Assisted Sol Gel Method Research Articles

Mechanically robust and durable polyurethane-based superhydrophobic coating containing silica nanoparticles derived from hydrothermal assisted sol–gel method

In the current study, a suspension of hydrothermal assisted sol–gel synthesised superhydrophobic silica nanoparticles (h-SNPs) are sprayed over apartially cured polyurethane (PUR) surface on aluminium substrate. The surface exhibited superhydrophobic (SH) property with a water contact angle of 166 ± 2° and awater sliding angle of < 5°. X-ray diffraction study confirmed the formation of amorphous silica nanoparticles. The particle size determined by field emission scanning electron microscope is about 19–21 nm. The roughness of the coating is 3.5 µm as characterised using a surface profilometer. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy investigations indicated the presence of urethane linkages from PUR and siloxane stretching from h-SNPs. The adhesion of the coating tested with a cross-hatch cutter as per ASTM D3359 shows a rating of 5B. The coating qualified mandrel bend test conducted according to ASTM D255. No cracks are observed at the deformed areas and water drops roll off the surface, demonstrating the integrity of the coating and its superhydrophobicity. The coating exhibits high robustness as evident from sandpaper abrasion and tape peel tests. When compared to superhydrophobic polyurethane (SH PUR) coating developed using commercial silica as reported in our previous work, the developed h-SNPs coating is much more durable as confirmed by accelerated weathering test and anti-icing test. The SH coating also exhibits superhydrophobicity even after 200 h of accelerated weathering test and 16 de-icing cycles. The coating withstands 15 days of water immersion and also displays self-cleaning property.

NiFe2O4 Nanoparticles: An Efficient Catalyst for One-Pot Three Component Synthesis of Acridinediones Derivatives

A nickel ferrite nanocatalyst was synthesized in the presence of simple and cost-effective polysorbates assisted sol gel method as an effective catalyst has been successfully used for one pot multicomponent Hantzsch condensation reaction of different aromatic aldehydes, dimedone and ammonium acetate under solvent-free condition at 110 °C-120 °C. The highlights feature for the synthesis of acridinediones are the recyclability of catalyst, solvent-free reaction condition, use of inexpensive catalyst, highly efficient, facile product isolation, clean reaction, nontoxic substances and great yields in short reaction time. The recovered catalyst can run four times without loss its activity.

Rich surface oxygen vacancies SmFeO3 for acetylene gas sensor with ppb-level detection

The concentration of acetylene (C2H2) is a key parameter to monitor the status of oil-immersed transformers. When the transformer is operated at 330 kV, the transformer oil dissolving 1 ppm of C2H2 is considered as red flag. Therefore, low detection limit of C2H2 is very necessary for transformer monitoring systems. In this work, a freeze-dry assisted sol-gel method is proposed to synthesize rich surface oxygen vacancies SmFeO3. Compared to the traditional sol-gel method, the freeze-dry synthesized SmFeO3 exhibits the increased oxygen vacancies and a higher proportion of larger pores (>100 nm). The response of the sensor based on above SmFeO3 (SFO-F) to C2H2 is higher than that of the sensor based on SmFeO3 synthesized by traditionally sol-gel method (SFO-S), and the SFO-F exhibits the low detection limit of 200 ppb C2H2. In addition, the response time for 200 ppb C2H2 of the SFO-F is relatively smaller than that of the SFO-S. Moreover, the sensors exhibit a high selectivity towards C2H2 in comparison to other gases (C2H4, CH4, NO, CO, H2), and five consecutive test cycles demonstrate the high stability of the sensors. The SmFeO3 prepared through freeze-drying may provide a viable approach to enhance the performance of C2H2 sensors and presenting a fresh perspective to fabricating oxygen-rich vacancy materials.

