Enhancing the pyridinic N content of Nitrogen-doped graphene and improving its catalytic activity for oxygen reduction reaction

Nitrogen-doped graphene (NG) has been extensively studied as an effective candidates of the oxygen reduction reaction (ORR) catalysts due to its high activities. Whereas, there are still some ambiguities or controversies on the contributions of the three N configurations (pyridinic N, pyrrolic N and graphitic N) for the ORR catalytic activity of NG. Herein, we adopt a facile hydrothermal method followed by the annealing treatment at the different temperatures to tailor the contents of the three N configurations in NG. Then, the contributions of the N configurations on the ORR catalytic activities can be evaluated. The annealing treatment can effectively enhance the content of pyridinic N in NG obtained from the hydrothermal method, and the pyridinic N content increases obviously with the increase of the annealing temperature from 600 degrees C to 800 degrees C. The increase of the pyridinic N content causes an improved catalytic activity of NG toward ORR, which confirms that pyridinic N is the active center of NG for ORR. In addition, the stability of NG also can be improved with the increase of the pyridinic N content. Our work will open up new avenues for the developments of the Nitrogen-doped graphene electrocatalysts of practical significance for ORR. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.