Physico-chemical properties of carbon nanotubes as supports for cathode catalysts of fuel cells. Surface structure and corrosion resistance

Abstract

Multiwalled carbon nanotubes (CNTs) were synthesized by catalytic pyrolysis of methane on iron-cobalt or cobalt-molybdenum catalyst and investigated by electrochemical and physico-chemical methods before and after chemical or electrochemical corrosion treatment. It is shown that CNTs have a higher corrosion resistance than does turbostratic carbon (carbon black) in corrosion testing under the same conditions. This is expressed in a smaller change in the amount of oxygen on the surface of the carbon material, the values of the electrochemically active surface area (EAS), and in significant differences of these quantities for the CNTs compared to carbon black. Quantitative comparison of the results of chemical and electrochemical treatment of CNT and carbon black, which was performed in this paper for the first time, leads to the conclusion regarding the advantages of corrosion testing by chemical method. Chemical testing simulates to a greater extent the long-term testing conditions of the supported catalysts composed of membrane-electrode assemblies of fuel cells in terms of evaluating the stability of the carbon material as a support of the catalytically active centers.