Dong Hua Xie

Gelatin-derived nitrogen-doped porous carbon via a dual-template carbonization method for high performance supercapacitors

High performance nitrogen-doped porous carbon for supercapacitors, named as Gelatin–Mg–Zn-1 : 5 : 3, has been successfully prepared via a dual-template carbonization method, without any physical/chemical activation process, in which gelatin serves as both carbon/nitrogen source, and low cost Mg(NO3)2·6H2O and Zn(NO3)2·6H2O as dual templates. It is revealed that the carbonization temperature, and the mass ratio of gelatin–Mg(NO3)2·6H2O–Zn(NO3)2·6H2O plays a crucial role in the determination of surface area, pore structure and the correlative capacitive behavior of the Gelatin–Mg–Zn-1 : 5 : 3 sample. It displays a high BET surface area of 1518 m2 g−1, large total pore volume of 4.27 cm3 g−1, and large average pore width of 11.3 nm. In a three electrode system, using 6 mol L−1 KOH solution as electrolyte, we can achieve a high specific capacitance of ca. 284.1 F g−1 at a current density of 1 A g−1 and high capacitance retention of ca. 31.2% is obtained at 150 A g−1, indicating high rate capability. It also possesses a high capacitance retention of ca. 96.1% even after charging/discharging for 10 000 cycles. More importantly, a two electrode system, using [EMIm]BF4/AN (weight ratio of 1 : 1) as electrolyte, has been adopted for the Gelatin–Mg–Zn-1 : 5 : 3 sample with different operation temperatures of 25/50/80 °C. As a result, wide voltage windows, broad operation temperatures, and high cycling stability achieved in the two electrode system make it possible for practical application under extreme conditions.

High performance porous carbon through hard–soft dual templates for supercapacitor electrodes

A hard–soft dual templates method has been developed for the first time to prepare porous carbons by the direct carbonization of phenol formaldehyde resins (PFs), Zn(NO3)2·6H2O and polyvinyl butyral (PVB) at 1000 °C under Ar gas, in which PFs serve as the carbon source. More importantly, Zn(NO3)2·6H2O and PVB acting as hard and soft template, respectively, can be readily removed through the evaporation process, resulting in pure carbon without any post-treatment, commonly employed. The PF-Zn-PVB-1:5:1 sample has a total BET surface area of 864 m2 g−1, and a total pore volume of 0.76 cm3 g−1. An electrode based on the porous carbons exhibits the high specific capacitances of 174.7 F g−1 and 152.8 F g−1 at the current densities of 0.5 and 1.0 A g−1, respectively. It also exhibits a superior rate capability, with high specific capacitance retention at ca. 63.1% at a high current density of 20 A g−1. Significantly, about 96.2% is retained after charging and discharging for 10000 cycles, revealing its long-term electrochemical stability. The hard–soft dual templates method proposed in the present work is straightforward and effective, and can be utilized to synthesize porous carbons on a large scale for the application of high performance supercapacitors.

High-performance supercapacitor based on nitrogen-doped porous carbon derived from zinc(II)-bis(8-hydroxyquinoline) coordination polymer.

Nitrogen-doped porous carbon electrodes with remarkable specific capacitance have been fabricated by the rational carbonization of zinc(II)-bis(8-hydroxyquinoline) (abbr. Znq(2)) coordination polymer, and heating treatment with CO(NH(2))(2). The experimental results demonstrate that the mass ratio of carbon precursor and CO(NH(2))(2) plays a key role in the formation of porous carbon with various nitrogen content as well as specific surface areas and pore structures. The cyclic voltammetry and galvanostatic charge-discharge measurements show that the capacitive performance has been remarkably improved by doping with nitrogen. The specific capacitance of 219.2 F g(-1) is achieved at the current density of 1 A g(-1) with nitrogen-doped porous carbon, increasing up to ca. 56.8% compared to that with pristine porous carbon. The nitrogen-doped porous carbon electrode exhibits enhance capacitance retention as ca. 45.2% at 20 A g(-1) as well as cycling stability (ca. 7.6% loss after 3000 cycles). The present carbonization method as well as the nitrogen-doping method for porous carbon from coordination polymer can enrich the strategies for the production of carbon-based electrodes materials in the application of electrochemical capacitors.

A general conversion of polyacrylate–metal complexes into porous carbons especially evinced in the case of magnesium polyacrylate

As a generalized synthetic protocol, porous carbons have been for the first time prepared by a direct carbonization of polyacrylate–metal complexes. The case of magnesium polyacrylate was emphatically studied. It reveals that the carbonization temperature can play a crucial role in the determination of surface areas, pore structures, surface functionalities of porous carbons as well as the correlative capacitive performances. The carbon-Mg-900 sample exhibits a high surface area of 942 m2 g−1 and a large total pore volume of 1.90 cm3 g−1, with a high specific capacitance of 262.4 F g−1 at 0.5 A g−1 in 6.0 mol L−1 aqueous KOH electrolyte. Moreover, it displays high capacitance retention even of 33.5% at 100 A g−1, and long-term cycling ability (∼91.3% retention after 5000 cycles). More importantly, the present synthetic strategy can be extended to prepare other polyacrylate–metal complexes, such as calcium polyacrylate and aluminum polyacrylate. The carbon-Al-900 sample can exhibit a high surface area of 1556 m2 g−1 and a large total pore volume of 0.97 cm3 g−1. To sum up, the carbon samples derived from magnesium polyacrylate possess the highest capacitive performances as supercapacitor electrode materials.

