Electrochemical oxygen reduction activity of metal embedded nitrogen doped carbon nanostructures derived from pyrolysis of nitrogen-rich guanidinium salt

Nitrogen and transition metal containing carbon composites are considered as promising non-platinum oxygen reduction catalysts with potential to replace Pt in fuel cell cathodes and metal-air batteries. Nitrogen-rich precursor guanidinium chloride, transition metal salts (Fe/Co) and high surface area carbon spheres are pyrolyzed to yield non-platinum composite electrocatalysts with new and interesting morphological features. Based on rotating ring-disk electrode (RRDE) experiments, both cobalt, and iron containing composite catalysts exhibited significant oxygen reduction activity in alkaline solutions with E_1/2 values (∼60 mV lower) of best catalyst comparable to Pt/C. The kinetic parameter analysis, using Koutecky-Levich relation, for the best catalyst made of cobalt, nitrogen and carbon (Co-N-C) show specific exchange current densities of 0.1 mA mg^-1, Tafel slopes of 75-80 mV dec^-1 and %H₂O₂ of 10-13% of the total current in alkaline solution. XRD, BET, XPS and Raman spectral study serve as a complementary tool to evaluate the structure of the composite electrocatalysts.