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Last Updated :2024/07/25
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202301014618898732
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- Kaiyue Dong, Bing Hu, Md Harun Al Rashid, Bang Lu, Keiko Miyabayashi, Kotaro Higashi, Tomoya Uruga, Yasuhiro Iwasawa, Daiki Kido, Satoru Takakusagi, Kiyotaka Asakurae-Journal of Surface Science and Nanotechnology 2024/02/15
- Cho Rong Kim, Honoka Maeda, Bang Lu, Yuto Nakamura, Yunli Lin, Yuki Wakisaka, Daiki Kido, Kiyotaka Asakura, Satoru TakakusagiChemistry Letters 2023/12 [Refereed]
- Can Liu, Bang Lu, Hiroko Ariga-Miwa, Shohei Ogura, Takahiro Ozawa, Katsuyuki Fukutani, Min Gao, Jun-ya Hasegawa, Ken-ichi Shimizu, Kiyotaka Asakura, Satoru TakakusagiJOURNAL OF THE AMERICAN CHEMICAL SOCIETY 145 (36) 19953 - 19960 0002-7863 2023/08Dynamic behavior of intermediate adsorbates, such as diffusion, spillover, and reverse spillover, has a strong influence on the catalytic performance in oxide-supported metal catalysts. However, it is challenging to elucidate how the intermediate adsorbates move on the catalyst surface and find active sites to give the corresponding products. In this study, the effect of the dynamic behavior of methoxy intermediate on methanol decomposition on a Pt/TiO2(110) surface has been clarified by combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. The methoxy intermediates were formed by the dissociative adsorption of methanol molecules on Pt nanoparticles at room temperature followed by spillover to the TiO2(110) support surface. TPD results showed that the methoxy intermediates were thermally decomposed at >350 K on the Pt sites to produce CO (dehydrogenation) and CH4 (C-O bond scission). A decrease of the Pt nanoparticle density lowered the activity for the decomposition reaction and increased the selectivity toward CH4, which indicates that the reaction is controlled by diffusion and reverse spillover of the methoxy intermediates. Time-lapse STM imaging and DFT calculations revealed that the methoxy intermediates migrate on the five-fold coordinated Ti (Ti-5c) sites along the [001] or [1 (1) over bar 0] direction with the aid of hydrogen adatoms bonded to the bridging oxygens (O-br) and can move over the entire surface to seek and find active Pt sites. This work offers an in-depth understanding of the important role of intermediate adsorbate migration in the control of the catalytic performance in oxide-supported metal catalysts.
- Dae-Yeong Kim, Hyungwon Ham, Xiaozhong Chen, Shuai Liu, Haoran Xu, Bang Lu, Shinya Furukawa, Hyun-Ha Kim, Satoru Takakusagi, Koichi Sasaki, Tomohiro NozakiJOURNAL OF THE AMERICAN CHEMICAL SOCIETY 144 (31) 14140 - 14149 0002-7863 2022/07Using nonthermal plasma (NTP) to promote CO2 hydrogenation is one of the most promising approaches that overcome the limitations of conventional thermal catalysis. However, the catalytic surface reaction dynamics of NTP-activated species are still under debate. The NTP-activated CO2 hydrogenation was investigated in Pd2Ga/SiO2 alloy catalysts and compared to thermal conditions. Although both thermal and NTP conditions showed close to 100% CO selectivity, it is worth emphasizing that when activated by NTP, CO2 conversion not only improves more than 2-fold under thermal conditions but also breaks the thermodynamic equilibrium limitation. Mechanistic insights into NTP-activated species and alloy catalyst surface were investigated by using in situ transmission infrared spectroscopy, where catalyst surface species were identified during NTP irradiation. Moreover, in in situ X-ray absorption fine-structure analysis under reaction conditions, the catalyst under NTP conditions not only did not undergo restructuring affecting CO2 hydrogenation but also could clearly rule out catalyst activation by heating. In situ characterizations of the catalysts during CO2 hydrogenation depict that vibrationally excited CO2 significantly enhances the catalytic reaction. The agreement of approaches combining experimental studies and density functional theory (DFT) calculations substantiates that vibrationally excited CO2 reacts directly with hydrogen adsorbed on Pd sites while accelerating formate formation due to neighboring Ga sites. Moreover, DFT analysis deduces the key reaction pathway that the decomposition of monodentate formate is promoted by plasma-activated hydrogen species. This work enables the high designability of CO2 hydrogenation catalysts toward value-added chemicals based on the electrification of chemical processes via NTP.
- Bang Lu, Daiki Kido, Yuta Sato, Haoran Xu, Wang-Jae Chun, Kiyotaka Asakura, Satoru TakakusagiJOURNAL OF PHYSICAL CHEMISTRY C 125 (22) 12424 - 12432 1932-7447 2021/06A novel operando X-ray absorption fine structure (XAFS) technique was developed that we have called the operando polarization-dependent total reflection fluorescence (PTRF)-XAFS technique, which can provide information on the valence state (XANES) and three-dimensional (3D) structure (EXAFS) of active metal species dispersed on a well-defined single-crystal surface during catalytic reactions. A new compact vacuum chamber, termed an operando PTRF-XAFS cell, was designed with an internal volume of 216 cm(3) for PTRF-XAFS measurements of deposited metal species at high temperatures (<800 K) in the presence of reactant gases (up to atmospheric pressure). Product gas analysis in the cell can be simultaneously conducted with a quadrupole mass spectrometer (QMS) during the PTRF-XAFS measurements. The developed operando PTRF-XAFS technique was applied to a Pt/alpha-Al2O3 (0001) model catalyst during the CO oxidation reaction. Pt clusters that favor an icosahedral Pt ss structure were formed on the alpha-Al2O3 (0001) surface after Pt deposition at room temperature, while they were converted to larger cuboctahedral clusters (Pt-147) under the CO oxidation reaction at 493 K. The turnover frequency (TOF) of the CO oxidation activity at 493 K was also estimated to be 0.06 s(-1) from simultaneous QMS and XAFS measurements. Thus, operando PTRF-XAFS has enabled the relationship between the 3D structure of a metal species on a well-defined oxide surface and its catalytic activity to be determined.