Improving Supercapacitance of Electrospun Carbon Nanofibers through Increasing Micropores and Microporous Surface Area

Abstract

Previous papers about electrospun carbon nanofibers do not provide systemic understandings about how in situ activation agents affect the porous structure of carbon nanofibers. In this study, poly(vinylpyrrolidone), poly(methyl methacrylate), and high‐amylose starch (HAS) are used as activation agent to separately prepare porous carbon nanofibers from electrospun polyacrylonitrile nanofibers, and the effects of the polymer activation agents on the porous structure and supercapacitive properties of the resulting carbon nanofibers are examined. The studies indicate that melting point and decomposition temperature are two important parameters deciding the pore size profile. The one with high melting point and low decomposition temperature, such as HAS, allows to form micropore‐dominant porous structure with large specific surface area. The HAS‐activated carbon nanofibers have a micropore specific surface area as high as ≈809 m2 g−1, total pore volume of ≈0.42 cm3 g−1, and micropore content as high as ≈59%. The corresponding electrodes have a capacitance of 282 F g−1 at the current density of 1.0 A g−1 with excellent cycling durability. These novel understandings may be useful for the development of effective carbon nanofibers for high‐performance supercapacitor and other applications.

Tailoring the Structure of Chitosan-Based Porous Carbon Nanofiber Architectures toward Efficient Capacitive Charge Storage and Capacitive Deionization

“…In line with this disordered graphitic structure, a broad (002) diffraction peak can be obtained during XRD analysis (Figures C,D and S12). The calculated lattice spacing differs ( d 002 ) only slightly between the samples (Table ); this value (∼3.9 Å) is similar to that reported for PCNFs prepared from poly­(acrylonitrile) at 1000 °C using different pore-forming agents . The crystallite size ( L c ) is around 1.4 nm for almost all of the samples, indicating relatively low stacking order (approximately 4 stacks based on the d 002 value), except the one with the highest amount of sacrificial polymer (CS/PEO900 2/3), where the value drops to 1.25 nm.…”

“…The Ragone plot based on the GCD experiments is shown in Figure B, inset. The energy density values are very similar to the performance of a multiwalled carbon nanotube-based electrode and are in a reasonable range compared to other supercapacitors based on mesoporous carbon from the biobased polymer lignin, on lignin-derived PCNF, on PCNF derived from lignin/poly­(vinyl alcohol) (PVA) precursor and on PCNF from a polyacrylonitrile precursor . Note that our device performance could be improved using a compact cell and more concentrated electrolyte (the above studies used 6 M KOH as electrolyte).…”

“…It is noteworthy to mention that based on the work of Wang et al, the crystallite size ( L c ) not only depends on the carbon precursor but is also sensitive to the nature of the applied pore-forming agent (they reported L c values between ∼0.9 and 1.7 nm depending on the pore-forming agent). Furthermore, it is known that by increasing the temperature of the carbonization process, the lattice spacing of the graphitic layers decreases and the crystallite size (stacking order) increases simultaneously in carbon fibers, , leading to enhanced electronic transport properties due to the improved carbon structure. , Therefore, the structure of our PCNFs might further improve by increasing the carbonization temperature, which will be further studied in the future.…”

High‐Performance All‐Solid‐State Supercapacitor Electrode Materials Using Freestanding Electrospun Carbon Nanofiber Mats of Polyacrylonitrile and Novolac Blends

“…Generally, there are three main methods to increase the specific surface area and regulate the pore size: 1) chemical agents etching (e.g., KOH, H 3 PO 4 or ZnCl 2 ), [8][9][10] 2) physical gas activation (e.g., ammonia, steam, or carbon dioxide), [11][12][13] and 3) blending of polymer sacrificial pore-making agents (e.g., polymethyl methacrylate, [14] polystyrene, [15] cellulose acetate, [16] polyvinylpyrrolidone, [17] polysulfone (PSF), [18] or high amylose starch [19] ) with carbon source polymer, and subsequent these sacrificial polymers can be removed by in situ decomposition during carbonization, leaving behind pores in ECNFMs. [14][15][16][17][18][19] Among these methods, although method (1) and (2) can prepare ECNFMs with a high specific surface area higher than 1000 m 2 g −1 , the graphitization structure will be destroyed and the carbon yield will be greatly decreased due to the serious etching of ECNFMs by chemical agents or gas activators during carbonization. In contrast, activation method (3) has many prominent advantages, such as simple operation, environmental friendliness, and low cost, and it also benefits to protect ECNFMs structure and produce high carbon yield.…”

Effect of magnetic lens on the electrospinning whipping instability, fiber diameter and its distribution

“…[2][3][4][5] Various polymer nanofibers have been successfully applied to numerous applications, such as filter materials, 6,7 adsorption materials, 8 sensors, 9 as well as for energy conversion and storage. [10][11][12] However, the difficulty in controlling the electrically charged liquid jets of polymer solution during electrospinning and the resulting heterogenous fiber distributions are challenging problems 13 that limit the effective use of polymer nanofibers. Therefore, achieving control over the stochastic processes in electrospinning is important for advancing the possible applications of polymer nanofibers.…”