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 °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 °C suggests that electrochemical oxidation leads to the passivation of the carbon, which when reduced in a potential excursion to ≤0.24 VRHE is lost allowing subsequent oxidation; however, CRC samples graphitised ≥2800 °C did not exhibit this same behaviour.

► We quantitatively determine electrooxidation of carbon support materials.
► We can distinguish between the total and partial electrooxidation.
► Non or mildly heat treated carbon forms passivating layer.
► Heat treated carbons are less sensitive to oxidation–reduction cycles.