity than the pillar-like ones at 280 mV overpotential although the pillar-like Au nanostructures have a higher CO selectivity and CO producing current density at high overpotentials. This potential-dependent CO2RR performance of the two different Au nanostructures is discussed.. |
| 26. |
Si Woo Lee, Jun Tae Song, Jaehoon Kim, Jihun Oh, Jeong Young Park, Enhanced catalytic activity for CO oxidation by the metal-oxide perimeter of TiO2/nanostructured Au inverse catalysts, NANOSCALE, 10.1039/c7nr08168e, 10, 8, 3911-3917, 2018.02, We report the effect of metal-oxide interfaces on CO oxidation catalytic activity with inverse TiO2-nano-structured Au catalysts. The inverse nanocatalysts were prepared by depositing TiO2 via the liquid-phase immersion method on electrochemically synthesized Au nanostructure supports. The catalytic performance for CO oxidation was investigated using various amounts of Ti (i.e. 0.1-1.0 wt%) on two different morphologies of Au nanostructures (i.e. nanoporous and nanorod). In comparing the different Au morphologies, we found an overall higher TOF and lower activation energy for the TiO2/nanoporous Au than those for the TiO2/nanorod Au. In addition, the CO oxidation activity increased as the Ti content increased up to 0.5 wt% probably due to active TiO2-Au interface sites enhancing CO oxidation via the supply of adsorption sites or charge transfer from TiO2 to Au. However, a higher titania content (i.e. 1.0 wt% TiO2) resulted in decreased activity caused by high surface coverage of TiO2 decreasing the number of TiO2 Au interface sites. These results implied that the perimeter area of the metal-oxide interface played a significant role in determining the catalytic performance for CO oxidation.. |
| 27. |
Minhyung Cho, Jun Tae Song, Seoin Back, Yousung Jung, Jihun Oh, The Role of Adsorbed CN and CI on an Au Electrode for Electrochemical CO2 Reduction, ACS CATALYSIS, 10.1021/acscatal.7b03449, 8, 2, 1178-1185, 2018.02, Electrochemical CO2 reduction is one of the promising ways to convert CO, to value-added products such as CO. Many studies have dealt with suppressing the hydrogen evolution reaction (HER) and increasing the CO, reduction reaction (CO2RR) through modification of the metal surface with additives such as anchoring agent, anion, etc. However, there are only a few studies about modifying the Au surface with additives. We present here a theoretical prediction that the addition of the CN and Cl species on an Au electrode would enhance the electrochemical CO2RR due to van der Waals interactions with these large anionic species. On the basis of this suggestion, we then prepared functionalized Au electrodes by electroplating in an aqueous solution containing CN- or Cl- and experimentally verified that the CO2RR of functionalized Au indeed shows exceptional CO2RR activity in comparison to pristine Au.. |
| 28. |
Minhyung Cho, Ji-Won Seo, Jun Tae Song, Jung-Yong Lee, Jihun Oh, Silver Nanowire/Carbon Sheet Composites for Electrochemical Syngas Generation with Tunable H-2/CO Ratios, ACS OMEGA, 10.1021/acsomega.7b00846, 2, 7, 3441-3446, 2017.07, Generating syngas (H-2 and CO mixture) from electrochemically reduced CO2 in an aqueous solution is one of the sustainable strategies utilizing atmospheric CO2 in value-added products. However, a conventional single-component metal catalyst, such as Ag, Au, or Zn, exhibits potential-dependent CO2 reduction selectivity, which could result in temporal variation of syngas composition and limit its use in large-scale electrochemical syngas production. Herein, we demonstrate the use of Ag nanowire (NW)/porous carbon sheet composite catalysts in the generation of syngas with tunable H-2/CO ratios having a large potential window to resist power fluctuation. These Ag NW/carbon sheet composite catalysts have a potential window increased by 10 times for generating syngas with the proper H-2/CO ratio (1.7-2.15) for the Fischer-Tropsch process and an increased syngas production rate of about 19 times compared to that of a Ag foil. Additionally, we tuned the H-2/CO ratio from similar to 2 to similar to 10 by adjusting only the quantity of the Ag NWs under the given electrode potential. We believe that our Ag NW/carbon sheet composite provides new possibilities for designing electrode structures with a large potential window and controlled CO2 reduction products in aqueous solutions.. |
| 29. |
