| 1. |
- Nordstrand, Johan
(författare)
-
At the Mountains of Modeling : Multiscale Simulations of Desalination by Capacitive Deionization
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- More than 2 billion people are living in water-scarce areas. Meanwhile, there are enormous amounts of water in the salty oceans. Capacitive deionization (CDI) rises to the challenge with electrochemical cells for desalinating the water. As the CDI field expands, modeling becomes an increasingly important part of the development landscape. Multiscale modeling could bring innovations from the material scale to pilot plants. The multiscale work in this thesis has been like climbing a mountain. At the start, we investigate the macroscopic device level. One milestone is the electrolytic-capacitor (ELC) model, which can simulate CDI process dynamics. Whereas previous 2D models were unsteady for a single CDIcell, the ELC model could accurately simulate stacks of over 100 cells at a fraction of the time. It also enables simulations of complex upscaled geometries, such as bipolar electrode stacks, ohmic charging, and asymmetric devices. Going up the mountain, the mesoscopic level reveals the local mechanisms behind the macroscopic behavior. One important stepping stone is the dynamic Langmuir (DL) model, which reveals how isotherm-based modeling can crease stable and tractable simulations. Also, developments in isotherm, double-layer, and circuit modeling make it possible to choose what model structures to lean on depending on the conditions. Near the top of the mountain, the microscopic level shows the fundamental atomic mechanisms behind the mesoscopic material properties. These investigations reveal a ladder mechanism of ion transport in crystals of Prussian blue analogs (PBA), meaning the cations climb frames formed by negative groups in the crystal structure.In the end, we plant a flag by combining the developments from the journey into a complete multiscale model. That model demonstrated that we could predict CDI charging trends from the atomic structure of PBA electrodes. Having the full multiscale model also made it possible to backtrack and determine atomic-level mechanisms by comparing the output of different mechanism cases with macroscopic experiment data. The multiscale mountain is massive and has big potential. A dream is that future research will expand these concepts, in CDI and beyond.
|
|
| 2. |
- Abiso, Ahmad Muhammad, et al.
(författare)
-
Advances in copper-based catalysts for sustainable hydrogen production via methanol steam reforming
- 2024
-
Ingår i: Chemical Engineering Journal Advances. - : Elsevier BV. - 2666-8211. ; 19
-
Forskningsöversikt (refereegranskat)abstract
- Efficient hydrogen production through Methanol Steam Reforming (MSR) is an area of high importance due to its environmental suitability and superior energy efficiency compared to methane steam reforming. Therefore, we present a comprehensive investigation into the development of copper-based catalysts for MSR. Over the past decades, research in this domain has intensified, encompassing Cu-based catalysts that exhibit notable promise. Strategies to enhance catalytic activity and stability involve the utilisation of mesoporous support materials with tuneable properties, novel promoters, and the introduction of mixed oxides and metal organic framework amongst others. Furthermore, the paper underscores the significance of catalyst morphology and metal precursors in determining their final performance. Several new catalysts have shown remarkable selectivity for hydrogen while minimizing carbon monoxide production even at elevated temperatures, positioning them as strong candidates for environmentally friendly commercial hydrogen production through methanol steam reforming. Valuable insights into synthesis approaches and catalyst performance variations across different research groups are also presented.
|
|
| 3. |
- Al-Abri, M., et al.
