Regulating Oxygen Configuration in Hierarchically Porous Carbon Nanosheets for High-Rate and Durable Na⁺ Storage

Surface oxygen functionalities (particularly C-O configuration) in carbon materials have negative influence on their electrical conductivity and Na⁺ storage performance. Herein, we propose a concept from surface chemistry to regulate the oxygen configuration in hierarchically porous carbon nanosheets (HPCNS). It is demonstrated that the C-O/C=O ratio in HPCNS reduces from 1.49 to 0.43 and its graphitization degree increases by increasing the carbonization temperature under a reduction atmosphere. Remarkably, such high graphitization degree and low C-O content of the HPCNS-800 are favorable for promoting its electron/ion transfer kinetics, thus endowing it with high-rate (323.6 mAh g^-1 at 0.05 A g^-1 and 138.5 mAh g^-1 at 20.0 A g^-1 ) and durable (96 % capacity retention over 5700 cycles at 10.0 A g^-1 ) Na⁺ storage performance. This work permits the optimization of heteroatom configurations in carbon for superior Na⁺ storage.