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Feng H.,South China Agricultural University | Hu H.,South China Agricultural University | Hu H.,Guangdong Provincial Engineering Technology Research Center for Optical Agriculture | Dong H.,South China Agricultural University | And 9 more authors.
Journal of Power Sources | Year: 2016

Bagasse-derived hierarchical structured carbon (BDHSC) with tunable porosity and improved electrochemical performance is prepared via simple and efficient hydrothermal carbonization combined with KOH activation. Experimental results show that sewage sludge acts as a cheap and efficient structure-directing agent to regulate the morphology, adjust the porosity, and thus improve the supercapacitive performance of BDHSC. The as-resulted BDHSC exhibits an interconnected framework with high specific surface area (2296 m2 g-1), high pore volume (1.34 cm3 g-1), and hierarchical porosity, which offer a more favorable pathway for electrolyte penetration and transportation. Compared to the product obtained from bagasse without sewage sludge, the unique interconnected BDHSC exhibits enhanced supercapacitive performances such as higher specific capacitance (320 F g-1), and better rate capability (capacitance retention over 70.8% at a high current density of 50 A g-1). Moreover, the BDHSC-based symmetric supercapacitor delivers a maximum energy density of over 20 Wh kg-1 at 182 W kg-1 and presents an excellent long-term cycling stability. The developed approach in the present work can be useful not only in production of a variety of novel hierarchical structured carbon with promising applications in high-performance energy storage devices, but also in high-value utilization of biomass wastes and high-ash-content sewage sludge. © 2015 Elsevier B.V.


Zhao X.,South China Agricultural University | Dong H.,South China Agricultural University | Dong H.,Guangdong Provincial Engineering Technology Research Center for Optical Agriculture | Xiao Y.,Guangdong Provincial Engineering Technology Research Center for Optical Agriculture | And 9 more authors.
Electrochimica Acta | Year: 2016

Three dimensional nitrogen-doped graphene (3DNG) with high nitrogen content and improved electrochemical performance is successfully prepared by a facile, lost-cost hydrothermal method with ammonia as reducing-doping agent. The as-prepared 3DNG exhibits a hierarchical and interconnected porous network, which offers favorable pathways for electrolyte penetration and transportation. Remarkably, as binder-free electrode in aqueous electrolyte, the resultant 3DNG-2 with both high nitrogen content (7.71 at%) and large active material density (1.31 g cm−3) exhibits an ultrahigh volumetric capacitance of 437.5 F cm−3 (334.0 F g−1) at current density of 0.5 A g−1 and superior cycling stability (93% capacitance retention after 20 000 cycles at high current density of 10 A g−1). Further analyses indicate that the N-configurations are of great significance to the improvement of electrochemical behavior as well as the N-content. This work provides an effective way to synthesize 3DNG with excellent electrochemical properties for high performance supercapacitor and promotes the in-depth understanding of the enhancement mechanism of N-doping to supercapacitor performance. © 2016 Elsevier Ltd


Feng H.,South China Agricultural University | Zheng M.,South China Agricultural University | Zheng M.,Guangdong Provincial Engineering Technology Research Center for Optical Agriculture | Dong H.,South China Agricultural University | And 11 more authors.
Journal of Materials Chemistry A | Year: 2015

In this work, we demonstrate for the first time that three-dimensional honeycomb-like hierarchically structured carbon (HSC) can be prepared by using high-ash-content sewage sludge as a carbon precursor. The fly-silicon process plays a crucial role in the formation of honeycomb-like hierarchical structures. The as-resulted HSC exhibits novel honeycomb-like frameworks, high specific surface area (2839 m2 g-1), large pore volume (2.65 cm3 g-1), interconnected hierarchical porosity, and excellent electrochemical performance. The high specific capacitance of 379 F g-1 as well as excellent rate capability and outstanding cycling stability (over 90% capacitance retention after 20000 cycles even at a high current density of 20 A g-1), makes it suitable for high-performance supercapacitor electrode materials. The assembled HSC//HSC symmetric supercapacitor presents enhanced supercapacitive behavior with a high energy density of 30.5 W h kg-1 in aqueous solution. This strategy provides an effective method to develop high-performance electrode materials derived from other high-ash-content biomass wastes for supercapacitors. © 2015 The Royal Society of Chemistry.


Feng H.,South China Agricultural University | Dong H.,South China Agricultural University | Dong H.,Guangdong Provincial Engineering Technology Research Center for Optical Agriculture | Lei B.,South China Agricultural University | And 11 more authors.
Science of Advanced Materials | Year: 2016

Water-soluble graphene quantum dots (GQDs) were prepared by a simple one-pot H2O2-assisted hydrothermal carbonization method, in which waste sewage sludge was used as the carbon precursor. Fluorescence spectra of the as-generated GQDs showed tunable emission wavelengths with a quantum yield of 10.3%. Fourier transform infrared spectroscopy analysis revealed the presence of abundant hydroxyl groups on the surface of the GQDs. A possible formation mechanism of the GQDs derived from sewage sludge under H2O2-assisted hydrothermal conditions is also proposed on the basis of the experimental results. The hydroxyl radical oxidation generated from the decomposition of H2O2 and the hydrothermal carbonization process are believed to play a key role in the formation of GQDs. The as-prepared GQDs were employed as safe fluorescent additives to fabricate fluorescent hybrids, such as thin films, fibers, and inks. © 2016 by American Scientific Publishers.

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