(författare)
-
Chlorination disadvantages and alternative routes for biofouling control in reverse osmosis desalination
- 2019
-
Ingår i: npj Clean Water. - : Nature Research. - 2059-7037. ; 2:1
-
Tidskriftsartikel (refereegranskat)abstract
- With an ever-increasing human population, access to clean water for human use is a growing concern across the world. Seawater desalination to produce usable water is essential to meet future clean water demand. Desalination processes, such as reverse osmosis and multi-stage flash have been implemented worldwide. Reverse osmosis is the most effective technology, which uses a semipermeable membrane to produce clean water under an applied pressure. However, membrane biofouling is the main issue faced by such plants, which requires continuous cleaning or regular replacement of the membranes. Chlorination is the most commonly used disinfection process to pretreat the water to reduce biofouling. Although chlorination is widely used, it has several disadvantages, such as formation of disinfection by-products and being ineffective against some types of microbes. This review aims to discuss the adverse effect of chlorination on reverse osmosis membranes and to identify other possible alternatives of chlorination to reduce biofouling of the membranes. Reverse osmosis membrane degradation and mitigation of chlorines effects, along with newly emerging disinfection technologies, are discussed, providing insight to both academic institutions and industries for the design of improved reverse osmosis systems.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Al-Soubaihi, Rola, et al.
(författare)
-
Comparative investigation of structure and operating parameters on the performance and reaction dynamic of CO conversion on silica aerogel and fumed-silica-supported Pd catalysts
- 2022
-
Ingår i: SURFACES AND INTERFACES. - : Elsevier BV. - 2468-0230. ; 29, s. 101776-
-
Tidskriftsartikel (refereegranskat)abstract
- The catalyst morphology, metal-support interaction, and reaction conditions greatly influence the catalytic performance and reaction dynamics. Similarly, the dispersion of the metal within the support plays a crucial in the thermal stability and sintering of the catalyst. Furthermore, temperature-dependent conversion hysteresis is well-known to occur during ignition and extinction of exothermic CO oxidation over supported Pd catalysts due to the variation of CO adsorption on the surface or bulk oxidation of Pd and the ability of the catalyst regenerate the active sites. Herein, the catalytic performance and the hysteresis behavior of mesoporous silica aerogel supported Pd (Pd/a-SiO2), and commercial fumed silica-supported Pd (Pd/f-SiO2) were investigated compared using CO oxidation as a probe reaction under different reaction conditions and operating parameters (i.e., catalyst weight, ramp rate, and flow rate). Surface and morphologic examination using XPS, FTIR, and of Pd/a-SiO2 and Pd/f-SiO2 reveal a strong correlation between the catalyst surface and structure and its catalytic performance and stability under different reaction parameters. Moreover, this study presents the effect of surface area, particle size, and size distribution on diffusion and mass transport of reactants (CO, O-2) and products (CO2) and active sites accessibility. This study showed that Pd/f-SiO2 had better efficiency under high (turbulence) flow. Moreover, intrinsic apparent activation energy (E-a) and the number of active sites were calculated from the Kinetics of CO oxidation fitted using Arrhenius plots indicate that the ramp rate has less effect on Pd/f-SiO2 catalytic behavior. though, Pd/f-SiO2 had higher relative active sites than Pd/a-SiO2, (E-a) was lower. Cyclic stability and long-term stabilities showed that both catalysts are stable and can regenerate the active sites. The current study contributes to understanding the catalysts' surface, structural and morphological properties on the catalysts' performance toward CO oxidation and other reactions under dynamic conditions.
|
|
| 7. |
- Al-Soubaihi, Rola, et al.
(författare)
-
Investigation of palladium catalysts in mesoporous silica support for CO oxidation and CO2 adsorption
- 2023
-
Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 9:7
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of Carbon monoxide (CO) to Carbon dioxide (CO2) is one of the most extensively investigated reactions in the field of heterogeneous catalysis, and it occurs via molecular rearrangements induced by catalytic metal atoms with oxygen intermediates. CO oxidation and CO2 capture are instrumental processes in the reduction of green-house gas emissions, both of which are used in low-temperature CO oxidation in the catalytic converters of vehicles. CO oxidation and CO2 adsorption at different temperatures are evaluated for palladium-supported silica aerogel (Pd/SiO2). The synthesized catalyst was active and stable for low-temperature CO oxidation. The catalytic activity was enhanced after the first cycle due to the reconditioning of the catalyst's pores. It was found that the presence of oxide forms of palladium in the SiO2 microstructure, influences the performance of the catalysts due to oxygen vacancies that increases the frequency of active sites. CO2 gas adsorption onto Pd/SiO2 was investigated at a wide-ranging temperature from 16 to 120 degrees C and pressures similar to 1 MPa as determined from the isotherms that were evaluated, where CO2 showed the highest equilibrium adsorption capacity at 16 degrees C. The Langmuir model was employed to study the equilibrium adsorption behavior. Finally, the effect of moisture on CO oxidation and CO2 adsorption was considered to account for usage in real-world applications. Overall, mesoporous Pd/SiO2 aerogel shows potential as a material capable of removing CO from the environment and capturing CO2 at low temperatures.
