Enhanced electrocatalytic activity of platinum nanoparticles supported on nitrogen-modified mesoporous carbons for methanol electrooxidation

摘要

Nitrogen-modified mesoporous carbons (N-MCs) are synthesized via a modified dual-templating approach, in which phenolic polymer is used as a carbon source, dicyandia-mide as a nitrogen source, silica nanospheres as a hard template, and triblock copolymer F127 as a soft template, respectively. Structural characterizations reveal that the N-MCs with large mesopore and uniform mesoporous networks possess three different nitrogen-containing groups, all of which can serve as catalytically active sites. Platinum nanoparticles supported on N-MCs (Pt/N-MCs) are prepared by polyol reduction method. As supported by transmission electron microscopy (TEM), homogeneously dispersed Pt nanoparticles are attached to the pore wall of N-MCs with an average size of ca. 2.0 nm, much smaller than that of commercial Pt/C. Electrochemical studies reveal that the Pt/N-MCs has higher electrocatalytic activities for methanol oxidation in comparison to the Pt/ MCs and commercial Pt/C, which may be attributed to pyridinic and pyrrolic nitrogen offering p electrons to the sp~2 hybridized graphitic carbon layers, leading to the decrease of inner electrical resistance and enhanced proton diffusion rate, as well as a more uniform particle size distribution of Pt on N-MCs.