Trace-H2O2 Boosting the Reaction Kinetics of H2SO4 Intercalation into Graphite for the High-Oxidation Efficiency Preparation of Graphene Oxide for Na Ion Storage

Graphite sulfate (H2SO4-GICs), as a key precursor for graphene oxide (GO) synthesis, is difficult to synthesize by spontaneously forming H2SO4-GICs due to its huge diffusion resistance. Therefore, it is still a crucial challenge for improving the reaction kinetics of graphite flakes to form H2SO4-GICs. In this work, we discover that the amount of H2O2 plays an important role in determining the formation of H2SO4-GICs in the intercalation process. The trace H2O2 can trigger more O* during the reaction process, leading to the lattice distortion and reducing the interlayer diffusion resistance of graphite, and it was found that reducing the volume ratio of H2O2 would promote the intercalation of H2SO4 into graphite and form the stage-I H2SO4-GICs. Exfoliation efficiency and oxidation degree were improved after oxidation reaction. We also confirm that this method works for the exfoliation of large graphite, demonstrating the high-efficiency energy supply by adding minimal stoichiometric H2O2. The pretreated GO by trace-H2O2 (PGO-100:1) exhibits a large interlayer spacing due to the complete exfoliation; after reduction as Na+ ion storage anode material, RPGO-100:1 displays a high rate performance as well as outstanding kinetic behavior, indicating that the increased interlayer space of graphite resulting from the deep oxidation benefits fast migration of Na+ ions toward a high capacity contribution and improved rate capability.