Abstract:

In Ar atmosphere,a novel N-doped carbon-based metal-free catalyst for the cathodic oxygen reduction reaction ( ORR) in fuel cells was prepared via the high-temperature carbonization of the hybrid precursors of melamine and polyaniline. Then,the effects of such factors as the precursors and the carbonization temperature on the catalyst performance were discussed,and the catalyst was characterized by means of XRD,TEM,DSC-TGA,Raman spectroscopy and FT-IR. The results show that ( 1) the optimal carbonization temperature is 900℃; ( 2) the process with the pyrolysis twice and with the acid treatment once benefits the enhancement of the catalyst activity; and ( 3) the catalyst is of excellent electrochemical activity and stability in the electrolyte with 0.1 mol /L of HClO₄,that is.after 10000 voltammetry circles,its electrochemical activity does not decrease but increases,with a half-wave potential of ORR of 0.42 V ( vs.Ag /AgCl) and a limited diffusion current nearly equal to that of the state-of-the-art Pt /C catalyst. In addition,it is found from Koutecky-Levich plots that the oxygen reduction on the catalyst is controlled by the four-electron transfer mechanism.

Key words: platinum-free catalyst, oxygen reduction reaction, melamine, polyaniline