All sprayed fluorine-free membrane electrode assembly for low-platinum and low-humidity proton exchange membrane fuel cells

Abstract

Reducing the platinum catalyst loading and humidity dependence of membrane electrode assemblies (MEAs) is highly desirable for commercializing proton exchange membrane fuel cells (PEMFCs). Meanwhile, replacing the perfluorinated sulfonic-acid PEMs with fluorine-free hydrocarbon membranes can reduce manufacturing costs. We present an all spraying (AS) method to fabricate a fluorine-free hydrocarbon-based MEA (AS-MEA). Such an MEA achieves a much higher H₂/O₂ fuel cell performance than the conventional catalyst-coated substrate MEA (CCS-MEA). The peak power density is 1.6 W cm⁻² for the AS-MEA vs. 1.2 W cm⁻² for the CCS-MEA with 100% relative humidity (RH) and 0.1/0.1 L per min H₂/O₂ and 0.1 MPa backpressure gas feeds. More importantly, the performance superiority is particularly prominent at low RH and catalyst loading. The AS-MEA achieves a competitive peak power density of 0.6 W cm⁻² at 40% RH with a low Pt loading of 0.1 mg cm⁻², which is more than 3-fold that of the CCS-MEA. Equivalent-circuits-based analyses of electrochemical impedance spectroscopy show that the exceptional performance arises from the tightly integrated PEM–catalyst layer boundary, as confirmed by the cross-sectional morphological investigations. Moreover, the AS-MEA shows appreciable in situ durability during a 100 h accelerated stress test.