Mesopore Content Research Articles

Design of honeycomb-like hierarchically porous carbons with engineered mesoporosity for aqueous zinc-ion hybrid supercapacitors applications

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) have aroused extensive research attention in the field of electrochemical energy storage. However, the practical application of ZHSCs is severely limited by their poor rate performance, which is mainly owing to the large hydrated zinc ions radius and high desolvation free energies. Herein, we have designed an efficient route for the environment-friendly production of 3D honeycomb-like hierarchically porous carbons (HHPCs) with high specific surface and tunable porosity, using commercial magnesium oxide microparticles as a template and potassium bicarbonate as the activator. Different from previous works, the magnesium oxide microparticles displayed not only aggregation-free and low-cost but also good structural stability, which plays key roles to achieve the unique 3D honeycomb-like hierarchically structures. Benefiting from the large surface, high mesopore content, and honeycomb-like hierarchically structures, the HHPC-6 sample demonstrates desired electrochemical performance as the cathode for ZHSCs, with the largest specific capacity up to 147 mAh g−1 at 0.2 A g−1, impressive rate performance (48.3% of capacity retention at 50 A g−1), ultrahigh specific power (40 kW kg−1 at 56.7 Wh kg−1). This strategy will offer a guiding function into the fabrication of nanocarbons for ZHSCs application.

Glycerol derived mesopore-enriched hierarchically carbon nanosheets as the cathode for ultrafast zinc ion hybrid supercapacitor applications

Direct transformation of small molecular organic solvents (SMOSs) into functional carbon materials have received paramount interests in recent years, although it remains a huge challenge. Herein, we demonstrate an efficient zinc acetate-assisted pyrolysis strategy to direct transformation of glycerol into mesopore‐enriched hierarchically carbon nanosheets (MEHCs). We found that the initial formed glycerin zinc would be one of the major ways in immobilization of glycerol from volatilization as well as determining the morphology of the resulting carbons. By optimizing the amount of zinc acetate, MEHCs with large specific surface area (1666.8 m2 g−1), ultra-high mesopore content (Smeso = 1488.7 m2 g−1) and total pore volume (2.42 cm3 g−1) were obtained. Benefiting from the unique structure features, the as-assembled aqueous zinc ion hybrid supercapacitors with the as-prepared MEHCs as the cathodes can deliver a specific capacity of 132.9 mAh g−1, and rate capability up to 49.1% at 50 Ag−1, which is one of the largest values in comparison with the previously reported values. Such promising results indicate that the newly developed strategy would offer a valuable avenue for the production of functional nanocarbon materials from SMOSs for electrochemical energy storage applications.

Influence of porosity on the reactivity of inertinite and vitrinite toward sodium hypochlorite: Implications for enhancing coal seam gas development

Sodium Hypochlorite (NaClO) oxidation has been reported as a promising method for coal seam permeability enhancement and extracting valuable hydrocarbons from coal. Different coal macerals, particularly vitrinite and inertinite behave differently in NaClO with varying reaction extent exhibited. The reasons for variability are not completely understood. This study aims to reveal the controlling factors of different coal maceral oxidation by comparing their molecular structures and pore characterization. A Permian coal from Bowen Basin, Australia, was collected and separated into vitrinite-rich concentrate (bright coal) and inertinite-rich concentrate (dull coal). Their reaction phenomena with NaClO are examined and their molecular structures and pore structures are compared with multiple techniques. The vitrinite-rich and inertinite-rich concentrates share similar organic molecular structures although there is some marginal difference with the bright coal being slightly more aliphatic with higher oxygen content. By contrast, their pore structures are significantly different such that the dull coal is more porous with higher content of mesopores and better connectivity. For coal powders vitrinite is more reactive than inertinite and yet for coal particles inertinite is more reactive. Given that inertinite is more porous, these results suggest that the porosity of the inertinite is the key property making the inertinite more reactive. Therefore, it is proposed that the different extent of oxidation for different macerals from isorank coal is controlled primarily by the difference in their porosity rather than molecular structures.

