Electrochemical Oxygen Reduction Activity of Cobalt-Nitrogen-Carbon Composite Catalyst Prepared by Single Precursor Pyrolysis under Autogenic Pressure

Abstract

The synthesis of high surface area nitrogen doped carbonaceous catalyst was performed by employing a simple and unique RAPET (Reaction under Autogenic Pressure at Elevated Temperature) method. RAPET procedure involves the utilization of reactive gases formed during the pyrolysis of unsupported cobalt phthalocyanine (CoPc) in a closed stainless steel vessel without the flow of any gases from external source, temperatures of 900°C and estimated pressure of 2.5 × 107 Pa. X-ray diffraction patterns and XPS of CCoPc-900 (CoPc heat treated at 900°C by RAPET) indicate the formation of metallic phases of cobalt. These materials are found to catalyze oxygen reduction reaction (ORR) in alkaline solution. CCoPc-900 exhibited an improved electroactivity toward ORR in comparison to CCoPc-700 (CoPc heat treated at 700°C by RAPET) and CCoPc-900-OV (CoPc heat treated at 900°C in an open vessel under nitrogen flow). The oxygen reduction in the above-said carbonized materials proceeds through the formation of hydrogen peroxide followed by further reduction to water. Using RRDE (rotating ring disk electrode) experiments, we show that the ORR kinetics on CCoPc-900 is marginally better than CCoPc-900-OV.