| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Energy Harvesting & Storage | Wednesday Sessions |
| Session EH-WeP |
| Session: | Energy Harvesting & Storage Poster Session |
| Presenter: | Naoki Yokoyama, Tohoku University, Japan |
| Authors: | N. Yokoyama, Tohoku University, Japan Y. Higuchi, Tohoku University, Japan N. Ozawa, Tohoku University, Japan H. Yugami, Tohoku University, Japan M. Kubo, Tohoku University, Japan |
| Correspondent: | Click to Email |
For an environmentally-friendly energy system, hydrogen is expected as a resource to replace fossil fuels. Recently, steam methane reforming (SMR) is mainly used for hydrogen production. However, the promotion and the cost reduction of hydrogen production in SMR is strongly desired for stable supply of hydrogen because SMR requires a large amount of heat. To increase hydrogen production, Maegami et al. proposed the vibrationally-excited method, in which infrared light vibrationally excites a C-H bond of a CH4 molecule [1] . While hydrogen production is promoted by the vibrational excitation of a CH4 molecule, the detailed analysis at atomic scale is necessary for higher efficient hydrogen production. Thus, by using the first -principles molecular dynamics (FPMD) simulation method, we examined the effect of vibrational excitation of the C-H bond on chemical reaction dynamics for hydrogen generation from CH4 and H2O.
To reveal the chemical reaction dynamics, we simulated collision process of a H2O molecule with a CH4 molecule in the vibrationally-excited state by using our development FPMD code “Violet” [2]. The vibrationally-excited state was reproduced by extending a C-H bond . After the collision, a dissociation of C-H bond was observed. Moreover, the H atom of the dissociated C-H bond reacted with a H atom of the H2O molecule, and H2 and CH3OH were generated. Next, to examine the effect of vibrational excitation, we simulated collision processes with the collision angle from -60° to 60° and collision energy from 9 eV to 20 eV in the ground state and the vibrationally-excited state. In the ground state, hydrogen molecules were generated in the range of collision angle from -50° to -10° and collision energy from 17 eV to 20 eV. On the other hand, in the vibrationally-excited state, hydrogen molecules were generated in the range of collision angle from -60° to 0° and collision energy from 14 eV to 20 eV. Therefore, in the vibrationally-excited state, H2 molecules were generated in a wider range of collision angle and lower collision energy than those in the ground state. This simulation result suggests that the H2 generation was promoted by vibrational excitation, which is consistent with the experiment [1] . We also examined the later process after the H2 and CH3OH were generated. Accordingly, CH2(OH)2, HCHO, HCOOH, and CO were observed as intermediate products. Consequently, we indicated the chemical reaction dynamics of H2 generation from H2O and vibrationally-excited CH4 in gas phase.
[1] Y. Maegami, F. Iguchi, and H. Yugami, Appl. Phys. Lett., 97, 231908 (2010).
[2] T. Shimazaki and M. Kubo, Chem. Phys. Lett., 503, 316 (2011).