Introduction of eicosane into biochar derived from softwood and wheat straw: Influence of porous structure and surface chemistry

Thermal energy storage using phase change materials (PCMs) has received great attention in a wide range of smart applications. However, the development of shape-stabilized organic composite PCMs is a significant barrier to further advancement. Herein we explore “green” composite PCMs using commercially available biochar materials, derived from two different biomaterials, wheat straw and softwood, at pyrolysis temperatures of 550 °C and 700 °C, and organic PCM, n-eicosane (ES), for efficient thermal energy storage applications. All the composite PCMs exhibited high thermal stability, medium thermal diffusivity, and good chemical compatibility with the composite constituents. Over the phase change temperature range 36.4–40.6 °C, the composite derived from wheat straw biochar pyrolyzed at 550 °C showed the largest latent heat storage capacity of 75.0 J/g due to the high mesopore content of its supporting structure, specific surface area, and active functional groups that enhance the capillary force during PCM adsorption. In contrast, softwood biochar produced at 550 °C had the lowest latent heat storage capacity of 52.0 J/g. The surface functionality, structural characteristics, type of biomaterials, intermolecular interaction between ES and biochars, and pyrolysis temperature play important roles in determining the thermal properties of the as-prepared composite samples.

Efficient utilization of interparticle mesopores in aluminosilicate towards thermal energy storage

Porous confinement, a method to prepare form-stable composite phase change materials (PCMs) by impregnating PCMs into the pores of porous scaffold materials, is proven to be an extraordinarily effective mean to address the leakage problem of PCMs during the phase transition process. For the energy storage capacities of composite PCMs are closely associated with the pore structure of scaffold materials, the research on the correlation between the structure of mesoporous scaffold materials and its loaded capability phase change materials is conducive to enriching the research system of heat storage materials. Herein, a novel form-stable composite PCM was fabricated successfully by integrating polyethylene glycol (PEG) into the mesopores of nano-aluminosilicate aggregates (n-ASA). The structure and the thermal properties of the samples were characterized. The results indicated that n-ASA had a self-sustaining microstructure by the aggregation of individual granules, and a very high mesopore content of 98.3 % and mesopore volume of 1.16 cm3/g. The maximum mass fraction of PEG loaded in the composite can reach up to 77.5 % and the melting latent heat of n-ASA/PEG were 133.8 J/g and 115.0 J/g, respectively. An increasement of 42.4 % in thermal conductivity of PEG was achieved after loading it into n-ASA with interconnected pores due to the provision of a faster heat transfer channel. Moreover, the thermal characteristics of n-ASA/PEG had no distinct change after 200 thermal cycles, indicating its prominent thermal reliability and stability. It is convinced that the mesopores of n-ASA are actually preferable over the micro- and macro-pores for holding PEG, and the synthesized n-ASA/PEG composite would be a prospective and potential candidate for low-temperature heat storage applications.

Regulation of the mesopore proportion of porous carbon for optimizing the performance of electric double layer capacitors

So far, there are still some difficulties in controlling the pore structure of porous carbon materials. Exploring the relationship between the structure and electrochemical behavior of porous carbon through optimizing pore structure is of great significance for its application in the field of energy storage.Here, we employ the interpenetrating polymer networks as the precursor to prepare ultra-microporous carbon with a pore diameter of 0.6 nm, and regulate the mesoporous content by chemical activation. The relationship between mesoporosity and electrochemical performance was studied. In our experimental results, the optimized sample has a mesoporous ratio of 55.1% and the specific surface area of 2453 m2g−1. As electrode material, its specific capacity reaches 247F g−1with excellent cycle performance. As the symmetric device, its specific energy reached 17.75Wh kg−1.

Characteristics of silicon carbide sludge-based geopolymers

In this study, metakaolin (MK) with silicon carbide sludge (SiC sludge) was used in the preparation of geopolymers, and its use as a structural material was demonstrated. The production of SiC sludge metakaolin-based (SCM) geopolymers was investigated by using solid/liquid (S/L) ratios of 0.4–1.0 and SiC sludge replacement levels of 0–40% to understand the effects of the geopolymerization process. The results indicated that for SCM geopolymers with SiC sludge replacement levels of 10–40% and a solid–liquid ratio of 1.0, the strength decreased from 70.02 MPa to 48.47 MPa after 56 days of curing. The heat evolution of the first exothermal peak clearly decreased from 990.6 W/g to 835.7 W/g as the SiC sludge content increased from 10 to 40%. After 56 days of curing, the mesopore content decreased from 98.94% to 95.24% in SCM geopolymers with 10% to 40% SiC sludge. After 56 days of curing, SiC sludge replacement levels of 0%, 10% and 40% increased, and the polymerization degree increased to 82.3%, 82.7% and 80.5%, respectively. At a solid–liquid ratio of 1.0, SCM geopolymers with a 10% SiC sludge content exhibited excellent mechanical properties, which accounted for the synergistic effect of the SiC sludge and MK. This study revealed that SCM geopolymers with a SiC sludge replacement level of 10% are beneficial to the geopolymerization process and that they can be used as a structural material.

