Abstract
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Metal-oxygen batteries are thought to be the ultimate energy storage solution due to their high specific energy. We report here on the synthesis of mesoporous boron-doped onion-like carbon (B-OLC) microspheres and their application in rechargeable sodium-oxygen (Na-O2) batteries. Low overpotential, high specific capacity (over 10200 mA h g-1), enhanced rate capability (���7500 mA h g-1 at 0.6 mA cm-2) and excellent cyclability (up to 125 cycles) can be achieved by using B-OLC based electrodes in Na-O2 batteries. The critical role of surface chemistry on the morphology and composition of products is studied and the optimum performance of Na-O2 batteries with B-OLC based electrodes is attributed to the synergistic effects arising from the combination of catalytic activity and the uniquely mesoporous carbon nanoarchitecture. This study indicates that mesoporous B-OLC demonstrated intriguing properties and great potential applications as effective metal-free bifunctional catalysts for Na-O2 batteries and encourages the development of heteroatom-doped carbon materials for performance improvement of metal-oxygen batteries.