Electrochemical oxidation of carbon black in concentrated phosphoric acid at 135°C

The electrochemical oxidation of a high surface area carbon black (1000 m2/g) was investigated in 96% H3PO4 at 135°C. The total anodic current, the amount of CO2 evolved and the oxygen content of the carbon were all measured as a function of time and potential. Two anodic processes occurred: the formation of a surface oxide and the evolution of CO2. Both decreased with time but at different rates so that CO2 evolution eventually became the major reaction. Various mechanisms to define the corrosion processes are discussed.