Pt-Au Film Catalyst for Formic Acid Oxidation

Abstract

Direct formic acid fuel cells (DFAFCs) have shown promise as efficient and renewable power sources for portable electronics. However, pure Pt catalysts exhibit poor activity for the formic acid oxidation reaction (FAOR) due to the formation of poisoning species, which slow down the rate of oxidation. Here, we report on the novel synthesis of a bimetallic, Pt-Au film electrocatalyst for the oxidation of formic acid (HCOOH). A bilayer stack composed of individual Pt and Au metal layers was deposited using magnetron sputtering, resulting in a smooth surface consisting of tightly packed nanocrystallites. At room temperature, the bilayer stack shows the electrochemical characteristics of a pure Pt surface. A post-synthesis heat treatment was carried out to form a bimetallic film consisting of the two metals. As a result, the heat-treated film showed electrochemical characteristic of both metals, indicating a mixed metal surface. The Pt-Au catalyst surface exhibited greatly enhanced activity for formic acid oxidation compared to a commercial bulk Pt catalyst. The presence of Au on the catalyst surface promotes the oxidation of formic acid through the direct dehydrogenation pathway, via the ensemble effect. Therefore, the heat treatment of a sputtered bilayer stack provides a simple method for forming stable bimetallic Pt-Au catalysts with high activity for the oxidation of formic acid.