Mineral Characteristics of Low-Rank Coal and the Effects on the Micro- and Nanoscale Pore-Fractures: A Case Study from the Zhundong Coalfield, Northwest China.

The mineral characteristics (occurrence, type, and content) of low-rank coal and their influence on coalbed methane (CBM) reservoirs are investigated at the micro- and nanoscales. Six coal samples of three representative coalmines were used to demonstrate the uniform tectonization from the Zhundong coalfield, NW China. Based on optical microscopy and scanning electron microscopyenergy dispersive spectrum (SEM-EDS) analysis, the mineral composition and occurrence characteristics were discussed. The micro- and nanoscale reservoir characteristics in low-rank coal (pore size distribution and adsorption capability) were studied by diverse methods, including lowtemperature N₂ adsorption/desorption, mercury intrusion porosimetry and CH₄ isotherm adsorption analysis. The coal reservoir nuclear magnetic T₂ spectra of porosity and movable fluid were obtained by combining low-field nuclear magnetic resonance (NMR) analysis, which has an advantage of determining pore fluid technology. The mineral content is highly variable (4˜16 vol.%) in the Xi Heishan prospecting area of the Qitai region. Kaolinite, goyazite, ankerite and anorthosite were microscopically observed to be filling in coal pores and microfractures, and the minerals are given priority to silicate minerals. There is a greater content of mesopores (100-1000 nm) and transition pores (10-100 nm), and they are well connected. The micropores (0-10 nm) are dominated by parallel plate, closed or wedge-shaped pores. Furthermore, the microfractures are mainly observed for types B (width ≥ 5 μm and length≤ 10 mm) and D (width<5 μm and length<300 μm). The results show that microfractures B and C (width< 5 μm and length ≥ 300 μm) are better connected, but the orientation and connectivity of type D are worse. The Langmuir volume and mesopore content decreased with increasing mineral content, which shows that the low-rank coal minerals filled some adsorption space; the reduced CBM adsorption capacity and cellular pore and intergranular pore filled with minerals affect the mesopore content. Therefore, mineral characterization significantly influences methane adsorption capacity and pore structure.

Evaluate the Impact of Porous Media Structure on Soil Thermal Parameters Using X-Ray Computed Tomography

Soil thermal parameters are affected by soil texture, soil moisture, and porous media structure. X-ray computed tomography (X-CT) is used for description of soil porosity. The aim of this study was to observe the changes in porous media structure and soil thermal parameters with changes in soil moisture. Moreover, the effect of soil porous media structure, including connectivity and size of pores, on soil thermal parameters was estimated. Soil thermal diffusivity was measured at three different values of soil moisture, whereas soil thermal conductivity and volumetric heat capacity were calculated. Furthermore, the percentages of open, closed, and total porosities, as well as mesopores content were calculated at the same soil moisture using X-CT software programs. The results show that soil thermal parameters decreased along with decreasing soil moisture. In addition to decreasing soil moisture, soil thermal parameters decreased with increasing percentage of total porosity and the content of mesopores. However, the negative correlation between the soil thermal diffusivity and the content of mesopores is weak (r = –0.24). At the same time, a more significant negative correlation coefficient was found between soil thermal diffusivity and tomographic total porosity (r = –0.64) for silty loamy Albic Glossic Retisols. The influence of total porosity on the values of soil thermal diffusivity and other soil thermal parameters is larger than the pore size distribution (mesopores content). Soil heat transfer proceeds through soil particles (solid phase) and is not directly related to pore size distribution. The variations of soil thermal parameters values were in harmony with a quantitative description of soil porous media with the use of X-CT.

