Lignin-based carbon nanofibe rs: Morphologies, properties, and features as substrates for pseudocapacitor electrodes

Synthesis and characterization of polyaniline-based composites using cellulose nanocrystals as biological templates

Polyaniline (PANI) is considered as an ideal electrode material due to its remarkable Faradaic activity, exceptional conductivity, and ease of processing. However, the agglomeration and poor cycling stability of PANI largely limit its practical utilization in energy storage devices. To address these challenges, PANI was synthesized via a facile one-pot, two-step process using cellulose nanocrystals (CNCs) as bio-templates in this work. Zeta potential and particle size measurements revealed that the CNC template could impart improved dispersion stability to the synthesized PANI, which exhibited a decrease in average particle size from 1100 nm to 300 nm as a function of 10 % CNCs. Furthermore, the effect of CNC loadings on the performance of PANI was systematically investigated. The results showed that the specific capacitance of PANI/CNC increased from 102.52 F·g-1 to 138.12 F·g-1 with the CNC loading increase from 0 to 10 wt%. Particularly, the PANI/CNC composite film with a 1:9 ratio (C-P-10 %) demonstrated a capacity retention of 84.45 % after 6000 cycles and an outstanding conductivity of 526 S·m-1. This work generally offers an effective solution for the preparation of high-performance PANI-based composites, which might hold great promise in energy storage device applications.

Novel metal-lignin assembly strategy for one-pot fabrication of lignin-derived heteroatom-doped hierarchically porous carbon and its application in high-performance supercapacitor

The conversion of renewable lignin with low-cost and high carbon content properties into porous carbon materials for supercapacitor applications has caught considerable interest. Herein, two dimensional lignin-derived carbon nanosheets (N-LHPC) with hierarchically porous structures were facilely synthesized via a novel metal-lignin assembly strategy and their performances for supercapacitor applications were investigated. During the carbonization process, the uniformly distributed Zn facilitates the coordinating development of micropores structure and the generated MgO embedded in the carbon matrix acts as a template to produce mesoporous structure after acid washing. Moreover, the melamine addition promotes the development of mesopores by formation of lamellae structure and realizes the N doping in the carbon materials. Therefore, the obtained N-LHPC presents an excellent specific capacitance of 235.75 F/g at 0.5 A/g owing to its hierarchical pore structure as well as the N/O functional groups. Moreover, at the power density of 450 W/kg, the N-LHPC achieves a maximum energy density of 14.75 Wh/kg, showing great application potential in energy storage. The metal-lignin assembly strategy followed by N-doping proposed in this paper provides N-LHPC materials with hierarchical nanostructure, good electron/ion transfer properties, and abundant pseudocapacitive active species, which improve the capacitance performances of the N-LHPC.

Construction of self-supporting ultra-micropores lignin-based carbon nanofibers with high areal desalination capacity

Lignin is a renewable biomacromolecule that can be used as precursors for carbon materials. In this work, highly flexible lignin-based carbon nanofibers with abundant ultra-micropores are constructed via electrospinning, oxidative stabilization and carbonization. The results indicate that replacing PAN with 80 % lignin is feasible in regulating ultra-micropores. The synthesized L4P1-CNFs possess many attractive properties (e.g., pore size distribution, electrochemical and deionization property) compared with that produced from other non-renewable precursors or more-complexed processes. It shows excellent electrochemical double-layer capacitance in 6 M KOH (233 to 162 F g^-1 at 0.5 to 5 A g^-1) and 1 M NaCl (158 to 82 F g^-1 at 0.5 to 5 A g^-1) electrolytes. Upon assembling into CDI cells, the average salt adsorption rate could reach 1.79 mg g^-1 min^-1 at 1.2 V and 3.32 mg g^-1 min^-1 at 2 V in 500 mg L^-1. Benefiting from the excellent flexibility, we innovatively stack four layers of L4P1-CNFs to improve the areal electrosorption capacity to 0.0817 mg cm^-2 at 500 mg L^-1, significantly higher than that of traditional carbon-based electrodes. The good desalination property makes lignin-based carbon nanofibers ideal for practical, low-cost capacitive deionization applications.