Self-Biotemplate Preparation of Hierarchical Porous Carbon with Rational Mesopore Ratio and High Oxygen Content for an Ultrahigh Energy-Density Supercapacitor

Abstract

Although hierarchical porous carbons (HPCs) are greatly emphasized in electrochemical energy storage, it is still difficult to develop a facile and cost-effective method for fabricating HPCs. Herein, we demonstrate a combination strategy to synthesize N-self-doped HPC from biomass (rice straw) on the basis of the following key consideration: well-dispersed intrinsic silica acts as an built-in biotemplate to form large numbers of mesopores, while chemical activation produces plenty of micropores. The as-prepared N-self-doped HPC has a reasonable mesopore ratio and high contents of O functionalities. This unique feature allows the fast transport of ions, highly accessible surface area, and additional pseudocapacitive behavior. As a result, the as-prepared HPC exhibits ultrahigh specific capacitance of 357 F g–1 (0.5 A g–1, 1 M H2SO4) for a three-electrode system and of 260 F g–1 (1 A g–1, 1 M Na2SO4) for a two-electrode system, excellent capacitance retention, and excellent cycling stability, superior to most of biomass-derived carbons. Moreover, the energy density of HPC is high up to 29.3 W h kg–1 at a power density of 900 W kg–1. In addition, the HPC exhibits high CO2 capture capacities of 6.57 mmol g–1 at 0 °C and 4.13 mmol g–1 at 25 °C.

Solvent‐Free Mechanochemical Preparation of Hierarchically Porous Carbon for Supercapacitor and Oxygen Reduction Reaction

“…Similarly, the high‐resolution O 1s spectrum of HPC‐0 could be deconvoluted into four peaks (Figure S3 b in the Supporting Information), corresponding to C(O)O/COOH (531.1 eV, 15.55 at %), C=O (532.0 eV, 25.30 at %), C−O (532.8 eV, 34.65 %), and O−H (533.7 eV, 24.50 at %) . Compared with nitrogen doping, the oxygen constituents of the HPC materials are more associated with capacitive performance: oxygen doping is capable of increasing the specific capacitance, owing to improved hydrophilicity; conducive to interfacial contact between the hydrated electrolyte ions and the electrode surface; and beneficial for faradaic redox reactions (e.g., C=O+e − →C−O − ); thus resulting in pseudocapacitance …”

“…[59] Similarly,t he high-resolution O1ss pectrumofH PC-0 could be deconvoluted into four peaks ( Figure S3 [60,61] Compared with nitrogen doping, the oxygen constituents of the HPC materials are more associated with capacitivep erformance:o xygen doping is capable of increasingt he specific capacitance, owing to improved hydrophilicity;c onducive to interfacial contact between the hydrated electrolyte ions and the electrode surface; and beneficial for faradaic redox reactions (e.g.,C =O + e À !CÀO À ); thus resultingi np seudocapacitance. [45,62,63] The following experimentsw ere conducted to determine if the HPCm aterials, with large specific surface areas anda bundant hierarchicalp ores, had fine electrochemical performance as supercapacitor electrodes, in both three-(for characterizing as ingle electrode) and two-electrode systems (for evaluating a symmetric supercapacitorc omposed of the two same electrodes) in 6 m KOH as an aqueouse lectrolyte. Figure4as hows the cyclic voltammetry (CV) curves of HPC-0, HPC-2, HPC-4, and HPC-6 at as can rate of 80 mV s À1 between À1.0 and 0Vin at hree-electrodec onfiguration.…”

Heteroatom-doped porous carbon with tunable pore structure and high specific surface area for high performance supercapacitors

“…The requirement for the depletion of using fossil-based carbon resources for producing porous carbon has motivated researchers to use sustainable biomass, which are abundant, renewable and non-expensive raw materials for carbon. Various biomass raw materials, including lignin, [13,14] gelatin, [15] starch, [16] wheat and rice straw, [17,18] plant organs, [19] plane tree fluff, [20] bamboo char, [21] pine tannins, [22] cellulose, [23] etc., have been used to produce porous carbons for SC electrodes with improved capacitive performance. Additionally, the performance of carbon nanomaterials as SC electrodes can be enhanced by several strategies, for example, by increasing the number of active charge sites with enlarged surface area and porosity, and by adding active heteroatoms such as N and S. The first strategy contributes to the enhancement of the electrical double-layer capacitance, while the doping of heteroatoms introduces the additional pseudo-capacitance.…”

Green synthesis of nitrogen-doped multiporous carbons for oxygen reduction reaction using water-caltrop shells and eggshell waste

“…As electric vehicles continue to develop and become more widespread, fuel cells and metal-air batteries have emerged as a mainstream technology for automotive applications. [1][2][3][4] However, the performance of modern fuel cells and metal-air batteries is limited by the slow reaction rate of the oxygen reduction reaction (ORR) at the cathode. 5,6 Although this problem can be solved by using Pt catalysts to enhance the ORR activity, Pt is expensive, lacks sufficient durability, and has low natural abundance.…”