Nanomaterials-Based PEM Electrodes by Combining Chemical and Physical Depositions

Abstract

The real market penetration of polymer electrolyte fuel cells is hindered by the high cost of this technology mainly due to the expensive platinum catalyst. Two approaches are followed to reduce the cost: one way is to increase the Pt utilization efficiency reducing at the same time the total load and the other way is to increase the catalytic activity of the catalyst/support assembly. In this work, the increase of utilization efficiency is addressed by optimizing the catalyst distribution on the uppermost layer of the electrode via electrodeposition and sputter deposition, while the improvement of the catalyst activity is pursued by nanostructuring the catalysts and the carbon-based supports. A very low Pt loading (0.006 mg cm−2) was obtained by sputter deposition on electrodes that exhibited a mass specific activity for methanol oxidation reaction better than a commercial product. Carbon nanofibers used as catalyst support of electrodeposited platinum nanoparticles resulted in improved mass specific activity and long term stability compared to conventional carbon-based supports. Finally, PtAu alloys developed by sputter deposition were found more efficient than commercial PtRu catalyst for the methanol oxidation reaction. In conclusion, polymer electrolyte membrane fuel cell electrode based on nanomaterials, developed by combining physical and chemical deposition processes, showed outstanding electrochemical performance.