Selectively oxygen reduction reaction and strongly suppressed CO poisoning on PtZn nanoalloys decorated on N-doped carbon sphere

Abstract

The development of a high-performance oxygen reduction reaction (ORR) catalyst with a low Pt content, high activity, and long-term durability is crucial as it can become a core item in the fuel cell market. In this study, the amount of Pt used in the catalyst is reduced by more than three-fold compared with commercial catalysts. Concurrently, a PtZn alloy, which does not use expensive transition metals, is introduced as an active species. Nitrogen-doped carbon sphere (CS), which serves as an electron sink, is used as a support; it acts as a Lewis base site and facilitates H+ adsorption during the ORR. The analytical results reveal that the introduction of Zn is significantly more favorable for the ORR compared with N-doping. O2-pulse temperature-programmed desorption (TPD) reveals that most of the O2 molecules are adsorbed on Zn, and CO-pulse TPD demonstrates that Zn suppresses CO poisoning in the PtZn alloys. The mass and specific activities of the Pt1Zn1/N-CS electrode at 0.9 V are 5.94 A mg–1 and 0.79 mA cm–2, respectively, and a rotational frequency of 2.5 e-site–1 s–1 is achieved. The electrochemical performance remains unchanged even after 5000 cycles. The ORR on the Pt1Zn1/N-CS electrode does not occur randomly on Pt and Zn; Pt and Zn selectively attract and reduce *O, *OH, or *OOH which generated as intermediates.