Xiang Ying Chen

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.

Synthesis and photoluminescence of ZnAl2O4:Eu3+ hollow nanophosphors using carbon nanospheres as hard templates

ZnAl(2)O(4):Eu(3+) hollow nanophosphors have been for the first time prepared by using carbon nanospheres as hard templates. The ZnAl(2)O(4):Eu(3+) hollow nanophosphors were well characterized by means of XRPD, FESEM, TEM, HRTEM, N(2) adsorption and desorption and PL techniques. The N(2) adsorption and desorption data reveal the porous nature of ZnAl(2)O(4):Eu(3+) hollow nanophosphors and high surface area of 195.3 m(2) g(-1). The PL measurement illustrates red-emitting feature of ZnAl(2)O(4):Eu(3+) hollow nanophosphors arising from the characteristic transitions of Eu(3+) from (5)D(0)→(7)F(j) (j=0, 1, 2, 3, and 4). This simple and efficient synthetic strategy could be extended to prepare other series of aluminates nanophosphors with novel hollow structures.

Porous carbon synthesized by direct carbonization of potassium biphthalate for high-performance supercapacitors

Porous carbons have been synthesized by a direct carbonization of potassium biphthalate without an activation process. The experimental results demonstrate that the carbonization temperature plays a crucial role in determining the surface area and pore structure as well as the correlative capacitive performance. The carbon-700/800/900 samples display surface areas of 672, 1,023, and 1,380xa0m2xa0g−1 and total pore volumes of 0.38, 0.56, and 0.78xa0cm3xa0g−1, respectively. The specific capacitances of the carbon-700/800/900 samples are 300.4, 272.3, and 243.4xa0Fxa0g−1, respectively, at a current density of 0.5xa0Axa0g−1. More importantly, the carbon-900 sample possesses the highest capacitance retention (~98.4xa0%) even undergoing charge–discharge 10,000 times. The potassium biphthalate used as a carbon source is inexpensive and commercially available, making it promising for the large-scale production of porous carbons as an excellent electrode material for supercapacitors.

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.

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-3u2006:u20061-800 sample that was obtained by carbonizing potassium biphthalate and magnesium powder (mass ratio of 3u2006:u20061) 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-3u2006:u20061-800 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 10u2006000 cycles. More importantly, the influence of the operation temperature of the carbon-3u2006:u20061-800 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.

Nitrogen-containing nanoporous carbons by a rational template carbonization method evinced in the cases of 1, 10-phenanthroline and benzimidazole

We demonstrate a rational template carbonization method to produce nitrogen-containing nanoporous carbons at 800xa0°C, using 1, 10-phenanthroline (or benzimidazole) as carbon/nitrogen source and magnesium citrate as template. The mass ratio of 1, 10-phenanthroline (or benzimidazole) and magnesium citrate has exerted the vital role in the determination of pore structures and the resulting electrochemical performances. It reveals that the carbon-P:Mg-1:1 (obtained by heating 1, 10-phenanthroline and magnesium citrate at 800xa0°C with the mass ratio of 1:1) and carbon-B:Mg-1:1 (obtained by heating benzimidazole and magnesium citrate at 800xa0°C with the mass ratio of 1:1) samples both are amorphous, nitrogen-containing, and highly nanoporous in nature. The carbon-P:Mg-1:1 sample has a large BET surface area of 1,657.4xa0m2xa0g−1 and high pore volume of 1.83xa0cm3xa0g−1, and those of carbon-B:Mg-1:1 sample are of 1,105.4xa0m2xa0g−1 and 1.67xa0cm3xa0g−1, respectively. Based on a three-electrode system using a 6-molxa0L−1 KOH aqueous solution as electrolyte, the carbon-P:Mg-1:1 and carbon-B:Mg-1:1 samples can deliver large specific capacitances of 289.0 and 255.6xa0Fxa0g−1 at a current density of 0.5xa0A g−1. They can also exhibit high energy densities of 40.1 and 35.5xa0Whxa0kg−1 when designated the power density as 0.25xa0kWxa0kg−1 as well as highly long-term cycling durabilities.