Oriented Multiwalled Organic-Co(OH)2 Nanotubes for Energy Storage

We report that in energy storage materials, large surface areas and oriented structures are key architecture design features for improving performance through enhanced electrolyte access and efficient electron conduction pathways. Layered hydroxides provide a tunable materials platform with opportunities for achieving such nanostructures via bottom-up syntheses. These nanostructures, however, can degrade in the presence of the alkaline electrolytes required for their redox-based energy storage. A layered Co(OH)2–organic hybrid material that forms a hierarchical structure consisting of micrometer-long, 30 nm diameter tubes with concentric curved layers of Co(OH)2 and 1-pyrenebutyric acid is reported. The nanotubular structure offers high surface area as well as macroscopic orientation perpendicular to the substrate for efficient electron transfer. Using a comparison with flat films of the same composition, it is demonstrated that the superior performance of the nanotubular films is the result of a large accessible surface area for redox activity. Finally, it is found that the organic molecules used to template nanotubular growth also impart stability to the hybrid when present in the alkaline environments necessary for redox function.