Durability Study on SWNT/Nanofiber Buckypaper Catalyst Support for PEMFCs

Abstract

Due to their unique microstructure, buckypaper-supported platinum (Pt) catalysts derived from carbon nanotube and carbon nanofiber have demonstrated a high Pt utilization in proton exchange membrane fuel cells (PEMFCs). [SWNT means single-walled carbon nanotube.] The durability of a buckypaper-supported Pt catalyst was investigated using an accelerated degradation test (ADT) in a mimic cathode environment of PEMFC. Compared to commercial carbon black-supported Pt, Pt/buckypaper showed a better catalyst durability after holding at 1.2 V for 400 h; specifically, almost 80% of the Pt electrochemical surface area was lost for Pt/carbon black, with only a 43% loss for Pt/buckypaper. Transmission electron microscopy and cyclic voltammetry were used to study the Pt degradation mechanism. It was concluded that Pt coarsening and Pt detachment from buckypaper support due to carbon corrosion make the major contribution to the Pt surface area loss under this condition. The Pt loss via detachment from supports after the ADT was calculated as 18% in Pt/buckypaper, while the Pt loss was 69% in Pt/C. It is supposedly due to the higher corrosion resistance of buckypaper because of its high graphitization degree, which is indicated by a slower formation rate of surface oxides in buckypaper than in carbon black. Further durability improvement of the Pt/buckypaper is expected by improving the dispersion of Pt on the buckypaper to reduce Pt sintering.