Enhanced Energy Density in All-in-One Device Integrating Si Solar Cell and Supercapacitor Using [BMIm]Cl/PVA Gel Electrolyte.

All-in-one systems integrating solar cells and supercapacitors have recently received significant attention because of their high efficiency and portability. Unlike conventional solar photovoltaics, which require external wiring to connect to a battery for energy storage, integrated devices with solar cells and supercapacitors share one electrode, eliminating wiring resistance and facilitating charge transfer. In this work, we designed and fabricated all-in-one devices by combining a silicon solar cell and a supercapacitor with polymer gel electrolytes. Our all-in-one devices incorporating H3PO4/PVA and [BMIm]Cl/PVA exhibited areal capacitances of 452.5 and 550 mF·cm -2 at 0.1 mA·cm-2, respectively, following 100 s of photocharging. Notably, the [BMIm]Cl/PVA-based all-in-one device demonstrated significantly higher maximum energy density and power density compared to both the H3PO4/PVA-based all-in-one device and the values reported in literature. In addition, the cyclic photocharge/galvanostatic discharge process for the [BMIm]Cl/PVA-based all-in-one device represented consistent retention of areal capacitance, affirming its stability across charge-discharge cycles. After 100 s of photocharging, the [BMIm]Cl/PVA-based all-in-one device achieved a total energy efficiency of 1.85%, surpassing the 1.45% efficiency observed in the device using H3PO4/PVA. These results provide valuable insights for the design of self-charging all-in-one devices for portable and wearable applications.

Effects of Ti-doping amount and annealing temperature on electrochromic performance of sol-gel derived WO3.

Fine control of structural and morphological features in electrochromic materials is of paramount importance for realizing practical electrochromic devices (ECDs), which can dynamically adjust indoor light and temperature of buildings. To this end, herein we investigate impacts of two variants such as Ti-doping amount and the annealing temperature on physical and chemical properties of sol-gel derived electrochromic WO3 films. We use a wide range of titanium coupling agents (TCAs) as Ti-dopants ranging from 0 wt% to 20 wt% and vary the annealing temperature between 200 °C and 400 °C with 50 °C interval. Both variants greatly influence the physical properties of the resulting WO3 films, resulting in different crystallinities and morphologies. Through complementary analytical techniques, we find that the WO3 film featuring an amorphous phase with nano-porous morphology enhances the electrochemical and electrochromic performances. The specific TCA used in this study helps stabilize the amorphous WO3 structure and generate the nano-pores during the following thermal treatment via its thermal decomposition. As a result, the WO3 film having an optimal 8 wt% TCA annealed at 300 °C shows a high optical density of 73.78% in visible light (400-780 nm), rapid switching speed (t c = 5.12 s and t b = 4.74 s), and high coloration efficiency of 52.58 cm2 C-1 along with a superior cyclic stability. Thus, understanding a structure-property relationship is of paramount importance in engineering the advanced electrochromic WO3 for use in practical ECDs and other optoelectronic applications.

Synthesis of SAPO-34 Nanoplates with High Si/Al Ratio and Improved Acid Site Density.

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles were characterized by various techniques using SEM, XRD, BET, EDX, and NH3-TPD. Various morphologies of particles including isotropic, hyper rectangle, and nanoplates were obtained. It was found that the Si/Al ratio of the SAPO-34 particles was in a direct relationship with the density of acid sites. Moreover, the gel composition and preparation affected the chemistry of the synthesized particles. The slow addition of phosphoric acid improved the homogeneity of synthesis gel and resulted in SAPO-34 nanoplates with high density of acid sites, 3.482 mmol/g. The SAPO-34 nanoplates are expected to serve as a high performance catalyst due to the low mass transfer resistance and the high density of active sites.

Two-Dimensional MFI Zeolite Nanosheets Exfoliated by Surfactant Assisted Solution Process.