Seungtaeg Oh, Jun Beom Kim, Jun Tae Song, Jihun Oh, Soo-Hyun Kim, Atomic layer deposited molybdenum disulfide on Si photocathodes for highly efficient photoelectrochemical water reduction reaction, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/c6ta10707a, 5, 7, 3304-3310, 2017.02, Molybdenum disulfide (MoS2) is an earth-abundant and low-cost hydrogen evolving electrocatalyst that can substitute noble metal catalysts. Atomic layer deposition (ALD) is a reliable and scalable process where MoS2 nanomaterials grow directly on Si with a precise film thickness and composition. Here, we demonstrate high-performance Si photocathodes with MoS2 cocatalysts using ALD for the photoelectrochemical (PEC) water reduction reaction. While the morphology and thickness of MoS2 is controlled by ALD reaction cycles, post-sulfurization at high temperatures is conducted to form stoichiometric MoS2 and dramatically enhances the crystallinity of MoS2 to maximize the catalytically active edge sites of basal planes. A systematic study was performed to investigate the role of ALD and post-sulfurization parameters on PEC performances of MoS2 on Si photocathodes. By optimizing the crystallinity, edge site density, stoichiometry, and morphology of MoS2 for maximum electrochemical HER performance and minimum optical and electrical losses, our Si photocathodes with ALD-MoS2 cocatalysts showed reduction of an overpotential of about 630 mV compared to bare Si. The photocathodes also showed a saturating photocurrent density of 31 mA cm(-2) without noticeable degradation during a 24 hour stability test in 0.5 M H2SO4 under a simulated 1 sun illumination.. |
| 30. |
Jun Tae Song, Hyewon Ryoo, Minhyung Cho, Jaehoon Kim, Jin-Gyu Kim, Sung-Yoon Chung, Jihun Oh, Nanoporous Au Thin Films on Si Photoelectrodes for Selective and Efficient Photoelectrochemical CO2 Reduction, ADVANCED ENERGY MATERIALS, 10.1002/aenm.201601103, 7, 3, 2017.02, An Si photoelectrode with a nanoporous Au thin film for highly selective and efficient photoelectrochemical (PEC) CO2 reduction reaction (CO2RR) is presented. The nanoporous Au thin film is formed by electrochemical reduction of an anodized Au thin film. The electrochemical treatments of the Au thin film critically improve CO2 reduction catalytic activity of Au catalysts and exhibit CO Faradaic efficiency of 96% at 480 mV of overpotential. To apply the electrochemical pretreatment of Au films for PEC CO2RR, a new Si photoelectrode design with mesh-type co-catalysts independently wired at the front and the back of the photoelectrode is demonstrated. Due to the superior CO2RR activity of the nanoporous Au mesh and high photovoltage from Si, the Si photoelectrode with the nanoporous Au thin film mesh shows conversion of CO2 to CO with 91% Faradaic efficiency at positive potential than the CO2/CO equilibrium potential.. |
| 31. |
Jaesuk Choi, Jun Tae Song, Ho Seong Jang, Min-Jae Choi, Dong Min Sim, Soonmin Yim, Hunhee Lim, Yeon Sik Jung, Jihun Oh, Interfacial band-edge engineered TiO2 protection layer on Cu2O photocathodes for efficient water reduction reaction, ELECTRONIC MATERIALS LETTERS, 10.1007/s13391-017-6316-1, 13, 1, 57-65, 2017.01, Photoelectrochemical (PEC) water splitting has emerged as a potential pathway to produce sustainable and renewable chemical fuels. Here, we present a highly active Cu2O/TiO2 photocathode for H-2 production by enhancing the interfacial band-edge energetics of the TiO2 layer, which is realized by controlling the fixed charge density of the TiO2 protection layer. The band-edge engineered Cu2O/TiO2 (where TiO2 was grown at 80 A degrees C via atomic layer deposition) enhances the photocurrent density up to -2.04 mA/cm(2) at 0 V vs. RHE under 1 sun illumination, corresponding to about a 1,200% enhancement compared to the photocurrent density of the photocathode protected with TiO2 grown at 150 A degrees C. Moreover, band-edge engineering of the TiO2 protection layer prevents electron accumulation at the TiO2 layer and enhances both the Faraday efficiency and the stability for hydrogen production during the PEC water reduction reaction. This facile control over the TiO2/electrolyte interface will also provide new insight for designing highly efficient and stable protection layers for various other photoelectrodes such as Si, InP, and GaAs.. |
| 32. |
Jun Tae Song, Takayuki Iwasaki, Mutsuko Hatano, Photoelectrochemical CO2 reduction on 3C-SiC photoanode in aqueous solution, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.54.04DR05, 54, 4, 2015.04, Photoelectrochemical (PEC) carbon dioxide (CO2) reduction on a 3C-SiC photoanode is demonstrated in aqueous solution with Pt and Ag counter electrodes. It is demonstrated that 3C-SiC has sufficient potential for CO2 reduction by confirming the band-edge structure. Then, the CO2 reduction is realized by connecting the 3C-SiC photoanode with the counter electrode. As the products of the PEC reaction with an applied bias of 1V (vs counter electrode) to the 3C-SiC photoanode, hydrogen (H-2) and carbon monoxide (CO) were analyzed by highly sensitive micro-gas chromatography, by which the time dependence of the gas products can be analyzed. Under light illumination of the 3C-SiC photoanode, CO2 reduction occurred while producing 2.5 and 9 nmol of CO gas with the Pt and Ag counter electrodes, respectively, after the reaction for 3000 s. (C) 2015 The Japan Society of Applied Physics. |
