High-efficiency pt catalyst supported on nitrogen-doped carbon nanotubes for methanol electrooxidation

Nitrogen-doped carbon nanotubes (NCNT) with N-content of 3%~5%(w/w) and specific surface area of 235 m²·g^-1 were used as support for the immobilization of Pt nanoparticles. Pt nanoparticles were highly dispersed on NCNT without needing pre-modification of the support by taking advantage of the inherent chemical activity of NCNT arising from the N-incorporation. A series of Pt/NCNT catalysts with the loadings of 18.2%~58.7%(w/w, the same below) were conveniently prepared via the microwave-assisted polyol reduction. With increasing Pt loading, the average sizes of Pt nanoparticles increase slightly from 2.2 to 3.7 nm. The mass activity for MOR first increases and reaches the maximum at Pt loading of 47.8%, then decreases dramatically, while the activity based on the Pt mass presents a high-value platform in the Pt-loading range of 27.6%~47.8%. Such a changing tendency is well correlated with the remarkable difference of MOR activity for Pt nanoparticles with the sizes smaller and larger than 3 nm, respectively. The dramatic activity deterioration for the catalyst with high Pt-loading of 58.7% comes from the serious agglomeration of Pt nanoparticles, leading to poor Pt utilization.