Electrochemical Properties and Single Cell Performance of Pd Core-Pt Shell Structured Catalyst Synthesized by a Simple Direct Displacement Reaction

• Published in: Journal of the Electrochemical Society 2020-02, Vol.167 (4), p.44513
• Main Authors: Aoki, Naoya, Inoue, Hideo, Yoshiura, Reiko, Hasegawa, Yuya, Miyazaki, Shunya, Suzuki, Ayono, Daimon, Hideo, Doi, Takayuki, Inaba, Minoru, Higashi, Kotaro, Uruga, Tomoya, Iwasawa, Yasuhiro, Tanida, Hajime, Yuan, Qiuyi, Takao, Naoki, Imai, Hideto, Mikami, Takefumi, Daimaru, Akimasa
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111; 1945-7111
• DOI: 10.1149/1945-7111/ab743e

A carbon supported Pd core-Pt shell structured catalyst (Pt/Pd/C) was synthesized by a very simple direct displacement reaction (DDR), in which Pd core nanoparticles (NPs) were directly displaced with [PtCl4]2− on stirring in N2 saturated H2SO4 aqueous solution at 70 °C instead of a modified Cu under potential deposition (Cu-UPD)/Pt displacement method. In DDR, potential difference between Pd core and [PtCl4]2− was decreased compared with the difference between Cu shell and [PtCl4]2− in Cu-UPD/Pt displacement method, which suppressed non-uniform Pt shell formation and increased Pt shell coverage, enhancing oxygen reduction reaction (ORR) activity. Furthermore, fine Pd core NPs were preferentially dissolved out by Cl− anions released from [PtCl4]2− during DDR performed in acidic H2SO4 solution at 70 °C and mean diameter of Pd@Pt core-shell NPs increased, improving durability of Pt/Pd/C catalyst by the size effect. Large Pd particles, however, were formed in Pt/Pd/C catalyst through a disproportionation reaction of Pd2+ cations generated in DDR, which was suppressed by addition of Br− anions as complexing agent. A single cell using Pt/Pd/C cathode catalyst synthesized by DDR with Br− anions and activated by H2-O2 chemical pretreatment showed 2.4-fold ORR mass activity of a commercially available Pt/C catalyst at a current density of 1.0 A cm−2. Thus, DDR was considered to be a suitable synthetic method for a mass production of highly active and durable Pt/Pd/C catalyst for ORR.