The Corrosion of Carbon Black Anodes in Alkaline Electrolyte: I . Acetylene Black and the Effect of Cobalt Catalyzation

14 C labeling of acetylene black was used together with mass spectroscopic analysis of the gas evolved to determine the current efficiencies for oxygen evolution, carbon dissolution, and carbon gasification (to carbon monoxide). The current efficiencies were found to depend dramatically on potential, temperature, and the presence of an evolution catalyst like . On uncatalyzed black, three regimes could be distinguished: ( i ) at potentials below 500 mV vs. and temperatures below 50°C, carbon dissolution is the primary anodic process, ( ii ) at 500–600 mV and 50°C or lower, carbon dissolution and oxygen evolution occur at equivalent rates, and ( iii ) above ca. 600 mV or above ca. 60°C, oxygen evolution and gasification of the carbon to carbon monoxide are the dominant processes. Catalyzation with collapsed these regimes so that all three anodic processes are concurrent throughout the potential region of interest, and the overall rate of corrosion increased significantly. In addition, catalyzation caused the production of organic products ( ca. 5% current efficiency) in a potential region where none is produced from acetylene black alone. The mechanism of action of on the acetylene black corrosion is not yet understood, but there is evidence that direct physical contact between the particles and carbon particles is not required to produce accelerated corrosion of the carbon.