ORR Activity and Surface Strain Relations of Commercial Pt Alloy Catalysts

Understanding and improving the catalysts for the ORR (Oxygen Reduction Reaction) is of great importance for the development of low temperature fuel cells. Within the past two decades great effort has been taken into the development of platinum alloy nano-catalysts and brought to commercialization. While thorough studies on the activity and stability of the individual catalysts have received great attention in the scientific literature, consistent comparisons of different platinum alloy nano-catalysts are scare: Due to different preparation methods and experimental conditions, the reported specific activities of, e.g. Pt3Co/C, vary by one order of magnitude [1][2]. In the first part of this talk we will present consistent electrochemical measurements on 7 different commercially available platinum alloy nano-catalysts (20% Pt loading on Vulcan XC-72R). In the second part we will present our results in context of the scientific understanding the ORR on platinum-based catalysts. Therefore, we conducted an extensive TEM survey on the measured nano-catalysts and gained further insights into the platinum surface strain. We find that the platinum surface strain of nano-catalysts is not only a phenomenon of an over-layer formation on platinum alloys, but also an inherent property of its nano-particular form. Wang, C. et al. “Monodisperse Pt3Co nanoparticles as a catalyst for the oxygen reduction reaction: Size-dependent activity.” Journal of Physical Chemistry C, 113(45), 19365–19368. https://doi.org/10.1021/jp908203p Koh, S. et al. “Activity-stability relationships of ordered and disordered alloy phases of Pt3Co electrocatalysts for the oxygen reduction reaction (ORR).” Electrochimica Acta, 52(8 SPEC. ISS.), 2765–2774. https://doi.org/10.1016/j.electacta.2006.08.039 Figure 1