▎ 摘　　要

The conventional Hummers' method involves intercalation, oxidation, hydrolysis, and exfoliation reactions for graphene oxide (GO) preparation, which generate atomic scale defects in the basal plane and unzip the plane to diminish lateral size. In this paper, processing conditions of the Hummers' method was engineered, especially graphite material, dose-by-dose injection of KMnO4 oxidant, oxidation temperature, and exfoliation conditions, for less defect concentration and larger size of GO. Natural graphite material processed under 10 degrees C throughout the whole reaction steps and dose-by-dose addition scheme of the oxidant result in GOs with reduced defect density. Additional carboxylation reaction facilitates the exfoliation of GO sheets, showing similar to 35 mu m in diameter and mass yield of 140%. This simple wet chemistry-based methodology reported here paves a way to facile and scaled-up production of large-sized GOs with low defect concentration. (C) 2021 Elsevier Ltd. All rights reserved.