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. 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.
Bibliographical noteFunding Information:
G.C.L. and N.A.S. contributed equally to this work. This work was primarily supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, under Award No. DE-FG02-00ER45810. STEM/TEM characterization was supported by the Center for Bio-Inspired Energy Science, and Energy Frontier Research Center funded by the U.S. DOE, Office of Science, Basic Energy Sciences, under Award No. DE-SC0000989 (H.S.). Molecular synthesis was supported by the National Science Foundation under NSF Award No. DMR-1121262. Long term cycling experiments were sponsored by the Air Force Research Laboratory under agreement number FA8650-15-2-5518. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory or the U.S. Government. G.C.L. and N.A.S. were supported by the Department of Defense (DoD), Air Force Office of Scientific Research, through the National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. N.A.S. also acknowledges support from Northwestern University through a Ryan Fellowship. E.A.B. acknowledges the Materials Research Science and Engineering Center REU program, supported by the National Science Foundation under NSF Award No. DMR-1121262. The authors also thank J. Strzalka and D. J. Fairfield for assistance with GIXS measurements, M. Bedzyk, J. A. Carsello, S. Kewalramani, and G. Campbell for assistance with XRD characterization and analysis, and S. Chen for assistance acquiring GISAXS measurements for form factor analysis of the nanotubular films. The authors thank J. Boekhoven for fruitful discussions and suggestions with regard to hybrid stability in alkaline electrolytes and M. Seniw for help with graphics of the nanotubular structures. This work made use of the following facilities at Northwestern University: the J. B. Cohen X-Ray Diffraction Facility, the EPIC facility (TEM and SEM), the Keck Biophysics facility (UV–vis), the Northwestern University Instrument Shop (custom electrodeposition cap), and the IMSERC facility. The J. B. Cohen X-Ray Diffraction Facility was supported by the MRSEC program of the National Science Foundation (DMR-1121262) at the Materials Research Center of Northwestern University. The EPIC facility of the NUANCE Center received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. The Keck Biophysics facility received support from a Cancer Center Support Grant (NCI CA060553). The Instrument Shop received support from the Northwestern University Office for Research, Shared and Core Facilities. IMSERC facility received support from the NSF (CHE-1048773); Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the State of Illinois and International Institute for Nanotechnology (IIN). Use of Advanced Photon Source sector 8-ID-E, an Office of Science User Facility operated for the U.S. DOE Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357.
- cobalt hydroxide
- energy storage
- hierarchical structures
- hybrid materials