Two-dimensional (2D) zeolite nanosheets are important for the synthesis of high flux zeolite membranes due to their lateral size in a preferred orientation. A way to obtain 2D zeolite nanosheets is to exfoliate interlocked structures generated during the hydrothermal synthesis. The mechanical and polymer assisted exfoliation process leads to mechanical damage in nanosheets and short lateral size. In the present study, polyvinylpyrrolidone (PVP) was introduced as an exfoliation agent and dispersant, so that multilamellar interlocked silicalite-1 zeolite nanosheets successfully exfoliated into a large lateral size (individual nanosheets 500~1200 nm). The good exfoliation behavior was due to the strong penetration of PVP into multilamellar nanosheets. Sonication assisted by mild milling helps PVP molecules to penetrate through the lamellar structure, contributing to the expansion of the distance between adjacent layers and thus decreasing the interactions between each layer. In addition, the stability of exfoliated nanosheets was evaluated with a series of organic solvents. The exfoliated nanosheets were well dispersed in n-butanol and stable for 30 days. Therefore, the PVP-assisted solution-based exfoliation process provides high aspect ratio MFI zeolite nanosheets in organic solvents for a long period.

Fabrication and Photocatalytic Properties of Electrospun Fe-Doped TiO2 Nanofibers Using Polyvinyl Pyrrolidone Precursors.

For the removal of pollutants, a modified TiO2 photocatalyst is attracting attention. Fe-doped TiO2 nanofibers were prepared through a combination of electrospinning and calcination. Morphological characterization of the sample was conducted using field-emission scanning electron and transmission electron microscopy. The crystal structure of each sample was analyzed using high-resolution transmission electron microscopy, selected area electron diffraction, and Fast Fourier Transform imaging. The average diameter of the Fe-doped TiO2 nanofibers was measured to be 161.5 nm and that of the pure TiO2 nanofibers was 181.5 nm. The crystal phase when heat treated at 350 °C was anatase for TiO2 nanofibers and rutile for Fe-doped TiO2 nanofibers. The crystal phase of the TiO2 matrix was easily transitioned to rutile by Fe-doping. The photocatalytic performance of each sample was compared via the photodegradation of methylene blue and acid orange 7 under ultraviolet and visible light irradiation. In the Fe-doped TiO2 nanofibers, photodegradation rates of 38.3% and 27.9% were measured under UV irradiation and visible light, respectively. Although other catalysts were not activated, the photodegradation rate in the Fe-doped TiO2 nanofibers was 9.6% using acid orange 7 and visible light. For improved photocatalytic activity, it is necessary to study the concentration control of the Fe dopant.

Prevention in Thermal Crack Formation in Chabazite (CHA) Zeolite Membrane by Developing Thin Top Zeolite and Thick Intermediate Layers.

Chabazite (CHA) zeolite membranes with an intermediate layer of various thicknesses were prepared using planetary-milled seeds with an average particle diameter of 300, 250, 200, 140, and 120 nm. The 120 nm seed sample also contained several smaller particles with a diameter of 20 nm. Such small seeds deeply penetrated into the pore channels of the α-alumina support during the vacuum-assisted infiltration process. During the secondary growth, the penetrated seeds formed a thick intermediate layer exiting between the zeolite layer and support. A decrease in seed size increased the penetration depth of seeds and the thickness of the intermediate layer, while the thickness of seed coating and zeolite layers was decreased. CHA zeolite membranes with a thin top zeoliate layer and a thick intermediate layer showed an excellent water/ethanol separation factor (>10,000) for 90 wt.% ethanol at 70 ℃ with a total flux of 1.5 kg m-2 h-1. There was no observation of thermal cracks/defects on the zeolite separation layer. The thick intermediate layer effectively suppressed the formation of thermal cracks during heating, since the tensile stress induced in the zeolite layer was well compensated by the compressive stress on the support. Therefore, it was successfully proven that controlling the microstructure of top surface and intermediate layers is an effective approach to improve the thermal stability of the CHA zeolite membrane.

Effects of Electrospinning Parameters on the Microstructure of PVP/TiO2 Nanofibers.

Titanium dioxide has excellent chemical, electrical, and optical properties, as well as good chemical stability. For that reason, it is widely used in many fields of study and industry, such as photocatalysts, organic solar cells, sensors, dental implants, and other applications. Many nanostructures of TiO2 have been reported, and electrospinning is an efficient practical technique that has a low cost and high efficiency. In various studies on improving performance, the researchers created nanofibers with suitable microstructures by changing various properties and the many process parameters that can be controlled. In this study, PVP/TiO2 nanofibers were fabricated by the electrospinning process. The diameters of the nanofibers were controlled by various parameters. To understand the effects on the diameter of the nanofibers, various process parameters were controlled: the molecular weight and concentration of the polymers, deionized water, applied voltage, fluid velocity, and concentration of titanium precursor. The average diameter of the PVP nanofibers was controlled in a range of 42.3 nm to 633.0 nm. The average diameter of the PVP/TiO2 nanofibers was also controlled in a range of 63.5 nm to 186.0 nm after heat treatment.

