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Abstract An efficient and economic approach for sustainable production of hierarchically interconnected porous carbons are designed and fabricated through the pyrolysis of Rhus typhina fruits and followed by KOH activation to create micropores or mesopores on the nano-sheet wall of macropores. The related N-doped carbon consists of a plenty of micropores and owns high specific surface area (up to 2675 m2 g−1), resulting in high performances for supercapacitors, such as ultrahigh specific capacitance (568 F g−1 at 1 A g−1), remarkable rate capability (310 F g−1 at 20 A g−1, 282 F g−1 at even 30 A g−1 current density) and good long-term stability (capacitance retention of 99% after 10000 cycles at 30 A g−1) in 1 mol L−1 H 2 SO 4. Moreover, the carbon derived from Rhus typhina fruits demonstrates 474 F g−1 at 1 A g−1, 281 F g−1 at 30 A g−1, and capacitance retention of 92% after 10000 cycles at 30 A g−1 in 6 mol L−1 KOH electrolyte. This novel and sustainable biomass-derived carbon material holds a bright future for fabricating high energy supercapacitors. Graphical abstract Image 1 Highlights • RTFs based carbon exhibits ultrahigh capacitance of 568 F g−1 at 1.0 A g−1. • Graphene like sheets built a hierarchical interconnected porous microstructure. • Functional groups induce Faraday reactions, and generate pseudocapacitance. • Biomass wastes provide sustainable and cheap raw materials for supercapacitors. [ABSTRACT FROM AUTHOR]

It is commonly accepted that different structural parameters of electrode materials (i.e. SBET, Smicro, Vtot, Rt and ID/IG) have different effects on the electrochemical properties (i.e. specific capacitance, power density, energy density, and rate capability) in terms of the influencing magnitude and trend. It's therefore extremely desirable to establish a relatively unified structure–function relationship using a single performance indicator. This work luckily finds a defined/composite performance indicator (Smicro/SBET), which can uniformly influence the capacitor performances. Such analysis is based on the characterization of the as-assembled symmetric electrochemical double-layer capacitors using a series of samples as electrodes (obtained by a dual-activator strategy with C3N3Na3S3 and KOH as dual activators and egg yolk as precursor). All the electrochemical performances (the specific capacitance, rate capability, energy storage performance, etc.) have the same tendency with Smicro/SBET changes and the peak for all the performances can be obtained when the Smicro/SBET value is 53.53% in this research. Herein, Smicro/SBET is expected to be one composite performance indicator to reflect the structure–function relationship and in turn judge the whole performances of the materials through the relationship of Smicro/SBET and a single performance, thus greatly simplifying the screening of electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

A series of sponge-like hierarchical porous carbons are prepared using semen cassiae as the precursor and potassium oxalate monohydrate as the activation agent. These sponge-like carbon materials have high surface areas, wide distributions of pore size, and the appropriate forms of nitrogen/oxygen derivatives. All these advantages in structures and surface states contribute to the outstanding performances of such materials as electrodes for high performance electric double-layer capacitors, which include high specific capacitance, high cycling stability, and high energy density. For example, the optimal sample exhibits a high specific capacitance of 401 F g−1, excellent cycling stability (94.5% retention after 10 000 cycles), high energy density (12.01 W h kg−1) and a high power density (10 200 W kg−1) in 1 M H2SO4 solution. [ABSTRACT FROM AUTHOR]

