Dual-functional phosphoric acid-loaded covalent organic framework for PEMFC self-humidification: Optimization on membrane electrode assembly

A novel enhanced membrane electrode assembly (MEA) was successfully developed by incorporating a phosphoric acid (PA)-loaded Schiff base network (SNW)-type covalent organic framework (COF) as an additive to the catalyst layer (CL) to improve the performance of proton exchange membrane fuel cells (PEMFCs) under low humidity conditions. The unique network structure and PA-loaded H3PO4@SNW-1 material have excellent water management and proton transfer abilities. Direct use of this material as a CL additive can significantly enhance the performance of PEMFCs under varying humidification conditions. The optimization of the additive content, the impact of the anode/cathode modification, and the operating temperature of PEMFCs were studied using electrochemical characterization and single cell tests. The maximum power density of MEAs with 15 wt.% H3PO4@SNW-1 added to the anode CL at a normal operating temperature of 60 °C was 745 mW cm−2 and 690 mW cm−2 under full humidification (100% RH) and low humidification (21% RH), respectively, both of which were higher than that of conventional MEAs. Furthermore, preliminary durability test and 10-day intermittent operation demonstrate the potential of the proposed PEMFCs in actual operation in harsh environments.