Graphene is an ideal electrode material for supercapacitors because of its excellent physical properties such as large specific surface area and high electron mobility. Because graphene has strong hydrophobicity, its liquid phase operability is low, and it is difficult to directly construct a macroscopic electrode material with adjustable structure through graphene. Graphite oxide can be regarded as a precursor of graphene. Through reduction treatment, most of the oxygen-containing functional groups on the graphene oxide sheet can be removed to obtain a graphene-based electrode material. The improved Hummers method is one of the common methods for the preparation of graphite oxide. It mainly includes strong oxidation treatment of graphite and post-treatment cleaning of graphite oxide. Among them, post-treatment cleaning involves two steps of pickling and deacidification. Pickling is the use of excess dilute hydrochloric acid to wash away impurities in graphite oxide. The product obtained here is named graphite without oxide removal. To obtain pure graphite oxide, appropriate post-treatment methods (such as dialysis and centrifugation) are required to further remove the acid. At present, these post-treatment acid removal methods either consume a large amount of water and time, making the acid removal step account for about half of the total synthesis time, resulting in low synthesis efficiency of graphite oxide, or the need to use toxic organic solvents for acid removal, bringing safety risks and Increase synthesis cost.
In view of the above problems, this study proposes to directly prepare graphene-based materials using non-deacidified graphite oxide as a precursor, and comparatively examine the effect of the presence of acid on the structure and properties of the final graphene-based material, and evaluate the use of non-deacidified graphite directly. Feasibility and practicability as a precursor of graphene-based materials. The paper reported for the first time that the graphene aerogel H-GA was obtained by hydrothermal and lyophilization treatments of the unoxidized graphite prepared as a precursor based on the improved Hummers method. For comparative research, the author also used pure graphite oxide as a precursor to obtain another graphene aerogel GA.
The results show that the micro-morphology of H-GA and GA is similar, but the surface chemistry is significantly different (as shown in Figure 2). The two aerogels show similar electrochemical energy storage performance in aqueous electrolytes. In ionic electrolytes, the electrochemical performance of H-GA is better than GA, mainly because H-GA shows better wettability in ionic electrolytes. In summary, graphite without oxide removal can be directly used as a precursor for preparing graphene-based materials; compared with pure graphite oxide as a precursor, it has more advantages, such as high efficiency, low cost, and large-scale preparation. The research results also imply that the unoxidized graphite has great application potential in the preparation of graphene-based materials such as graphene fibers and graphene films.