Besides a lack of low-cost electrode materials, the match between the electrode materials and electrolytes is one of the top issues to achieve high-rate electrochemical supercapacitors. Herein, we report an environmentally friendly strategy to prepare three-dimensionally interconnected carbon nanorings (TDICNs) from biomass waste, batata leaves and stalks (BLS). The microstructure of TDICNs matches well with acidic and alkaline electrolytes, making them exhibit high specific capacitances of 532.5 F g−1 (1 A g−1) and 264.0 F g−1 (30 A g−1), excellent capacitance retention (95.1% and 91.7% after 1000 cycles at 1 A g−1 and 10 000 cycles at 30 A g−1, respectively) and a high energy density of 25.8–11.9 W h kg−1 with a power density of 249.5–13 068.0 W kg−1 in 1 mol L−1 H2SO4 aqueous electrolyte. In 6 mol L−1 KOH electrolyte, they still exhibit high specific capacitances of 350.0 F g−1 (1 A g−1) and 246.9 F g−1 (30 A g−1), excellent cycling stability (95.06% and 91.1% of capacitance retention after 1000 (1 A g−1) and 10 000 (30 A g−1) cycles, respectively), a high energy density of 24.5 W h kg−1 and a power density of 12 918.0 W kg−1. [ABSTRACT FROM AUTHOR]

Substituting sustainable/cost-effective catalysts for scarce and costly metal ones is currently among the major targets of sustainable chemistry. Herein, we report the synthesis of N-, S-, and P-tridoped worst-weed-derived carbon nanorings (WWCNRs) that can serve as a metal-free and selective electrocatalyst for the oxygen reduction reaction (ORR). The WWCNRs are synthesized via activation-free polymerization of worst weed, Eclipta prostrata, and then removal of the metallic residues by using HCl. The WWCNRs exhibit good catalytic activity towards the 4 electron-transfer ORR with a low onset potential and high kinetic limiting current density, along with high selectivity (introducing CO, the sample loses only ＜7% of its original activity, in contrast to more than 30% loss of the original activity for 20 wt% Pt/C over 4000 s of the continuous ORR) and long durability (94% of the initial current still persists at the sample electrode compared with a 87% current retention at commercial Pt/C electrodes after 18 000 s). The present work highlights the smart transformation of organic-rich worst weed into value-added functional materials with great potential for applications such as fuel cells, lithium–air batteries, photocatalysis, and heterocatalysis. [ABSTRACT FROM AUTHOR]

The urgent need for sustainable energy development depends on the progress of green technologies, which have steered hot research areas into environmentally benign approaches via inexpensive precursors and abundant resources obtained directly from nature for energy devices such as fuel cells and supercapacitors. By using fermented rice as starting materials, we herein demonstrate a facile, green and scalable approach to synthesize porous N-doped carbon spheres characterised by high specific surface areas (2105.9 m2 g−1) and high porosity (1.14 cm3 g−1), which exhibit not only excellent electrocatalytic activity toward the four-electron oxygen reduction reaction with long-term stability for fuel cells, but also have excellent resistance to crossover effects and CO poisoning superior to that of the commercial Pt/C catalyst. Furthermore, the naturally derived porous N-doped carbon spheres, used as the active electrode materials, present superior performance for capacitors with a capacitance of 219 F g−1 at a high discharge current density of 15 A g−1 and good cycling stability for over 4400 cycles. This work shows a good example for taking advantage of the abundant resources provided by nature, and opening the door for the creation of functional materials with promising applications in high-performance renewable devices related to energy conversion and storage. [ABSTRACT FROM AUTHOR]

Electrocatalysts for the oxygen reduction reaction (ORR) present some of the most challenging vulnerability issues reducing ORR performance and shortening their practical lifetime. Fuel crossover resistance, selective activity, and catalytic stability of ORR catalysts are still to be addressed. Here, a facile and in situ template-free synthesis of Pt-containing mesoporous nitrogen-doped carbon composites (Pt-m-N-C) is designed and specifically developed to overcome its drawback as an electrocatalyst for ORR, while its high activity is sustained. The as-prepared Pt-m-N-C catalyst exhibits high electrocatalytic activity, dominant four-electron oxygen reduction pathway, superior stability, fuel crossover resistance, and selective activity to a commercial Pt/C catalyst in 0.1 m KOH aqueous solution. Such excellent performance benefits from in situ covalent incorporation of Pt nanoparticles with optimal size into N-doped carbon support, dense active catalytic sites on surface, excellent electrical contacts between the catalytic sites and the electron-conducting host, and a favorable mesoporous structure for the stabilization of the Pt nanoparticles by pore confinement and diffusion of oxygen molecules. [ABSTRACT FROM AUTHOR]

