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1.
Mater Horiz ; 2024 Jun 19.
Artículo en Inglés | MEDLINE | ID: mdl-38894689

RESUMEN

A facile reduction and doping process is employed with the supercritical ethanol drying method to form RuNi alloy aerogels. The optimized heterostructure comprising RuNi metal, RuO2, and NiO phases is synthesized through partial oxidation. When applied to the surface of Ni foam, the multiphase aerogels form a morphology of highly porous 0D colloidal aerogel networks on the surface. RuNi alloy-Ni foam oxidized at 350 °C (RuNi-350@NF) has an overpotential of 89 and 61 mV in 1 M KOH and 0.5 M H2SO4 media at 50 mA cm-2, as well as satisfactory long-term stability. Additionally, the Tafel slopes in alkaline and acidic media are found to be 34 and 30.9 mV dec-1, respectively. Furthermore, it exhibits long-term stability (35 h) in alkaline and acidic media at high current densities of 50 mA cm-2, respectively. This study presents a novel strategy for developing exceptionally efficient and free-standing 3D porous aerogel electrocatalysts with potential applications in hydrogen production.

2.
Gels ; 10(6)2024 Jun 02.
Artículo en Inglés | MEDLINE | ID: mdl-38920927

RESUMEN

Due to their high surface area and low weight, silica aerogels are ideally suited for several uses, including drug delivery, catalysis, and insulation. Oil-water-oil (OWO) double emulsion is a simple and regulated technique for encasing a volatile oil phase in a silica shell to produce hollow silica (SiO2) aerogel particles by using hydrophilic and hydrophobic emulsifiers. In this study, the oil-water-oil (OWO) double emulsion method was implemented to synthesize surface-modified hollow silica (SiO2) aerogel particles in a facile and effective way. This investigation mainly focused on the influence of the N-hexane-to-water glass (OW) ratio (r) in the first emulsion, silica (water glass) content concentration (x), and surfactant concentration (s) variations. Furthermore, surface modification techniques were utilized to customize the aerogel's characteristics. The X-ray diffraction (XRD) patterns showed no imprints of impurities except SiO2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images highlight the hollow microstructure of silica particles. Zeta potential was used to determine particle size analysis of hollow silica aerogel particles. The oil-water-oil (OWO) double emulsion approach was successfully employed to synthesize surface-modified hollow silica (SiO2) aerogel particles, providing precise control over the particle characteristics. By the influence of the optimization condition, this approach improves the aerogel's potential applications in drug delivery, catalysis, and insulation by enabling surface modifications.

3.
J Colloid Interface Sci ; 666: 101-117, 2024 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-38588623

RESUMEN

Electrode materials must be rationally designed with morphologies and electroactive sites manipulated through cations' synergy in bimetal compounds in order to maximize the performance of energy storage devices. Therefore, the present study emphasizes binder-free scalable preparation of cobalt nickel vanadate (CNV) thin films by a facile successive ionic layer adsorption and reaction (SILAR) approach with specific cations (Co:Ni) alternation. Increasing the Ni cation content in the CNV notably transforms its microflower structure comprising nanoflakes (252 nm) into nanoparticles (74 nm). An optimized S-CNV5 thin film cathode with Co:Ni molar ratio of âˆ¼ 0.4:0.6 and a high specific surface area of 340 m2 g-1, provided the excellent specific capacitance (Csp) and capacity (Csc) of 1382 F g-1 and 691 C g-1, respectively at 1 A g-1 current density. A hybrid aqueous supercapacitor (HASc) device with positive and negative electrodes comprising optimized CNV and reduced graphene oxide (rGO), respectively, in a 1 M KOH electrolyte delivered a Csp of 133 F g-1 and a specific energy (SE) of 53 Wh kg-1 at a specific power (SP) of 2261 kW kg-1. Additionally, a fabricated hybrid solid-state supercapacitor (HSSc) device with the same electrodes applying PVA-KOH gel electrolyte displayed a Csp of 119 F g-1, and SE of 46 Wh kg-1 at SP of 1184 W kg-1. This boosted electrochemical activity is due to the synergetic effects of Ni and Co species in the CNV thin film electrodes, emphasizing the potential of CNV electrodes as cathodes in hybrid energy storage devices.

