Bifunctional metal-free catalysis of mesoporous noble carbons for oxygen reduction and evolution reactions.

Electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key reactions in lithium-oxygen batteries (LOBs) being a promising candidate to store renewable energies due to their high specific energy. However current development on LOBs is suffering from unsuitable catalysts. In particular, carbon-based catalysts were found to perform poorly in this system. Here, we show that metal-free mesoporous nitrogen-doped carbons (meso-NdCs) offer highly promising performances in both ORR and OER; they act as bifunctional catalysts, and can be synthesized by a very simple method. The efficient electrocatalytic activity of ORR and OER was used in a LOB cell during discharge and charge, respectively, and the present system showed a lower overpotential comparable to metal-based catalysts in LOB system. Thus, we demonstrate that meso-NdCs act as a new and affordable candidate for the efficient bifunctional oxygen catalysis, therefore can be applied to many energy-related applications.