Incorporation of Waste Glass as an Activator in Class-C Fly Ash/GGBS Based Alkali Activated Material.

In this study, an alkaline activator was synthesized by dissolving waste glass powder (WGP) in NaOH-4M solution to explore its effects on the formation of alkali-activated material (AAM) generated by Class-C fly ash (FA) and ground granulated blast furnace slag (GGBS). The compressive strength, flexure strength, porosity and water absorption were measured, and X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) were used to study the crystalline phases, hydration mechanism and microstructure of the resulting composites. Results indicated that the composition of alkali solutions and the ratios of FA/GGBS were significant in enhancing the properties of the obtained AAM. As the amount of dissolved WGP increased in alkaline solution, the silicon concentration increased, causing the accelerated reactivity of FA/GGBS to develop Ca-based hydrate gel as the main reaction product in the system, thereby increasing the strength and lowering the porosity. Further increase in WGP dissolution led to strength loss and increased porosity, which were believed to be due to the excessive water demand of FA/GGBS composites to achieve optimum mixing consistency. Increasing the GGBS proportion in a composite appeared to improve the strength and lower the porosity owing to the reactivity of GGBS being higher than that of FA, which contributed to develop C-S-H-type hydration.

A stable polymeric chain configuration producing high performance PEBAX-1657 membranes for CO2 separation.

Although PEBAX-1657 is one of the promising polymeric materials for selective CO2 separation, there remain many questions about the optimal polymeric structure and possibility of improving performance without adulterating its basic structure by impregnating inorganic fillers. In order to improve the gas separation performance, low thickness PEBAX membranes were synthesized under steady solvent evaporation conditions by keeping in mind that one of its segments (nylon 6) shows structural variance and molecular orientation with a change in the evaporation rate. Furthermore, phase pure zeolite nanocrystals with cubic (zeolite A) and octahedral (zeolite Y) shapes have been synthesized through liquid phase routes using microwave hydrothermal reactors. The average sizes of zeolite A and Y crystals are around 55 and 40 nm, respectively. The inspection of XRD, DSC and Raman shift of PEBAX membranes demonstrates the formation of a stable polymeric structure with an improved crystalline state which results in high CO2 permeability membranes. The CO2 permeability as well as diffusivity increase with a decrease in membrane thickness and reach a maximum value of 184.7 Barrer and 2.6 × 10-6 cm2 s-1, respectively. The as-fabricated pristine PEBAX membrane shows much better performance in terms of permeance (CO2 184.7 Barrer), diffusivity (CO2 2.6 × 10-6 cm2 s-1) and selectivity (CO2/N2 59.7), which substantiate its promising prospects for CO2 capture. This exceptional performance of the pristine PEBAX membrane arises from the free volume generated during the steady polymerization. This reported approach for PEBAX membrane synthesis provides a direction in the design of membrane fabrication processes for economic CO2 separation.

Defect-Free Mixed-Matrix Membranes with Hydrophilic Metal-Organic Polyhedra for Efficient Carbon Dioxide Separation.

Defect-free mixed-matrix membranes (MMMs) were prepared by incorporating hydrophilic metal-organic polyhedra (MOPs) into cross-linked polyethylene oxide (XLPEO) for efficient CO2 separation. Hydrophilic MOPs with triethylene glycol pendant groups, which were assembled by 5-tri(ethylene glycol) monomethyl ether isophthalic acid and CuII ions, were uniformly dispersed in XLPEO without particle agglomeration. Compared to conventional neat XLPEO, the homogenous dispersion of EG3 -MOPs in XLPEO enhanced CO2 permeability of MMMs. Upon increasing the amount of EG3 -MOPs, the membrane performance such as CO2 /N2 selectivity was steadily improved because of unsaturated CuII sites at paddle-wheel units, which was confirmed by Cu K-edge XANES and TPD analysis. Therefore, such defect-free MMMs with unsaturated metal sites would contribute to enhance CO2 separation performance.

