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[Display omitted] • Solvent-free strategy was developed to synthesize porous carbon (MIC x) doped with rich Faradaic active oxygen (5.8–8.2 atom%). • The resultant MICx owns surface area of 326–427 m2/g and large packing density of 1.12–1.28 g/cm3. • The MICx based electrode achieves superior supercapacitor performances with both high gravimetric and volumetric performances. In the selection of carbon-based electrode materials for supercapacitive energy storage, it is hard to get one that is high in both gravimetric and volumetric performance because there is a trade-off between them. In the presented work, microporous carbon materials denoted herein as MIC x were synthesized through catechol polymerization in the presence of molten FeCl 3. As complexing agent, the iron species coordinate with catechol oligomers, functioning as template as well as catalyst in the synthesis of the microporous carbon. The in situ formation of micropores and carbonaceous skeleton is induced by the carbonyl/hydroxyl redox pairs upon catalytic graphitization during carbonization. The derived nanocarbons have high microporosity (70.6 %–79.2 %) and rich oxygenate functionalities (carbonyl: 3.3–4.0 atom% and hydroxyl: 2.5–4.2 atom%). The FeC x materials are high in faradaic activity. For example, the FeC873-based electrode displays excellent supercapacitor performances: capacitance of 440F/g@1.0 A/g (equivalent to 537F/cm3@1.0 A/g) and 289F/g@20 A/g (equivalent to 353F/cm3@20 A/g), large energy density of 25.5 Wh/kg@900 W/kg (equivalent to 31.1 Wh/L@1098 W/L), and good cycling stability (ca.100 % capacitance retention after 20 000 continual charge/discharge cycles). [ABSTRACT FROM AUTHOR]

[Display omitted] • Expired coffee derived carbons (HCDC) achieves high packing density of 1.81–1.83 cm3/g. • The derived HCDC owns rich nitrogen (4.5 atom%) and oxygenic (12.0 atom%) functionalities. • The HCDC electrode achieves high gravimetric and volumetric capacitance of 312F/g and 567F/cm3. • The HCDC electrode exhibits a high volumetric energy density of 27.8 Wh/L@1820 W/L. Clean production of activated carbon from household expired food provide an alternative way to get value-added product thus benefits waste reutilization and environmental protection. Herein, we fabricated N, O co-doped activated carbons (HCDC) from expired coffee to by a green route of direct water vapor carbonization/activation approach. In our approach, the expired coffee was firstly grinded and then carbonized under water vapor atmosphere. The derived HCDC owns low surface area (172–184 m2/g), large packing density (1.81–1.83 cm3/g), rich redox-active nitrogen (4.5 atom%) and oxygenic (12.0 atom%) functionalities. As electrode for supercapacitor, the HCDC achieves a high gravimetric capacitance of 312F/g at 1.0 A/g (vs 258F/g of commercial AC) and the value can be maintained 223F/g at 20 A/g, showing a high rate capability of 71.5%. Particularly, because of the large packing density, the HCDC exhibits an excellent volumetric supercapacitor performances: ultrahigh volumetric capacitance of 567F/cm3 (vs 165F/cm3 of commercial AC) and large energy density of 27.8 Wh/L@1820 W/L (vs 7.5 Wh/L@576 W/L for commercial AC) and superlong cycling stability with near 100 capacitance retention after continual 30 000 cycles at large current density of 9.0 A/g, suggesting a promising application for practical energy storage devices. [ABSTRACT FROM AUTHOR]

Three alkaline metal carbonates of MgCO 3 , CaCO 3 and BaCO 3 with different morphology, surface basicity and thermal stability were used as templates to find the template effect towards the morphology, oxygen species as well as supercapacitor performance of the derived nanocarbons. [Display omitted] • Three alkaline carbonates were adopted as catalytic templates for the fabrication of nanocarbons. • Residual oxygen and morphology of nanocarbons are greatly influenced by the nature of templates. • Residual oxygen in final products mainly exists in forms of redox-active carbonyl and hydroxyl. • The derived MgC displays superior surface area and supercapacitor performance. Nanocasting techniques are widely adopted for the fabrication of nanocarbons. However, there is little research on the effect of template nature on the physicochemical properties and performances of the nanocarbons. Herein, we investigated how the morphology, oxygen species as well as supercapacitor performance of the derived nanocarbons were governed by the morphology, surface basicity and thermal stability of MgCO 3 , CaCO 3 and BaCO 3 when the alkaline metal carbonates were used as templates. Using MgCO 3 as catalytic template, the MgC973 produced after carbonization at 973 K has ultrathin nanosheet morphology (∼20 nm), large specific surface area (952 m2/g), and superior supercapacitor performances, showing high capacitance of 421F/g@1.0 A/g (maintaining 306F/g@20 A/g), and large energy density of 31.1 Wh/kg@1000 W/kg. The superiority can be ascribed to the ultrathin morphology and thermal instability of the MgCO 3 template, which upon decomposition generates CO 2 and in situ activates the carbon skeleton. Moreover, the surface alkalinity of templates is conducive to the retention of electrochemically active oxygen, and BaC973 is with oxygen content (9.1 atom%) higher than MgC973 (7.9 atom%) and CaC973 (8.8 atom%). The present work provides insightful ideas for the synthesis of unique carbon materials with specific functionalities through the selection of suitable templates. [ABSTRACT FROM AUTHOR]

