Composite Aerogels of Carbon Nanocellulose Fibers and Mixed-Valent Manganese Oxides as Renewable Supercapacitor Electrodes

Abstract

Bio-waste derived nanocelluloses show excellent mechanical flexibility and self-aggregated capability, which enable them to be good supporting substrates for the synthesis of electroactive materials. Herein, we present a facile route for fabricating composite aerogels consisting of carbonized nanocellulose fibers (CNF) and mixed-valent manganese oxide (MnOx), toward supercapacitor applications. Mixed solutions of nanocellulose and manganese acetate with different ratios were prepared and freeze-dried into hybrid aerogels. The hybrid aerogels were then transformed into CNF/MnOx composites by a calcination process. The CNF membranes served as porous carbon nano-reservoirs for MnOx and electrolyte. The CNF/MnOx composites also kept a 3D porous aerogel structure with hierarchical pores, which enabled stable transport of both electrolyte ions and electrons to the electrode surface, leading to low a charge-transfer impedance and good electrochemical kinetics. The CNF/MnOx-based symmetric supercapacitor showed a satisfied energy density and power density of 37.5 Wh kg−1 and 2.75 kW kg−1, respectively. All the above results demonstrate the feasibility of using sustainable nanocellulose as a nanoscale carbon substrate for the synthesis of hybrid composite electrodes toward renewable supercapacitor applications.

Recent Progress on Nanocellulose Aerogels: Preparation, Modification, Composite Fabrication, Applications

“…Owing to the synergistic effect of porous nanostructures and conductive frameworks from CAs and the high capacitive property provided by electroactive nanomaterials, resulting hybrid aerogels presented superior electrochemical properties. Inorganic materials with high theoretical specific capacity have been widely selected in composites such as nickel sulfide (NiS), [ 136 ] mixed‐valent manganese oxide (MnO x ), [ 137 ] tin (IV) oxide (SnO 2 ), [ 138 ] and metal oxynitride (MO x N y ). [ 20c,89b ] For example, Zheng et al.…”

Structural Engineering of Ultrathin, Lightweight, and Bendable Electrodes Based on a Nanowire Network Current Collector Enables Flexible Energy-Storage Devices

“…Therefore, the invariable capacitance confirms the long-term mechanical stability of the Ag@NiCo/MnO x NW electrode. In addition, we compared the performances of flexible energy-storage electrodes using MnO x as the active material but on different current collectors − to the Ag@NiCo/MnO x NW network (Table S1). The comparison result reveals that our electrode has a high specific capacity and good flexibility.…”

Biomass and Industrial Wastes as Resource Materials for Aerogel Preparation: Opportunities, Challenges, and Research Directions

“…While common adsorbents, such as activated carbon, have sorption capacity less than 100 g g –1 , carbon aerogels, as important solid adsorbents, have shown unique adsorption capacity of up to 900 g g –1 . ,, Their hydrophobic surfaces allow selective and effective adsorption of oils, organic pollutants, and heavy metals from wastewater . Moreover, their unique electrical conductivity is beneficial in electrical/electrochemical applications, such as supercapacitors, electrocatalysis, and electrosensing, as well as batteries . Since the sol–gel reaction chemistry controls the morphology and properties of carbon aerogels, aerogels with specified applications and properties could be developed considering sol–gel precursors, polymerization catalysts, and reaction solvents (Figure ).…”

“…106 Moreover, their unique electrical conductivity is beneficial in electrical/electrochemical applications, such as supercapacitors, 181 electrocatalysis, and electrosensing, 182 as well as batteries. 104 Since the sol−gel reaction chemistry controls the morphology and properties of carbon aerogels, aerogels with specified applications and properties could be developed considering sol−gel precursors, polymerization catalysts, and reaction solvents (Figure 9). 183 As shown, the carbon aerogel (CA) structure can be modified either during the sol−gel polymerization step, through the introduction of additives or templates to the reaction mixture, or through gas-or solution-phase reactions on the surfaces of the CA framework after the pyrolysis step.…”