A general approach for producing nanoporous carbon, especially as evidenced for the case of adipic acid and zinc

In this work, we demonstrate a novel and general synthetic approach for producing nanoporous carbon materials, using adipic acid and zinc powder as raw materials. The mass ratio and carbonization temperature have crucial effects on the structure and electrochemical behavior of the carbon samples. The optimum sample is carbon-1:2-700; it is amorphous in nature and has a high BET surface area of 1426 m2 g−1 and a very large pore volume of 5.92 cm3 g−1. Whats more, the sample takes on sheet-like structures entirely composed of nanopores. The electrochemical performance is measured in a three-electrode system using 6 mol L−1 KOH as the electrolyte, and a two-electrode system using [EMIm]BF4/AN as the electrolyte, respectively. In the three-electrode system, it delivers a high specific capacitance of 373.3 F g−1 at a current density of 2 A g−1. Furthermore, it displays a good cycling durability of 93.9% after 10 000 cycles. In the two-electrode system, the voltage window has been largely broadened and a series of temperature-dependent measurements are adopted. More importantly, the present synthetic method can be extended to other chemical substances as carbon precursors to produce porous carbon, which can greatly enrich the field of porous carbon synthesis as well as their application as supercapacitors.

Temperature-dependent structure and electrochemical performance of highly nanoporous carbon from potassium biphthalate and magnesium powder via a template carbonization process

We present a simple template carbonization method to produce nanoporous carbons in which potassium biphthalate and magnesium powder serve as the carbon source and hard template, respectively. It reveals that increasing the carbonization temperature can lead to an increase in crystallinity but porosity and the resultant electrochemical performance in supercapacitor application also decreases. The carbon-3 : 1-800 sample that was obtained by carbonizing potassium biphthalate and magnesium powder (mass ratio of 3 : 1) at 800 °C exhibits the best electrochemical performance. It has the largest BET surface area of 1745.6 m2 g−1 and a high pore volume of 1.46 cm3 g−1. When measured in a three-electrode system, the carbon-3 : 1-800 sample delivers a large specific capacitance of 234.2 F g−1 at a current density of 1 A g−1 and high capacitance retention of 96.6% even after 10 000 cycles. More importantly, the influence of the operation temperature of the carbon-3 : 1-800 sample on the electrochemical behavior was also investigated in a two-electrode system. The energy density can reach up to 96.9 W h kg−1 in the case of the power density of 1.5 kW kg−1; it also reveals that a higher operation temperature can result in better electrochemical performance, enabling its implementation under extreme circumstances.

Nitrogen/manganese oxides doped porous carbons derived from sodium butyl naphthalene sulfonate.

High-performance porous carbons have been prepared as supercapacitor electrode materials by co-doped with nitrogen and MnOx via a direct carbonization method, using sodium butyl naphthalene sulfonate (abbr. BNS-Na) as carbon source. It is believed that the in situ formed Na6(SO4)2(CO3) in the product would probably serve as temporary template for producing porous structures. The impacts of nitrogen/MnOx contents as well as the structures upon the capacitive performances were emphatically discussed. It indicates that introducing nitrogen and/or MnOx into the carbon matrix can remarkably improve their capacitive performances based on the cyclic voltammetry and galvanostatic charge-discharge measurements in 6 mol L(-1) KOH aqueous solution. The specific capacitances of doped carbons can reach up to ca. 167.0-241.8 F g(-1) compared with that of the undoped carbon of ca. 105.6 F g(-1). Of these samples, the carbon-Mn-1:30-N-1:15 sample co-doped with nitrogen and MnOx exhibits the highest specific capacitance and energy density up to 241.8 F g(-1) and 33.6 Wh kg(-1), respectively. In particular, these carbons also exhibit high intrinsic capacitances (i.e., capacitance per surface area) up to ca. 0.66-1.92 F m(-2).

Conversion of a zinc salicylate complex into porous carbons through a template carbonization process as a superior electrode material for supercapacitors

High performance porous carbons for supercapacitors have been successfully prepared through a template carbonization process with the help of magnesium acetate, using a zinc salicylate complex as a carbon source. The carbon–Zn–Mg-900 sample has amorphous features and a developed porous structure. Note that it has a high BET surface area of 2008 m2 g−1, a large pore volume of 3.44 cm3 g−1 and a rationally hierarchical pore size distribution. In a three-electrode system using 6 mol L−1 KOH as the electrolyte, it displays a high specific capacitance of 288.3 F g−1 at 1 A g−1, as well as a good rate capability and long term cycling durability (the retention is 96.6% after cycling 10000 times). Furthermore, in a two-electrode system using [EMIm]BF4/AN as a mixed electrolyte, it reveals that operation temperatures of 25, 50, and 80 °C can greatly influence the electrochemical behavior. Higher operation temperatures can usually result in a better electrochemical performance. The measurements in a two-electrode system especially at different operation temperatures can, to a large extent, amplify the application scope of practical supercapacitors.