Carbon-nitrogen/graphene composite as metal-free electrocatalyst for the oxygen reduction reaction

Sheet-like carbon-nitrogen （CNx）/graphene composites with a high content of nitrogen （x 〈 0.15） was prepared by the carboniza- tion of polypyrrole （PPy）/reduced-graphene-oxide （rGO） composite at 600-800℃. We used rGO instead of graphene oxide （GO） sheets as a template and a substrate to immobilize PPy since the PPy/GO composite agglomerates easily because of the dehydration of excess oxygen-containing groups on the GO sheets during the drying process. The dried PPy/rGO intermediate and its derived CNJgraphene products retain their high dispersion and loose-powder features. The as-prepared CNJgraphene composites have a total nitrogen content of about 10 at% and their nitrogen state is mainly of pyridinic and graphitic type. CNJgraphene composites exhibit excellent performance for the oxygen reduction reaction （ORR） in terms of electrocatalytic activity, stability and immunity towards methanol crossover and CO poisoning, suggesting their potential as metal-free electrocatalysts for the ORR.