Jing Liu,1 Jie Wang,1 Linjuan Zhang,2 Chaohua Fan,1 Xin Zhou,3 Bingsen Zhang,4 Xuejing Cui,1 Jianqiang Wang,2,* Yi Cheng,5,* Shuhui Sun,6 Luhua Jiang1,*
1 Electrocatalysis & Nanomaterial Laboratory, College of Materials Science & Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China
2 Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
3 College of Environment and Chemical Engineering, Dalian University, Dalian 116622, China
4 Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
5 Department of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
6 Institute National de la Recherche Scientifique (INRS), Centre Énergie Matériaux et Télécommunications, Varennes, Québec J3X 1P7, Canada
ABSTRACT: Phosphoric acid-doped polybenzimidazole (PA-PBI) membrane fuel cells are gaining popularity as a promising technology for generating electricity due to their high operating temperature (150-200oC) and thus accelerated electrode reaction kinetics. However, strong phosphate anions (PA) absorption on Pt surface severely limits catalytic activity and thus degrades the device efficiency. Developing active and stable catalysts that are resistant to phosphate anions is of great significance for PA-PBI fuel cells. Herein, a highly active and PA tolerant catalyst is obtained by elaborately designing the coordination environment of the iron center. The experimental and theoretical studies show that the planar Fe-N4 moiety with an axial O ligand weakens PA adsorption on Fe active centers, while promotes oxygen molecule dissociation, resulting in excellent PA tolerance and ORR activity with the half-wave potential remaining at 0.81 V. The axial-ligand promoted Fe-N-C catalyst also delivers a high peak power density of 229 mW cm-2 in a PA-PBI fuel cell with no back-pressure. This study shed light on the intrinsic cause for the PA-tolerance of Fe-N-C catalysts at the molecular level, which provides guidance for designing highly active and stable electrocatalysts for PA-PBI fuel cells.
Keywords: high temperature polymer electrolyte fuel cells; phosphate anion poisoning; axial ligand; Fe-N-C; oxygen reduction reaction
DOI: 10.1039/D2TA03312G
