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Increasing water content in fixed beds is a prospective way to improve the gas storage density by means of hydrate formation. However, the high water content strongly hinders the hydrate formation. In this study, diesel oil was mixed into highly water-saturated activated carbon beds to establish gas channels so that to improve methane hydrate formation. Hydrate formation experiments in four activated carbons with different particle sizes were conducted at 274.15 K and 6.0 MPa. For wet carbon beds without diesel oil, both of the storage capacity of hydrate (Sw) and the storage density of bed (Sb) increased with an decrease in particle size. When the mass ratio of water to activated carbon was set to 2.0, the highest Sw of 67.98 V/Vw and corresponding Sb of 51.92 V/Vbed among the beds were obtained in the bed with particle size of 100–400 mesh. Sodium dodecyl sulfate (SDS) was found to suppress hydrate formation in fine-particle beds. By adding diesel oil, both the formation kinetics and Sw in highly water-saturated beds especially in small-particle ones were significantly improved. The Sw and Sb in the bed with particle size of 100–400 mesh were increased to 180.41 V/Vw and 111.75 V/Vbed, respectively. Furthermore, by adjusting the proportions of water, oil and activated carbon in the bed, the Sw was further improved. The successive gas storage tests suggested that the oil-contained bed can be simply renewed by manual stirring. Gas recovery experiments showed that the hydrate dissociated faster in the oil-contained bed than that in SDS solution, suggesting more efforts should be made to control the hydrate dissociation to drive this method into practical application.

Porous materials are deemed to be capable for promoting hydrate formation, while for the purpose of hydrate-based gas storage, those systems containing porous materials often cannot meet the requirement of high storage density. To increase the storage density, an adsorption-hydration sequence method was designed and systematically examined in this study. Methane storage and release in ZIF-8 slurries and fixed beds were investigated. The ZIF-8 retained 98.62%, while the activated carbon lost 62.17% of their adsorption capacities in slurry. In ZIF-8 fixed beds, methane storage density of 127.41 V/Vbed was acquired, while the gas loss during depressurization accounted for 21.50% of the gas uptake. In the ZIF-8 slurry, the storage density was effectively increased with the adsorption-hydration sequence method, and the gas loss during depressurization was much smaller than that in fixed beds. In the slurry, the gas uptake and gas loss decreased with the decrease of the chilling temperature. The largest gas uptake and storage density of 78.84 mmol and 133.59 V/Vbed were acquired in the slurry with ZIF-8 content of 40 wt.% at 268.15 K, meanwhile, the gas loss just accounted for 14.04% of the gas uptake. Self-preservation effect was observed in the slurry, and the temperature for the slowest gas release was found to be 263.15 K, while the release ratio at 10 h reached to 43.42%. By increasing the back pressure, the gas release rate could be effectively controlled. The gas release ratio at 1.1 MPa at 10 h was just 11.08%. The results showed that the application of adsorption-hydration sequence method in ZIF-8 slurry is a prospective manner for gas transportation.

Core–shell Cu2O@ZnO composites were synthesized successfully based on a one-pot hydrothermal method in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The Cu2O can be converted to rough core–shell Cu2O@ZnO structure by adjusting the amount of zinc powder added. The as-synthesized Cu2O@ZnO composites exhibited excellent photocatalytic activity and the amount of H2 generated using these composites was 4.5-fold more than that produced with Cu2O cubes. A possible photocatalytic mechanism for the Cu2O@ZnO composites with enhanced photocatalytic activity could be the separation by ZnO of the effective charge carriers.

