Preparation of gas diffusion electrodes using PEG/SiO_2 hybrid materials and the effect of their composition on microstructure of the catalyst layer and on fuel cell performance

摘要

Gas diffusion electrodes for proton-exchange membrane fuel cells (PEMFC) have been prepared using poly(ethylele glycol) (PEG)/SiO_2 hybrid materials. The catalyst layers were composed of carbon-supported Pt catalyst (Pt-CB) and PEG/SiO_2 hybrid materials. During the course of the catalyst ink preparation, a proton-conducting hybrid material-coated catalyst was obtained in paste form through sol-gel processes. PEG/SiO_2 hybrid materials were incorporated into the catalyst layer by two different approaches. In the first approach, the sol-gel reaction was initiated well before mixing the hybrid materials with catalyst while in the second approach, the gelling reaction was initiated only after mixing of all the constituents. For the optimized composition, the performance of electrodes prepared by the first approach was higher compared to the second approach. The microstructures of the catalyst layers of former electrodes were investigated using mercury porosimetry as a function of composition. It was found that beyond the optimum composition, the cell performance decreased continuously due to excess hybrid materials in the catalyst layer, which blocks the gas diffusion channels. The PEG/SiO_2 hybrid material is demonstrated to be a promising electrode material for the PEMFC.