Optimizing graphene oxide reduction: A multistep approach for enhanced electrochemical performance

The present work reduces graphene oxide (GO) using thermal, chemical, and a multistep method by combining both techniques. The effects of reduction methodologies on the structure and electrochemical performance of the reduced graphene oxide (rGO) specimens are investigated. The reduction methodology not only influences the carbon content and intercalation of carbon layers but also significantly affects the porosity features in terms of micro and mesopores, resulting in different electrochemical behaviours. Despite the high surface area of thermally reduced graphene oxide, the absence of micropores and high defect density hinder charge storage. Chemical reduction eliminates epoxy functionalities to partially restore the sp² network, promoting charge storage and transport. In contrast, the multistep reduction technique produces appreciable intercalation, eliminates functionalities such as epoxy and hydroxyl to restore the sp² network, and introduces significant micropores beneficial to improved charge storage. The specific capacitance of multistep-reduced graphene oxide is found to be five times greater than thermally reduced graphene oxide and two times greater than chemically reduced graphene oxide in a symmetric cell. Furthermore, such a multistep rGO type of cell provides excellent rate capability with stable cyclic performance and delivers a specific energy of 17 Wh kg⁻¹ at a specific power of 0.9 kW kg⁻¹.