Multifractal analysis of coal pore structure based on NMR experiment: A new method for predicting T2 cutoff value

Nuclear magnetic resonance (NMR) is a commonly used method to quantitatively characterize the pore structure of coal. T2 cutoff value is closely related to the microscopic pore structure of coal reservoirs, which directly affects the calculation of porosity, permeability, movable and irreducible fluid saturation. In this study, the pore structure of four types of coal samples were studied based on NMR experiments and the multifractal characteristics of saturated coal samples were analyzed with multifractal theory. Furthermore, the correlation between T2 cutoff values and multifractal characteristic parameters were discussed. The results show that the pore structure characteristics of CZ, GD and GHS coal samples are basically the same, all of which are mainly micropores, with relatively less content of mesopores, macropores and microcracks, while PDS coal samples have relatively more content of mesopores, macropores and microcracks. Different types of coal samples have similar multifractal characteristics and all coal samples are dominated by micropores. There is an obvious linear relationship between T2 cutoff values and the multifractal characteristic parameters. Five models of T2 cutoff values changing with the multifractal characteristic parameters are obtained by linear fitting. The error range between T2 cutoff values calculated by the five models and the experimental values are within 0.1 ms, among which T2 cutoff values calculated by model 5 are highly consistent with the experimental values, indicating that model 5 can better predict T2 cutoff values. The results can provide theoretical reference for the characterization of coal pore structure and the prediction of T2 cutoff values.

Control of porous size distribution on solvent-free mesoporous carbon and their use as a superadsorbent for 17α-ethinylestradiol removal

This work reports the synthesis of mesoporous carbon using the solvent-free soft template method and their application for the adsorption of the emerging contaminant 17α-ethinylestradiol. For the first time, for the flexible solvent-free method, we evaluated how the precursor carbon/surfactant ratio (p/s), heating rate, stabilization time and self-assembly temperature, can influence textural properties of the materials. According to the results, the carbon source/surfactant ratio was the one which influenced textural characteristics most. The materials synthesized in p/s-1 had a smaller medium pore diameter (3.4 nm) while materials synthesized in p/s-0.5 showed an average diameter of larger pores (4.9 nm). Transmission micrographs indicated the formation of two types of pore ordering: wormholes and honeycombs. However, despite some differences in pore ordering, all materials showed textural quality. We found that the adsorption of 17α-ethinylestradiol is more affected by the diameter, volume and mesoporous content than by the type of pore ordering. Thus, materials with a high diameter and mesoporous content showed 99% removal with a maximum adsorption capacity of 157 mg/g. Also, the adsorption capacity of the material remained almost 100% until the fourth cycle and above 85% until the tenth cycle.

Coal Petrology Effect on Nanopore Structure of Lignite: Case Study of No. 5 Coal Seam, Shengli Coalfield, Erlian Basin, China

The pore structure of lignite reservoirs is affected mainly by the maceral composition of coal and depositional conditions due to geothermal effects without thermogenic hydrocarbon generation. Low-temperature nitrogen adsorption (LT-NA) and low-temperature carbon dioxide adsorption (LT-CA) were used to characterize nanopore structure. Sub-maceral identification allowed characterization of coal petrology features. The coal samples were rich in huminite—mainly attrinite and densinite—and had medium inertinite content, dominated by fusinite. The micropore volume varied from 0.036 to 0.077 cm3/g, controlling the pore specific surface area. Three pore types were identified from LT-NA isotherms. Hysteresis coefficients were used to describe quantitatively the pore types. Low tissue preservation index and vegetation index, moderate gelification index, and groundwater influence values indicate that the No. 5 coal seam (Shengli coalfield, Erlian basin, China) was deposited in limnic to limno-telmatic environments with relatively high levels of reduction and supply of marginal aquatic/herbaceous vegetation. Poor preservation of plant structure and hydrodynamic conditions, more developed marginal aquatic/herbaceous vegetation, and high ratio of huminite to inertinite contributed to high micropore content and low mesopore content. Based on sharp variations in coal macerals, coal facies indices, dried ash yield (Ad), and organic sulfur (So,d), three sedimentary cycles were distinguished. Pore structures were controlled by the sedimentary environment. Micropores increased with enhanced reduction and reduced oxidation. When the redox of the sedimentary environment showed little variation, mesopores increased with rising hydrodynamic conditions.

