(A) study on PtZn intermetallic ORR catalyst using MOF-derived carbon support

Abstract

Commercialization of polymer electrolyte membrane fuel cells (PEMFCs) requires a dramatic reduction in the price of catalysts, which account for a significant portion of the total cost. Therefore, since most catalysts in PEMFCs are present in cathode where the oxygen reduction reaction (ORR) occurs, it is necessary to ensure sufficient durability after the reaction and activity of the catalysts for the ORR. In this work, using metal-organic framework (MOF)-based carbon support, platinum (Pt) catalysts were converted into platinum-zinc (Pt-Zn) intermetallic catalysts to enhance the durability of the catalysts, moreover, the additional interaction was introduced between nanoparticles and supports, improving the stability of the catalyst. High-magnification transmission electron microscopy and X-ray diffraction analysis confirmed the ordered structure of intermetallic Pt-Zn nanoparticles. In the half-cell test, the mass activity and the specific activity of the L1$_0$-PtZn/Zn-NC catalyst were 3.8 and 5.7 times as great as that of commercial Pt/C, respectively. Furthermore, to evaluate the stability of the catalysts while the ORR condition, we conducted the durability cycles from 0.6 V to 1.0 V versus RHE. After the durability cycles of 30k, the electrochemically active surface areas (ECSAs) of the L1$_0$-PtZn/Zn-NC(103.1% of the initial ECSA) showed significantly enhanced stability compared to that of the commercial Pt/C(66.2% of the initial ECSA). This work provides us a new strategy to obtain the high stability of the intermetallic catalysts as well as the enhanced activity using MOF-derived carbon support.