Layer-by-Layer Polydimethylsiloxane Modification Using a Two-Nozzle Spray Process for High Durability of the Cathode Catalyst in Proton-Exchange Membrane Fuel Cells

The catalyst layer's high durability is essential in commercializing polymer electrolyte membrane fuel cells (PEMFCs), particularly for vehicle applications, because their frequent on/off operation can induce carbon corrosion, which affects surface properties and morphological characteristics of the carbon and results in aggregation and detachment of Pt nanoparticles on the carbon surface. Herein, to address the carbon corrosion problem while delivering a high-performance PEMFC, polydimethylsiloxane (PDMS) with high gas permeability, chemical stability, and hydrophobicity was employed to protect the catalyst layer from carbon corrosion and improve the mass transport. Because the catalyst slurry using alcohol-based solvents showed low compatibility with nonpolar solvents of the PDMS solution, a parallel two-nozzle system with separated solution reservoirs was developed by modifying a conventional three-dimensional printing machine. To determine the optimal PDMS amount in the cathode catalyst layer, PDMS solution concentration was varied by quantitatively controlling the PDMS amount coated on the electrode layer. Finally, the PEMFC with the PDMS-modified cathode of 0.1 mg_PDMS cm^-2 loading showed enhanced durability due to increased electrochemical surface and maximum power density by 37.2 and 21.7%, respectively, after the accelerated stress test. Furthermore, an improvement in the initial performance from enhanced water management was observed compared to those of PEMFCs with a conventional electrode.