Template-synthesized cobalt porphyrin/polypyrrole nanocomposite and its electrocatalysis for oxygen reduction in neutral medium

For the first time, a linear J-aggregate of cobalt porphyrin and its templated, nanostructured cobalt porphyrin/ polypyrrole composite are formed in neutral aqueous solutions. With the assistance of ultrasonication under different preparation procedures, the nanocomposite can be electrochemically synthesized with uniform 2-D and 3-D nanostructures. The 3-D nanocomposite is synthesized by a three-step method and has an interesting regular nanoarray-structure: a vertical nanorod array with uniform diameters (∼50 nm). The resultant nanoarray catalyzes the oxygen reduction mainly through a four-electron pathway to form H₂O in a neutral medium, exhibiting excellent electrocatalytic activity. The mechanisms of formation of the nanocomposite and its good electrocatalysis for oxygen reduction are suggested. The new nanocomposite could have broad potential applications in energy storage systems and electrochemical sensors, particularly in a neutral medium for the biofuel cells and biosensors.