Shuling Shen

Strengthening of Graphene Aerogels with Tunable Density and High Adsorption Capacity towards Pb2

Graphene aerogels (GAs) with high mechanical strength, tunable density and volume have been prepared only via soaking graphene hydrogels (GHs) in ammonia solution. The density and volume of the obtained GAs are controlled by adjusting the concentration of ammonia solution. Although volume of the GAs decreases with increasing the concentration of ammonia solution, its specific surface area maintains at about 350 m2 g−1, and the inner structure changes to radial after ammonia solution treatment. Thus, GAs are particularly suitable for the adsorption and energy storage applications owing to their high specific surface area and unique porous structure. The adsorption capacity of GAs for Pb2+ from aqueous solution maintains at about 80 mg g−1, which could reach as high as 5000 g m−3 per unit volume and they can be separated easily from water after adsorption.

Facile Synthesis of Zn0.5Cd0.5S Ultrathin Nanorods on Reduced Graphene Oxide for Enhanced Photocatalytic Hydrogen Evolution under Visible Light

A new contact model between ZnxCd1−xS nanorods and reduced graphene oxide (RGO) was obtained by rational formation of ultrathin Zn0.5Cd0.5S (ZCS) nanorods on RGO through a facile oleylamine–DMSO mediated synthesis approach. The 1 D/2 D model of ZCS/RGO provides a strong contact line‐to‐line interface, which is not only conducive for the fast collection and transfer of photogenerated electrons but also stabilizes the ultrathin nanorod structure of ZCS. The photocatalytic test results indicated that the ZCS/RGO nanocomposites exhibit significantly enhanced photocatalytic H2 evolution rate and cycling stability under visible light compared with free ZCS and the physical mixture of ZCS and RGO.

Effects of sacrificial reagents on photocatalytic hydrogen evolution over different photocatalysts

Abstract The effect of sacrificial reagents (SRs) on photocatalytic H2 evolution rate over different photocatalysts was systematically studied. Zn0.5Cd0.5S, graphitic carbon nitride (g-C3N4), and TiO2 were chosen as typical photocatalysts, while alcohols, amines, carboxylic acids, and inorganic Na2S/Na2SO3 were chosen as SRs. The results indicate that Na2S/Na2SO3, methanol, and triethanolamine are the most suitable SRs for Zn0.5Cd0.5S, TiO2, and g-C3N4, respectively. It was found that in selecting organic SRs, both the permittivity and oxidation potential have profound effects on the H2 production efficiency, which will provide basis for choosing appropriate SRs for different photocatalysts.

One-step synthesis of hydrophobic-reduced graphene oxide and its oil/water separation performance

Graphene oxide (GO) was functionalized to form hydrophobic-reduced graphene oxide (rGO) by a one-step hydrothermal method, and oleylamine was used as both reductant and modifier of GO. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and contact angle measurement were used to determine the successful functionalization and reduction of GO. Results indicated that the color of obtained sample was changed from yellow brown to black, and contact angle between water and the graphene paper was over 130°, which was close to the typical hydrophobic material of PTFE; at the same time, the functionalized rGO can be dispersed in some of the typical organic solvents, such as cyclohexane, chloroform, and benzene, proving that oleylamine was effective for the reduction and functionalization of GO. Based on the results, the possible reactions were proposed. Furthermore, the hydrophobic rGO was assembled to film by filtration, which demonstrated its efficient separation ability for oil/water.

Controlled synthesis of ZnxCd1−xS nanorods and their composite with RGO for high-performance visible-light photocatalysis

Monodisperse and ultrafine ZnxCd1−xS (ZCS) nanorods with hexagonal phases were controllably synthesized by a facile one-pot approach. The band gap of these alloyed nanocrystals can be tuned in a broad range from 2.41 to 3.78 eV by simply changing the molar ratio of the two precursors. All the ZCS samples exhibit a band gap-related and aspect ratio-dependent photoresponse to visible light. Zn0.5Cd0.5S nanorods with a suitable band gap and aspect ratio display the highest photoresponse, even 25 times higher than that of Zn0.875Cd0.125S. Graphene was chosen as a co-catalyst for 1D Zn0.5Cd0.5S nanorods due to its 2D structure and excellent conductivity. The Zn0.5Cd0.5S/RGO nanocomposites with a RGO content of 2.0 wt% showed the highest photocatalytic activity for the degradation of methylene blue (MB), which is mainly due to the uniform dispersion of ZCS nanorods on RGO and the enhanced separation rate of photoinduced electrons and holes by fast transfer of the photogenerated electrons through the contact line-to-line interface between ZCS nanorods and RGO nanosheets.