Free-standing, flexible and stable potassium–sulfur battery enabled by controllable porous carbon cloth

Potassium-sulfur (K–S) battery benefits from high specific capacities and natural abundance, which is deemed to be a rational choice to realize large-scale energy-storing applications. Here, a free-standing activated carbon fiber (ACF)@sulfur composite cathode (ACF@S) is designed for K–S batteries through a simple impregnation of melted sulfur into hierarchically porous ACF cloth. Taking advantages of the microstructural diversity manifested as various specific surface area, pore size and morphology, the ACF@S yields remarkable energy-storing capability due to effective dispersion, adsorption and physicochemical anchoring of soluble polysulfides. More importantly, their fiber geometries endow them with continuous channels which facilitate fast reaction kinetics. The relationships between specific surface area of ACF and electrochemical performance are also probed. Compared with ACF-1000@S (1000 is denoted as SSA = 1000 m2 g−1 and so on) and ACF-1200@S, the ACF-1500@S electrode with high content of mesopores delivers high reversible capacity of 310 mA h g−1, indicating great promise for shuttle suppression. Besides, quantitative investigations prove that surface capacitive-controlled processes play crucial role and K2Sn (n = 1,2,3) is verified as the final discharging products through multiple characterizations, including ex situ XPS and HRTEM. Our findings aim to provide essential designs and electrochemistry interpretations of structurally-controlled ACF-based composite cathode for high-performance K–S batteries.

Surfactant-modified biosolid-derived materials as efficient H2S removal media: Synergistic effects of carbon phase properties and inorganic phase chemistry on reactive adsorption

A new H2S reactive adsorbent was prepared from a biosolid by the addition of pluronic surfactant F127 prior to a simple pyrolysis at 950 °C at two heating regimes. The materials were extensively characterized and tested as H2S removal media from air. The results show an over 250% increase in the H2S removal efficiency compared to the adsorbent obtained without the surfactant addition. Hydrogen sulfide was converted mainly to elemental sulfur. While the surfactant increased the carbon content and volume of mesopores, slow pyrolysis additionally contributed to the development of micropores, increased a carbon structural order, and resulted in an enhanced dispersion of catalytic centers (Ca and Fe oxides) on the surface. It also increased the amount of nitrogen in pyridinic configurations. All of these facilitated electron transfers, thus promoting oxidation reactions, and provided the sites increasing H2S interactions with the surface and also those acting as a storage system for elemental sulfur.

Acetone Conversion to Isobutylene over Magnesium-Containing Micro-Mesoporous MOR Zeolites

Isobutylene synthesis from acetone in the presence of micro–mesoporous MOR zeolites obtained by hydrothermal recrystallization and modified with magnesium acetate by incipient wetness impregnation has been studied. A kinetic study of the reaction has been conducted, and product formation routes have been determined. It has been found that an increase in the mesopore content leads to an increase in the catalyst activity owing to the removal of diffusion restrictions. It has been shown that isobutylene formation occurs on both Lewis and Bronsted acid sites. The modification of the initial aluminosilicates with magnesium has been found to decrease the number and strength of Bronsted acid sites and thereby lead to a decrease in the number of side reactions and an increase in the time-on-stream stability of the catalysts.

Synthesis of USY Zeolite with a High Mesoporous Content by Introducing Sn and Enhanced Catalytic Performance

A method for the introduction of trace Sn atoms into zeolite Y to impart a large mesoporous pore volume is proposed, whereby the mesoporous pore volume, the framework SiO2/Al2O3 molar ratio, and th...

Sludge‐based mesoporous activated carbon: the effect of hydrothermal pretreatment on material preparation and adsorption of bisphenol A

AbstractBackgroundThe excess sludge produced by sewage treatment plants contains a large number of pollutants, which is of huge environmental risk. Transforming this kind of solid waste into adsorption materials is an effective approach to realize the resource utilization of sludge. Combined with hydrothermal pretreatment and chemical activation, the synthesis of sludge‐based mesoporous carbon is used to remove bisphenol A (BPA) in wastewater.ResultsA resource recycling measure to prepare mesoporous activated carbons (MACs) from sewage sludge was developed via the combination of hydrothermal pretreatment and chemical activation using sewage sludge and sulfuric acid as carbon precursor and activating agent, respectively. The combination of hydrothermal pretreatment and chemical activation not only can make efficient use of the activating agents but also facilitate the deep pyrolysis of the sludge. The resultant MAC obtained using the hydrothermal pretreatment possessed a larger total surface area, less crystalline phase and a narrower pore size distribution compared to other samples. Meanwhile, the MAC obtained from hydrothermal pretreatment presented the highest amount of adsorption of BPA and achieved a better capture than the reference commercial activated carbons. In addition, a possible adsorption mechanism has been proposed to further analyze the enhanced adsorption performance.ConclusionsThe yield and mesoporous content of the obtained MAC is 59.19% and 31.51%, respectively. The maximum adsorption capacity for BPA is 137.87 mg g−1. Microporosity, hydrogen bonding and π–π effect introduced by the hydrothermal pretreatment play an important role in BPA adsorption. © 2020 Society of Chemical Industry

