Highly Localized C-N2 Sites for Efficient Oxygen Reduction

The search for oxygen reduction reaction (ORR) catalysts outperforming Pt, the state-of-the-art material, continues. Doped carbon-based materials offer a viable means for replacing Pt, but their activity improvement still remains a great challenge. Here, configurations of N-doped carbons are first analyzed using ab initio simulations toward ORR. The results show that a certain short-range ordered structure labeled as C-N2, which comprises of two nitrogen atoms flanking carbon, is the optimal choice. The predicted configuration of C-N2 is experimentally realized by triazine-doped carbon (triNC). The triNC with C-N2 sites demonstrates high ORR activity (onset potential 0.98 V, halfwave potential 0.89 V) comparable to commercial 20% Pt/C. The highly localized and positive-charged carbon atom in the C-N2 structure facilitates the dissociation of O-2 to increase the ORR kinetics, proved by theoretical calculation. A Zn-air cathode is fabricated using the triNC ORR electrocatalyst and outperforms the cathode using Pt/C in terms of specific capacity, energy density and long-term durability. The atomic-scale approach reported here provides a good strategy to achieve active carbon-based electrocatalysts for potential and scalable use in energy conversion and storage.