Showing papers by "Zhuangjun Fan published in 2015"

Sulfate radicals induced from peroxymonosulfate by magnetic ferrospinel MFe2O4 (M = Co, Cu, Mn, and Zn) as heterogeneous catalysts in the water

Abstract: Magnetic ferrospinel MFe 2 O 4 (M = Co, Cu, Mn, and Zn) prepared in a sol–gel process was introduced as catalyst to generate powerful radicals from peroxymonosulfate (PMS) for refractory di-n-butyl phthalate (DBP) degradation in the water. Various catalysts were described and characterized, and the catalytic activities in PMS oxidation system were investigated. Most important of all, the mechanism of different catalysts in the catalytic PMS solution was illustrated. The results showed that the incorporation of CoFe 2 O 4 had the highest catalytic performance in PMS oxidation for DBP degradation. All catalysts presented favorable recycling and stability in the repeated batch experiment. The catalytic process showed a dependence on initial pH, and an uncharged surface of the catalyst was more profitable for sulfate radical generation. H 2 -TPR and CVs analysis indicated that the sequence of the catalyst's reducibility in PMS solution was CoFe 2 O 4 > CuFe 2 O 4 > MnFe 2 O 4 > ZnFe 2 O 4 , which had a close connection with the activity of metal ion in A site of the catalysts. The surface hydroxyl sites played an important role in the catalytic process, and its quantity determined the degradation of DBP. Moreover, the reactive species in PMS/MFe 2 O 4 system were identified as sulfate radical and hydroxyl radical. The promotion of these radical's reaction was due to the fact that a balance action in the process of M 2+ /M 3+ , O 2− /O 2 , occurred, and at the same time, PMS was catalyzed.

Dual Support System Ensuring Porous Co–Al Hydroxide Nanosheets with Ultrahigh Rate Performance and High Energy Density for Supercapacitors

Abstract: Layered double hydroxides (LDHs) are promising supercapacitor electrode materials due to their high specific capacitances. However, their electrochemical performances such as rate performance and energy density at a high current density, are rather poor. Accordingly, a facile strategy is demonstrated for the synthesis of the integrated porous Co–Al hydroxide nanosheets (named as GSP-LDH) with dual support system using dodecyl sulfate anions and graphene sheets as structural and conductive supports, respectively. Owing to fast ion/electron transport, porous and integrated structure, the GSP-LDH electrode exhibits remarkably improved electrochemical characteristics such as high specific capacitance (1043 F g−1 at 1 A g−1) and ultra-high rate performance capability (912 F g−1 at 20 A g−1). Moreover, the assembled sandwiched graphene/porous carbon (SGC)//GSP-LDH asymmetric supercapacitor delivers a high energy density up to 20.4 Wh kg−1 at a very high power density of 9.3 kW kg−1, higher than those of previously reported asymmetric supercapacitors. The strategy provides a facile and effective method to achieve high rate performance LDH based electrode materials for supercapacitors.

Functional Pillared Graphene Frameworks for Ultrahigh Volumetric Performance Supercapacitors

Abstract: Supercapacitors, also known as electrochemical capacitors, can provide much faster charge–discharge, greater power density, and cyclability than batteries, but they are still limited by lower energy densities (or the amount of energy stored per unit volume). Here, a novel strategy for the synthesis of functional pillared graphene frameworks, in which graphene fragments in-between graphene sheets, through simple thermal-treatment of ozone (O3)-treated graphene oxide at very low temperature of 200 °C is reported. Due to its high packing density, high content of stable oxygen species, and continues ion transport network in-between graphene sheets, the functional pillared-graphene framework delivers not only high gravimetric capacitance (353 F g−1 based on the mass of the active material) and ultrahigh volumetric capacitance (400 F cm−3 based on total mass of electrode material) in aqueous electrolyte but also excellent cyclic stability with 104% of its initial capacitance retention after 10 000 cycles. Moreover, the assembled symmetric supercapacitor achieves as high as 27 Wh L−1 of volumetric energy density at a power density of 272 W L−1. This novel strategy holds great promise for future design of high volumetric capacitance supercapacitors.

Bubble‐Decorated Honeycomb‐Like Graphene Film as Ultrahigh Sensitivity Pressure Sensors

Abstract: A flexible, bubble‐decorated, honeycomb‐like graphene film (BHGF) is fabricated by a low‐temperature heat treatment of graphene oxide film. The as‐prepared BHGF exhibits an ultrahigh sensitivity of 161.6 kPa−1 at a strain less than 4%, due to the switching effect depended on “point‐to‐point” and “point‐to‐face” contact modes.