4.
J Colloid Interface Sci ; 666: 424-433, 2024 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-38608637

RESUMEN

High-nickel cobalt-free layered cathode is regarded as a highly potential cathode material for the next generation lithium ion batteries (LIBs) because of its high energy density, low cost and environmentally benign. However, the poor cycle performance caused by its intrinsic unstable structure and chemo-mechanical instability frustrates its practical applications. Herein, we have developed a new core-shell high-nickel cobalt-free layered LiNi0.95Mg0.02Al0.03O2@Li2ZrO3 (LZO-NMA9523) cathode for high-performance LIBs. The Li2ZrO3 coating layer firstly helps to suppress and reduce the degree of Li+/Ni2+ cation mixing during the material preparation process. In addition, the Li2ZrO3 coating layer can not only accommodate the volume variations and enhance the electricity of the active materials, but also effectively inhibit the harmful irreversible phase transition during the charging/discharging process, thus greatly stabilizing the structure of the high-nickel cobalt-free cathode. As an advanced cathode for LIBs, the LZO-NMA9523 exhibits an excellent reversible capacity of 146.9 mAh g-1 after 100 cycles at 0.5 C with capacity retention of about 80%. This study provides a possible high-nickel cobalt-free layered cathode material for the next generation LIBs.

5.
Adv Mater ; : e2307772, 2023 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-37916304

RESUMEN

In recent decades, aerogels have attracted tremendous attention in academia and industry as a class of lightweight and porous multifunctional nanomaterial. Despite their wide application range, the low mechanical durability hinders their processing and handling, particularly in applications requiring complex physical structures. "Mechanically strengthened aerogels" have emerged as a potential solution to address this drawback. Since the first report on aerogels in 1931, various modified synthesis processes have been introduced in the last few decades to enhance the aerogel mechanical strength, further advancing their multifunctional scope. This review summarizes the state-of-the-art developments of mechanically strengthened aerogels through multicompositional and multidimensional approaches. Furthermore, new trends and future directions for as prevailed commercialization of aerogels as plastic materials are discussed.

6.
Materials (Basel) ; 16(22)2023 Nov 19.
Artículo en Inglés | MEDLINE | ID: mdl-38005161

RESUMEN

The layered fibers of carbon-fiber-reinforced polymer (CFRP) composites exhibit low thermal conductivity (TC) throughout their thickness due to the poor TC of the polymeric resin. Improved heat transmission inside the hydrogen storage tank during the filling process can reduce further compression work, and improved heat insulation can minimize energy loss. Therefore, it is crucial to understand the thermal properties of composites. This paper reports the thermal behavior of plain-woven CFRP composite using simulation at the micro-, meso-, and macro-scales. The TC was predicted numerically and compared to experimental findings and analytical models. Good results were found. Using the approach of multi-scale modeling, a parametric study was carried out to analyze in depth the influence of certain variables on thermal properties. The study revealed that both fiber volume fraction and temperature significantly influenced the TC of the composite, with the interphase fiber/matrix thickness following closely in terms of impact. The matrix porosity was found to have a relatively slighter impact, particularly within the porosity range of 5 to 15%.

7.
ACS Appl Mater Interfaces ; 15(41): 48485-48494, 2023 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-37792023

RESUMEN

Biomass-derived value-added materials such as levulinic acid (LA) are favorable natural resources for producing ester-based biolubricants owing to their biodegradability, nontoxicity, and excellent metal-adhering properties. However, highly active catalysts must be developed to carry out efficient esterification of LA with aliphatic alcohols, especially long-chain aliphatic alcohols. In this study, we developed a novel porous covalent organic polymer catalyst (BPOP-SO3H) with dual acid sites, phosphate and sulfonic acid sites, for the esterification of LA. The prepared BPOP-SO3H catalyst was verified using various surface analysis techniques. BPOP-SO3H exhibited 98% LA conversion with n-butanol and 99% selectivity for butyl levulinate ester within 30 min, which is superior to that of most reported catalysts. BPOP-SO3H also showed high LA conversion and ester selectivity when other aliphatic alcohols were used. Moreover, BPOP-SO3H showed good recyclability for five consecutive cycles. We believe that incorporating a high density of acid sites into a porous polymer with a large surface area and hierarchical pores is a promising approach for developing heterogeneous acid catalysts for the production of alkyl levulinate esters from LA.

