Accessing effects of aliphatic dicarboxylic acid towards the physical and chemical changes in low temperature hydrothermally reduced graphene hydrogel

To date, studies pertaining the usage of aliphatic dicarboxylic acids (DCAs) in the preparation of graphene-based hydrogels are limited and mainly has been applied either as a reducing agent or cross-linkers. The modification of the hydrogels' properties can be achieved via the introduction of small amount of additive into the starting material, graphene oxide (GO). The facile synthetic protocol enables the impartation of desired properties to the graphene-based hydrogel as intended for their specific applications. In this study, the in-situ preparation of reduced graphene hydrogel (rGH) was carried out in the presence of a series of aliphatic DCAs namely oxalic acid (OA), malonic acid (MA), succinic acid (SA), glutaric acid (GA) and adipic acid (AA) in the GO reaction mixture via green hydrothermal method and freeze-drying. The as-prepared hydrogels were systematically characterized to probe the changes in their chemical and physical changes. Higher specific surface (SSA) of the hydrogel is obtained for shorter chain length DCAs. The FTIR and XPS results also indicated that shorter chain DCAs exhibited better reducing capability in the removal of oxygen functional groups. The C/O ratio obtained showed decrement with the increase in the chain length of the DCA. On the other hand, good dispersity was found for longer chain DCAs in polar solvent. Overall, this study should provide a comprehensive understanding on hydrothermally reduced graphene hydrogels prepared in the presence of dicarboxylic acids.

Automated summary

This study demonstrates the in-situ preparation of reduced graphene hydrogel using a series of aliphatic dicarboxylic acids via green hydrothermal method and freeze-drying. Shorter chain length DCAs led to higher specific surface area and better reducing capability in removing oxygen functional groups, while longer chain DCAs exhibited good dispersity in polar solvent. Overall, understanding was provided on the properties of hydrothermally reduced graphene hydrogels prepared with dicarboxylic acids.