Investigation of the Effect of Pt Location in Catalyst Layer on Fuel Cell Performance Using Pt-photodeposited Polyaniline-Nafion Composite Film

Abstract

Photodeposition of platinum metal on one face of a polyaniline-Nafion composite membrane has been made in aqueous solution containing chloroplatinate and ascorbic acid as a hole scavenger to prepare a catalyst layer for O₂ electrode in a polymer electrolyte fuel cell. Fluorescent X-ray analysis of the Pt -deposited composite has revealed gradation of Pt amount is built in direction of membrane thickness by choosing conditions of membrane preparation and irradiation. Two types of membrane-electrode assemblies are fabricated using the Pt-deposited composite membrane; the Pt-deposited face is attached to polyelectrolyte of Nafion membrane or an O₂ gas electrode. The former fuel cell exhibits higher performance than the latter one, indicating that diffusibility of H⁺ in the catalyst layer tends to determine the cell performance. Changes in the cell performance caused by changing Pt amount allow to confirm that Pt amount is certainly gradated in the composite membrane.