Abstract
High performing proton exchange membrane fuel cells (PEMFCs) that can operate at low relative humidity is a continuing technical challenge for PEMFC developers. In this work, micro-patterned membranes are demonstrated at the cathode side by solution casting techniques using stainless steel moulds with laser-imposed periodic surface structures (LIPSS). Three types of patterns, lotus, lines, and sharklet, are investigated for their influence on the PEMFC power performance at varying humidity conditions. The experimental results show that the cathode electrolyte pattern, in all cases, enhances the fuel cell power performance at 100% relative humidity (RH). However, only the sharklet pattern exhibits a significant improvement at 25% RH, where a peak power density of 450 mW cm−2 is recorded compared with 150 mW cm−2 of the conventional flat membrane. The improvements are explored based on high-frequency resistance, electrochemically active surface area (ECSA), and hydrogen crossover by in situ membrane electrode assembly (MEA) testing.
Highlights
The extensive commercialisation of proton exchange membrane fuel cells (PEMFCs) is still limited by several technical challenges, which have been identified as performance, cost, and durability [1,2]
The catalyst layer conforms to the pattern’s shape, with the medium features being visible from the images
The results show that the Ion exchange capacity (IEC) values remain nearly the same for all membranes despite the surface topography change (Figure 2), which confirms that IEC is a bulk property controlled by the material (Nafion for all samples) and not the surface properties
Summary
The extensive commercialisation of proton exchange membrane fuel cells (PEMFCs) is still limited by several technical challenges, which have been identified as performance, cost, and durability [1,2]. The membrane’s water content influences its properties, ionic conductivity. The water improves the transport of protons through the cell, changing the transport mechanism from “Grotthus” to “Vehicular”, as discussed by Elliot et al [9], and proton-conducting ability increases with the water content. When the membrane is saturated with water, it has the highest conductivity. The only downfall of saturation is that the cathode can become ‘flooded’ with water, which prevents the transport of oxygen to the cathode catalyst layer, reducing the cell’s performance. Water balance in a fuel cell is vital to avoid ‘flooding’ and to maintain high performance [10]
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