High-Quality Graphene Aqueous Dispersion Green Preparation Technology
Overview: Over the past decade, graphene has been extensively studied due to its excellent physical and chemical properties, leading to groundbreaking technological breakthroughs in various application fields. Currently, the production of high-quality graphene aqueous dispersions remains a key factor limiting research and application. Achieving high-quality graphene aqueous dispersions through green chemical technology is especially crucial.
Recently, a research team developed a new green preparation technology for high-quality graphene aqueous dispersions. They used an electrochemical separation method to prepare surface hydrophilic modified graphene layers and further prepared polydopamine-graphene composite films as electrode materials for micro-supercapacitors. The green preparation process of high-quality graphene dispersion, as shown in Figure 1, involves dispersing the electrochemically pre-treated graphite layers into a graphite dispersion and further depositing polydopamine to form functionalized graphite layers. The prepared graphene dispersion has good stability and stable colloidal characteristics.
Electrochemical Exfoliation Method for Preparing High-Quality Graphene Aqueous Dispersions
The spectrum and morphological characterization of the graphene nanochips prepared using this new green chemical technology are shown in Figure 2. High-resolution XPS results of the C1s spectrum indicate that the electrochemically exfoliated graphene surface is in a slightly oxidized state, with carboxyl and hydroxyl groups introduced during the electrochemical exfoliation process. The oxygen content in exfoliated graphene is only 12%, lower than that in graphene oxide (31%) and thermally reduced graphene oxide (14%). Raman spectroscopy (532 nm laser excitation) results of bilayer graphene show a 2D peak to G peak ratio of 0.7. AFM characterization of graphene layers dispersed on a SiO2 substrate reveals that most slices are less than 3 nm thick, with about 60% being 1-2 nm thick. The graphene layers prepared using this technology mainly consist of bilayer graphene. Transmission electron microscopy images confirm this result, while selected area electron diffraction indicates a high degree of crystallinity in the bilayer graphene.
Spectral and Morphological Characteristics of Graphene Layers
Graphene nanochips manufactured using this new green chemical technology exhibit good electrical properties. High-frequency (Terahertz) conductivity measurements show a charge carrier mobility of up to 1000 cm²/V·s. This hydrophilic high-quality graphene layer can be used to prepare various functional materials. After loading a suitable amount of polydopamine onto the graphene layer, the charge carrier mobility is only 20%, but the polydopamine-graphene composite film electrode micro-supercapacitor, as shown in Figure 3, exhibits excellent electrochemical performance. The volumetric capacity of the polydopamine-graphene micro-supercapacitor reaches 340 F/cm³, with a power density of 1000 W/cm³. This result surpasses most recently reported graphene-based micro-supercapacitors. In summary, this green preparation technology for high-quality graphene dispersions has great application potential and is expected to develop more applications in the field of energy storage as a platform material.