Faculty Profiles - Yamakata Akira

Papers - Yamakata Akira

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In situ observation of the exchange reaction of formate with molecular formic acid on Ni(110) Reviewed

A Yamakata, J Kubota, JN Kondo, C Hirose, K Domen, F Wakabayashi, K Tamaru

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 141 ( 1-3 ) 73 - 82 1999.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The exchange reaction of adsorbed formate on Ni(110) with formic acid in gas phase was studied by the time-resolved infrared reflection absorption spectroscopy (TR-IRAS). It was found that the pre-adsorbed deuterated formate (DCOO(a)) was changed to HCOO(a) in the presence of HCOOD(g) at the temperature region from 240 to 300 K. In such a temperature region, the formate was stable on the surface in vacuum and the decomposition of formate was not observed. It was suggested that the pre-adsorbed DCOO(a) was desorbed as DCOOD accepting deuterium atom from HCOOD. The activation energy of the exchange reaction was estimated to be 23 +/- 2 kJ mol(-1). The reaction order with respect to formic acid pressure was 0.3 +/- 0.1, while that as to the coverage of DCOO(a), was unity. Taking into account all the experimental results, the exchange of pre-adsorbed formate with post-exposed formic acid is suggested to proceed via forming a hydrogen-bonded intermediate complex on the formate's site, because all the sites were already occupied by formate. The small activation energy of the exchange reaction is discussed on the basis of 'adsorption-assisted desorption'. We propose that when desorption and adsorption are coupled, the activation energy of the exchange reaction should be described as a sum of the potential energy profiles of a desorbing and an adsorbing molecule. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1381-1169(98)00251-9

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Exchange reaction of adsorbed formate with gaseous formic acid on Ni(110) studied by time-resolved Fourier transform infrared reflection absorption spectroscopy Reviewed

A Yamakata, J Kubota, JN Kondo, C Hirose, K Domen, F Wakabayashi, K Tamaru

JOURNAL OF PHYSICAL CHEMISTRY B 102 ( 22 ) 4401 - 4403 1998.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The dynamic behavior of adsorbed formate on Ni(110) in the presence of gaseous formic acid was studied by time-resolved infrared reflection absorption spectroscopy. The preadsorbed formate (DCOO(a)) was replaced by the postexposed formic acid (HCOOD) to form HCOO(a) on Ni(110) in the temperature region between 230 and 300 K, where the formate was stable under vacuum and no decomposition of formate was observed. It was confirmed that the preadsorbed DCOO(a) desorbed as DCOOD accompanied by formation of HCOO(a) via the deuterium atom transfer from HCOOD.

DOI： 10.1021/jp981192b

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The IRAS Study of the Exchange Reaction of Formate with Gaseous Formic Acid on Ni(110) Reviewed

YAMAKATA Akira, KUBOTA Jun, NOMURA Junko, HIROSE Chiaki, DOMEN Kazunari, WAKABAYASHI Fumitaka

J. Surf. Sci. Soc. Jpn. 19 ( 7 ) 441 - 445 1998

Publisher：The Surface Science Society of Japan

The exchange reaction of formate (DCOO(a)) with gaseous formic acid (HCOOD) on Ni(110) was investigated below the decomposition temperature of formate (340 K) by means of time-resolved infrared reflection absorption spectroscopy (TR-IRAS). When HCOOD gas was admitted on DCOO(a)-covered Ni(110) at 300 K, the pre-adsorbed DCOO(a) was replaced by HCOO(a). Similar replacement was also observed by introducing H<SUP>12</SUP> COOH gas onto H-<SUP>13</SUP>COO(a)-covered Ni(110). In such a temperature region from 240 to 300 K, no decomposition of formate was observed. Thus it was confirmed that those pre-adsorbed formate desorbed as formic acid accompanied by the transfer of hydrogen (deuterium) atom from post-introduced formic acid. The kinetics of the exchange reaction is investigated and the mechanism of that is also discussed.

