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Zheng Q.,Jimei University | Ji X.,Shenzhen Dovelet Sensors Technology Co. | Gao S.,Jimei University | Wang X.,Jimei University
International Journal of Hydrogen Energy | Year: 2013

The adsorption equilibrium of hydrogen on graphene sheets (GS) was studied based on a sample of GS with SBET = 300 m2/g at the temperatures of 77.15 K-293.15 K and the pressures of 0 MPa-6 MPa. In the meantime, the adsorptions (Excess adsorption measurements) of hydrogen on granular coconut shell SAC-02 activated carbon (SBET = 2074 m 2/g) and carbon nanofiber (CNFs, SBET = 205 m 2/g) were investigated at the pressures of 0-8 MPa and the temperature of 77.15 K. The outcomes from experiments were used to determine the parameters in Toth equation by way of Non-linear fit. The absolute adsorption amounts of hydrogen on the GS, which were calculated from the equation, were used to calculate the isosteric heat of hydrogen adsorption by use of adsorption isosteres. It shows that, under the experimental conditions, the excess adsorption amount of hydrogen on the GS increases monotonically and correlatively as pressure increases, and the mean relative deviation between the experimental data and those predicted from Toth equation is less than 1%. The result also shows that the storage density of hydrogen on the GS is 1.75 wt% and 0.168 gH2/L at pressure 5.4 MPa and temperature 77.15 K, which is lower than that of hydrogen on the activated carbon but is higher than that of hydrogen on the CNFs. The isosteric heat of hydrogen adsorption on the GS falls within 5.14 kJ/mol-6.37 kJ/mol, which is comparable to that of hydrogen adsorption on the activated carbon. It suggests that interaction between hydrogen molecules and the graphene layer is stronger than that between hydrogen and carbon surface, and the hydrogen storage capacity of GS is closely related to its physical properties. Copyright © 2013, Hydrogen Energy Publications, LLC. Source

Zhu L.,Tsinghua University | Jia Y.,Tsinghua University | Gai G.,Tsinghua University | Ji X.,Shenzhen Dovelet Sensors Technology Co. | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2014

A Pt-functionalized graphene (PFG) was prepared, whose hydrogen gas sensing behaviors were studied within the hydrogen concentration range from 1 × 102 to 1 × 104 ppm. The results indicated that resistance of the as-prepared PFG increased with hydrogen at room temperature and 40 C. On the contrary, the PFG showed decrease in resistance when it interacted with 10,000 ppm of H2 at 65 C, or with 500 ppm of H 2 at 105 C. A model based on the ambipolarity of graphene was suggested to explain these phenomena. © 2013 Elsevier B.V. Source

Zhu L.F.,Sun Yat Sen University | She J.C.,Sun Yat Sen University | Luo J.Y.,Sun Yat Sen University | Deng S.Z.,Sun Yat Sen University | And 3 more authors.
Sensors and Actuators, B: Chemical | Year: 2011

Self-heating effect can be applied to develop gas sensors avoiding use of external heaters. We report here a prototype self-heated hydrogen gas sensor based on Pt-coated W18O49 nanowire networks. Such a sensor has been shown to have promising performance, e.g., high sensitivity (able to detect down to 50 ppm of H2), good selectivity (poor response to ethanol, CH4, CO, and C3H8), and low power consumption of 30-60 mW at 6 V compatible to a portable device. Coaxial cable model and percolation theory are applied to explain the gas sensing effect of the Pt-coated W18O49 nanowire networks. © 2010 Elsevier B.V. All rights reserved. Source

Liang S.,Shenzhen University | Zhu L.,Tsinghua University | Gai G.,Tsinghua University | Yao Y.,Tsinghua University | And 5 more authors.
Ultrasonics Sonochemistry | Year: 2014

Controllable ZnO architectures with flower-like and rod-like morphologies were synthesized via a microwave-assisted hydrothermal method. By adjusting the concentration of Zn2+ in the aqueous precursors, different morphologies of ZnO microstructures were obtained. The size of ZnO was uniform after ultrasonic treatment. The growth process of ZnO in solution was studied by monitoring the intermediate products, which were extracted at different stages of the reactions: (i) precursor preparation, (ii) microwave irradiation heating, (iii) natural cooling. Studies of the SEM images and XRD data revealed that the formation of ZnO occurred via in situ assembly or dissolution-reprecipitation of zinc hydroxide complexes. The morphology-dependent ethanol sensing performance was observed; the seven-spine ZnO structures exhibit the highest activity. © 2013 Elsevier B.V. All rights reserved. Source

Wang M.,Tsinghua University | Zhu L.,Tsinghua University | Zhang C.,Tsinghua University | Gai G.,Tsinghua University | And 3 more authors.
Sensors and Actuators, B: Chemical | Year: 2016

An ethanol-sensing powder (La2O3@Sb-SnO2), mixture composed of 1.00 wt.% La2O3 and 99.00 wt.% Sb-doped SnO2 (Sb-SnO2), was found to possess enhanced sensitivity towards ethanol: typically, for La2O3@Sb-SnO2, the ratio of the response towards 1000 ppm ethanol vapor to that of 1000 ppm CO is 26.1 (60.0/2.3) under operating temperature of 250 °C; while for Sb-SnO2, the ratio is only 4.5 (9.0/2.0). A suggestive mechanism on enhanced ethanol sensing is discussed. © 2015 Elsevier B.V. All rights reserved. Source

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