Towards an optimal synthesis route for the preparation of highly mesoporous carbon xerogel-supported Pt catalysts for the oxygen reduction reaction

Abstract

Pt particles were supported on a highly mesoporous carbon xerogel and used as catalysts for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). Different synthesis routes were followed in order to study their influence on the characteristics and the performance of Pt electrocatalysts, therefore determining the optimal synthesis method for the preparation of these carbon xerogel supported catalysts, leading to the highest catalytic activity. The highest active catalyst was compared to a Pt catalyst supported on commercial carbon support, Vulcan, synthesized in the same conditions. Synthesis methods studied were impregnation, following two different reduction protocols (sodium borohydride and formic acid), and microemulsion, used for the first time for carbon xerogels. The electrochemical characterization proved that the catalysts’ synthesis method strongly influenced the catalytic behavior. The impregnation method and reduction with formic acid lead to the highest active catalyst towards ORR. When compared to an analogously prepared Vulcan carbon black-supported catalyst, the carbon xerogel-based one still showed enhanced performance, in spite of higher ohmic loss, due to the lower electrical conductivity of this carbon material.