8.
Environ Res ; 239(Pt 2): 117409, 2023 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-37838191

RESUMEN

The lack of crystallinity of the aerogel materials has limited their significance which otherwise have found huge potential in wide variety of applications. In current work, we have developed TiO2 aerogels by solid-state gelation method using commercially available P25 and ST-01 (commercial Ishihara TiO2 Powder). The lack of crystallinity in the aerogel framework was resolved via utilizing crystalline TiO2 nanoparticles and the phase transformation was assessed as a function of phase composition. Via controlled solid-state gelation, surface area retention of 88.7% was achieved whereas the rutile-to-anatase weight fraction (WR) was considerably enhanced to 0.50. Interestingly, the phase transformation occurred only in P25, which suggests the mixed phase (anatase + rutile) composition as prerequisite for successful phase transformation. Favorably, TiO2 aerogels imbibe high degree of oxygen vacancies (Vo) responsible for photocatalytic applications. Interestingly, Vo induction is higher for the TiO2 with anatase phase composition (ST-01) followed by the sample with mixed phase composition (P25). The developed TiO2 aerogel photocatalysts were employed to dye degradation of Rhodamine B (RhB) and Methylene Blue (MB). The samples attained 94.8% and 96.8% degradation efficiency within 15 min for RhB and MB with nearly 2-fold improvement in the photocatalytic efficiency compared to parent P25 TiO2 respectively.


Asunto(s)
Nanopartículas , Titanio , Catálisis , Titanio/química , Nanopartículas/química , Azul de Metileno/química
9.
Gels ; 9(8)2023 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-37623106

RESUMEN

Silica aerogels and their derivatives have outstanding thermal properties with exceptional values in the thermal insulation industry. However, their brittle nature restricts their large-scale commercialization. Thus, enhancing their mechanical strength without affecting their thermal insulating properties is essential. Therefore, for the first time, highly thermally stable poly(acrylamide-co-acrylic acid) partial sodium salt is used as a reinforcing polymer to synthesize hybrid P(AAm-CO-AAc)-silica aerogels via epoxy ring-opening polymerization in the present study. Functional groups in P(AAm-CO-AAc) partial sodium salts, such as CONH2 and COOH, acted as nucleophiles for the epoxy ring-opening reaction with (3-glycidyloxypropyl)trimethoxysilane, which resulted in a seven-fold enhancement in mechanical strength compared to that of pristine silica aerogel while maintaining thermal conductivity at less than 30.6 mW/mK and porosity of more than 93.68%. Moreover, the hybrid P(AAm-CO-AAc)-silica aerogel demonstrated improved thermal stability up to 343 °C, owing to the synergetic effect between the P(AAm-CO-AAc) and the silica aerogel, corresponding to the thermal stability and strong covalent bonding among them. These excellent results illustrate that this new synthetic approach for producing hybrid P(AAm-CO-AAc)-silica aerogels is useful for enhancing the mechanical strength of pristine silica aerogel without impairing its thermal insulating property and shows potential as an industrial heat insulation material.

10.
Chemosphere ; 338: 139503, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37453522

RESUMEN

Sulfur dioxide (SO2) gas at trace levels challenges the consumption of fuel gases and cleaning of flue gases originating from diverse anthropogenic sources. We have demonstrated Zn-Al layered double hydroxide (LDH) and layered double oxide (LDO) as low-cost and effective adsorbents in removing lowly concentrated SO2 gas at room temperature. Water in the adsorbent bed significantly improved the performance, where the maximum adsorption capacity of 38.0 mg g-1 was achieved for LDO. Based on the spectroscopic findings, the adsorbed gas molecules were oxidized to surface-bound sulfate/bisulfate species, showing complete mineralization of SO2 molecules. By employing an inexpensive NaOH-H2O2 solution-based regeneration strategy, we successfully regenerated the spent LDO, significantly restoring its gas uptake capacity. The regenerated oxide exhibited an increased gas uptake capacity ranging from 38.0 to 98.5 mg g-1, highlighting the practicality and economic feasibility of our approach. LDH/LDO materials are promising regenerable adsorbents for removing low concentrations of SO2 gas in ambient conditions.