TiO2 hollow heterophase junction with enhanced pollutant adsorption, light harvesting, and charge separation for photocatalytic degradation of volatile organic compounds

The performances of a photocatalyst in volatile organic compound (VOC) adsorption, photon harvesting, and charge separation largely determine its VOC mineralization efficiency. To simultaneously optimize these properties, this work constructed a hollow heterophase junction by coating anatase TiO2 hollow spheres with amorphous TiO2. Toluene and acetone were selected as model VOC pollutants. Results showed that the amorphous TiO2 coating increased the content of micropores and mesopores for the photocatalyst, enhanced the adsorption of toluene and acetone, and improved light absorption. The heterophase junction, formed by the external amorphous TiO2 shell and inner anatase TiO2 shell, reduced the photon energy required for electron excitation and facilitated charge carrier separation. Given these distinct advantages, the material with the hollow heterophase junction realized efficient mineralization of toluene and acetone.

Direct Microwave Conversion from Lignin to Micro/Meso/Macroporous Carbon for High‐Performance Symmetric Supercapacitors

AbstractEnzymatic hydrolysis lignin (EHL) is a common biomass that is difficult to use for the synthesis of porous carbon (PC) via direct microwave heating because it absorbs very little microwave energy. In this study, a novel method was developed to synthesize high‐performance PC directly from EHL using only 8 min of microwave heating. The resulting PC exhibits a high specific surface area of 2482 m2 g−1 and a hierarchical pore distribution with a high mesopore content of 35.6 % and oxygen content of 17.1 %. Nitrogen (as a protecting gas) passes through water molecules provided by steam to absorb microwave energy and acts as a physical porogen to form mesopores. Using solid KOH allows one to bypass the time‐consuming drying process and generate sufficient micropores. Additionally, fast self‐pyrolysis and a high heating rate lead to the generation of both mesopores and macropores in a PC framework. Furthermore, multiple active centers can be formed during microwave heating and subsequently stabilized by oxidation once the PC is exposed to an air atmosphere, resulting in the attachment of oxygen functional groups to the PC surface. Based on these desirable physicochemical characteristics, the PC electrodes fabricated in this study exhibit a high specific capacitance of 338 F g−1 at 1 A g−1 and high capacitance retention of 86 % at 10 A g−1. The final PC‐based supercapacitor delivers a maximum energy density of 17.1 Wh kg−1 in a Na2SO4 electrolyte and 8.6 Wh kg−1 in a KOH electrolyte.

Fast microwave self-activation from chitosan hydrogel bead to hierarchical and O, N co-doped porous carbon at an air-free atmosphere for high-rate electrodes material

As ZnCl2 is a good microwave absorber, it was usually used as an porogen to produce porous carbon from biomass by microwave heating. In this study, a facile microwave self-activation with the absence of ZnCl2 was proposed to produce chitosan-hydrogel-bead-based porous carbons (CPC-Air) for a short duration of 10 min. KOH was used as a substitute for the typically used NaOH to form chitosan-based hydrogen beads. During microwave irradiation, KOH acted as a chemical porogen to generate abundant micropores with a pore volume of 0.39 cm3 g−1 in CPC-Air, while water wrapped in hydrogel beads was transformed into steam, serving as a physical porogen to form a considerable content of mesopores (41.8%) and creating a air-free atmosphere. Microwave irradiation led to fast pyrolysis of chitosan, generating meso-/macropores. Combined with self-activation process, it resulted in a high defects degree in CPC-Air. Nitrogen with a high content of 3.4% remained in CPC-Air after self-activation. In addition, a significantly high oxygen content of 17.5% was introduced by the post-oxidation in air atmosphere. Consenquently, the proposed approach can produce a hierarchical and O, N co-doped CPC material with a high defects degree at air-free atmosphere, and with comparable electrochemical properties but with much simpler process and less production duration than the conventional method using ZnCl2. Particularly, owing to the combined effects of those characteristics in CPCs, an excellent rate capability was achieved in the prepared electrode, demonstrating an ultra-high capacitance retention of 87.5% when the current load was increased from 0.5–10 A g−1. The supercapacitor prepared by this electrode can deliver the energy densities of 17.3–20.6 W h kg−1 and the power densities of 0.5–9.0 kW kg−1.