Thermal activation of graphitic carbon nanosheets for high-performance oxygen electrocatalysis

Carbon–based electrocatalysts have considerable application potential in renewable clean energy conversion systems. Although graphitic carbons have advantages of high conductivity and electrolyte corrosion resistance, its sp2–hybridized skeleton often leads to poor porosity and intrinsic active sites, resulting in unsatisfied catalytic activity for sluggish multi–electron redox reactions. Herein, we demonstrate an efficient strategy for activating of low–active graphitized carbon nanosheets by thermal–driven nitrogen atom–removal process. The elimination of nitrogen atoms at high temperature facilitates rearrangement of neighbor carbon atoms, leading to numerous carbon defects and increased surface area with long–range ordered graphitic structure retained. As a result, the as–obtained defect–enriched porous graphitized carbon nanosheets (DPGCNSs) simultaneously combine abundant high–active intrinsic defects with high graphitization degree and numerous micro/mesopores, and thus demonstrates low overpotential and favorable kinetics towards oxygen reduction and oxygen evolution reactions. Remarkably, rechargeable Zn–air battery with DPGCNSs catalysts demonstrates superior cycling performance of over 700 cycles with no obvious voltage fading.