(A) study on Zn-introduced platinum-cobalt intermetallic catalyst for oxygen reduction reaction

Abstract

Extensive commercialization of polymer electrolyte membrane fuel cells (PEMFCs) is restricted by high price of Pt which is commonly used to promote the oxygen reduction reaction (ORR). Therefore, reducing the dosage of Pt in the ORR catalysts while maintaining high activity and stability is important key for accelerating PEMFCs’ commercialization. In this study, Zn-introduced PtCo intermetallic nanoparticles supported on Zn-NC substrate (Zn-PtCo/Zn-NC) were synthesized, demonstrating superior performances toward the acidic ORR in half-cell. The Zn-PtCo/Zn-NC catalyst was synthesized via the gas phase reduction method for the deposition of PtCo nanoparticles (NPs) on Zn-NC, and subsequent post-annealing process. During the annealing procedure, diffusion of Zn atoms into PtCo NPs occurred and leaded to enhanced atom-ordering of the intermetallic NPs. In the half-cell tests, the Zn-PtCo/Zn-NC catalyst showed about 7-fold enhancement in the mass activity, compared to that of the commercial Pt/C. The high activity of the Zn-PtCo/Zn-NC was attributed to the incorporation of Zn atoms and the ordered structure which synergistically enhanced the ligand effects. In addition, the polarization curve of the Zn-PtCo/Zn-NC showed only a slight shift (-9 mV) in a half-wave potential after the accelerated durability test (ADT), indicating the excellent stability of the catalyst. The robustness of the Zn-PtCo/Zn-NC was reinforced due to the structural stability of the atom-ordered intermetallic phase. The synthesis strategy presented in this work suggests a pathway for developing the electrocatalysts applicable to the energy conversion devices.