Acta Phys. -Chim. Sin. ›› 2021, Vol. 37 ›› Issue (9): 2009049.

Special Issue: Fuel Cells

• ARTICLE •

### Enhanced Performance and Durability of High-Temperature Polymer Electrolyte Membrane Fuel Cell by Incorporating Covalent Organic Framework into Catalyst Layer

Liliang Tian1, Weiqi Zhang1, Zheng Xie1, Kai Peng1, Qiang Ma1, Qian Xu1, Sivakumar Pasupathi2, Huaneng Su1,*()

1. 1 Institute for Energy Research, Jiangsu University, Zhenjiang, 212013, Jiangsu Province, China
2 South African Institute for Advanced Materials Chemistry, University of the Western Cape, Bellville 7535, South Africa
• Received:2020-09-15 Accepted:2020-10-18 Published:2020-10-23
• Contact: Huaneng Su E-mail:suhuaneng@ujs.edu.cn
• About author:Huaneng Su, Email: suhuaneng@ujs.edu.cn; Tel.: +86-511-88799500
• Supported by:
the National Key Research and Development Program of China(2018YFE0121200);the National Natural Science Foundation of China(21676126);the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions

Abstract:

Proton exchange membrane fuel cells (PEMFCs) are considered one of the most promising technologies for efficient power generation in the 21st century. However, several challenges for the PEMFC power technology are associated with low operating temperature, such as complex water management and strict fuel purification. PEMFC operating at high temperature (HT, 100–200 ℃) has in recent years been recognized as a promising solution to meet these technical challenges. At present, HT-PEMFC based on phosphoric acid (PA)-doped polybenzimidazole (PBI) is considered to be the trend of PEMFC future development due to its good environmental tolerance and simplified water/ thermal management. In this HT-PEMFC system, the proton transfer in both catalyst layer (CL) and membrane relies on liquid PA. Thus, a proper amount of PA is required to impregnate the membrane and the CL in order to achieve good proton conductivities in an HT-PEMFC system. Therefore, reducing the loss of PA electrolyte in the membrane electrode assembly (MEA) is crucial to maintaining the good durability of HT-PEMFC. In this work, a Schiff base networks (SNW)-type covalent organic framework (COF) material is proposed as the CL additive to enhance the durability of HT-PEMFC. The well-defined porous structure and tailored functional groups endow the proposed COF network with not only excellent PA retention capacity but also good proton transfer ability, thus leading to the superior durability of the HT-PEMFC in an accelerated stress test (AST). After 100 h operation at heavy load (0.2 V) and high flow rate of air purge, the accumulative PA loss of the COF-based MEA was ~4.03 mg, which is almost an order of magnitude lower than that of the conventional MEA (~13.02 mg), consequently leading to a much lower degradation rate of current density (~0.304 mA·cm-2·h-1) than that of the conventional MEA (~1.01 mA·cm-2·h-1). Moreover, it was found that the electrode incorporating a proper amount (5%–10%, mass fraction) of the COF material possessed a higher electrochemical surface area (ECSA) and lower ohmic and charge transfer resistances, which further improved the performance of the HT-PEMFC. At the usual operating voltage of 0.6 V, the current density of the MEA containing 10% COF was up to 0.361 A·cm-2, which is ~30% higher than that of the conventional MEA at 150 ℃, H2/Air and ambient pressure. These results indicate that incorporating COF materials into CL is a promising strategy to enhance the performance and durability of HT-PEMFC.

MSC2000:

• O646