DOI： 10.1380/jsssj.19.441

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An IRAS Study of the Decomposition of Formate Adsorbed on Ni(110) Reviewed

YAMAKATA Akira, KUBOTA Jun, NOMURA Junko, HIROSE Chiaki, DOMEN Kazunari, WAKABAYASHI Fumitaka

Journal of the Surface Science Society of Japan 18 ( 7 ) 417 - 423 1997.7

Language：Japanese Publisher：日本表面科学会

The decomposition of the surface formate on Ni(110) was studied by temperature programmed desorption (TPD) and timeresolved infrared reflection absorption spectroscopy (TR-IRAS). It was observed that dehydration proceeded simultaneously with dehydrogenation. The rate-determining step of dehydration was found to be the C-H bond cleavage of formate as is the case of dehydrogenation by analysis of the kinetic isotope effect using HCOO(a) and DCOO(a). These results suggest that the rate-determining steps of dehydration and dehydrogenation are common. We propose a mechanism in which the CO₂(a) species formed via the C-H bond cleavage of formate acts as the intermediate not only for dehydrogenation but also for dehydration; dehydration takes place by dissociation of the C-O bond of CO₂(a).

DOI： 10.1380/jsssj.18.417

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In situ observation of the dehydration of formate on Ni(110) Reviewed

A Yamakata, J Kubota, JN Kondo, C Hirose, K Domen, F Wakabayashi

JOURNAL OF PHYSICAL CHEMISTRY B 101 ( 26 ) 5177 - 5181 1997.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The dehydration of formate adsorbed on Ni(110) has been studied by the direct observation of the CO(a) produced on the surface by means of time-resolved infrared reflection absorption spectroscopy (TR-IRAS). By the quantitative analysis of the temperature-programmed desorption and TR-IRAS results, it was found that the dehydration proceeds simultaneously with the dehydrogenation. The primary kinetic isotope effect (k(H)/k(D)) using HCOO(a) and DCOO(a) was observed not only in the dehydrogenation but also in the dehydration (k(H)/k(D) = 3.3 at 300 K). This result suggests that the rate-determining step (RDS) is the C-H bond dissociation in both processes. These suggestions let us propose a possible mechanism of the dehydration of formate on Ni(110); the RDS of the dehydration is the C-H bond dissociation which is the same as that of the dehydrogenation, and the produced CO2(a) is the precursor of the production of CO(a) and O(a).

DOI： 10.1021/jp9703418

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Isotope exchange reaction of formate with molecular hydrogen on Ni(110) by IRAS Reviewed

A Yamakata, J Kubota, JN Kondo, K Domen, C Hirose

JOURNAL OF PHYSICAL CHEMISTRY 100 ( 46 ) 18177 - 18182 1996.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Kinetics of the CH/CD isotope exchange reaction of formate (HCOO(a)/DCOO(a)) on Ni(110) with gaseous D-2/H-2 was investigated below the decomposition temperature (360 K) by infrared reflection absorption spectroscopy (IRAS). The apparent activation energies of HCOO(a) --> DCOO (a) and DCOO(a) --> HCOO(a) reactions were derived as 52 +/- 5 and 58 +/- 5 kJ . mol(-1), respectively. A half-order dependence of the reaction rate on hydrogen pressure was observed, suggesting that the rate-determining step was the reaction of the adsorbed formate with reversibly adsorbed hydrogen atom. The reaction of HCOO(a) with D-2 was 2.1 +/- 0.3 times faster than that of DCOO(a) with H-2 at 300 K, and the origin of the isotope effect is discussed.

DOI： 10.1021/jp9611986

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SFG study of formic acid on a Pt(110)-(1x2) surface Reviewed

N Watanabe, K Iwatsu, A Yamakata, T Ohtani, J Kubota, JN Kondo, A Wada, K Domen, C Hirose

SURFACE SCIENCE 357 ( 1-3 ) 651 - 655 1996.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Infrared-visible sum frequency generation (IR-vis SFG) spectroscopy, infrared reflection absorption spectroscopy (IRAS), and temperature programmed desorption (TPD) spectroscopy were used to investigate the systems prepared by the adsorption of formic acid (HCOOH) onto a Pt(110)-(1 X 2) reconstructed surface. In the SFG spectra, we observed that several vibrational bands which can be assigned to the CH strerching, the OH stretching and combination modes of formic acid adsorbed in multilayers show a strong dose temperature dependence. From the IRAS measurements, it was found that the formic acid adsorbed in multilayers forms the chain structure which is called the alpha-crystalline form. By combining the results of the dose temperature dependence of SFG spectra with that of IRAS spectra, we conclude that the length of the chain, the orientation of the chain axis, and the size of the single crystalline region of formic acid strongly depend on the dose temperature. Furthermore, we found that the SFG signal of the C-H stretching band shows the intensity oscillation during the exposure to formic acid.

DOI： 10.1016/0039-6028(96)00239-7

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