|
|
| 8. |
- Al-Soubaihi, Rola, et al.
(författare)
-
Low-temperature CO oxidation by silver nanoparticles in silica aerogel mesoreactors
- 2023
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 455, s. 140576-
-
Tidskriftsartikel (refereegranskat)abstract
- Low-temperature carbon monoxide (CO) oxidation on silver/silica aerogel (Ag/SiO2 AG) catalyst prepared by one-pot sol-gel synthesis followed by supercritical ethanol drying method is reported. Highly stable and sinterproof catalyst led to easy reactant diffusion to the active sites. The Ag/SiO2 AG catalyst showed enhanced catalytic activity toward low-temperature CO oxidation by preventing agglomeration of silver nanoparticles inside pores and facilitating well-dispersed active sites to enhance the mass heat transfer in the mesopores. Catalyst pretreatment conditions were found to play a crucial role in achieving high CO conversion efficiency at low light-off temperatures. Inverse counter-clockwise CO oxidation hysteresis was found to occur after the first run. The active sites contributing to this enhanced catalytic behavior were confirmed to be Ag0 from XPS, XRD, and TEM analysis. The catalyst exhibited good thermal stability up to 450 degrees C over repeated number of cycles.
|
|
| 9. |
- Al Soubaihi, Rola Mohammad, et al.
(författare)
-
CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst
- 2021
-
Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (T-ig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than T-ig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at T-ig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.
|
|
| 10. |
- Al-Soubaihi, Rola, et al.
(författare)
-
Silica and carbon decorated silica nanosheet impact on primary human immune cells
- 2018
-
Ingår i: Colloids and Surfaces B. - : Elsevier B.V.. - 0927-7765 .- 1873-4367. ; 172, s. 779-789
-
Tidskriftsartikel (refereegranskat)abstract
- Silica nanosheets (SiO 2 NS) are considered to be a promising material in clinical practice for diagnosis and therapy applications. However, an appropriate surface functionalization is essential to guarantee high biocompatibility and molecule loading ability. Although SiO 2 NS are chemically stable, its effects on immune systems are still being explored. In this work, we successfully synthesized a novel 2D multilayer SiO 2 NS and SiO 2 NS coated with carbon (C/SiO 2 NS), and evaluated their impact on human Peripheral Blood Mononuclear Cells (PBMCs) and some immune cell subpopulations. We demonstrated that the immune response is strongly dependent on the surface functionalities of the SiO 2 NS. Ex vivo experiments showed an increase in biocompatibility of C/SiO 2 NS compared to SiO 2 NS, resulting in a lowering of hemoglobin release together with a reduction in cellular toxicity and cellular activation. However, none of them are directly involved in the activation of the acute inflammation process with a consequent release of pro-inflammatory cytokines. The obtained results provide an important direction towards the biomedical applications of silica nanosheets, rendering them an attractive material for the development of future immunological therapies.
|
|
| 11. |
- Al-Soubaihi, Rola, et al.
