BiOxCly/BiOmBrn/BiOpIq/g-C3N4 was prepared by using the hydrothermal synthesis. The composition and morphologies of the composites were controlled by adjusting the reaction pH value, temperature, and molar ratio. The optimized BiOxCly/BiOmBrn/BiOpIq/g-C3N4 photocatalyst increased the rate of photocatalytic conversion from CO2 to CH4 to 0.036 μmol g−1 h−1 and these samples were subjected to photocatalytic degradation with CV. The enhanced photocatalytic activity can be attributed to the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at these heterostructure interfaces, the transfer of photogenerated electrons through the g-C3N4 skeleton, and the favorable alignment of the straddling band structure from BiOxCly/BiOmBrn/BiOpIq/g-C3N4.
Accurate characterization of coal reservoir micro- and nanopores is crucial in evaluating coalbed methane storage and gas production capacity. In this work, 12 coal-bearing rock samples from the Jurassic Yan’an Formation, Longdong area, Ordos Basin were taken as research objects, and micro- and nanopore structures were characterized via scanning electron microscopy, high-pressure mercury pressure, low-temperature N2 adsorption and low-pressure CO2 adsorption experiments. The main factors controlling coal pore structure development and the influence of pore development on the gas content were studied by combining the reflectivity of specular samples from the research area, the pore microscopic composition and the pore gas content determined through industrial analyses and isothermal absorption experiments. The results show that the coal strata of the Yan’an coal mine are a very important gas source, and that the coal strata of the Yan’an Formation in the study area exhibit remarkable organic and clay mineral pore development accompanied by clear microfractures and clay mineral interlayer joints, which together optimize the coal gas storage conditions and form efficient microseepage pathways for gas. Coalstone, carbonaceous mudstone and mudstone show differential distributions in pore volume and specific surface area. The general trend is that coal rock is the best, carbonaceous mudstone is the second best, and mudstone is the weakest. The coal samples’ microporous properties are positively correlated with the coal sample composition for the specular group, whereas there is no clear correlation for the inert group. An increase in the moisture content of the air-dried matrix promotes adsorption pore development, leading to increases in the microporous volume and specific surface area. CH4 adsorption in coal rock increases with increasing pressure, and the average maximum adsorption is approximately 8.13 m3/t. The limit of the amount of methane adsorbed by the coal samples, VL, is positively correlated with the pore volume and specific surface area, indicating that the larger the pore volume is, the greater the amount of gas that can be adsorbed by the coal samples, and the larger the specific surface area is, the greater the amount of methane that can be adsorbed by the coal samples. The PL value, pore volume and specific surface area are not correlated, indicating that there is no direct mathematical relationship between them.
Patterning is a crucial fabrication step for successfully applying two-dimensional materials in electronic and optoelectronic devices. It can realize miniaturization and help explore new physical phenomena of 2D materials. However, the manufacturing process inevitably introduces defects, which require harsh conditions to recover. Here, we propose a sputtering-lithography-annealing (SLA) strategy for patterning graphene nanofilm with pattern sizes ranging from microns to 100 nm scale without lattice damage. The sputtered masking agents can introduce easily repairable defects into graphene films. Especially, defects introduced by aluminum can be removed entirely. To confirm the validity of the SLA strategy, we prepared macro-assembled graphene nanofilms (nMAG)/Ge and nMAG/Si heterojunction arrays for infrared detection. The patterned detectors present a responsivity of 0.09 A/W at 2 μm (nMAG/Ge) and 26.4 mA/W at 1550 nm (nMAG/Si) with a high array homogeneity, similar to the devices without patterning. This strategy lays the foundation for further exploration of new superstructures of nMAG and can be extended to other 2D materials.
The processing capability is vital for the wide applications of materials to forge structures as-demand. Graphene-based macroscopic materials have shown excellent mechanical and functional properties. However, different from usual polymers and metals, graphene solids exhibit limited deformability and processibility for precise forming. Here, we present a precise thermoplastic forming of graphene materials by polymer intercalation from graphene oxide (GO) precursor. The intercalated polymer enables the thermoplasticity of GO solids by thermally activated motion of polymer chains. We detect a critical minimum containing of intercalated polymer that can expand the interlayer spacing exceeding 1.4 nm to activate thermoplasticity, which becomes the criteria for thermal plastic forming of GO solids. By thermoplastic forming, the flat GO-composite films are forged to Gaussian curved shapes and imprinted to have surface relief patterns with size precision down to 360 nm. The plastic-formed structures maintain the structural integration with outstanding electrical (3.07 × 105 S m-1) and thermal conductivity (745.65 W m-1 K-1) after removal of polymers. The thermoplastic strategy greatly extends the forming capability of GO materials and other layered materials and promises versatile structural designs for more broad applications.
The use of visible-light-driven photocatalysts in wastewater treatment, photoreduction of CO2, green solar fuels, and solar cells have elicited substantial research attention. Bismuth oxyhalide and its derivatives are a group of visible-light photocatalysts that can diminish electron–hole recombination in layered structures and boost photocatalytic activity. The energy bandgap of these photocatalysts lies in the range of visible light. A simple hydrothermal method was applied to fabricate a series of bismuth oxychloride/bismuth oxyiodide/grafted graphitic carbon nitride (BiOmCln/BiOpIq/g-C3N4) sheets with different contents of g-C3N4. The fabricated sheets were characterized through XRD, TEM, SEM-EDS, XPS, UV-vis DRS, PL, and BET. The conversion efficiency of CO2 reduction to CH4 of BiOmCln/BiOpIq 4.09 μmol g-1 can be increased to 39.43 μmol g-1 by composited with g-C3N4. It is approximately 9.64 times improvement. The rate constant of BiOmCln/BiOpIq photodegradation CV k = 0.0684 can be increased to 0.2456 by composited with g-C3N4. It is approximately 3.6 times improvement. The electron paramagnetic resonance results and the quenching effects indicated that 1O2, •OH, h+, and •O2− were active species in the aforementioned photocatalytic degradation. Because of their heterojunction, the prepared ternary nanocomposites possess the characteristics of heterojunction of type II band alignment.
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