Influence of support porosity and Pt content of Pt/carbon aerogel catalysts on metal dispersion and formation of self-assembled Pt–carbon hybrid nanostructures

Abstract

Three carbon aerogels with different meso–macropore networks were used as supports for Pt catalysts using [Pt(NH3)4]Cl2 as precursor salt. Results obtained showed mesopore volume and mean mesopore size to be important parameters that control Pt particle size and dispersion in catalysts containing 2 wt.% Pt. Once the most appropriate porosity to obtain the highest dispersion was determined, the metal content was increased to 20 wt.% Pt. However, the mean Pt particle size only increased from 1 to 2 nm, indicating the importance of an appropriate mesoporosity for obtaining a high dispersion at high metal loading. Mean Pt particle size was always slightly smaller by transmission electron microscopy than by H2 chemisorption, because some Pt particles were not reduced during pre-treatment, as confirmed by X-ray photoelectron spectroscopy. Finally, transmission electron microscopy observations of catalysts with metal loading of 8–20 wt.% before pre-treatment showed the formation of self-assembled Pt–carbon hybrid nanorods and nanowires. To the best of our knowledge, this is the first observation of this phenomenon in Pt/C catalysts.