Control Mechanism of a Modified Buffer Layer on Interfacial Mass Transfer Efficiency for a Proton Exchange Membrane Fuel Cell at Varying Humidity

Abstract

The proton exchange membrane fuel cell (PEMFC) is one of the most important devices for the conversion of hydrogen energy to electricity. However, it is difficult to obtain an interfacial gas−liquid mass transfer balance at varying humidity. In this work, buffer layers were prepared at the interface of the gas diffusion layer (GDL) and catalyst layer. Different inorganic oxides (SiO 2 , Al 2 O 3 , and CeO 2 ) were used to modify the morphology, hydrophobicity, and gas permeability. It is found that particle size and agglomeration degree in the slurry significantly influence the physicochemical characteristic of buffer layers. The membrane electrode assemblies (MEAs) were operated at varying humidity levels to evaluate water management efficiency. Compared with a commercial GDL, these buffer layers effectively improve the interfacial mass transfer balance. Significantly, for the buffer layer containing CeO 2 , the rough surface and porous structure accelerated oxygen transfer and water removal. The mean maximum power density at varying humidity was 1.562 W cm −2 , which was 16.6% higher than that of an MEA containing a commercial GDL. In addition, the phenomenon of the gas−liquid separate flow process was also verified by interfacial two-phase flow simulation. According to electrochemical impedance spectroscopy, the charge transfer resistance and mass transfer resistance of MEAs containing a buffer layer were effectively controlled. In summary, this paper pointed out a novel strategy to improve the interfacial mass transfer efficiency of PEMFCs at complex operating conditions.