(författare)
-
Synthesis of hierarchically porous silica aerogel supported Palladium catalyst for low-temperature CO oxidation under ignition/extinction conditions
- 2020
-
Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 292
-
Tidskriftsartikel (refereegranskat)abstract
- Synthesis of well-dispersed palladium nanoparticles within silica aerogel pores with controlled size was carried out using sol-gel synthesis under supercritical ethanol drying. The high concentration of silanol groups on silica (SiO2) surface facilitated a superior palladium (Pd) loading up to 10 wt %. The synthesized Pd/SiO2 nanocomposite aerogels were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopic methods. The silica aerogel supported catalysts were found to have a wide pore size distribution. TEM investigations confirmed that Pd nanocrystals were located within the SiO2 microspores and mesopores. The catalyst was evaluated for carbon monoxide (CO) oxidation reaction under ignition/extinction conditions. The synthesized catalyst demonstrated a high catalytic activity at low operating temperatures (<200 °C) compared to unsupported Pd nanoparticles or bare SiO2 aerogels. This enhancement in CO oxidation activity with Pd/SiO2 aerogel catalysts are attributed to the small Pd particles, Pd interaction with the surface of the underlying SiO2 and the better dispersion of Pd particles within the SiO2 pores. Porosity played a more important role during the extinction cycle as a result of the slow dissipation of the heat leading to hysteresis. We demonstrate the influence of porosity of catalyst supports on the size, dispersion, and catalytic activity of Pd nanoparticles.
|
|
| 12. |
- Alvarado Ávila, María Isabel, et al.
(författare)
-
Cellulose as sacrificial agents for enhanced photoactivated hydrogen production
- 2023
-
Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry (RSC). - 2398-4902. ; 7:8, s. 1981-1991
-
Tidskriftsartikel (refereegranskat)abstract
- The search for new energy sources together with the need to control greenhouse gas emissions has led to continued interest in low-emitting renewable energy technologies. In this context, water splitting for hydrogen production is a reasonable alternative to replace fossil fuels due to its high energy density producing only water during combustion. Cellulose is abundant in nature and as residuals from human activity, and therefore a natural, ecological, and carbon-neutral source for hydrogen production. In the present work, we propose a sustainable method for hydrogen production using sunlight and cellulose as sacrificial agents during the photocatalytic water splitting process. Platinum (Pt) catalyst activates hydrogen production, and parameters such as pH of the system, cellulose concentration, and Pt loading were studied. Using different biomasses, we found that the presence of hemicellulose and xyloglucan as part of the molecular composition considerably increased the H-2 production rate from 36 mu mol L-1 in one hour for rapeseed cellulose to 167.44 mu mol L-1 for acid-treated cellulose isolated from Ulva fenestrata algae. Carboxymethylation and TEMPO-oxidation of cellulosic biomass both led to more stable suspensions with higher rates of H-2 production close to 225 mu mol L-1, which was associated with their water solubility properties. The results suggest that cellulosic biomass can be an attractive alternative as a sacrificial agent for the photocatalytic splitting of water for H-2 production.
|
|
| 13. |
- Alvarado Ávila, María Isabel, et al.
(författare)
-
Cerium Oxide on a Fluorinated Carbon-Based Electrode as a Promising Catalyst for Hypochlorite Production
- 2022
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:42, s. 37465-37475
-
Tidskriftsartikel (refereegranskat)abstract
- Sodium hypochlorite (NaOCl) is widely used as a disinfectant agent for water treatment and surface cleaning. A straightforward way to produce NaOCl is by the electrolysis of an aqueous sodium chloride (NaCl) solution. This process presents several side reactions decreasing its efficiency with hypochlorite reduction on the cathode surface being one of the main detrimental reactions. In this work, we have studied carbon-based electrodes modified with cerium oxide (CeO2), fluorine, and platinum nanoparticles as cathodes for hypochlorite production. Fluorination was carried out electrochemically; the polyol method was used to synthesize platinum nanoparticles; and the hydrothermal process was applied to form a CeO2 layer. Scanning electron microscopy, FTIR, and inductively coupled plasma (ICP) indicated the presence of cerium oxide as a film, fluorine groups on the substrate, and a load of 3.2 mg/cm2 of platinum nanoparticles and 2.7 mg/cm2 of CeO2. From electrochemical impedance spectroscopy, it was possible to demonstrate that incorporating platinum and fluorine decreases the charge transfer resistance by 16% and 28%, respectively. Linear sweep voltammetry showed a significant decrease in hypochlorite reduction when the substrate was doped with fluorine from -16.6 mA/cm2 at -0.6 V to -9.64 mA/cm2 that further reduced to -8.78 mA/cm2 with cerium oxide covered fluorinated electrodes. The performance of the cathode materials during hypochlorite production improved by 80% compared with pristine activated carbon cloth (ACC) electrodes. The improvement toward hindering NaOCl reduction is probably caused by the incorporation of a partial negative charge upon doping with fluorine.
