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Carbon dioxide (CO2) is one of the main factors contributing to the greenhouse effect. The dependence on fossil fuels has led to increasing levels of carbon dioxide in the atmosphere every year. And it is far from enough to solve the climate problem by reducing the consumption of fossil fuels to cut down carbon dioxide emissions. In recent years, a series of researches on Carbon Capture, Utilization and Storage (CCUS) have been carried out in various countries around the world. CO2 is a nontoxic, tasteless and stable gas at normal temperature. However, when it reaches supercritical state after rising temperature and pressure, it has the characteristics of low viscosity, high diffusivity and high density, and is widely used in green, pollution-free and efficient development technology. Because of these unique properties, supercritical carbon dioxide (sCO2) has attracted more and more attention from researchers. sCO2 has been widely used in many aspects by virtue of its high solubility and easy compression. Different from previous reviews which only introduced the application of sCO2 property, this paper introduces the current research status of the application of the thermodynamic property of carbon dioxide in extraction, dyeing, pharmaceutical, power generation, heat transfer and exploitation of unconventional oil and gas, and mainly analyzes each application in detail from the aspects of working mechanism and improving working efficiency. Finally, the research direction and problems needed to be solved for the application of CO2 thermal physics are proposed, which pave the way for other new applications. [ABSTRACT FROM AUTHOR]

With the rising concerns on environmental pollution and emission reduction, plastic waste disposal draws great attention from governors and scientists. Instead of landfilling and incineration, chemical treatments are considered less polluting and resources recovering. Hydrothermal processing is considered a prospective technology for this issue. To regulate the conversion process and improve efficiency, a key step is to know the dominant stages and clarify the controlled part of the reaction. However, there is very limited number of researches on the visualized exhibition of this process. In this paper, a hydrothermal process visualization measure is adopted, to intuitionally demonstrate the whole conversion process. Polyoxymethylene (POM) spheres are employed as the feedstock in this experiment. A fixed-focus camera records the plastic sphere particle undergoing three stages of heated, swelling and dissolution, under hydrothermal condition. At the heated stage, the solid sphere becomes transparent, then during the swelling stage, the transparent sphere expands to around 130 % of the original size (sectional area), finally the expanded sphere is dissolved into fragments dispersing in the water. During the hydrothermal conversion, the carbon component of the plastic sphere immigrated into the aqueous phase, carbon recovery rate of the process reached as high as 90 %. The visualized results well demonstrate the physical and chemical transition of hydrothermal process, which would be a promising direction for future study. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Important progress has been made in the development of energetic molecules with high performance by computer‐aided molecular design in recent years, but structural novelty of organic scaffolds is insufficient. In this work, we propose an intra‐ring bridging strategy inspired by the known energetic nitramines to design novel polycyclic and cage energetic molecules. More than 100 energetic structures were designed by introducing the C—C bridges and increasing the ring size. The synthesis difficulty is considered besides the two most concerned properties of EMs, energy and safety. After a comprehensive estimation, a symmetric cage molecule labeled as 8U‐30 was finally selected because of its relatively high detonation performance, and comparable impact sensitivity as well as synthetic accessibility with CL‐20. Hopefully, the proposed strategy could be utilized in further molecular design to gain various scaffolds, especially cage structures, for different demands. [ABSTRACT FROM AUTHOR]

In semiconductor system for solar-energy utilization by photoelectrochemical (PEC) water splitting, the effective absorption of visible light and the efficient separation and transfer of photogenerated charge carriers are still of key importance. In this manuscript, composite photo-anodes of PbO sensitized ZnO nanorod arrays were prepared by a two-step hydrothermal process and used as anodes for PEC test under visible-light irradiation. The photocurrent achieved the highest value of 94 µA cm-2 at 0.8 V (versus Ag/AgCl electrode) when the amount of Pb source was optimized to form only a thin layer (a few nanometers) of PbO nanoparticles on the surfaces of ZnO nanorods. Such a nanostructure enabled the visible-light absorption, and also ensured the sufficient contact of PbO with ZnO to form junction with a type II band alignment and the sufficient contact with aqueous solution to form interfaces, thus facilitating the excitation, separation, and transfer of charge carriers to generate photocurrent and finally enhancing the PEC activity. [ABSTRACT FROM AUTHOR]

In this work, composites of silica and graphitic carbon nitride (g-C3N4) were conveniently synthesized through polymerization of melamine and ethyl silicate. Some basic physicochemical properties of these metal-free photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), Fourier transform infrared spectrometer (FTIR) spectra, transmission electron microscope (TEM), UV-visible diffuse reflectance spectrum and N2 adsorption-desorption measurement. The XRD patterns of all the prepared materials were dominated by the characteristic (002) peak at 27.5° of a graphitic structure, indicating that the induced Si did not destroy the crystal structure of g-C3N4). As the initial molar ratio of Si to C increased, enhanced photocatalytic activity was observed for H2 evolution from a triethanolamine aqueous solution under visible-light irradiation over the series of composites. It was proved that the introduction of Si resulted in large surface area, which is favorable for reactant-transfer and charge-migration, beneficial for photocatalysis. [ABSTRACT FROM AUTHOR]

Co3O4 quantum dots were synthesized by a facile reverse micelle method for the first time, and were capable of splitting pure water into O2 and H2 stoichiometrically under visible-light irradiation (λ > 420 nm) without any cocatalyst. [ABSTRACT FROM AUTHOR]

A series of WO3/g-C3N4 composites with different WO3 contents were prepared via a facile one-pot pyrolysis method, and showed notably enhanced visible-light-driven photocatalytic H2-evolution activities, with the highest rate of 400 μmol h−1 gcat−1 that was 15.0 times of that for pristine g-C3N4. Contents and sizes of WO3 crystallites in the composites were easily adjusted by changing the molar ratios of (NH4)2WS4 to C3H6N6 in the feed reagents, thereby successfully optimizing the Z-scheme system constructed by WO3 and g-C3N4 and thus effectively reducing the recombination of photogenerated charge carriers in g-C3N4. Moreover, pore volumes and surface areas of the composites were gradually enlarged by introducing WO3 into g-C3N4 via the one-pot preparation strategy, therefore promoting the redox reactions to evolve H2. This work presented an effective route to simultaneously optimize the phase compositions and textural structures of photocatalysts for enhanced H2 evolution. [ABSTRACT FROM AUTHOR]