Evaluation of oxygen reduction activity of non-ideal Pt based catalyst thin films

The polymer exchange membranes fuel cells cathode electrocatalyst activity and durability are still a major challenge hindering the commercialization of these devices, despite the use of noble materials like platinum alloys. Dealloying, that is removal of less noble metals, has become one promising strategy for producing Pt-based catalysts in all design categories (skeletal surface, nanoporous, core–shell nanoparticle configuration) (1).  Generally, dealloying can be triggered either chemically by acid leaching, or electrochemically by potential hold or cycling above critical potential (2-4). In this presentation I will discuss on the impact of Pt-alloy composition (5), size (6), structural ordering (4), and also the dealloying conditions on the formation of different morphologies, as well as the resulting ORR performance. By utilizing advanced characterization techniques (electrochemical scanning flow cell coupled with ICP-MS, identical location TEM and SEM – see Figure 1 and electrochemical in-situ TEM) together with conventional thin film rotating disc electrode I will provide new insights in to dealloying phenomena of PtCu alloy. 

Figure 1: SEM sequential images of a dealloying and degradation of PtCu₃ electrocatalyst: a) as-synthesized, b) after 500 cycles between 0 and 1.2 V with 0.5 V/s, c) after 5k cycles between 0.6 and 1.2 V z 1 V/s in d) after 50k cycles between 0.6 and 1.2 V z 1 V/s in 0.1 M HClO₄; (scale bar is 20 nm)

Acknowledgements

Nejc Hodnik would like to acknowledge the FP7-PEOPLE-2013-IEF Marie Curie Intra-European Fellowship (project 625462 - ElWBinsTEM).

References:

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

2.            L. Gan, M. Heggen, R. O’Malley, B. Theobald and P. Strasser, Nano Letters, 13, 1131 (2013).

3.            D. Wang, Y. Yu, J. Zhu, S. Liu, D. A. Muller and H. D. Abruña, Nano Letters, 15, 1343 (2015).

4.            N. Hodnik, C. Jeyabharathi, J. C. Meier, A. Kostka, K. L. Phani, A. Recnik, M. Bele, S. Hocevar, M. Gaberscek and K. J. J. Mayrhofer, Physical Chemistry Chemical Physics, 16, 13610 (2014).

5.            A. K. Schuppert, A. A. Topalov, A. Savan, A. Ludwig and K. J. J. Mayrhofer, ChemElectroChem, 1, 358 (2014).

6.            N. Hodnik, M. Zorko, M. Bele, S. Hočevar and M. Gaberšček, The Journal of Physical Chemistry C, 116, 21326 (2012).