[Display omitted] • An all-solid-state (ASS) strategy without using any solvents and activators was developed. • The ASS strategy derived carbon owns abundant nitrogen species and large packing density. • The resultant product show superior supercapacitor performances with both high gravimetric and volumetric performances. Template synthesis of porous carbon with rich functionalities by a scalable strategy without using any solvents and activators will be a green and promising route. Herein, we reported an all-solid-state synthesis strategy by mixing glucose and graphitic carbon nitride (g -C 3 N 4) by milling and then undergoing a segmented carbonization in which first at low temperature of 573 K to polymerize sucrose onto g -C 3 N 4 , then at high temperature of 973 K to carbonized the composite to obtain a porous carbon (denoted as GNC) with abundant nitrogen species over 20 atom% and large packing density (0.91–1.25 g cm−3). Due to the features of large packing density and rich electrochemically-active N species, as electrode for supercapacitive energy storage, the developed GNC exhibit a comparable energy storage level with both high gravimetric energy density of 26.8 Wh kg−1@1000 W kg−1 and volumetric energy density of 30.8 Wh L−1@1150 W L−1, suggesting a potentiality in energy storage field. Importantly, the present strategy owns characteristics of ease of operation, green and scalable, which would be a promising synthesis route towards the fabrication of functional carbon utilizing in many fields like sorption & separation, catalysis, energy storage and so on. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co 3 O 4 nanoneedle arrays is grafted on V 2 O 5 nanosheet arrays to form VNSAs/CNNAs. • The VNSAs/CNNAs composite shows a high C s value of 1023 F g−1at 5 mV s−1. • The VNSAs/CNNAs composite can work under a large voltage window of 1.6 V. • The VNSAs/CNNAs composite has a high E d value of 127.3 Wh kg−1 at 400 W kg−1. • The high performance is ascribed to the synergistic effect of V 2 O 5 and Co 3 O 4. In this work, two-dimensional V 2 O 5 nanosheet arrays/one-dimensional Co 3 O 4 nanoneedle arrays (2D VNSAs/1D CNNAs) composite is successfully prepared on nickel foam substrate. A variety of structural characterization techniques (SEM, XRD, EDS, TEM, and XPS) show that the as-prepared composite is V 2 O 5 monocrystal with a layered structure grafting by Co 3 O 4 polycrystal with a 1D needle-like structure. The VNSAs/CNNAs composite is used as supercapacitor electrode material. In a three-electrodes system, it shows high specific capacitance (C s) values (1023 F g−1@5 mV s−1 from CV curve and 826 F g−1@0.5 A/g from GCD curve), a high coulombic efficiency (98.6 %@10 A/g), a good cyclic stability (92.7 % after 6000 cycles), a low charge transfer resistance (2.7 Ω), and a fast ionic diffusion rate (2.01 × 10−8 cm2 s−1). In a two-electrodes system, the assembled VNSAs/CNNAs//VNSAs/CNNAs symmetric supercapacitor has C s values of 445 F g−1@5 mV s−1 and 363 F g−1@0.5 A/g. Its cycle stability and rate capability could reach up to 92.3 % and 90.7 % after 6000 cycels, respectively. It also shows a high energy density (E d) of 127.3 Wh kg−1@400 W kg−1 and can retain 72.2 Wh kg−1@8000 W kg−1. The excellent electrochemical properties indicate that VNSAs/CNNAs composite can greatly increase the E d of supercapacitors. [ABSTRACT FROM AUTHOR]