|
|
| 14. |
- Alvarado Ávila, María Isabel, et al.
(författare)
-
Improved chlorate production with platinum nanoparticles deposited on fluorinated activated carbon cloth electrodes
- 2020
-
Ingår i: Cleaner Engineering and Technology. - : Elsevier BV. - 2666-7908. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- Sodium chlorate is one of the main oxidizing agents used in the wood industry due to their capability of use as an elemental chlorine-free (CEF) bleaching. A simple way to produce chlorates is by the electrolysis of an aqueous sodium chloride (NaCl) solution. In the present study activated carbon cloth electrodes (ACC) modified with fluorine and platinum nanoparticles (Pt–F/ACC and Pt/ACC) were used as one of the electrodes. Electrofluorination was used for fluorination of the anodes and polyol method was used for the synthesis of platinum nanoparticles. Chlorate production using a typical solution of 100 g/l of sodium chloride (NaCl) and 2 g/l sodium chromate (Na2Cr2O7) and an applied current of 0.540 A was studied. Prior to the electrolysis assays, the microstructural properties of the electrodes were characterized by scanning electron microscopy and surface modifications and bonding using infra-red (FTIR) spectroscopy. Electrochemical properties were determined using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Interaction between fluorine (F) and platinum (Pt) on the electrode leads to an improvement of the electrocatalytic properties for chlorine evolution as observed from the increase in the current efficiency from 37.5% at 78.5% after 150 min of continuous electrolysis using Pt–F/ACC anodes. The results suggest that modified activated carbon material is an attractive and economical alternative as electrodes for chlorate production.
|
|
| 15. |
- Bahari, Helma Sadat, et al.
(författare)
-
Chitosan nanocomposite coatings with enhanced corrosion inhibition effects for copper
- 2020
-
Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 162, s. 1566-1577
-
Tidskriftsartikel (refereegranskat)abstract
- A biopolymer coating on copper was prepared based on chitosan nanocomposite and its corrosion inhibition efficiency was investigated. Inclusion of silica nanoparticles substantially reduces swelling ratio of chitosan coating while enhancing its thermal stability. The corrosion resistance of chitosan-based coatings is improved by introducing 2-mercaptobenzothiazole and silica in the matrix. It is found that upon crosslinking the chitosan coatings, a higher corrosion resistance could be achieved and the highest inhibition efficiency for chitosan nanocomposite coatings is calculated as 85%. The corrosion mechanism is found closely related to mass transition and diffusion process, and also the polarization resistance contributes to the impedance. Calculated impedance using Kramers-Kronig transformation shows good agreement with experimental values, thus validating the impedance measurements. This study exhibits the enhanced efficiency of nanocomposite and potential of chitosan coatings in corrosion prevention for copper.
|
|
| 16. |
- Basumatary, Indra Bhusan, et al.