Asunto(s)
Aluminio , Dióxido de Azufre , Dióxido de Azufre/química , Aluminio/química , Óxidos , Hidróxido de Aluminio , Zinc , Temperatura , Peróxido de Hidrógeno , Hidróxidos , Ácidos , Adsorción
11.
Nanomaterials (Basel) ; 13(9)2023 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-37177045

RESUMEN

Aerogels are highly porous materials with fascinating properties prepared using sol-gel chemistry. Due to their unique physical and chemical properties, aerogels are recognized as potential candidates for diverse applications, including thermal insulation, sensor, environmental remediation, etc. Despite these applications, aerogels are not routinely found in our daily life because they are fragile and have highly limited scale-up productions. It remains extremely challenging to improve the mechanical properties of aerogels without adversely affecting their other properties. To boost the practical applications, it is necessary to develop efficient, low-cost methods to produce aerogels in a sustainable way. This comprehensive review surveys the progress in the development of aerogels and their classification based on the chemical composition of the network. Recent achievements in organic, inorganic, and hybrid materials and their outstanding physical properties are discussed. The major focus of this review lies in approaches that allow tailoring of aerogel properties to meet application-driven requirements. We begin with a brief discussion of the fundamental issues in silica aerogels and then proceed to provide an overview of the synthesis of organic and hybrid aerogels from various precursors. Organic aerogels show promising results with excellent mechanical strength, but there are still several issues that need further exploration. Finally, growing points and perspectives of the aerogel field are summarized.

12.
ACS Omega ; 8(2): 2183-2196, 2023 Jan 17.
Artículo en Inglés | MEDLINE | ID: mdl-36687033

RESUMEN

The binary as well as ternary nanocomposites of the square-facet nanobar Co-MOF-derived Co3O4@Co/N-CNTs (N-CNTs: nitrogen-doped carbon nanotubes) with Ag NPs and rGO have been synthesized via an easy wet chemical route, and their supercapacitor behavior was then studied. At a controlled pH of the precursor solution, square-facet nanobars of Co-MOF were first synthesized by the solvothermal method and then pyrolyzed under a controlled nitrogen atmosphere to get a core-shell system of Co3O4@Co/N-CNTs. In the second step, different compositions of Co3O4@Co/N-CNT core-shell structures were formed by an ex-situ method with Ag NPs and rGO moieties. Among several bare, binary, and ternary compositions tested in 6 M aqueous KOH electrolyte, a ternary nanocomposite having a 7.0:1.5:1.5 stoichiometric ratio of Co3O4@Co/N-CNT, Ag NPs, and rGO, respectively, reported the highest specific capacitance (3393.8 F g-1 at 5 mV s-1). The optimized nanocomposite showed the energy density, power density, and Coulombic efficiency of 74.1 W h.kg-1, 443.7 W.kg-1, and 101.3%, respectively, with excellent electrochemical stability. After testing an asymmetrical supercapacitor with a Co3O4@Co/N-CNT/Ag NPs/rGO/nickel foam cathode and an activated carbon/nickel foam anode, it showed 4.9 W h.kg-1 of energy density and 5000.0 W.kg-1 of power density.

13.
ACS Nano ; 16(1): 1625-1638, 2022 Jan 25.
Artículo en Inglés | MEDLINE | ID: mdl-36350111

RESUMEN

Dispersing the minuscule mass loading without hampering the high catalytic activity and long-term stability of a noble metal catalyst results in its ultimate efficacy for the electrochemical hydrogen evolution reaction (HER). Despite being the most efficient HER catalyst, the use of Pt is curtailed due to its scarcity and tendency to leach out in the harsh electrochemical reaction environment. In this study, we combined F-doped tin(IV) oxide (F-SnO2) aerogel with Pt catalyst to prevent metallic corrosion and to achieve abundant Pt active sites (approximately 5 nm clusters) with large specific surface area (321 cm2·g-1). With nanoscopic Pt loading inside the SnO2 aerogel matrix, the as-synthesized hybrid F-SnO2@Pt possesses a large specific surface area and high porosity and, thus, exhibits efficient experimental and intrinsic HER activity (a low overpotential of 42 mV at 10 mA·cm-2 in 0.5 M sulfuric acid), a 22-times larger turnover frequency (11.2 H2·s-1) than that of Pt/C at 50 mV, and excellent robustness over 10,000 cyclic voltammetry cycles. The existing metal support interaction and strong intermolecular forces between Pt and F-SnO2 account for the catalytic superiority and persistence against corrosion of F-SnO2@Pt compared to commercially used Pt/C. Density functional theory analysis suggests that hybridization between the Pt and F-SnO2 orbitals enhances intermediate hydrogen atom (H*) adsorption at their interface, which improves the reaction kinetics.