GIS-NaP1 zeolite microspheres as potential water adsorption material: Influence of initial silica concentration on adsorptive and physical/topological properties.

GIS-NaP1 zeolite samples were synthesized using seven different Si/Al ratios (5-11) of the hydrothermal reaction mixtures having chemical composition Al2O3:xSiO2:14Na2O:840H2O to study the impact of Si/Al molar ratio on the water vapour adsorption potential, phase purity, morphology and crystal size of as-synthesized GIS-NaP1 zeolite crystals. The X-ray diffraction (XRD) observations reveal that Si/Al ratio does not affect the phase purity of GIS-NaP1 zeolite samples as high purity GIS-NaP1 zeolite crystals were obtained from all Si/Al ratios. Contrary, Si/Al ratios have remarkable effect on the morphology, crystal size and porosity of GIS-NaP1 zeolite microspheres. Transmission electron microscopy (TEM) evaluations of individual GIS-NaP1 zeolite microsphere demonstrate the characteristic changes in the packaging/arrangement, shape and size of primary nano crystallites. Textural characterisation using water vapour adsorption/desorption, and nitrogen adsorption/desorption data of as-synthesized GIS-NaP1 zeolite predicts the existence of mix-pores i.e., microporous as well as mesoporous character. High water storage capacity 1727.5 cm(3) g(-1) (138.9 wt.%) has been found for as-synthesized GIS-NaP1 zeolite microsphere samples during water vapour adsorption studies. Further, the total water adsorption capacity values for P6 (1299.4 mg g(-1)) and P7 (1388.8 mg g(-1)) samples reveal that these two particular samples can absorb even more water than their own weights.

A Modified Oxidative Refinement Process for Removing Boron from Molten Silicon Under Enhanced Electromagnetic Force.

The removal of boron is one of the main challenges in the purification of metallurgical grade silicon destined for low-cost photovoltaic applications. However, boron is very difficult to remove in its elemental form due to its large segregation coefficient in silicon and its low vapor pressure. The removal of boron by slag treatment is today regarded as a highly promising method, but its refining efficiency is relatively low. Also, the reduction of boron by plasma treatment exhibits a high refining efficiency, but the processing cost is high due to the large amount of electricity consumed by the process. In this regard, the use of an oxidizing reactive gas in the refinement process offers some advantages both in terms of low energy consumption and promising refinement rates. Boron can be extracted in various gaseous forms as B(x)O(y) and/or B(x)H(z)O(y) phases, but the vapor pressure of B(x)H(z)O(y) is much greater than that of the other specie at a temperature of 1700 K. The present study reports a modified oxidative refining method designed to enhance the vaporization of boron as B(x)H(z)O(y) by blowing gaseous water onto the silicon melt in a segmented crucible to enhance the electromagnetic force, whereby the processing cost can be dramatically reduced due to the use of a reusable quartz crucible in a graphite crucible. An initial boron content of 13 ppm in the metallurgical grade silicon was significantly decreased to 0.3 ppm by the employment of 1.7SLM Ar + 100 ml/h H2O. Also, a mechanism capable of reducing boron based on thermodynamic considerations is proposed.

An emulsion-based droplet hydrothermal synthesis method for the production of uniform sized zeolite nanocrystals.

A droplet based new hydrothermal synthesis method for nano-zeolite synthesis in bulk amount with uniform size, shape and morphology is presented. The proposed process addresses the limitation and shortcomings of droplet based microfluidic reactors and conventional hydrothermal methods. The process has been designed on the concept of mixing two immiscible solutions at high speed which then produces nano/submicron size droplets. Confinement within the droplet provides uniform heat transfer, enhanced mass transfer to growing crystal, chaotic advection within droplet facilitate rapid mixing, prevent the contact between growing crystals etc. Fine-tuned nano-cubic LTA zeolite crystals of size ∼100 nm with uniform morphology and size distribution were prepared. Just within 4h of reaction time (aging+crystallization) well shaped cubic crystals with high crystallinity and size uniformity can be synthesized by the proposed synthesis process. Diffraction and electron microscopic studies reveal the high phase purity and size uniformity of as-synthesized LTA zeolite particles.