Supercapacitors are a critical technology for energy applications that require rapid charge/discharge cycles. Electrochemical pseudocapacitors use metal oxides that undergo redox reactions to generate additional charge storage. A factor that regulates charge storage is the surface area of the capacitor, which can be greatly improved per unit mass by implementing a porous structure. While porous metal oxide pseudocapacitors have been fabricated previously, the mechanical durability of the materials has not been adequately demonstrated. A porous, mechanically strong, composite material with tunable pore size, nanowire length, diameter, and material phase offers the possibility of electro-mechanical materials that enable device fabrication at multiple length scales with an overall decrease of systems mass and corresponding increase in performance metrics. Previous studies demonstrate the use of biopolymer hydrogels to biotemplate composite metal nanowire porous electrodes.
[1â3] In this work, we demonstrate a Co
3O
4 biotemplated pseudocapacitor synthesized using a carboxymethyl cellulose nanofiber (CNF)-alginate composite hydrogel scaffold. The hydrogels are equilibrated in CaCl
2 / CoCl
2 salt solutions and chemically reduced with NaBH
4, where the ratio of cations determines the resulting degree of ionic crosslinking and transition metal phase. After supercritical drying, aerogel pyrolysis and thermal oxidation enhance the composite material conductivity and achieve electrochemically active Co
3O
4. Material characterization is demonstrated with scanning electron microscopy, x-ray diffractometry, thermal gravimetric analysis, electrochemical impedance spectroscopy, cyclic voltammetry, and compressive loading. The resulting free-standing electrodes provide rapid charge and discharge and a mechanically robust material, providing potential applications as both a structural and energy storage material for a wide range of military and commercial applications demanding light-weight power and energy materials.
[1] F.J. Burpo, M.Y. Ryu, E.A. Nagelli, E. Onuomadonkeng, Gelatin-Cellulose Nanofiber Biotemplated Platinum Nanowire Porous Fibers, (2019).
[2] J.F. Burpo, N.A. Mitropoulos, A.E. Nagelli, L.J. Palmer, A.L. Morris, Y.M. Ryu, K.J. Wickiser, Cellulose Nanofiber Biotemplated Palladium Composite Aerogels, 23 (2018). https://doi.org/10.3390/molecules23061405.
[3] J.F. Ohmura, F.J. Burpo, C.J. Lescott, A. Ransil, Y. Yoon, W.C. Records, A.M. Belcher, Highly adjustable 3D nano-architectures and chemistries via assembled 1D biological templates, Nanoscale. 11 (2019) 1091â1102. https://doi.org/10.1039/C8NR04864A.
