Abstract
Developing self-humidifying membrane electrode assembly (MEA) is of great significance for the practical use of proton exchange membrane fuel cell (PEMFC). In this work, a phosphoric acid (PA)-loaded Schiff base networks (SNW)-type covalent organic framework (COF) is proposed as the anode catalyst layer (CL) additive to enhance the PEMFC performance under low humidity conditions. The unique polymer structure and immobilized PA endow the proposed COF network with not only excellent water retention capacity but also proton transfer ability, thus leading to the superior low humidity performance of the PEMFC. The optimization of the additive content, the effect of relative humidity (RH) and PEMFC operating temperature are investigated by means of electrochemical characterization and single cell test. At a normal operation temperature of 60 °C and 38% RH, the MEA with optimized COF content (10 wt%) showes the maximum power density of 582 mW cm−2, which is almost 7 times higher than that of the routine MEA (85 mW cm−2). Furthermore, a preliminary durability test demonstrates the potential of the proposed PEMFC for practice operation under low humidity environment.
•A COF network was proposed to develop MEA with self-humidifying ability.•The COF network possesses water retention and proton transfer abilities simultaneously.•The COF network has excellent compatibility with Nafion ionomer and membranes.•The MEA shows excellent low humidity performance at 60 °C and 38% RH.•Durability test reveals the good stability of the MEA for low humidity operation.