DFT Study of Oxygen Reduction Reaction on Pt-Zr Catalysts

The sluggish oxygen reduction reaction (ORR) kinetics at cathode and expensive Pt electrocatalysts are two main issues that retard fuel cell technology commercialization.^1-3 To overcome these problems, alloying Pt with transition metals, core-shell structures, and non-Pt catalysts are applied to improve the catalytic activity and reduce the catalyst cost.^4-8 It was found that Pt₃Ni, Pt₃Co, and Pt₃Fe have better activity than pure Pt.^9-11 However, stability of these alloys needs to be improved. Pt₃Zr, Pt₃Y, Pt₃Sc show greater stability and high catalytic activity,^9,10,12but these materials need further experimental and theoretical investigations.

We used DFT calculations to study the origins of the better ORR performance and greater stability of Pt-Zr catalysts. To accurately evaluate the activity of Pt-Zr catalysts, we examined binding energies of ORR intermediates and reaction energy barriers for ORR steps both in gas phase and solution. Based on the results obtained, ORR mechanisms on Pt-Zr catalysts will be considered and compared to pure Pt and Pt alloys. Some related experimental results will be discussed as well.

 Acknowledgement. This work is financially supported by the National Science Foundation (grant CBET-1067848).

References

1. K. Kordesch and G. Simader, Fuel Cell and Their Applications, VCH: New York (1996).

2. R. P. O'Hayre, S. W. Cha, W. Colella and F. B. Prinz, Fuel Cell Fundamentals, John Wiley and Sons: New York (2006).

3. A. J. Appleby and F. R. Foulkes, Fuel Cell Handbook, Van Nostrand Reinhold: New York (1989).

4. R. Bashyam and P. Zelenay, Nature, 443, 63 (2006).

5. M. K. Debe, Nature, 486, 43 (2012).

6. R. Othman, A. L. Dicks and Z. Zhu, Int. J. Hydrogen Energy, 37, 357 (2012).

7. H. Yang, Angew. Chem. Int. Ed., 50, 2674 (2011).

8. B. Wang, J. Power Sources, 152, 1 (2005).

9. J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff and J. K. Norskov, Nat Chem, 1, 552 (2009).

10. V. Stamenkovic, B. S. Mun, K. J. J. Mayrhofer, P. N. Ross, N. M. Markovic, J. Rossmeisl, J. Greeley and J. K. Nørskov, Angew. Chem., 118, 2963 (2006).

11. V. R. Stamenkovic, B. S. Mun, M. Arenz, K. J. Mayrhofer, C. A. Lucas, G. Wang, P. N. Ross and N. M. Markovic, Nature materials, 6, 241 (2007).

12. S. J. Hwang, S. K. Kim, J. G. Lee, S. C. Lee, J. H. Jang, P. Kim, T. H. Lim, Y. E. Sung and S. J. Yoo, J. Am. Chem. Soc., 134, 19508 (2012).