Novel Deposition of Pt∕C Nanocatalysts and Nafion® Solution on Carbon-Based Electrodes via Electrophoretic Process for PEM Fuel Cells

Abstract

Nanosized platinum particles supported on carbon black carriers (Pt∕C) are popular for use in fabrication of proton exchange membrane fuel cells (PEMFCs). Here, an electrophoretic deposition (EPD) process is proposed to investigate the power performance of Pt∕C nanopowders onto various carbon-based electrodes for the PEMFC applications in a better controlled and cost-effective manner. Novel deposition of Pt∕C nanocatalysts and Nafion® solution via electrophoretic process give rise to higher deposition efficiency and a uniform distribution of catalyst and Nafion ionomer on the electrodes of PEMFCs. Preparation of an EPD suspension with good dispersivity is much desirable for an agreeable overall performance of catalyst coating in terms of types of organic solvents, milling processes, and use of pH adjusting agents and surfactants in the EPD suspension. The EPD suspension was prepared by sonication of mixture of Pt∕C nanopowders, Nafion solution and isopropyl alcohol, the optimal pH value of which was reached by using acetic acid or ammonium hydroxide. The colloidal stability of EPD suspension was achieved at pH ∼10 for an EPD suspension of either Pt∕C catalysts or mixture of Pt∕C catalysts and Nafion ionomer. A nicely distributed deposition of Pt∕C nanocatalysts and Nafion ionomer on both hydrophilic or hydrophobic carbon-based electrodes was successfully obtained by using Pt∕C concentration of 1.0g∕l, electrical field of 300V∕cm, and deposition time of 5min. Microstructural analysis results indicate that Pt∕C nanopowders not only embrace the entire surface of carbon fibers but also infiltrate into the gaps and voids in fiber bundles such that a higher contact area of the same loading of Pt∕C nanocatalysts through the EPD process is thus expected. At present, the EPD process can effectively save more of Pt catalyst loading on electrodes in PEMFC, as compared to conventional methods, such as screen printing, brushing, or spraying through the similar level of power performance for PEMFCs.