Comparative DEMS study on the electrochemical oxidation of carbon blacks

The intention of the study presented here is to compare the electrochemical oxidation tendencies of a pristine Ketjen Black EC300 high surface area (HSA) carbon black, and four graphitised counterparts heat-treated between 2100 and 3200 degrees C, such as those typically used as corrosion resistant carbon (CRC) supports for polymer electrolyte membrane fuel cell (PEMFC) catalysts. A methodology combining cyclic voltammetry (CV) and differential electrochemical mass spectrometry (DEMS) is used, which allows the characterisation and comparison of the complete electrochemical oxidation rates and behaviours of the various carbon blacks. It is observed that the behaviour of the carbon black towards electrochemical oxidation is highly dynamic, and dependent on the properties of the pristine carbon back, the degree of electrochemical oxidation and the potential pre-history. The behaviour of the non-graphitised and CRC samples graphitised <= 2450 degrees C suggests that electrochemical oxidation leads to the passivation of the carbon, which when reduced in a potential excursion to <= 0.24 V-RHE is lost allowing subsequent oxidation; however, CRC samples graphitised >= 2800 degrees C did not exhibit this same behaviour. (C) 2012 Elsevier B.V. All rights reserved.