(666f) Dispersion Microstructure and Aerogel Properties of Graphene/Manganese Oxide Mixtures and Hybrids

The focus of this work is to investigate the effects of dispersion properties on the porous three-dimensional microstructure and electrochemical properties of aerogels produced by freeze-drying ultra-large reduced graphene oxide (RGO) and manganese dioxide nanowire (MnO₂) dispersions. The inclusion of MnO₂ nanowires as guest materials in assemblies of ultra-large RGO was achieved via two techniques: a) mixing both dispersions that have been synthesized separately to form a mixture and b) growing the nanowires along the ultra-large graphene sheets to form a hybrid material. Scanning electron and atomic force microscopy were used to image the starting materials and gain initial insights into the interactions between the nanowires and sheets. The effects of concentration on the microstructures of dispersions of these materials were investigated using polarized optical microscopy (POM) and rheology. Next, aerogels were produced by freeze-drying hybrids and mixtures with different concentrations and qualitatively assessed for mechanical integrity. Aerogels that could retain their shape with handling were further characterized for morphology using SEM, specific surface area using Brunauer–Emmett–Teller (BET) and capacitive behavior using cyclic voltammetry. Further understanding the relationships between the initial materials, their dispersion microstructure, and the resulting aerogels will enable their application for capacitive deionization and other electrochemical applications requiring high electrical conductivity, large surface area, and interconnected porous architectures.