Effect of Pt-loaded carbon support nanostructure on oxygen reduction catalysis

This work demonstrates the impact of the nanostructure (pore size, wall thickness and wall crystallinity) of several carbon materials on their performance as oxygen reduction reaction (ORR) catalyst supports in PEM fuel cell applications. Two different mesoporous carbons [a surfactant-templated ordered mesoporous carbon (OMC) with 1.6 and 3.3 nm pores, and a silica colloid-imprinted carbon (CIC) with a 15 nm pore size], selected as being the most active in their class, were compared with microporous Vulcan Carbon. After loading with 20 and 40% Pt, both 3D transmission electron microscopy and electron tomography revealed that the Pt nanoparticles reside inside the majority of the pores of the OMC and CIC, but are located only on the outer surface of the VC particles. ORR performance studies on a rotating glassy carbon disc electrode in O2-saturated 0.5 M H2SO4 showed that the Pt-loaded CIC outperforms both Pt-loaded OMC and VC. This is attributed to the higher electronic conductivity (due to the thicker and more crystalline walls, seen by both X-ray diffraction and thermogravimetric analysis) and facilitated mass transport in the larger pores of the CIC support.

Research highlights
► First-time comparison of ORR activity at several Pt-loaded mesoporous carbons.
► Catalyst sequence: Pt/CIC > Pt/OMC > Pt/Vulcan Carbon.
► CIC support has larger pores and thicker, more crystalline walls compared to OMC.
► Superior performance of Pt/CIC due to larger pores and improved mass transport.
► TEM tomography shows Pt is uniformly inside mesoporous carbon pores.