PGM-Free Fe/N/C and Ultralow Loading Pt/C Hybrid Cathode Catalysts with Enhanced Stability and Activity in PEM Fuel Cells

Xiaohua Yang; Gaixia Zhang; Lei Du; Jun Zhang; Fu-Kuo Chiang; Yuren Wen; Xiaomin Wang; Yucheng Wu; Ning Chen; Shuhui Sun

doi:10.1021/acsami.9b18085

PGM-Free Fe/N/C and Ultralow Loading Pt/C Hybrid Cathode Catalysts with Enhanced Stability and Activity in PEM Fuel Cells

ACS Appl Mater Interfaces. 2020 Mar 25;12(12):13739-13749. doi: 10.1021/acsami.9b18085. Epub 2020 Mar 16.

Authors

Xiaohua Yang¹, Gaixia Zhang¹, Lei Du¹, Jun Zhang¹, Fu-Kuo Chiang², Yuren Wen³, Xiaomin Wang⁴, Yucheng Wu⁴, Ning Chen⁵, Shuhui Sun¹

Affiliations

¹ Institut National de la Recherche Scientifique-Énergie Matériaux et Télécommunications, Varennes, QC J3X 1S2, Canada.
² National Institute of Low-Carbon-and-Clean-Energy, P.O. Box 001, Shenhua NICE, Future Science Park, Changping District, 102211 Beijing, China.
³ School of Materials Science and Engineering, University of Science and Technology Beijing, 100083 Beijing, China.
⁴ College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
⁵ Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK S7N 2 V3, Canada.

PMID: 32130853
DOI: 10.1021/acsami.9b18085

Abstract

In this work, the stability behaviors of the state-of-the-art Fe/N/C and Pt/C catalysts (as well as the activation time of the latter) were first systematically investigated, under different cathode catalyst loadings, in the membrane electrode assemblies (MEA) in PEM fuel cells. Based on that, two types of cathode electrodes with the combination of Fe/N/C and Pt/C catalysts were developed (type I: layered hybrid catalysts with Pt/C next to the membrane and type II: uniformly mixed catalysts). In this way, the shortcomings of the Fe/N/C catalyst (the fast decay) and the Pt/C catalyst (the long activation time) can be compensated at the same time. The hybrid catalysts also showed a very short activation time (a few hours vs over 10 h for Pt/C with the same Pt loading). Comparing the two types of hybrid catalysts, type I shows a much higher current density. The loadings of the Fe/N/C and Pt/C catalysts in the hybrid electrode were systematically studied, with optimal values of 1.0 mg cm^-2 for Fe/N/C and 0.035 mg_Pt cm^-2 for Pt/C. The Pt loading of this hybrid catalyst (type I) at the cathode only takes ca. 30% of the U.S. Department of Energy (DOE) target of Pt usage (0.100 mg_Pt cm^-2), while its mass activity of Pt (in H₂/O₂ PEMFC) is 0.22 A mg_Pt^-1 at 0.9_iR-free V, reaching half of the DOE activity target (0.44 A mg_Pt^-1), which is among the best performances reported so far. Via both half-cell and single-cell electrochemical evaluations together with other characterizations, the origin of the improved activity and stability is believed to be the synergistic effect between Pt/C and Fe/N/C catalysts to ORR. This work provides an effective strategy for engineering highly performing MEA for the industrialization of PEM fuel cells.

Keywords: Fe/N/C; PEMFCs; Pt/C; hybrid catalyst; peroxide; stability.