14.
Environ Technol ; : 1-14, 2022 Oct 30.
Artículo en Inglés | MEDLINE | ID: mdl-36263910

RESUMEN

In this study, inverse spinel cubic ferrites MFe2O4 (M = Fe2+, and Co2+) have been fabricated for the high-capacity adsorptive removal of Hg(II) ions. The PXRD analysis confirmed ferrites with the presence of residual NaCl. The surface area of Fe3O4 (Fe-F) and CoFe2O4 (Co-F) material was 69.1 and 45.2 m2 g-1, respectively. The Co-F and Fe-F showed the maximum Hg(II) adsorption capacity of 459 and 436 mg g-1 at pH 6. The kinetic and isotherms models suggested a spontaneous adsorption process involving chemical forces over the ferrite adsorbents. The Hg(II) adsorption process, probed by X-ray photoelectron spectroscopy (XPS), confirmed the interaction of Hg(II) ions with the surface hydroxyl groups via a complexation mechanism instead of proton exchange at pH 6 with the involvement of chloride ions. Thus, this study demonstrates a viable and cost-effective solution for the efficient remediation of Hg ions from wastewater using non-functionalized ferrite adsorbents. This study also systematically investigates the kinetics and isotherm mechanism of Hg(II) adsorption onto ferrites and reports one of the highest Hg(II) adsorption capacities among other ferrite-based adsorbents.

15.
ACS Appl Mater Interfaces ; 14(39): 44561-44571, 2022 Oct 05.
Artículo en Inglés | MEDLINE | ID: mdl-36164762

RESUMEN

To implement artificial neural networks (ANNs) based on memristor devices, it is essential to secure the linearity and symmetry in weight update characteristics of the memristor, and reliability in the cycle-to-cycle and device-to-device variations. This study experimentally demonstrated and compared the filamentary and interface-type resistive switching (RS) behaviors of tantalum oxide (Ta2O5 and TaO2)-based devices grown by atomic layer deposition (ALD) to propose a suitable RS type in terms of reliability and weight update characteristics. Although Ta2O5 is a strong candidate for memristor, the filament-type RS behavior of Ta2O5 does not fit well with ANNs demanding analog memory characteristics. Therefore, this study newly designed an interface-type TaO2 memristor and compared it to a filament type of Ta2O5 memristor to secure the weight update characteristics and reliability. The TaO2-based interface-type memristor exhibited gradual RS characteristics and area dependency in both high- and low-resistance states. In addition, compared to the filamentary memristor, the RS behaviors of the TaO2-based interface-type device exhibited higher suitability for the neuromorphic, symmetric, and linear long-term potentiation (LTP) and long-term depression (LTD). These findings suggest better types of memristors for implementing ionic memristor-based ANNs among the two types of RS mechanisms.

16.
Surf Interfaces ; 34: 102349, 2022 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-36160476

RESUMEN

Following the global corona virus pandemic and environmental contamination caused by chemical plastic packaging, awareness of the need for environmentally friendly biofilms and antibacterial coatings is increasing. In this study, a biodegradable hybrid film, comprising of green-synthesized zinc oxide nanoparticles (ZnO NPs) with a chitosan (CS) matrix, was fabricated using a simple casting procedure. The ZnO NPs were synthesized using wild Mentha pulegium extract, and the synthesized NPs and films were characterized using different approaches. The structural, morphological, mechanical, antibacterial, and optical properties, as well as the hydrophilicity, of the prepared samples were investigated using various techniques. Gas chromatography-mass spectrometry measurements revealed the presence of phenolic compounds in the M. pulegium extract. In addition, a strong coordination connection between Zn2+ and the chitosan matrix was confirmed, which resulted in a good dispersion of ZnO in the chitosan film. The surface of the composite films was transparent, smooth, and uniform, and the flexible bio-based hybrid films exhibited significant antibacterial and antioxidant characteristics, strong visible emission in the 480 nm region, and UV-blocking properties. The ZnO/CS films displayed a potential to extend the shelf life of fruits by up to eight days when stored at 23°C, and also acted as an acceptable barrier against oxygen and water. The biodegradable ZnO/CS film is expected to keep fruit fresher than general chemical plastic films and be used for the packaging of active ingredients.

17.
ACS Appl Mater Interfaces ; 14(15): 17682-17690, 2022 Apr 20.
Artículo en Inglés | MEDLINE | ID: mdl-35394742

RESUMEN

The present study pioneered an oxygen migration-driven metal to insulator transition Mott memory, a new type of nonvolatile memory using lanthanum titanium oxide (LTO). We first show the reset first bipolar property without an initial electroforming process in LTO. We used oxygen-deficient ZnO as an interlayer between LTO and a W electrode to clarify whether oxygen migration activates LTO as the Mott transition. ZnO oxygen deficiency provides oxygen ion migration paths as well as a reservoir, facilitating oxygen migration from LTO to the W electrode. Thus, including the ZnO interlayer improved oxygen migration between LTO and the W electrode, achieving a 10-fold increased on/off current ratio. The current research contributes to a better understanding of valence change Mott memory by exploring the LTO resistive switching mechanism and ZnO interlayer influences on the oxygen migration process.

