Three-dimensional Polypyrrole Derived N-doped Carbon Nanotube Aerogel as a High-performance Metal-free Catalyst for Oxygen Reduction Reaction

摘要

A novel N-doped carbon nanotube aerogel has been synthesized by pyrolysis of the three-dimensional tubular polypyrrole networks and evaluated as a metal-free electrocatalyst for the oxygen reduction reaction. The carbon aerogel catalysts are pyrolyzed at 500 degrees C (PPy/C-500), 700 degrees C (PPy/C-700), 900 degrees C (PPy/C-900) and 1050 degrees C (PPy/C-1050), and display the pyrolyzed temperature-dependent activity and stability. The catalytic activity is increased with the increase of pyrolysis temperature from 500 degrees C to 1050 degrees C, ascribed to the high electronically conductive graphitic phases, the thin wall of the three-dimensional tubular carbon aerogel framework and the increased effective active sites. The nitrogen content is reduced with the increase of pyrolysis temperature, and which plays an important role in the stability of the pyrolyzed catalyst. After 1500 cycles, the PPy/C-1050 catalyst shows more positive half-wave potential than the commercial Pt/C catalyst, and displays a quasi-four-electron pathway toward the oxygen reduction reaction in the acid solution. This work provides an effective strategy for preparing the low cost and metal-free N-doped carbon aerogel catalyst from the conjugated conducting polymer, to achieve high activity and stability.