Advanced Characterization of Electrocatalyst Interfaces

Abstract

In PEM fuel cells, electrocatalyst interfaces including Pt-C, Pt-ionomer, C-ionomer interfaces, play a critical role for both performance and durability.1-3 Pt-C interface influences the stability and activity of Pt dramatically; electrocatalyst/ionomer interfaces4 in fuel cell catalyst layers determine the electrochemical surface area (ECSA), local transport, and structural stability of catalyst layer. Delineating the structure evolution of the interfaces in response to PEM fuel cell operating environment will provide the science foundation for new electrocatalyst/catalyst layer design therefore improve the performance and durability of PEM fuel cells. We have developed an aberration corrected environmental transmission electron microscopy (ETEM), which allows unprecedented spatial and temporal resolution in the relevant gas environment, such as O2, H2, H2O, CO, CH4, and CO2. With customized intelligent gas delivery system, the gas environment relevant to PEM fuel cell anode and cathode (H2/H2O, O2/H2O) can be simulated and precisely controlled through the residual gas analyzer (RGA). The ETEM opens new avenue to study the dynamic changes of electrocatalyst interfaces. In order to study the surface chemistry of catalysts under different environment, a specially-designed pre-treatment system is integrated into X-ray photoelectron spectroscopy (XPS), which allows us to move catalysts seamlessly between the pre-treatment system and XPS chamber so that surface contamination from external environment will be eliminated. In this talk, we will present our recent progress on identifying both structure and surface chemistry evolution and their correlation in electrocatalysts under PEM fuel cell relevant environment through the combination of ETEM and XPS capabilities. 1. Y. Y. Shao, G. P. Yin and Y. Z. Gao, J. Power Sources, 2007, 171, 558-566. 2. S. Park, Y. Y. Shao, H. Y. Wan, V. V. Viswanathan, S. A. Towne, P. C. Rieke, J. Liu and Y. Wang, J. Phys. Chem. C, 2011, 115, 22633-22639. 3. R. Kou, Y. Y. Shao, D. H. Mei, Z. M. Nie, D. H. Wang, C. M. Wang, V. V. Viswanathan, S. Park, I. A. Aksay, Y. H. Lin, Y. Wang and J. Liu, J. Am. Chem. Soc., 2011, 133, 2541-2547. 4. A. Z. Weber and A. Kusoglu, J. Mater. Chem. A, 2014, 2, 17207-17211.