Unlocking thermogravimetric analysis (TGA) in the fight against "Fake graphene" materials

The absence of rapid, reliable and cost-effective quality control for industrially manufactured graphene materials is an immediate problem for the emerging graphene industry. Recent studies have alarmingly revealed that a large percentage of manufactured graphene materials traded worldwide have a large variation of properties, and some of them are overpriced graphite powders. Currently, benchmark graphene characterization methods based on localized analysis can provide information of key properties of graphene such as the number of layers, particle size, and defects, only on individual graphene particles, which do not represent the properties of "bulk" material. To address these limitations, we developed and validated thermogravimetric analysis (TGA) as a simple analytical tool for characterization and quality control of manufactured few-layer graphene (FLG) and their non-graphene impurities in powder forms. Our results, using verified control and industrial samples, revealed that the derivative TGA graphs of FLG, graphene oxide and graphite powders have signatory distinctive peaks with temperature of maximum mass decomposition rates (T-max) in specific ranges, reflecting differences of their structural, chemical, and thermal properties, which are suitable for their qualitative and quantitative analysis. The method is applicable for graphene manufacturers and end-users for simple, low-cost and reliable quality control of graphene materials that will not fail to detect "fake" graphene. (C) 2021 Elsevier Ltd. All rights reserved.