In this work, the isobaric vapor−liquid equilibrium (VLE) data for ethyl acetate + propyl acetate, ethyl acetate + propylene carbonate, and propyl acetate + propylene carbonate systems were measured at a pressure of 101.3 kPa by a modified Rose vapor recirculating-type equilibrium still. The experimental results show that no azeotrope was detected between the three binary systems. Two thermodynamic consistency tests of Herington and van Ness were employed to check the experimental data, respectively. The measured VLE data were correlated by Wilson, universal quasichemical, and nonrandom two-liquid models. The calculated root-mean-square deviation values of the equilibrium temperature and vapor phase mole fractions are not more than 1.07 and 0.0113, respectively. The relative volatilities were calculated and the deviations between the experimental data and Wilson model calculations were compared. All the correlated results are in good agreement with the measured data. Meanwhile, the binary interaction parameters were regressed by the three models for all the binary systems.
Toxic organic solvents are widely used in fabricating perovskite solar cells, which pose a potential threat to human health and the environment. Here, we try to prepare high-quality all-inorganic perovskite films from all aqueous solutions using a traditional two-step method. A continuous PbBr2 precursor film is first prepared from a HBr/H2O solution added with a certain amount of poly(ethylene glycol) (PEG). The PEG plays important roles in adjusting the viscosity of the aqueous solution and affecting the growth of the PbBr2 precursor crystals. A high concentration of the CsBr/H2O solution is then spin-coated on the PbBr2 precursor film followed by annealing to form a high-quality CsPbBr3 film. The CsPbBr3 perovskite solar cells prepared from the aqueous solutions show an efficiency of 7.19%, which is higher than those prepared from the organic solvents in the same conditions. It is a facile and green method to eliminate the solvent toxicity derived from organic solvents in fabricating perovskite solar cells.
Materials containing planar hypercoordinate motifs greatly enriched the fundamental understanding of chemical bonding. Herein, by means of first-principles calculations combined with global minimum search, we discovered the two-dimensional (2D) SrB 8 monolayer, which has the highest planar coordination number ( 12) reported so far in extended periodic materials. In the SrB 8 monolayer, bridged B 8 units are forming the boron monolayer consisting of B 12 rings, and the Sr atoms are embedded at the center of these B 12 rings, leading to the Sr@B 12 motifs. The SrB 8 monolayer has good thermodynamic, kinetic, and thermal stabilities, which is attributed to the geometry fit between the size of the Sr atom and cavity of the B 12 rings, as well as the electron transfer from Sr atoms to electron-deficient boron network. Placing the SrB 8 monolayer on the Ag(001) surface shows good commensurability of the lattices and small vertical structure undulations, suggesting the feasibility of its experimental realization by epitaxial growth. Potential applications of the SrB 8 monolayer on metal ions storage (for Li, Na, and K) are explored.
Nanocarbon materials have the advantages of biocompatibility, thermal stability and chemical stability and have shown excellent electrical properties in electronic devices. In this study, Al/MWCNT:GQD/ITO memristors with rewritable nonvolatile properties were prepared based on composites consisting of multiwalled carbon nanotubes (MWCNTs) and graphene quantum dots (GQDs). The switching current ratio of such a device can be tuned in two ways. Due to the ultraviolet light sensitivity of GQDs, when the dielectric material is illuminated by ultraviolet light, the charge capture ability of the GQDs decreases with an increasing duration of illumination, and the switching current ratio of the device also decreases with an increasing illumination duration (103–10). By exploiting the charge capture characteristics of GQDs, the trap capture level can be increased by increasing the content of GQDs in the dielectric layer. The switching current ratio of the device increases with increasing GQD content (10–103). The device can be programmed and erased more than 100 times; the programmable switching state can withstand 105 read pulses, and the retention time is more than 104 s. This memristor has a simple structure, low power consumption, and enormous application potential for data storage, artificial intelligence, image processing, artificial neural networks, and other applications.
To improve the catalytic efficiency of nanotitanium dioxide, this research investigated the phase transformation, crystal growth, and hydrogen production efficiency of nanotitanium dioxide at different temperatures and pressures. The RGO/TiO2 photocatalyst was prepared by a hydrothermal method using graphene oxide and butyl titanate as raw materials. Different types of photocatalyst samples were prepared by adjusting the reaction temperature and time in the hydrothermal process. X‐ray diffraction and transmission electron microscope techniques were employed to investigate the nucleation and growth processes of rutile and anatase in the hydrothermal process from the perspectives of thermodynamics and kinetics. The evolution of the titanium dioxide structure with hydrothermal temperature and hydrothermal time was analyzed. Finally, photocatalytic decomposition of water data shows that the photocatalyst with the best hydrogen production effect was obtained by 12 hr of hydrothermal treatment at a hydrothermal temperature of 180°C. The total hydrogen production of this sample was 0.037 mmol/g under a xenon lamp for 3 hr.
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