Electrocatalysis of oxygen reduction reaction on polyaniline-derived nitrogen-doped carbon nanoparticle surfaces in alkaline media

Abstract

Nitrogen-doped carbon nanomaterials were synthesized by the carbonization of three different nanostructured polyaniline (PANI) salt precursors: PANI 3,5-dinitrosalicylate nanorods, PANI 5-sulfosalicylate nanorods/nanotubes, and PANI hydrogen sulfate nanorods/nanotubes/nanosheets. A comparative study of the electrocatalytic activity of these materials for oxygen reduction reaction (ORR) in alkaline solution was performed by using rotating disk electrode voltammetry. The electrochemical data were correlated to the structural and textural data obtained by Raman spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, elemental analysis and nitrogen sorption analysis. A fine interplay of textural characteristics, overall content of surface nitrogen and content of specific surface nitrogen functional groups were found to be responsible for a considerable variations in electrocatalytic properties toward ORR, involving variations in apparent number of electrons exchanged per O2 molecule (from 2 to nearly 4) and variations in onset potential. The catalyst loading was found to influence remarkably the ORR kinetics. The excellent electrocatalytic activity was found for carbonized PANI 5-sulfosalicylate. Namely, it exhibited the most positive onset potential amounting to −0.05 V vs. SCE at a catalyst loading of 500 μgcm−2. The interrelation between the electrocatalytic activity and the electrical double layer charging/discharging characteristics of the investigated N-doped nanocarbon materials was revealed.