R. Wang, K. Pupek, T. Dzwiniel, N. Becknell, P.P. Lopes, H. Lv, N. Markovic, V. Stamenkovic
Argonne National Lab,
United States
Keywords: scale up, fuel cell, oxygen reduction reaction, PtNi nanoparticles, membrane electrode assembly
Summary:
In the last few decades, varieties of new functions or improved performance have been achieved in nanomaterials with well controlled structures. One example is the development of Pt based nanocatalysts with different sizes, shapes, compositions, and morphologies using wet chemistry methods for oxygen reduction reaction (ORR). These advanced fuel cell catalyst show promising performance improvement in rotating disk electrode (RDE) measurements. However, their device level performance have been rarely tested because the wet chemistry method although is very capable to control the particle structure at lab scale synthesis, it is very challenging to produce large quantity of uniform, high quality nanoparticles for membrane electrode assembly (MEA) testing. In order to transfer the activity enhancement observed on RDE into performance improvement in MEA, gram scale high quality catalyst should be synthesized to enable MEA level studies. Using multilayered Pt-skin nanoparticle catalyst (1) as an example, here we show the process engineering and scale up synthesis of advanced fuel cell catalyst. A process capable to synthesize 5 g catalyst per batch with good reproducibility is developed by modifying three key steps of the synthesis procedure. The quality of the catalyst was validated with physical characterization and electrochemistry testing. Compared with commercial Pt/C catalyst, these advanced catalysts show 10-fold activity improvements toward ORR in RDE measurement. In MEA measurement, Pt mass activity of 0.5 A/mg at 0.9 V was achieved which is higher than DOE 2020 target. Significant higher performance and lower non-Fickian oxygen transport resistance than commercial catalyst were observed in MEA testing which were ascribed to high activity and accessibility of the multilayered Pt-skin nanoparticle catalyst. Revealed by TEM tomography, all the catalytic particles are located on the surface of carbon indicating the superiority of the synthesis method than commercial impregnation method. These results demonstrate the application potential of advanced fuel cell catalysts with tailored morphology and could inspire future fuel cell catalyst development. (1). Chao Wang, Miaofang Chi, Dongguo Li, Dusan Strmcnik, Dennis van der Vliet, Guofeng Wang, Vladimir Komanicky, Kee-Chul Chang, Arvydas P. Paulikas, Dusan Tripkovic, John Pearson, Karren L. More, Nenad M. Markovic, and Vojislav R. Stamenkovic, “Design and Synthesis of Bimetallic Electrocatalyst with Multilayered Pt-Skin Surfaces”, J. Am. Chem. Soc. 2011, 133, 14396-14403.