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Charge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high-valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X-ray photoelectron spectroscopy (APXPS) on a model LiCoO

Developing low-cost and efficient oxygen electrocatalysts for oxygen reduction and evolution reaction (ORR&OER) is critical for various energy conversion technologies. Herein, we report an arc discharge strategy coupled with an controllable oxidation to prepare Co/Co3O4 nanoparticles confined in ultrathin O-doped graphitic carbon layer (Co/Co3O4@ODGC) as highly active bifunctional oxygen electrocatalysts for Zn-air batteries (ZABs). The resultant Co/Co3O4@ODGC shows an impressive ORR performance with a half-wave potential of 0.80 V in 0.1 M KOH. It also exhibits remarkable OER performance with a small overpotential of 300 mV to reach a current density of 10 mA cm−2. Both experimental studies and theoretical calculations indicate that the high ORR and OER activities are attributed to the synergistic electronic effect between the Co/Co3O4 heterostructures and ultrathin O-doped graphitic layer (~1.5 nm). Particularly, the electron redistribution in graphitic layer caused by O-doping and carbon defects significantly decreases the energy barrier for oxygen adsorption/desorption. More attractively, the as-constructed ZABs with Co/Co3O4@ODGC cathode show an impressive open voltage (1.60 V), a high power density of 107 mW cm−2, and good stability without nearly no performance decay for 40 h at 2.0 mA cm−2. This work provides both fundamental understanding and easy strategy for developing the efficient bifunctional oxygen electrocatalysts for high performance metal-air batteries.