Pyridinic-N-dominated Doped Defective Graphene as Superior Oxygen Electrocatalyst for Ultrahigh-Energy-Density Zn-Air Batteries

Qichen Wang, Yujin Ji, Yongpeng Lei, Yaobing Wang, Yingde Wang, Youyong Li, Shuangyin Wang

Index: 10.1021/acsenergylett.8b00303

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Abstract

Identification of catalytic sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in carbon materials and design of efficient metal-free bifunctional electrocatalysts remain a great challenge. Here, we construct a novel pyridinic-N-dominated doped graphene with abundant vacancy defects. The optimized sample with an ultrahigh pore volume (3.43 cm3 g−1) exhibits unprecedented ORR activity with a half-wave potential of 0.85 V and an efficient OER activity in alkaline. For the first time, density functional theory results indicate that the quadri-pyridinic N-doped carbon site synergized with vacancy defect is the active site, which presents the lowest overpotential of 0.28 V for ORR and 0.28 V for OER. As a proof of concept, the primary Zn-air batteries were assembled and display a maximum power density of 115.2 mW cm-2 and an energy density as high as 872.3 Wh kg-1, superior to those of Pt/C catalyst. The rechargeable Zn-air batteries illustrate a low discharge-charge overpotential and excellent stability (> 78 h). This work provides the new insight into the correlation between N configuration synergized with vacancy defect and ORR/OER catalysis, which is helpful for exploiting more efficient and robust electrocatalysts in energy conversion devices.