| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Energy Harvesting & Storage | Wednesday Sessions |
| Session EH-WeE |
| Session: | Surfaces & Interfaces for Efficient Power Conversion |
| Presenter: | Tsuyoshi Kaji, Tohoku University, Japan |
| Authors: | T. Kaji, Tohoku University, Japan Y. Ootani, Tohoku University, Japan T. Nishimatsu, Tohoku University, Japan Y. Higuchi, Tohoku University, Japan N. Ozawa, Tohoku University, Japan M. Kubo, Tohoku University, Japan |
| Correspondent: | Click to Email |
Platinum (Pt) catalyst is used in an anode of polymer electrolyte fuel cell. It is reported that carbon monoxide (CO) in the fuel adsorbs on an active site of Pt catalyst and degrades the catalytic activity. Thus, a development of a CO tolerant catalyst is required. Some experiments show that an addition of metal oxide nano-particles improves the CO tolerance of the Pt-based catalyst[1]. This result may be due to a decrease in an adsorption energy of CO on the Pt-based catalyst, but the detail mechanism is under consideration. In order to develop a higher CO tolerant catalyst, it is necessary to reveal an effect of the metal oxide nano-particle on the CO tolerance. In this work, we calculated an adsorption energy of a CO molecule on a Pt4 cluster on an anatase TiO2(101) surface with first-principles calculation to investigate the effect of the metal oxide on the CO tolerance of the Pt catalyst.
First, we placed the Pt4 cluster on the anatase TiO2(101) surface with several configuration, and decided the stable configuration. The Pt4 cluster had a tetragonal structure. Three Pt atoms adsorbed on two-coodinated O atoms on the TiO2(101) surface. Then, we calculated the adsorption energy of the CO molecule on each adsorption sites of the Pt4 cluster. The adsorption energies are defined by the difference of a total energy between the adsorption structure and dissociation structure. The largest adsorption energy of –49.31 kcal/mol was obtained for the on-top site on the Pt atom which is located on the undermost layer of the Pt4 cluster. Whereas, the adsorption energy of the CO molecule on the on-top site of the isolated Pt4 cluster is –68.66 kcal/mol. These results indicate that the adding of TiO2 improves the CO tolerance of the Pt catalyst.
Next, we examined the effects of the doping elements on TiO2. Since the doping modifies electronic structure of TiO2, improvement of the CO tolerance of the Pt catalyst is expected. Thus, we substituted a F atom for the O atom or a Nb atom for the Ti atom of the TiO2(101) surface. When we substituted the F atom and the Nb atom, the adsorption energies of the CO molecule on the Pt4 cluster are –41.75 and –40.61 kcal/mol, respectively. These adsorption energies are lower than the adsorption energy on Pt4 cluster on the undoped TiO2(101) surface. Thus, we suggest that the substitution of F and Nb atoms improves the CO tolerance of the Pt cluster on the TiO2 surface. At the conference, we discuss the reason why the doping of F and Nb atoms decrease the adsorption energy of a CO molecule on the Pt4 cluster on the TiO2(101) surface based on the density of states.
[1] T. Takeguchi et al., Catal. Sci. Technol., 6, 3214 (2016).