Date of Award
Master of Science in Chemical Sciences (MSCB)
With the reliance on renewable energy resources expected to grow in the near future, the world looks towards advancing electrochemical energy systems that can be scaled up to meet such demands. These systems must adhere to being environmentally friendly, cost-effective, and safe. Abundant earth metals (Zn, Mn, Fe) have been looked at extensively as they meet all of these criteria. Under these classes of metals, nanostructured manganese dioxides have garnered attention as cathode materials due to meeting all these requirements as well as having a rich electrochemical profile owing to their multitude of crystal structures and properties. This work reports a novel room-temperature solid-state synthesis of layered birnessite manganese dioxide. This synthetic method produces materials with variable physiochemical properties that can be tuned depending on the oxidant amount used in the synthesis. To further understand the physiochemical tunability of this material, Elemental Dispersion X-ray (EDX) spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), X-ray Diffraction (XRD), Gas-sorption analysis using nitrogen gas, Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and X-ray photoelectron spectroscopy (XPS). This material is then subjected to cyclic voltammetry (CV) and cyclic charge and discharge (CCD) to gauge its applicability for aqueous zinc-ion battery systems. It was found that increasing oxidant amounts also caused an increase in oxidation state, plate thickness, and potassium ion content found in the final product. Increasing the amount of superoxide reagent used in the synthesis was also met with the consequence of degradation of porous structure in the resultant material which greatly decreased amount of surface area available. Electrochemical testing shows the effect of this consequence with the capacity lowering from 75 mA·h/g to 13 mA·h/g when the loss of porous structure occurs.
Rodriguez Campos, Armando, "Superoxide-assisted solid-state synthesis of birnessite type MnO2 materials: physiochemical properties and electrochemical viability" (2022). Master of Science in Chemical Sciences Theses. 54.
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