Origin of the Catalytic Activity Improvement of Electrochemically Treated Carbon – An Electrical and Electrochemical Investigation

Improvement in catalytic activity of electrochemically treated carbon (relative to the untreated carbon) toward various redox reactions is widely reported in the literature. In this work, the origin of such activity enhancement due to electrochemical treatment in a 1 M H2SO4 electrolyte in a potential range of 1-2.5 V is investigated using physical, electrical, and electrochemical methods. The physical characterizations suggest intercalation of anions (bisulfate) between the graphite layers from the H2SO4 electrolyte. Electrical characterizations (both Hall measurement and Mott-Schottky analysis) show that the samples switch from n-type to p-type behavior upon electrochemical treatment. The improvement in the catalytic activity on electrochemical treatment of carbon is explained on the basis of the change in surface characteristics, carrier concentration (N-D), and active site density. The same is validated with oxygen reduction reaction in alkaline media.