Photocatalyst Interface Engineering: Spatially Confined Growth of ZnFe2O4 within Graphene Networks as Excellent Visible-Light-Driven Photocatalysts

Abstract: High-performance photocatalysts should have highly crystallized nanocrystals (NCs) with small sizes, high separation efficiency of photogenerated electron–hole pairs, fast transport and consumption of photon-excited electrons from the surface of catalyst, high adsorption of organic pollutant, and suitable band gap for maximally utilizing sunlight energy. However, the design and synthesis of these versatile structures still remain a big challenge. Here, we report a novel strategy for the synthesis of ultrasmall and highly crystallized graphene–ZnFe2O4 photocatalyst through interface engineering by using interconnected graphene network as barrier for spatially confined growth of ZnFe2O4, as transport channels for photon-excited electron from the surface of catalyst, as well as the electron reservoir for suppressing the recombination of photogenerated electron–hole pairs. As a result, about 20 nm ZnFe2O4 NCs with highly crystallized (311) plane confined in the graphene network exhibit an excellent visible-light-driven photocatalytic activity with an ultrafast degradation rate of 1.924 × 10−7 mol g−1 s−1 for methylene blue, much higher than those of previously reported photocatalysts such as spinel-based photocatalysts (20 times), TiO2-based photocatalysts (4 times), and other photocatalysts (4 times). Our strategy can be further extended to fabricate other catalysts and electrode materials for supercapacitors and Li-ion batteries.

Approaching the Downsizing Limit of Silicon for Surface‐Controlled Lithium Storage

Abstract: Graphene-sheet-supported uniform ultrasmall (≈3 nm) silicon quantum dots are successfully synthesized using a simple and effective self-assembly strategy. They exhibit unprecedented fast, surface-controlled lithium-storage behavior and outstanding lithium-storage properties including extraordinary rate capability and remarkable cycling stability, attributable to the intrinsic role of approaching the downsizing limit of silicon. (Chemical Equation Presented).

Synthesis of magnetic ZnO/ZnFe2O4 by a microwave combustion method, and its high rate of adsorption of methylene blue.

Abstract: The magnetic ZnO/ZnFe2O4 particles have been synthesized by a microwave combustion method using NaAc as fuel. The as-obtained ZnO/ZnFe2O4 was characterized and applied for the removal of methylene blue (MB) from aqueous solution in the batch system. The ZnO/ZnFe2O4 particles display larger SBET and smaller size with increase of NaAc dosage. Because a certain amount of gas is generated during NaAc decomposing and the gas prevent the particles from growing larger. More interestingly, even at neutral pH value, the ZnO/ZnFe2O4 obtained with 24 mL NaAc shows high-rate adsorption properties with the MB removal efficiency up to 90% in 0.5 min and a maximum adsorption capacity of 37.27 mg/g.

A Highly Sensitive and Selective Hydrogen Peroxide Biosensor Based on Gold Nanoparticles and Three-Dimensional Porous Carbonized Chicken Eggshell Membrane.

Abstract: A sensitive and noble amperometric horseradish peroxidase (HRP) biosensor is fabricated via the deposition of gold nanoparticles (AuNPs) onto a three-dimensional (3D) porous carbonized chicken eggshell membrane (CESM). Due to the synergistic effects of the unique porous carbon architecture and well-distributed AuNPs, the enzyme-modified electrode shows an excellent electrochemical redox behavior. Compared with bare glass carbon electrode (GCE), the cathodic peak current of the enzymatic electrode increases 12.6 times at a formal potential of −100mV (vs. SCE) and charge-transfer resistance decreases 62.8%. Additionally, the AuNPs-CESM electrode exhibits a good biocompatibility, which effectively retains its bioactivity with a surface coverage of HRP 6.39×10−9 mol cm−2 (752 times higher than the theoretical monolayer coverage of HRP). Furthermore, the HRP-AuNPs-CESM-GCE electrode, as a biosensor for H2O2 detection, has a good accuracy and high sensitivity with the linear range of 0.01–2.7 mM H2O2 and the detection limit of 3μM H2O2 (S/N = 3).

Preparation method of carbon nano-tube and graphene-based oil absorption foam material

Abstract: The invention provides a preparation method of a carbon nano-tube and graphene-based oil absorption foam material. The method comprises the steps that 1, a carbon nano-tube, graphene oxide and strong oxidant are mixed and subjected to ultrasound treatment for 10-200 min for deep oxidation, subjected to suction filtration and washing to be neutral and then prepared into aqueous dispersion liquid; 2, polymer porous sponge is immersed into the aqueous dispersion liquid for 0.5-30 min; 3, microwave irradiation or light wave irradiation is conducted first and then vacuum drying is conducted; 4, further reduction is conducted. The material prepared through the method is good in oil-water selectivity, high in oil absorption speed and high in oil absorption ratio; moreover, absorbed oil can be recovered through simple extrusion, and especially a coating layer and a sponge base body are good in chemical bonding, stable in structure, high in cyclic utilization rate and capable of being used repeatedly for thousands of times without falling off.