Zeolite-templated electrocatalysts for fuel cells

Abstract

Abstract A method for the preparation of size-controlled Pt clusters on nanostructured carbon is described. The carbon possesses tunable micro- and meso-porosity, and forms an integrated matrix around the size-controlled Pt clusters. The process involves stabilization of Pt clusters in a zeolite host, pore-filling of the host with a carbon precursor, pyrolysis, and removal of the host. The properties of the catalysts vary over a wide range depending on the precise synthesis conditions. On one end of the spectrum, Pt clusters as small as 1.4 nm (average), with narrow size distribution in intimate contact with a predominantly microporous carbon network are obtained; on the other end, Pt clusters of average size 2.0 nm were obtained within a hybrid microporous/mesoporous carbon matrix. Low-angle X-ray diffraction shows periodic nanostructuring (d∼ 1.4 nm) for Pt/C with Pt loadings ≤ 17 wt.-%, which is confirmed by TEM imaging. Electrochemical evaluation showed these catalysts to have high electro-active surface areas, and to be at least as active as a commercial Pt/C in the reduction of oxygen.