| About this Abstract |
| Meeting |
Materials Science & Technology 2020
|
| Symposium
|
Synthesis, Characterization, Modeling and Applications of Functional Porous Materials
|
| Presentation Title |
Hierarchical Porosity in δ-MnO2 Nanosheet Assemblies via Layer-tunnel Conversion |
| Author(s) |
Alec Ladonis, Peter Metz, Trevyn Hey, Peng Gao, Scott Misture |
| On-Site Speaker (Planned) |
Alec Ladonis |
| Abstract Scope |
Temperature induced layer-tunnel conversion of alkali free δ-MnO2 nanosheet agglomerates derived from highly crystalline potassium birnessite was systematically investigated. Assemblies dried from room temperature to 400°C exhibit high specific surface areas between 90-130m2g-1. Scanning electron microscopy reveals crumpled newspaper-like morphology where the pore walls are comprised of single and restacked nanosheets which condense at higher temperatures to pore walls that have atomic-scale tunnels as in the alpha polymorph of MnO2. Raman spectroscopy and X-ray total scattering techniques elucidate structural trends throughout the conversion, where tunnel fragment formation below 100°C occurs while the overall microstructure remains unaffected up to 400°C. Pseudocapacitive effects due to the conversion were observed by cyclic voltammetry in Na2SO4 aqueous electrolyte where the intercalative pseudocapacitance diminishes with increased tunnel fragment formation. Overall, the results demonstrate that the conversion can be tailored for applications ranging from sequestering of nanosolids or aqueous ions to kinetically accessible Na+ ion intercalation. |