Among all the challenges for the development of renewable energies including fuel cells, metal-air batteries, the catalyst for oxygen reduction reaction (ORR) is the a main obstacle that limits the large scale applications of such new technologies. The fuel cells or metal-air batteries will find outstanding applications in the real life of human beings when the expensive platinum (Pt)-based electrocatalysts are replaced by efficient, low-cost, and stable cathodes. Graphitic carbon materials modified with nitrogen (N) substitution, or substitutional N-doping, have been recognized to be powerful catalysts for the ORR. For instance, several reports have demonstrated that N-doped activated carbon, carbon nanotubes and graphene, possess surprising catalytic activities for the ORR. The improved catalytic performance was attributed to the electron withdrawing ability of the N atoms, which creates a net positive charge on adjacent carbon atoms to attract electrons from the anode more easily, so as to facilitate the ORR.
Graphdiyne (GD), a novel 2D structure in the carbon family that contains both sp and sp2 carbon atoms, was proposed by Haley et al in 1997, and was predicted to be the most stable among the various diacetylenic non-natural carbon allotropes. It has been predicted that some GD allotropes, which do not have hexagonal symmetry and two self-doped nonequivalent distorted Dirac cones, could possess electronic properties superior to that of graphene. Besides, due to the extra alkyne units between benzene rings in the GD, the pore size of the network is increased to approximately 2.5 Å, which will facilitate air adsorption in the pores when the sample is exposed to air. Thus, this would be a natural advantage of GD which is therefore ranked amidst the best metal-free catalysts for the ORR. Furthermore, considering the intriguing properties of N-doped graphitic carbon materials, the doping of GD with N only remains predictive and theoretical, without sufficient experimental support to date. Herein, we report for the first time that N-doped GD was successfully prepared and it can act as a metal-free catalyst with a comparable electrocatalytic activity, but with a better stability and an increased tolerance to the crossover effect than commercial Pt/C for oxygen reduction in alkaline fuel cells.
This work has been published on the Nanoscale, 2014, 6, 11336–11343. The related research work was supported by the National Natural Science Foundation of China (no. 21371173) and the China Postdoctoral Science Foundation (2014M550846).
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