A simple method for estimating the electrochemical stability of the carbon materials

摘要

The corrosion stability of a series of carbon supports of various porous structure and morphology: commercial carbon blacks, carbon carbon composite, and multiwall carbon nanotubes was studied using start-stop protocol cycling (1-1.5 V vs reversible hydrogen electrode (RHE) potential range with 0.5 V/s of scan rate) in an electrochemical cell at 25 degrees C using 0.1 M HClO4 as electrolyte. Two stability regions were revealed for the first time depending on the cycle number. The first one is characterized by a constant value of quinone/hydroquinone (QH) transition potential. In the second part anode and cathode QH peaks gradually shift toward higher and lower potentials respectively, which is due most likely to a complete degradation of the supports. We proposed an effective resistance (R-eff) as the corrosion stability parameter that can be easily obtained from the cyclic voltammetry (CV) data. Based on these results, a model of corrosion of porous carbon materials supported on glassy carbon rod was proposed. It was shown that the decrease in the R-eff of the samples in the initial stages of degradation is due to the increase in the number of QH groups on the surface, while a sharp increase in the R-eff upon further cycling can be explained by a decrease in the number of contacts between the carbon grains. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.