Correction for ‘Biomass-derived interconnected carbon nanoring electrochemical capacitors with high performance in both strongly acidic and alkaline electrolytes’ by Xianjun Wei et al., J. Mater. Chem. A, 2017, 5, 181–188. [ABSTRACT FROM AUTHOR]

Carbon electrode materials are fabricated from bean curd to replace costly Pt-based electrodes to degrade methyl red (MR) as self-driven by a multilayer linkage triboelectric nanogenerator (ML-TENG). With the sponge as the buffer layer and precharge injection, the peak open-circuit voltage, V oc , short-circuit current, I sc , and maximum power density of the ML-TENG can reach and remain stable at 1300 V, 1.2 mA, and 7.4 W m -2 (load resistance = 500 KΩ), respectively. Using the electric power generated by such an updated TENG, highly toxic and carcinogenic MR can be indirectly degraded to CO 2 through an oxidation process induced by active chlorine produced at the as-obtained carbon-based electrode interface. Such an electrochemical degradation mechanism is proposed based on the cyclic voltammogram, gas chromatograph-mass spectrometer, and mass spectrometer. With compelling features of the TENG and carbon materials, such as sustainable energy, high and stable output performance, cost savings, and high degradation efficiency, this work pioneers the marriage of the TENG with carbon-based materials to self-power electrochemical degradation of organic pollutants for environmental protection.

A rotary disc-structured triboelectric nanogenerator (rd-TENG) on the basis of free-standing electrification has been designed, where the aluminum composite panel has not been tailored to the stator becauseit is commercially available and cost-effective, has good electronic conductivity, and is easily processed. With the rotating speed increasing from 200 to 1000 rpm, the short-circuit current (I sc ) is sharply enhanced from 50 μA to 200 μA, while the measured open-circuit voltage (V oc ) and transferred charge (Q tr ) almost keep constant, 600 V and 0.4 μC, respectively. The matched load for the rd-TENG at a rotating speed of 600 rpm is 2.7 MΩ, generating a maximum power of 19.75 mW, which corresponds to a maximum power density of 2.28 W m -2 . Using the electric power generated by such a rd-TENG, highly toxic and carcinogenic 4-aminoazobenzene can be selectively treated to produce CO 2 or an oligomer via reasonably controlling electrochemical oxidation potentials. The underlying mechanism is tentatively proposed based on the cyclic voltammogram, gas chromatograph-mass spectrometer, electrochemical impedance spectroscopy, and UV-vis spectra. Here the electrochemical degradation in a single-compartment cell is more valid, preferable, and feasible. The output V oc and rectified current of rd-TENG guarantee its extensive application to self-power electrochemical degradation of other azo compounds, i.e., 2-(4-dimethylaminophenylazo) benzoic acid, to CO 2 . This work suggests that rd-TENG, sustainable energy, can be feasibly designed to self-power a practical electrochemical treatment of dyeing wastewater by harvesting vibration energy.

An efficient soft-template method is proposed for the synthesis of peanut shell-like porous carbon as high-performance supercapacitor electrode materials. The procedure is based on the pyrolysis and chemical activation processes using N-phenylethanolamine as precursor and KOH as activation agent. In a three-electrode system, the resultant carbon material has a specific capacitance of 356 F g(-1) at 1 A g(-1) and a good stability over 1000 cycles. Besides, at a high current density of 30 A g(-1), it has a specific capacitance of 249 F g(-1) and maintains 96% after 10,000 cycles. In two-electrode cell configuration, it delivers about 21.53 Wh kg(-1) at a current density of 20 A g(-1), which is about 7 times higher than the commercial device (<3 Wh kg(-1)). Both high specific capacitance and excellent cycling stabilities guarantee its utilization in supercapacitors.