A novel Pt/CeO2 catalyst coated with nitrogen-doped carbon with excellent performance for DMFCs

Abstract

In an attempt to improve the poor electron conductivity of CeO₂ as the catalyst support and enhance the activity and long-term durability of the Pt/CeO₂ catalyst, a novel catalyst has been developed based on in situ carbonization of ionic liquid to provide an N-doped carbon layer for the Pt/CeO₂ catalyst. X-ray diffraction, energy dispersive analysis of X-ray, high resolution transmission electron microscopy, electron energy loss spectroscopy, scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping, cyclic voltammetry and accelerated aging tests have been performed to characterize the catalyst. The as-prepared Pt/CeO₂ catalyst coated with ionic liquid showed significantly enhanced electrochemically active specific surface areas, and superior activity and durability compared to the uncoated Pt/CeO₂ catalyst for methanol oxidation, which may be attributed to the reasons as follows: the pyridine-like and pyrrole-like nitrogen with the enhanced π-bonding in N-doped carbon layers greatly enhance the electrical conductivity of the CeO₂ support through a change in the electronic delocalization effect of carbon atoms and a decrease in the loss of electron transfer energy; the surface of the coated CeO₂ support contains more active sites for Pt deposition and reduces the surface energy with more uniform Pt dispersion; the lone pair electrons of the N atoms can form a delocalized conjugated system with the sp²-hybridized carbon frameworks and strengthen the support–metal interactions; the increase of Lewis basicity of the CeO₂ surface results in strong anchoring of Pt to CeO₂; the increase of Pt(0) composition during the carbonization of ionic liquid. Different contents of ionic liquid coating the CeO₂ support were also investigated and the optimal content is 15 μL.