Habibullah Dalal

Cathodic exfoliation of graphite has emerged as an attractive method to synthesize high-quality and lo- defect graphene. Here, it is demonstrated that the type of starting graphite material influences the properties of exfoliated graphene. Graphite foil, natural graphite, and graphite rods were examined in the exfoliation processes performed in 3.0 M KCl at −15 V. The use of a graphite foil facilitates the rapid cathodic exfoliation process in comparison with structurally more compact natural graphite and graphite rods. For the graphite foil, the cathodically exfoliated graphene exhibits a low defect density (I_D/I_G of 0.09, a C/O ratio of 35) with graphite exfoliation yield of 92.8%. In contrast, the exfoliated graphene from natural graphite exhibits an I_D/I_G of 0.15, a C/O ratio of 28, and a graphite exfoliation yield of 30.5%, whereas graphene from graphite rod exhibits an I_D/I_G of 0.86, a C/O ratio of 30, and a graphite exfoliation yield of 19.5%. The dense structure of natural graphite and graphite rods led to longer exfoliation times. Exfoliation of graphite rods produced few-layer graphene with the smallest sheet size, whereas natural graphite and graphite foil yielded multilayer graphene with larger sheets. This study demonstrates the feasibility of using aqueous-based cathodic exfoliation to produce graphene from various graphite sources, leading to variations in sheet thickness, size, defect density, and solvent dispersibility.

Electrochemical exfoliation of graphite offers a scalable and efficient approach to synthesise graphene nanomaterials. This process is commonly performed either anodically or cathodically, whereas simultaneous dual processes offer an attractive energy efficient means to produce graphene materials with tuneable properties. Here, we demonstrate a simple electro synthetic approach to produce graphene simultaneously from both a graphite anode and a graphite cathode in K₂SO₄ aqueous solution. Graphite exfoliation was facilitated by employing 0.5 M K₂SO₄ as an electrolyte at 10 V, where efficient exfoliation simultaneously occurs at graphite foils serving as both anode and cathode. The anodically exfoliated graphene has a high defect density (I_D/I_G=0.58) and higher degree of oxidation (C/O=11.36), in comparison to graphene produced at cathode having a lower defect density (I_D/I_G=0.06) and a low oxidation degree (C/O=31.68). The usage of aqueous solution for scalable and efficient concurrent‐dual electrochemical exfoliation of graphite electrodes will facilitate the development of large‐scale production of graphene.

The abundance of sodium in the Earth's crust as well as its high energy density make sodium ion batteries (SIBs) an excellent alternative to lithium ion batteries for large-scale energy storage applications. The performance and widespread deployment of SIBs are highly dependent on the electrode materials and electrode design principles. Recently, three-dimensional graphene-based macrostructures have been demonstrated as a promising new class of electrode materials due to their interconnected porosity and many intriguing physiochemical properties. In this chapter, we provide an overview of the most significant advancements in 3D graphene-based anodes and cathodes for applications in SIBs. In addition, existing challenges and commercial opportunities towards the development of next generation of 3D graphene-based electrodes for future large-scale applications in SIBs are also presented.