(författare)
-
Chitosan-based active coating for pineapple preservation : Evaluation of antimicrobial efficacy and shelf-life extension
- 2022
-
Ingår i: Lebensmittel-Wissenschaft + Technologie. - : Elsevier BV. - 0023-6438 .- 1096-1127. ; 168, s. 113940-
-
Tidskriftsartikel (refereegranskat)abstract
- Pineapple is a tropical fruit that is the most economically significant member of the Bromeliaceae family that are rich in flavonoids, phenolic acids, and antioxidants, which protect human cells from free radicals known to cause chronic diseases. However, short postharvest shelf-life of the fruit limits its long-distance distribution and consumption. Chitosan is a positively charged polysaccharide consisting of N-acetyl D-glucosamine and D-glucosamine units that can be used as a promising sustainable biopolymer for active coating of the fruit. In this work, chitosan-based nanocomposite formulations were prepared with added eugenol (clove essential oil) and Aloe vera gel as antioxidant, antibacterial and antifungal agents. The results showed that the incorporation of eugenol oil nanoemulsion and Aloe vera gel in the coatings enhanced their physico-chemical and functional properties including antimicrobial activities against four foodborne bacterial pathogens (Escherichia coli, Alcaligenes faecalis, Staphylococcus aureus, and Bacillus subtilis) and two fungal isolates. The developed coatings not only kept the pineapple fresh, but also preserved its quality and prolonged their shelf-life by up to three weeks during storage in ambient conditions.
|
|
| 17. |
- Basumatary, I. B., et al.
(författare)
-
Chitosan-based antimicrobial coating for improving postharvest shelf life of pineapple
- 2021
-
Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- Rapid postharvest losses and quality deteriorations in pineapple are major challenges to growers and handlers. Chitosan-based coatings on fruit surfaces have gained importance in recent years to enhance postharvest shelf life of the fruits. In this study, aloe vera gel was added as a natural antioxidant in chitosan-based composite coating containing ZnO nanoparticles. The developed formulation was applied on the surface of freshly harvested pineapple fruits. ZnO nanoparticles were used as an antimicrobial agent. Coated pineapple fruits were evaluated for weight loss, total soluble solids, titratable acidity, decay index, maturity index, and sensory attributes, including visual appearance, periodically at 5 day interval during storage. The results showed that the coating of the fruit reduced weight loss by about 5%, and also delayed ripening and oxidative decay compared to the uncoated fruit. Thus, the developed coating formulation is a promising sustainable solution to reduce postharvest losses and to extend shelf life of pineapples.
|
|
| 18. |
- Batvandi, Mohammadreza, et al.
(författare)
-
Visible-light-driven photocatalysis with Z-scheme Ag3PO4@N-GQDs@g-C3N4 nano/hetero-junctions
- 2022
-
Ingår i: Applied Physics A. - : Springer Nature. - 0947-8396 .- 1432-0630. ; 128:10
-
Tidskriftsartikel (refereegranskat)abstract
- The fabrication and improved performance of Z-scheme visible-light-driven Ag3PO4@N-GQDs@g-C3N4 ternary nano/hetero-junctions have been described in this study. Fern-like silver orthophosphate (Ag3PO4) microstructures have been modified using nitrogen-doped graphene quantum dots (N-GQDs) and then have been coated by ultrathin graphitic carbon nitride (g-C3N4) sheets via a combined technique including freeze-drying and refluxing methods. Photocatalytic studies have been conducted through visible-light photo-degradation of standard methylene blue dye in aqueous media. The Ag3PO4@N-GQDs@g-C3N4 ternary nano/hetero-junctions have exhibited the promoted photocatalytic efficiency of 97.91%, which is about 1.07 and 1.34 times higher than that of Ag3PO4@g-C3N4 binary nano/hetero-junctions (91.46%) and pristine-Ag3PO4 microstructures (85.91%), respectively. The excellent recyclability of the Ag3PO4@N-GQDs@g-C3N4 photo-catalyst has been verified in the cycle operations in which the recycling efficiency could have been maintained at 94.92% after five runs of experiments. The quenching effects of scavengers have suggested that the superoxide radicals (O-2(-center dot)) and holes (h(+)) are the predominant active species governing the photocatalytic reaction of the Ag3PO4@N-GQDs@g-C3N4 ternary composite due to a Z-scheme junction. The improved photocatalytic activity of Ag3PO4@N-GQDs@g-C3N4 nano/hetero-junctions could have been ascribed to the higher visible-light harvesting capacity, better charge carrier separation and stronger oxidation and reduction ability relevant to the indirect Z-scheme system where N-GQDs act as an efficient electron transfer media.
|
|
| 19. |
- Ciobanu, V., et al.
