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Schematic illustration of the preparation of dense microporous carbons. [Display omitted] • The dense microporous carbons were prepared by a universal and facile strategy of pre-oxidation carbonization–activation. • The prepared microporous carbons not only possess well-developed porous structure but also have a large packing density. • The optimum microporous carbon shows high specific capacitance and excellent rate performance. • This work offers a good cost-efficiency strategy to prepare electrode materials with prospects for practical applications. The compact carbon materials with huge specific surface area (SSA) and proper pore structure are highly desirable towards high-performance supercapacitors at the cell level. However, to well balance of porosity and density is still an on-going task. Herein, a universal and facile strategy of pre-oxidation–carbonization–activation is employed to prepare the dense microporous carbons from coal tar pitch. The optimized sample POCA800 not only possesses a well-developed porous structure with the SSA of 2142 m2 g−1 and total pore volume (V t) of 1.540 cm3 g−1, but also exhibits a high packing density of 0.58 g cm−3 and proper graphitization. Owing to these advantages, POCA800 electrode at areal mass loading of 10 mg cm−2 shows a high specific capacitance of 300.8 F g−1 (174.5 F cm−3) at 0.5 A g−1 and good rate performance. The POCA800 based symmetrical supercapacitor with a total mass loading of 20 mg cm−2 displays a large energy density of 8.07 Wh kg−1 at 125 W kg−1 and remarkable cycling durability. It is revealed that the prepared density microporous carbons are promising for practical applications. [ABSTRACT FROM AUTHOR]

Schematic illustration of the preparation of hierarchical porous carbons. [Display omitted] • Coal tar pitch derived porous carbons with high specific surface area and tunable pore structure were synthesized. • Pore structure of the porous carbons was efficiently regulated by air pre-oxidation treatment. • The optimum sample shows outstanding supercapacitor performance. • The contribution of micropore and small mesopore to the performance of supercapacitors is discussed. Carbon materials with rational pore structure have attracted tremendous attention in high-performance supercapacitor applications. However, designing and constructing such carbon materials with excellent performances via a simple and low-cost route is still a challenge. Herein, the nitrogen self - doped oxygen-rich hierarchical porous carbons (OTS x -PC) derived from coal tar pitch are constructed via a facile strategy of air pre-oxidation-activation. The air pre-oxidation treatment can effectively regulate the small-sized mesopore structure (2–4 nm) of samples. The optimal OTS 350 -PC sample exhibits a high specific capacitance of 298 F g−1 at 0.5 A g−1, and delivers a high energy density of 14.9 Wh kg−1 at a power density of 0.15 kW kg−1 with remarkable cycling stability in KOH aqueous electrolyte. This excellent electrochemical performance is attributed to its ultrahigh specific surface area (SSA, 2941 m2 g−1), huge total pore volume (V t , 1.9 cm3 g−1), rational pore structure and reasonable heteroatom configuration, which ensure sufficient charge storage, rapid electrolyte ions diffusion, as well as the contributed pseudocapacitance. This research not only offers a facile route for high-value utilization of coal tar pitch but also provides the cost-effective and excellent porous carbons for supercapacitor with high performance. [ABSTRACT FROM AUTHOR]

Schematic illustration of the preparation of porous carbons. [Display omitted] • The porous carbons with controllable architecture were fabricated by a dual-role KCl-assisted activation method. • KCl not only serves as an auxiliary template but also contributes to an enhancement in the melting of K 2 CO 3. • The prepared porous carbons possess well-developed pore structure and excellent electrochemical performance. • This work paves a path to prepare porous carbons via an environment-friendly and cost-effective route for supercapacitors. Preparation of high-performance electrode materials in a low-cost and simple way is of great significance for the application and development of supercapacitors. Herein, a dual-role KCl-assisted KOH activation method with low KOH consumption was employed to fabricate porous carbons with controllable architecture, using the coal liquefaction residue (CLR) as the raw material. It is indicated that KCl not only serves as an auxiliary template for pore-forming but also contributes to an enhancement in the melting of K 2 CO 3 , an intermediate of KOH activation, resulting in an improvement in the efficiency of KOH activation. As a consequence, the prepared samples possess highly developed pore structure even at a low KOH consumption, which endow them with excellent capacitive performance. The as-fabricated optimal porous carbon (LR-KPC-4) displays a maximum specific capacitance of 375 F g−1 at 0.5 A/g and superior rate capacity, which are much better than those of the porous carbon prepared without KCl. The fabricated symmetric supercapacitor shows a high specific capacitance of 256 F g−1 at 0.5 A/g, energy density of 8.9 Wh kg−1 at 125 W kg−1 and great cycling stability. This work demonstrates a facile strategy to efficiently convert CLR into porous carbons for high-performance supercapacitors. Meanwhile, it paves a promising way for value-added utilization of CLR. [ABSTRACT FROM AUTHOR]

Construction of hierarchically porous carbon electrode materials is considered as an efficient strategy for improving the performance of supercapacitors. Nevertheless, how to precisely control the pore structure for preferable improvement the capacitance performance and fabricate in a cost-efficient way is still a scientific challenge. In this paper, an industrial by-product of coal tar pitch is used as precursor to prepare interconnected hierarchically porous carbons, with another domestic waste of eggshell as a pore-forming template and an inner-activator, combined with KOH in-situ activation. The as-prepared porous carbons exhibit large specific surface area (S BET , 1398–2103 cm2 g−1), well-developed interconnected hierarchically architecture, and excellent electrochemical performance. Among them, the optimal TS-PCE-4 based symmetric supercapacitor possesses a high capacitance of 238 F g−1 at 0.5 A g−1 with an excellent rate capability, exhibits long cycle stability with capacitance retention of 95.85 % after 10,000 cycles, and delivers energy densities of 8.27–5.47 Wh kg−1 at power density in the range of 125–4925 W kg−1 in 6 M KOH aqueous electrolyte. This work offers a facile and low-cost route to construct interconnected hierarchically porous carbons for energy storage devices. [Display omitted] • An industrial by-product of coal tar pitch was used to fabricate the hierarchically porous carbons via a facile route. • The domestic waste of eggshell was served as a pore-forming template and an inner-activator. • The carbons show large specific surface area and well-developed interconnected hierarchically porous architecture. • The optimum sample displays outstanding supercapacitor performance. [ABSTRACT FROM AUTHOR]