Lignin-based hierarchical porous carbon nanofiber films with superior performance in supercapacitors

Lignin-Based Electrospun Carbon Nanofibers

“…The improved supercapacitor performances were explained by the MnO 2 surface coating, which provided high specific/gravimetric capacitance and a large reaction surface area, resulting in fast reaction kinetics. Same authors, Ma et al (2018) used magnesium nitrate hexahydrate (Mg(NO 3 )·6H 2 O) as an additive in lignin-polyvinylpyrrolidone (PVP)-based carbon nanofibers resulting in a carbon nanofiber mat with a specific surface area of 1,140 m 2 g −1 , increased mesoporosity (2-4 nm pore size) (shown in Figure 1C), and specific capacitance of 248 F/g −1 at a current density of 0.2 Ag −1 . They also reported a good cycling stability of 97% capacitance retention after 1,000 cycles.…”

“…Preparation of lignin-based electrospun carbon nanofibers (ECNFs), their structure and electrochemical properties. (A) Schematic of electrospinning of the lignin/PVA suspension (75/25) and electrospun lignin/PVA nanofibers before post-processing, after stabilization, and after carbonization; (B-D) methods which are used to reach very high specific surface area on the carbon fibers: (B) KOH treatment prior the carbonization process resulting in a mesoporous carbon nanofiber byAgo et al (2016) reproduced under the terms of the Creative Commons Attribution (CC BY 3.0) license, (C) magnesium nitrate treated ECNFs resulting in carbon nanofibers with improved porosity, surface area and electrochemical performance byMa et al (2018) with permission from Elsevier, (D) nickel cobaltite (NiCo 2 O 4 ) decorated ECNFs which resulted in high specific surface area and high specific capacitance byLei et al (2017) with permission from Elsevier; (E-G) electrochemical characterization of lignin-based ECNFs as electrode material using three-electrode cell configuration in 0.5 M Na 2 SO 4 electrolyte byAgo et al (2016) reproduced under the terms of the Creative Commons Attribution (CC BY 3.0) license: (E) cyclic voltammograms at varying scan rates; (F) galvanostatic charge/discharge curve at varying current densities, (G) cycling stability of ECNFs and powder at 10 mV s −1 .…”

Transforming lignin into porous graphene via direct laser writing for solid-state supercapacitors

“…[6][7][8][9] The obtained porous carbon may stand out in terms of porosity distribution and energy storage capacities. 10,11 However, these methods suffer from complicated fabrication procedures and high energy inputs. Template-free and solvent-free methods can simplify fabrication, but still require prolonged high-temperature treatment, like pyrolysis.…”

Strategies to Hierarchical Porosity in Carbon Nanofiber Webs for Electrochemical Applications

“…Hard templates can also form during the carbonization treatment itself, as is the case when introducing metal salts (e.g., Co(NO 3 ) 2 6H 2 O, Ni(CH 3 COO) 2 , ZnCl 2 ) in the electrospun polymer solution. The transition metal salts form metallic or metal oxide particles (e.g., Co, Ni, ZnO), which then serve as porogen, and in some cases, as a catalyst for enhanced graphitization of the CNF formed from the polymer precursor carbonization [19][20][21][22][23]. Other templates including Prussian blue analogues [24] and metal organic frameworks [25][26][27] have been used in conjunction with polymer precursors, conferring both porosity and heteroatom doping to CNFs obtained by electrospinning and carbonization.…”

“…Different kinds of templates can further be combined to produce hierarchical porosity, which is crucial for the transport of different species (ions, gases, liquids) in the electrodes of various electrochemical devices. For instance, the combination of PVP with Mg salts [22,39] gave rise to hierarchical meso-and microporosity inside CNFs prepared by electrospinning. For the post-synthetic approach, various chemical activations have been investigated to create porosity in preformed CNFs.…”