(författare)
-
Large-Sized Nanocrystalline Ultrathin β-Ga2 O3 Membranes Fabricated by Surface Charge Lithography
- 2022
-
Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:4
-
Tidskriftsartikel (refereegranskat)abstract
- Large-sized 2D semiconductor materials have gained significant attention for their fascinat-ing properties in various applications. In this work, we demonstrate the fabrication of nanoperforated ultrathin β-Ga2 O3 membranes of a nanoscale thickness. The technological route includes the fabrication of GaN membranes using the Surface Charge Lithography (SCL) approach and subsequent thermal treatment in air at 900◦ C in order to obtain β-Ga2 O3 membranes. The as-grown GaN membranes were discovered to be completely transformed into β-Ga2 O3, with the morphology evolving from a smooth topography to a nanoperforated surface consisting of nanograin structures. The oxidation mechanism of the membrane was investigated under different annealing conditions followed by XPS, AFM, Raman and TEM analyses.
|
|
| 20. |
- Das, Biswanath, et al.
(författare)
-
Bifunctional and regenerable molecular electrode for water electrolysis at neutral pH
- 2023
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 11:25, s. 13331-13340
-
Tidskriftsartikel (refereegranskat)abstract
- The instability of molecular electrodes under oxidative/reductive conditions and insufficient understanding of the metal oxide-based systems have slowed down the progress of H2-based fuels. Efficient regeneration of the electrode's performance after prolonged use is another bottleneck of this research. This work represents the first example of a bifunctional and electrochemically regenerable molecular electrode which can be used for the unperturbed production of H2 from water. Pyridyl linkers with flexible arms (–CH2–CH2–) on modified fluorine-doped carbon cloth (FCC) were used to anchor a highly active ruthenium electrocatalyst [RuII(mcbp)(H2O)2] (1) [mcbp2− = 2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine]. The pyridine unit of the linker replaces one of the water molecules of 1, which resulted in RuPFCC (ruthenium electrocatalyst anchored on –CH2–CH2–pyridine modified FCC), a high-performing electrode for oxygen evolution reaction [OER, overpotential of ∼215 mV] as well as hydrogen evolution reaction (HER, overpotential of ∼330 mV) at pH 7. A current density of ∼8 mA cm−2 at 2.06 V (vs. RHE) and ∼−6 mA cm−2 at −0.84 V (vs. RHE) with only 0.04 wt% loading of ruthenium was obtained. OER turnover of >7.4 × 103 at 1.81 V in 48 h and HER turnover of >3.6 × 103 at −0.79 V in 3 h were calculated. The activity of the OER anode after 48 h use could be electrochemically regenerated to ∼98% of its original activity while it serves as a HE cathode (evolving hydrogen) for 8 h. This electrode design can also be used for developing ultra-stable molecular electrodes with exciting electrochemical regeneration features, for other proton-dependent electrochemical processes.
|
|
| 21. |
- Das, Biswanath, et al.
