Evaluation of TiO 2 as catalyst support for the proton exchange membrane fuel cell

1. N.V.Krstajić Faculty of Technology and Metallurgy University of Belgrade Evaluation of TiO2 as catalyst support for the proton exchange membrane fuel cell

3. Damaged of the anode by cell reversal during fuel starvation Fig. 2. The time-dependent changes of the anode and cathode potential during the cell reversal experiment. Fig. 1. Schematic drawing of single cell A.Taniguchi et.al. J.Power Sources, 130(2004)42

4. Oxidation of carbon support of cathode in the potentialrange of oxygen reduction reaction Fig.4 Electrochem. active surface area as a function of cyclic number Fig. 3. Cyclic voltammgramms recorded on Pt/XC-72 (a) and Pt/BP-2000 (b)thin-film electrodes before and after 1200 potential cycles, scan rate: 0.01Vs−1, J.Wang et al. J Power Sources 17 (2007) 331

5. Fig.5 TEM micrographs and histogram of Pt particle size distribution on (a) Vulcan XC-72, before durability test, (b) Vulcan XC-72, after durability test for 168 h, Histogram of Pt particle size distribution on (a) Vulcan XC-72, before durability test, (b) Vulcan XC-72, after durability test for 168 h, C + 2H2O → CO2 + 4H+ + 4e Irreversible oxidation C + H2O → CO + 2H+ + 2e Reversible oxidation → Surface oxide X.Wang et.al. J.Power Sources, 158 (2006) 154

6. Table 1. Characteristics of some supporting materials and carbon Vulcan VC-72 , and catalytic activity and stability in fuel cell conditions.

7. Ti sub-oxides support • Ceramic mainly consisting of a mixture of Ti4O7 and Ti5O9 (TinO2n-1) • Conductivity comparable to graphitized carbon (103 S cm-1) • High overpotential for hydrogen and oxygen evolution • Slow electrode transfer kinetics • Stability in a aqueous solutions including acidic fluoride solution • It does not hydride

8. Journal of Power Sources 193 (2009) 99–106 Journal of Electroanalytical Chemistry 587 (2006) 99–107 Fig.6. X-Ray diffraction spectra of Ti sub-oxides with specified composition Fig.7. CV curves for Au/Ebonex and (Ebonex Pt (5 g) in N2 saturated 0.5 M HClO4 at 50 mV s-1

9. Fig.9. Tafel plots normalized to the electrochem. active surface area for O2 reduction at Pt and Ebonex/Pt electrodes Fig.8. TEM image of Pt particles on Ti sub-oxide support Journal of Power Sources 193 (2009) 99–106 Journal of Electroanalytical Chemistry 587 (2006) 99–107

10. Fig.10. Charge density required for reduction of oxygen species as a function of potential a) Pt; b)Ebonex/Pt Insents: I-E relationship for different initial potenial, with sweep rate of 5 V s-1. Journal of Power Sources 193 (2009) 99–106 Journal of Electroanalytical Chemistry 587 (2006) 99–107

11. Acid-catalyzed sol-gel method of Nb-TiO2 preparation

12. Nb doped TiO2 support characterization Fig.11. X-Ray diffraction spectra of Nb-TiO2 support with specified composition Fig.12. Cyclic voltammetry curves for: (a) Nb-TiO2 substrate and (b) Nb-TiO2/P (8 µg) electrode with sweep rate of 100 mV s-1, in N2 saturated 0.5 mol dm-3 HClO4 solution

13. Fig.12. Fig.14. Polarization curves of a prepared Nb-TiO2/Pt and C/Pt catalyst in 0.5 mol dm-3 HClO4 solution saturated with O2 at a scan rate of 20 mV s-1 and rotation rate of 3700 rpm. Current density are normalized to the geometric surface are Fig.13. TEM images of pt nanoparticles on Nb-TiO2 support and Pt particle size distribution obtained from the micrograph obtained from a).

14. Fig.15. Tafel plots normalized to the electrochemically active surface area for O2 reduction in 0.5 mol dm-3 HClO4 solution at C/Pt and Nb-TiO2/Pt electrodes

15. Dr. Ljiljana Vračar, Faculty of Technology and Metallurgy, University of Belgrade, Dr. Snežana Gojković Faculty of Technology and Metallurgy, University of Belgrade, Dr. Biljana Babić, The Vinca Institute of Nuclear Sciences Dr. Nevenka Elezović Institute of Multidisciplinary Research, Belgrade Dr. Ljiljana Gajić-Krstajić Institute of Technical Sciences, SASA, Belgrade Dr. Velimir Radmilović National Center for Electron Microscopy, LBL University of California, USA