Effect of drying conditions on the structure of three-dimensional N-doped graphene and its electrochemical performance

Freeze drying is a general method for preparing three dimensional (3D) graphene based materials, however, in this paper, we used N-doped graphene as a model material and found that if the N-doped graphene hydrogel was pre-frozen, instead of an interconnected porous structure, a loosely packed layered structure was obtained. Furthermore, the effects of drying conditions on the pore and chemical structure have been discussed. Results demonstrated that when the graphene hydrogel was directly freeze dried, an interconnected porous structure can be obtained, whereas, heat dried and pre-frozen samples had layered structures. The structure determines the performance; the sample prepared by direct freeze drying with an interconnected porous structure had the highest specific capacitance of 218 F g−1 when the current density was 0.01 A g−1, and the specific capacitance still remained at about 85% of its initial value even at a high current density (1 A g−1). The excellent electrochemical performance is mainly attributed to the fast electrolyte diffusion paths provided by the interconnected porous channels.

Preparation of nanoporous carbons with hierarchical pore structure for CO2 capture

Abstract Nanoporous carbons with a hierarchical pore structure were prepared by a combination of hard-templating of a thermosetting phenolic resin containing silica nanoparticles, pyrolysis and KOH activation. The influence of the amount of KOH on the pore structure of the templated and activated carbons was investigated by N2 adsorption and the effect of pore structure on the CO2 adsorption capacity was investigated by thermogravimetric analysis. Results indicated that KOH activation promoted the formation of micropores and small mesopores for the templated carbon. The utilization ratio of mesopores for the capture of CO2 is high compared with that of micropores. The porous carbon prepared under a mass ratio of KOH to templated carbon of 2:1 has both developed mesopores and micropores, and has a largest adsorption capacity for CO2 among all samples investigated.

In4SnS8 ultrathin nanosheets: a ternary sulfide with fast adsorption–visible-light photocatalysis dual function

Ultrathin In4SnS8 nanosheets have been successfully synthesized via a facile thermal decomposition method. The average thickness of these In4SnS8 nanosheets is only 3.8 nm, comprising about five atomically thick layers. To our knowledge, this is the thinnest In4SnS8 nanosheet synthesized using a solution-phase chemical method. The resulting ultrathin In4SnS8 nanosheets exhibit fast adsorption–visible-light photocatalysis dual function for various organic dyes, suggesting their potential application in environmental remediation, solar energy conversion, and advanced optical/electric nanodevices.

Controllable crumpling of N-doped graphene induced by capillary force resistance

Turning the 2D nanosheets into three-dimensional (3D) crumpled balls driven by the capillary force arising from water surface tension has proved to be an effective way to solve restacking. However, such a spherical form has a closed structure and the utilization of the inner surface is limited. Preparing crumpled graphene with an open structure, which can improve the utilization of the inner surface as well as maintain the excellent dispersion ability, is still a challenge. Herein, N-doped crumpled graphene (NCG) with controllable morphology and open structure is achieved by heating a microdroplet containing graphene oxide (GO) and urea; GO is the precursor of crumpled graphene and urea acts as both soft template to control the morphology of graphene and the nitrogen donor after template removal. ​N-doped crumpled graphene (NCG) with controllable morphology and open structure is achieved by heating a microdroplet containing graphene oxide (GO) and urea; GO is the precursor of crumpled graphene and urea acts as both soft template to control the morphology of graphene and the nitrogen donor after template removal. During the drying process, GO diffuses on the liquid–vapor interface and urea is adsorbed on the surface of GO driven by its different diffusion rate and free energy reduction. Results indicate that when the mass ratio of urea to GO is less than 10, a completely crumpled ball is formed; an open structure is obtained at the mass ratio of 100; a semi-open NCG ball is collected when the mass ratio is 50. NCG with different morphologies shows different dispersibility and electrochemical performance. The NCG ball can be dispersed in almost all the selected solvents, semi-open and open NCG can be dispersed in the majority of solvents, but the open one precipitates faster than the semi-open NCG. Semi-open NCG demonstrates better electrochemical performance than that of the crumpled NCG ball and open NCG because of its higher effective surface area and suitable morphology.