Durability of Active ORR Electrocatalysts

Obtaining extended life of active oxygen reduction reduction (ORR) electrocatalysts is still one of the hardest barriers to overcome for the successful implementation of low-temperature fuel cells. Significant research activity during the last decade has allowed the development of a variety of electrocatalyst materials with excellent activity.  Among them, core-shell alloys are the most popular. However, in general their cycle life is very limited.

First-principles calculations based on density functional theory (DFT) have advanced to the point where they are able to provide reasonable predictions not only for activity but also to help elucidating the factors causing catalyst degradation and giving trends for durability of materials in harsh environments.

In this work, we first discuss the requirements of a core-shell alloy for extended durability, on the basis of DFT analysis. We then report results of experiments and DFT simulations about changes induced by the presence of oxides in core-shell structures. Physical and electrochemical characterization confirms the presence of core-shell nanoparticles with a high electrochemical activity towards the ORR. Periodic DFT calculations are used to analyze the shift in the onset of the oxidation potential for Pt, Ni@Pt and NiO@Pt with different number of layers in the shell, and associated changes in electrochemical activity. We conclude with a general discussion of the potential effect of catalyst/substrate interactions to improve the durability of ORR electrocatalysts.