(författare)
-
Cobalt Electrocatalyst on Fluorine Doped Carbon Cloth – a Robust and Partially Regenerable Anode for Water Oxidation
- 2022
-
Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 14:18
-
Tidskriftsartikel (refereegranskat)abstract
- The low stability of the electrocatalysts at water oxidation (WO) conditions and the use of expensive noble metals have obstructed large-scale H2 production from water. Herein, we report the electrocatalytic WO activity of a cobalt-containing, water-soluble molecular WO electrocatalyst [CoII(mcbp)(OH2)] (1) [mcbp2−=2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine] in homogeneous conditions (overpotential of 510 mV at pH 7 phosphate buffer) and after anchoring it on pyridine-modified fluorine-doped carbon cloth (PFCC). The formation of cobalt phosphate was identified only after 4 h continuous oxygen evolution in homogeneous conditions. Interestingly, a significant enhancement of the stability and WO activity (current density of 5.4 mA/cm2 at 1.75 V) was observed for 1 after anchoring onto PFCC, resulting in a turnover (TO) of >3.6×103 and average TOF of 0.05 s−1 at 1.55 V (pH 7) over 20 h. A total TO of >21×103 over 8 days was calculated. The electrode allowed regeneration of∼ 85 % of the WO activity electrochemically after 36 h of continuous oxygen evolution.
|
|
| 22. |
- Das, Bhaswati, et al.
(författare)
-
Eugenol and Aloe vera blended natural wax-based coating for preserving postharvest quality of Kaji lemon (Citrus jambhiri)
- 2024
-
Ingår i: Food Chemistry: X. - : Elsevier BV. - 2590-1575. ; 22
-
Tidskriftsartikel (refereegranskat)abstract
- Edible coatings on fruits and vegetables preserve postharvest quality by reducing water loss and lowering respiration, and metabolic activities. The primary objectives of this study were to develop composite coating formulations using natural waxes (carnauba and shellac wax), eugenol nanoemulsion, and Aloe vera gel, and assess the potential impacts of the coating formulations on the postharvest quality and shelf-life of the Kaji lemon. The results show that eugenol nanoemulsion and Aloe vera gel enhanced the physico-chemical, antimicrobial and antioxidant properties of the developed coating. Notably, the fruits coated with optimized nanocomposite of wax with eugenol and aloe vera gel inclusion (SW + CW/EuNE-20/AVG-2) showed the lowest weight loss (16.56%), while the coatings of wax with only aloe vera gel (SW + CW/AVG-2) exhibited the highest firmness (48 N), in contrast to the control fruit, which had 27.33% weight loss and 9.6 N firmness after 28 days of storage, respectively.
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
- Ebrahimzadeh, Mina, et al.
(författare)
-
Improved third-order optical nonlinearities in Ag/MoS2 Schottky-type nano/hetero-junctions?
- 2021
-
Ingår i: Optics and Laser Technology. - : Elsevier BV. - 0030-3992 .- 1879-2545. ; 140
-
Tidskriftsartikel (refereegranskat)abstract
- Molybdenum disulfide (MoS2) nanostructures have been prepared by a hydrothermal treatment and were decorated with metallic silver (Ag) using the conventional wet incipient impregnation process to form Ag/MoS2 nano/hetero-junctions. The physiochemical functionalities were characterized using X-ray diffraction, Fourier transfer infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. UV?Vis (ultraviolet?visible) spectroscopy shows an improved light absorption in visible region for Ag/MoS2 nano/hetero-junctions due to the surface plasmon resonance absorption. Photoluminescence (PL) studies suggest efficient photoexcited charge separation to occur in Ag/MoS2 nano/hetero-junctions due to an internal electric field formed across Schottky interface. The nonlinear responses of as-prepared samples to intense laser fields were examined using standard single-beam Zscan technique under a 532 nm CW second-harmonic Nd:YAG laser irradiation wherein demonstrated reverse saturable absorption behaviors and self-defocusing responses due to negative lens effects were observed. The third-order nonlinear refractive index and absorption coefficient for Ag/MoS2 nano/hetero-junctions were found to be 6.5 ? 10-7 cm2/W and 3.5 ? 10-4 cm/W, respectively, showing 1.44 and 1.5 times enhancement than in MoS2 nanostructures.
|
|