Monodisperse Cu 2 O-cubes, Cu 2 O-concave cubes and Cu 2 O-octapods supercrystals have been synthesized successfully using a self-assembly approach in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. Specifically, the supercrystals can be prepared by adding aqueous Cu(Ac) 2 solution into butyl alcohol solution of AOT to first assemble nanoreactors and then perform hydrothermal reactions. The structures of the supercrystals can be tailored by simply varying the amount of Cu (Ac) 2 with the same ratio of the Cu(Ac) 2 to ascorbic acid. AOT surfactant was crucial to precisely control the supercrystal morphology. It was demonstrated that the ratio of growth rate along different planes varied by adjusting the amount of Cu(Ac) 2 and the volume ratio of alcohol to water, thus Cu 2 O crystals with cubes, concave cubes, and octapods with the size of 1.2–2.2 μm were obtained. The morphology evolution from cubes, concave cubes to octapods was systematically studied and a facet etching mechanism is proposed. Hence, precise control of the amount of Cu(Ac) 2 enables this facet etching, novel Cu 2 O with concave {100} facets can be fabricated. Photocatalysis investigation on the morphology-controlled Cu 2 O indicates that the Cu 2 O-octapods supercrystals showed the highest amount of H 2 and the best cyclic-stability. This work reveals that morphology-control of supercrystals is important to the development of novel photocatalysis.

The CO sensing and magnetic properties of pristine and metal-doped MoS2 monolayers (defined as MoS2M, where M = Pd, Co, and Fe) were investigated by anchoring CO onto 2D nanosheets with first-principles calculations. Pristine MoS2 exhibits weak physisorption to CO, whereas MoS2-M monolayers show enhanced interaction with CO by forming a metal CO bond, and narrow band gaps and spontaneous magnetization upon CO adsorption. MoS2-Co and MoS2-Fe systems are ferromagnetic (FM) half metals (HM), whereas MoS2-Pd is a nonmagnetic (NM) metal. After CO adsorption, MoS2-Fe coverts to NM metal to maintain the unchanged ground states. Results indicate that MoS2-M systems are promising candidates for future applications in designing novel gas sensors, nanoelectronics, and spintronics. (C) 2017 Elsevier B.V. All rights reserved.

The relationship between the hydrate-bearing sediments with physical properties such as wave velocity is of importance for the exploration and exploitation of natural gas hydrate. The distribution modes of naturally occurring gas hydrates in sediments are diverse and have significant influence on physical properties of rocks. However, hydrates in homogeneous distribution are in general investigated in laboratory currently. In this work, to simulate the diverse distribution modes of naturally occurring gas hydrates, a novel method to prepare the hydrate-bearing sediments with heterogeneous distribution including layered distribution was proposed by controlling the temperature, water migration, and water saturation distribution. Velocity and amplitude of P-wave are investigated to evaluate the physical properties of hydrate-bearing sediments with homogeneous or heterogeneous distribution. The results showed that the hydrate formation process apparently consists of unconsolidated and consolidated steps according to the amplitude curve. The amplitude of P-wave in the unconsolidated stage increases slowly, while it increases suddenly and rapidly in the consolidated stage. The P-wave velocity of the hydrate deposits with homogeneous distribution is faster than that with heterogeneous distribution when under a same hydrate saturation. This is also verified from the experiments performed on hydrate-bearing sediments with layered distribution, which provided direct evidence and quantification about heterogeneous degree of hydrate distribution in sediment. This difference of the P-wave velocity between heterogeneous and homogeneous hydrate-bearing sediments would provide a guidance in the future development of natural gas hydrate.

CaCu3Ti4O12 (CCTO) ceramics were prepared by the sol–gel process and sintered by the spark plasma sintering (SPS) process at different temperatures. The SPS process temperature has an important effect on the microtopography of CCTO ceramics. The results of EDS and positron annihilation spectroscopy indicate that Cu2+ diffuses from the inside to the surface of grains during the sintering process at high temperature. The permittivity (er) of CCTO ceramics at the corresponding frequencies increases with increasing SPS temperature. However, the frequency stability of er over the frequency range 40–106 Hz wanes gradually. The CCTO ceramics sintered at 900°Cand 950 °C present very low dielectric loss values(about 0.02) near 10 kHz. The change in er and tanδ for CCTO ceramics can be explained by the internal barrier layer capacitance (IBLC) model and AC (alternating current) impedance spectra. The results of I–V nonlinear characteristics for CCTO ceramics make clear that the potential barrier height has a positive effect on the value of nonlinear coefficient.