| 33. |
Jun Tae Song, Takayuki Iwasaki, Mutsuko Hatano, Pt co-catalyst effect on photoelectrochemical properties of 3C-SiC photo-anode, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.53.05FZ04, 53, 5, 2014.05, The effect of Pt co-catalyst fabricated with various annealing temperatures on photoelectrochemical (PEC) properties of 3C-SiC photo-anode was investigated. 3C-SiC with Pt co-catalyst shows the greater PEC reaction compared with bare 3C-SiC. A further enhancement is found by annealing process due to the Pt particle structure and enhanced contact of 3C-SiC and Pt. The formation of Pt particles improves the PEC reaction of samples annealed at 500 and 700 degrees C. Here, 3C-SiC with the Pt annealed at 500 degrees C shows the largest photocurrent, 3.47mA/cm(2) at an applied bias of 1V (vs Ag/AgCl) and the lowest onset potential, 0.74V with the optimum particle size. It is also considered to have appropriate contact by the proper Pt2Si formation, revealed by X-ray photoelectron microscopy. Although photocurrent is improved after anneal at 700 degrees C, the onset potential becomes almost same as bare 3C-SiC. Furthermore, the photo-activity after anneal at 900 degrees C is even degraded compared to the bare 3C-SiC because of the evolution of immoderate carbon compounds suppressing Pt co-catalyst effect. (C) 2014 The Japan Society of Applied Physics. |
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Jun Tae Song, Hisanori Mashiko, Masayuki Kamiya, Yoshifumi Nakamine, Akira Ohtomo, Takayuki Iwasaki, Mutsuko Hatano, Improved visible light driven photoelectrochemical properties of 3C-SiC semiconductor with Pt nanoparticles for hydrogen generation, APPLIED PHYSICS LETTERS, 10.1063/1.4832333, 103, 21, 2013.11, We propose the n-type 3C-SiC with Pt nanoparticles (Pt NPs) as photo-anode for photoelectrochemical hydrogen (H-2) generation. We found that band-edge structure of 3C-SiC is suitable for H-2 generation, and the property can be optimized by dopant (nitrogen) concentration in 3C-SiC. We also confirmed that Pt NPs enhance photoelectrochemical properties showing 0.2%-0.8% higher Incident Photon-to-Current Efficiency than bare 3C-SiC in visible wavelength despite diminished light absorption. Solar-conversion efficiency increases approximately 6.3 times, and H-2 production is improved by 6.5 times with 33% of Faradaic efficiency. Lastly, 3C-SiC surface corrosion is effectively inhibited. (C) 2013 AIP Publishing LLC.. |
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Jun Tae Song, Joong Hee Park, June Kyoo Lee, Ju Chan Choi, Seong Ho Kong, Square-Patterned Narrow-Band Infrared Emitter for Filter Less Infrared Gas Sensor, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.51.06FL18, 51, 6, 2012.06, In this study, we proposed a square-patterned narrow-band infrared (IR) emitter for a filterless IR gas sensor. As a new method of infrared gas sensing compared with previous research, it is proposed that a narrow-band IR emitter fabricated by micro-electro-mechanical-systems (MEMS) technology be applied to analyze dimethyl ether [(CH3)(2)O] gas. The proposed IR emitter consists of a TiN/SiO2/TiN trilayer, where the top TiN layer is square-patterned. The IR emitter radiates emissions at wavelengths of 7.68 and 7.88 mu m in accordance with the type of sample. The wavelength can be adjusted by changing the period of the surface pattern. The proposed IR emitter shows a narrow peak width (Delta lambda/lambda) of 0.16-0.23. The apparatus for gas detection consists of the proposed IR emitter, a gas cell and a bolometric IR sensor based on amorphous SiGe:H. The change in electrical resistance of the gas detector during inflow of (CH3)(2)O gas, which has a fingerprint wavelength in the range of 7.6-10 mu m, was much smaller than that during inflow of CO2 gas, because (CH3)(2)O absorbed its corresponding wavelength in the range of 7.6-10 mu m. Because of the concentrated radiation of the IR emitter at the wavelength of 7.88 mu m, (CH3)(2)O absorbs relatively large amounts of infrared energy. The electrical resistance of the gas detector changed linearly as the concentration of (CH3)(2)O gas increased in the range of 0 to 500 ppm. (C) 2012 The Japan Society of Applied Physics. |
