Type of presentation: Poster

MS-1-P-5796 3D structural & chemical analysis of ternary PtRh/SnO2 catalysts for Ethanol Oxidation in Direct Ethanol Fuel Cells

Parlinska M.1,2, Li M.3, Kowal A.4,5,6,7
1Facility for Electron Microscopy & Sample Preparation, Univ. of Rzeszow, Poland, 2Int. Centre of Electron Microscopy for Materials Science, Dept. of Physical & Powder Metallurgy, Faculty of Metal Engineering & Industrial Computer Science, AGH University of Science and Technology, Krakow, Poland , 3Dept of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, United States, 4Dept of Mat. & Natural Sci., Univ. of Rzeszow, Poland, 5Center for Synthesis and Char. of Nanomaterials, Univ. of East Sarajevo, Bosnia & Herzegovina, 6Central Lab. of Batteries & Cells, Forteczna 12, Poznan, Poland , 7Elcatak, ul. Pod Sikornikiem 8, Krakow, Poland
nckowal@cyf-kr.edu.pl

One possible solution for new, efficient, and environmentally-friendly technologiy for transforming chemical energy into electricity are fuel cells [1]. Ethanol seems to be an ideal fuel, as it is a non-toxic liquid and can be produced cheaply and efficiently from grasses. The best performance in ethanol oxidation reaction, was obtained for PtRh/SnO2 nanoparticles designed and synthesized by the Adzic group [2-5]. Additives such as F or Sb can be added into SnO2 in order to enhance its catalytic activity [6]. Structural and chemical investigations of the nanocatalysts with different Pt:Rh:Sn ratio were performed by TEM Osiris FEI operating at 200 kV and equipped with Super-EDX. Fig. 1(a) shows a STEM HAADF image of the PtRh/SnO2 catalyst with a Pt:Rh:Sn ratio = 1:1/3:1, which is relatively homogeneously distributed on the Vulcan carbon substrate. Unfortunately, a direct distinction between the tin oxide and PtRh particles is not possible, Fig. 1(b). Individual particles with a size from 2-10 nm are observed. Fig.2 shows the HAADF image of the PtRh/SnO2 particles with quantified EDX maps of Pt, Rh and Sn. Individual Pt particles of 2-5nm in the map are distinguishable, what is not the case for the SnO2 particles. The Rh signal is rather weak and is located in the same areas as Pt. The SnO2 particle size starts from 4-5 nm for individual particles. In the sum EDX map of Pt, Rh and Sn, it can be clearly seen, that the SnO2 particles are not completely coated by PtRh particles, therefore areas with pure tin are visible (blue in Fig. 3). The Pt:Rh ratio determined by EDX in this sample is 3:1. The right image in Fig. 3 shows the HRTEM image of the PtRh/SnO2 particles, which are visible as dark dots on the amorphous, circular Vulcan carbon substrate.

[1] V.S. Bagotsky, Fuel Cells: Problems and Solutions 2nd Ed.; John Wiley & Sons: Hoboken, New Jersey, 2012 pp. 3-5
[2] A. Kowal, M. Li, M. Shao, K. Sasaki, M.B. Vukmirovic, J. Zhang, N. S. Marinkovic, P. Liu, A. Frenkel, R. R. Adzic, Nature Materials, 2009, 9, 325-330.
[3] A. Kowal, S.Lj. Gojković, K.-S. Lee, P. Olszewski, Y.-E. Sung, Electrochem. Comm. 2009, 11, 724-727.
[4] R. Adzic, A. Kowal, (Brookhaven National Laboratory), Patent Application Publication, Pub. No. US2009/0068505 A1 (Mar. 12, 2009).
[5] M. Li, A. Kowal, K. Sasaki, N. Marinkovic, D. Su, E. Korach, P. Liu, R. Adzic, Electrochima Acta, 2010, 55, 4331-4338.
[6] M. Parlinska-Wojtan, R. Sowa, M. Pokora, A. Martyła, K. S. Lee and A. Kowal, Surf. & Interfaces Anal. Published on-line 15 Feb. 2014, DOI: 10.1002/sia.5384

Fig. 1: HAADF STEM images of the PtRh/SnO2 catalyst deposited on the Vulcan carbon substrate: (a) overview image showing a uniform distribution of the catalyst nanoparticles; (b) magnified view – the PtRh and tin oxide particles are not directly distinguishable in the HAADF detector.

Fig. 2: (left to right) STEM HAADF image of the PtRh/SnO2 particles and the corresponding quantified EDX maps of Pt, Rh and Sn.

Fig. 3: left image: EDX map of the catalyst showing the distribution of Pt, Rh and Sn in the sample; right image: HRTEM image of the PtRh/SnO2 (dark dots) particles on amorphous carbon.