▎ 摘　　要

Graphene oxide (GO) is not only a unique class of two-dimensional (2D) materials but also an important precursor for scalable preparation of graphene. The efficient size fractionation of GO is of great importance to the fundamental and applied studies of chemically modified graphene, but remains a great challenge. Herein, we report an efficient and scalable fractionation method of GO employing reversible adsorption/desorption of temperature-responsive poly(N-isopropylacrylamide) on GO to amplify its mass difference and significantly improve the fractionation efficiency. Furthermore, size-dependent sodium ion storage of the resulting fractionated reduced GO (RGO) is revealed for the first time with high sodium storage performance achieved for the smallest RGO because of its largest d-spacing and most defect sites. This work provides valuable insights into the size fractionation and size-dependent electrochemical performance of graphene, which can be potentially extended to other 2D materials.