Dealloyed Octahedral PtCu Nanoparticles as High-Efficiency Electrocatalysts for the Oxygen Reduction Reaction

Pt-based nanoparticles (NPs) are used as electrocatalysts for the oxygen reduction reaction (ORR) that occurs at the cathode of a proton exchange membrane fuel cell, because of their high efficiency. Among these NPs, PtCu electrocatalysts are an important subclass, in which composition, morphology, size, crystal structure, and atomic distribution are tuned to optimize the performance and durability of the catalyst. Most of the efforts so far in the field have been dedicated toward increasing the catalytic activity and stability of these NPs, while reducing the amount of precious material. In this paper, we present a solvothermal method used for the synthesis of carbon-supported octahedral PtCu NPs that show high efficiency toward the ORR. In particular, a specific activity of 1.02 mA cm-2 was achieved after 10,000 cycles (accelerated degradation test) in which 84% of the electrochemical surface area was maintained. This work analyzes the relationship between the structure and durability of the electrocatalysts by advanced electron microscopy techniques, focusing on the copper dealloying process. Two key factors enhance the stability of the material, the capping agent (cetyltrimethylammonium bromide) and the synthesis duration, which promotes the formation of a thick and durable Pt shell around the Cu core.