Positive Impact of Acid-Heat Treatment on the Electrocatalytic Performance of Highly Active and Low Pt-Based Nanostructured Alloy Catalysts for Oxygen Reduction Reactions to Electrochemical Energy Conversion Devices

Platinum-based catalysts have been widely examined for energy conversion devices and other applications. However, a significant reduction in costs by reducing the amount of precious Pt in the catalyst without reducing its effectiveness is necessary for large-scale commercialization. In this regard, low-Pt alloyed with 3d transition-metal (M = Co, Ni, Cr) catalysts supported by carbon have been synthesized. Here, an inexpensive, simple, and fast dry-mixing method and an alloying process using a rapid quenching technique are used for the synthesis of PtM/C catalysts. After synthesis, an acid-heat treatment is conducted to reconstruct the surface of nanoparticle (NP) catalysts. The result shows that acid-heat treatment eliminates surface oxidation and reduces the size of NPs, resulting in increased active surface area and the number of Pt-active sites. Acid-heat treatment also modifies the composition ratio of NPs, leading to the uniform dispersion of Pt and M atoms in the alloy. Oxygen reduction reaction activity of PtM/C alloy catalysts after acid-heat treatment has improved considerably, and this improvement depends on the unique structural features of Pt and M. Among the different catalysts, PtCo/C has the highest electrocatalytic activity because of the effective modification of electronic surface structure and the increased number of active sites.