18.
J Hazard Mater ; 432: 128734, 2022 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-35334269

RESUMEN

2D-2D lattice engineering route is used to synthesize intimately coupled nanohybrids of layered double hydroxide (LDH) and potassium hexaniobate. The 2D-2D lattice engineering route is based on the electrostatically derived self-assembly of delaminated zinc-chromium-layered double hydroxide (ZC-LDH) nanosheets and potassium hexaniobate (HNb) nanosheets (ZCNb nanohybrids). The 2D-2D lattice-engineered ZCNb nanohybrids display expanded surface area, mesoporous anchored nanosheets network morphology, and intimate coupling between nanosheets. The 2D-2D lattice engineered ZCNb nanohybrids are used for the low temperature operated gas sensor. The ZCNb nanohybrids display outstanding selectivity for the SO2, with the high response of 61.5% compared to pristine ZC-LDH (28.08%) and potassium niobate (8%) at 150 °C. Moreover, ZCNb sensors demonstrate superior response and recovery periods of 6 and 167 s at 150 °C, respectively. This result underscores the exceptional functionality of the ZCNb nanohybrids as efficient SO2 sensors. Moreover, these findings vividly demonstrate that the 2D-2D lattice-engineered ZCNb nanohybrids are quite effective not only in improving the gas sensor activity but also in developing of new type of intimately coupled mesoporous LDH-metal-oxide based hybrid materials.

19.
ACS Appl Mater Interfaces ; 14(4): 5673-5681, 2022 Feb 02.
Artículo en Inglés | MEDLINE | ID: mdl-35043617

RESUMEN

Emerging energy-efficient neuromorphic circuits are based on hardware implementation of artificial neural networks (ANNs) that employ the biomimetic functions of memristors. Specifically, crossbar array memristive architectures are able to perform ANN vector-matrix multiplication more efficiently than conventional CMOS hardware. Memristors with specific characteristics, such as ohmic behavior in all resistance states in addition to symmetric and linear long-term potentiation/depression (LTP/LTD), are required in order to fully realize these benefits. Here, we demonstrate a Li-based composite memristor (LCM) that achieves these objectives. The LCM consists of three phases: Li-doped TiO2 as a Li reservoir, Li4Ti5O12 as the insulating phase, and Li7Ti5O12 as the metallic phase, where resistive switching correlates with the change in the relative fraction of the metallic and insulating phases. The LCM exhibits a symmetric and gradual resistive switching behavior for both set and reset operations during a full bias sweep cycle. This symmetric and linear weight update is uniquely enabled by the symmetric bidirectional migration of Li ions, which leads to gradual changes in the relative fraction of the metallic phase in the film. The optimized LCM in ANN simulation showed that exceptionally high accuracy in image classification is realized in fewer training steps compared to the nonlinear behavior of conventional memristors.

20.
Materials (Basel) ; 14(21)2021 Oct 21.
Artículo en Inglés | MEDLINE | ID: mdl-34771806

RESUMEN

The one-step hydrothermal method was used to synthesize Sn-doped TiO2 (Sn-TiO2) thin films, in which the variation in Sn content ranged from 0 to 7-wt % and, further, its influence on the performance of a dye-sensitized solar cell (DSSC) photoanode was studied. The deposited samples were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the existence of the rutile phase of the synthesized samples with crystallite size ranges in between 20.1 to 22.3 nm. In addition, the bare and Sn-TiO2 thin films showed nanorod morphology. A reduction in the optical band gap from 2.78 to 2.62 eV was observed with increasing Sn content. The X-ray photoelectron spectroscopy (XPS) analysis confirmed Sn4+ was successfully replaced at the Ti4+ site. The 3-wt % Sn-TiO2 based DSSC showed the optimum efficiency of 4.01%, which was superior to 0.87% of bare and other doping concentrations of Sn-TiO2 based DSSCs. The present work reflects Sn-TiO2 as an advancing material with excellent capabilities, which can be used in photovoltaic energy conversion devices.

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