Electrochemical Energy Storage and Conversion Applications of Graphene Oxide: A Review

Graphene oxide (GO), a single sheet of graphite oxide, has shown its potential applications in electrochemical energy storage and conversion devices as a result of its remarkable properties, such as large surface area, appropriate mechanical stability, and tunability of electrical as well as optical properties. Furthermore, the presence of hydrophilic functionalities on basal and edge planes induces other relevant properties, which make GO an attractive material for electrochemical applications. On account of having structural diversity and enhanced overall crucial properties, GO and its composites have attracted much attention in contribution of energy storage devices, such as batteries, supercapacitors, and energy conversion devices, such as fuel cells and water electrolyzers. Previous review reports demonstrated the individual applications of GO or reduced graphene oxide (RGO) in either of the electrochemical energy devices. The present review highlights all of the recent developments of GO and RGO in both the energy storage and conversion devices along with the recent synthesis methodologies, which are crucial to unveil all of the outperforming properties of GO and RGO. The transition in the synthesis of GO with various chemical methods, including the Brodie and improved Hummers methods, to electrochemical approaches have been described with recent developments as well as highlights of the importance of electrochemical energy in the synthesis of GO. Utilization of GO in energy storage applications predominantly as electrodes and electrolytes and membranes in energy conversion devices further diversify its multiple applicability as a result of its variable functional properties. Multiple energy storage devices, such as Li-ion, Na-ion, Li–S, and flow batteries and supercapacitors, have shown the enhanced performance with the introduction of GO and RGO. Furthermore, GO has also shown excellent applicability in energy conversion devices, such as proton-exchange membrane fuel cells, methanol fuel cells, and water electrolyzers, which have also been discussed in this review. This review further summarizes the recent synthesis methodologies of GO and RGO along with their importance in electrochemical energy devices with allied challenges and future perspectives.