Palladium Nanodendrites for Electrocatalytic Applications

Abstract

Polymer electrolyte membrane fuel cells (PEMFC) are attractive energy conversion devices for portable applications and electric vehicles owing to their high efficiency, high power density and low operating temperature. However, the high price and the limited resources of platinum catalysts are among the main challenges hindering their further commercialization. As palladium (Pd) possesses a similar valence electronic configuration to platinum and also has high methanol-tolerant ability, researchers have devoted to develop palladium-based catalysts as a promising alternative to platinum. A number of wet-chemical routes have been developed to produce Pd nanostructures to improve the catalytic activity and selectivity. However, they have been limited due to the use of organic surfactants, polymeric stabilizers at elevated temperature or template techniques relying on the use of nanometer-sized pores as structure-directing agents, which are technically complicated, due to the requirements for template removal to obtain pure products.In this work, Pd dendrites were prepared by electrochemical deposition directly on carbon-based substrates, which are widely used as support material in fuel cells. Electrodeposition of Pd was carried out on an electrochemically activated carbon black substrate using potentiostatic and cyclic voltammetric techniques. Comparison was also made with Pt dendritesprepared by the electrochemical deposition. The effects of electrochemical activation, deposition potential, time, precursor concentration and carbon loading were studied in relation to the morphology and development of the nanostructures. The results indicated that controlled insertion of defects on the carbon black during electrochemical activation favored a good metal-support interaction and improved the hydrophilicity of the surface, resulting in a dendritic morphology with enhanced catalytic activity towards oxidation and reduction reactions in fuel cells.