Preparation of Na3V2(PO4)3 Cathode Materials by Hydrothermal Assisted Sol-Gel Method for Sodium -Ion Batteries

Na3V2(PO4)3 (NVP) cathode material of the sodium ion battery (1 C=117 mAh g-1) has a NASICON-type structure, which not only facilitates the rapid migration of sodium ions, but also has a small volume deformation during sodium ion de-intercalation and the main frame mechanism remains unchanged, and thus is seen as an energy storage material for a wide range of applications, but has a limited electronic conductivity due to its structure. In this paper, NVP cathode materials with finer primary particles are successfully prepared using a simple hydrothermal treatment-assisted sol-gel method. The increased pore size of the NVP materials prepared under the hydrothermal process allows for more active sites and more effective resistance to the volume deformation of sodium ions during insertion/extraction processes, effectively facilitating the diffusion of ions and electrons. The Na3V2(PO4)3 material obtained by the optimized process exhibited good crystallinity in XRD characterization, as well as superior electrochemical properties in a series of electrochemical tests. A specific capacitance of 106.3 mAh g-1 at 0.2 C is demonstrated, compared to 96.5 mAh g-1 for Na3V2(PO4)3 without hydrothermal treatment, and cycling performance is also improved with 93% capacity retention. The calculated sodium ion diffusion coefficient (DNa = 5.68 × 10-14) obtained after EIS curve fitting of the improved sample illustrates that the pore structure is beneficial to the performance of the Na3V2(PO4)3 cathode material.

Microstructural, optical, and morphological investigations of SnO2 nanomaterials grown by microwave assisted sol gel method

Tin Oxide (SnO2) nanomaterials were grown using the microwave-assisted sol–gel method at different concentrations of tin precursor (namely 0.05, 0.1, 0.2, and 0.3 M). Stannous chloride is used as a Sn precursor. Liquid ammonia was used to maintain the pH in the range of 12–13. Synthesis was carried out in an aqueous medium using a Teflon container in a microwave oven for 1 hour. Precipitate was annealed in ambient air for 600oC. Structural, optical, and morphological investigations were done. XRD reveals the growth of the tetragonal phase of SnO2. The prominent presence of (110), (101), and (211) reflections was noticed at 26.6, 33.7, and 52 two-theta values. Tin oxide is transparent in the visible region of the electromagnetic spectrum. However, several attempts have been made to decrease the visible blindness of tin oxide. The band gap is a property of nanomaterials that can tailor their application in the optoelectronic field. Band gap and crystallite size show a prominent relationship in the nano-domain. Strain was not considered while calculating crystallite size using the Scherrer formula. In this investigation, we have measured the crystallite size and other structural features such as strain, stress, deformation energy, dislocation de\ sity, etc using the W-H plot method. All modified models of the W-H method have been utilized for this measurement. A comparative and comprehensive study of structural features was carried out using the Scherrer method, the Williamson–Hall method, and all its modified models. The crystallite size measured by the Scherrer method and various models of the W-H method shows a peak at 0.2 M concentration. Crystallite size plots of various modified W-H methods show similar trends, followed by the Scherrer plot. Strain calculated by Brag’s theory as well as all modified W-H depicts similar behaviour upon changing the concentration. Globular agglomerated morphology was revealed by scanning electron microscopy (SEM). The presence of tin (Sn) and oxygen (O) was confirmed by energy dispersive x-ray spectroscopy. The band gap was obtained using the Tauc theory, which portrays variation in the range of 3.4 to 3.6 eV.

Vanadium substituted Fe, Cr co-doped high performance C/Na3V2(PO4)2F3 cathode for sodium-ion batteries

In recent years, Na3V2(PO4)2F3 (NVPF) has been considered as one of the most promising candidates for cathodes in sodium ion batteries (SIBs). However, presence of vanadium makes the material costly. Besides, its electrochemical properties are hampered due to its low electronic conductivity. Herein, carbon coated Fe, Cr co-doped Na3V2(PO4)2F3 has been synthesized using rota-tumbler assisted sol–gel method. The effects of co-doping on structure, morphology and electrochemical performances are systematically studied. It is confirmed that co-doping of Fe and Cr can enhance the electrochemical performances of NVPF. Among all, Na3V1.9Fe0.095Cr0.005(PO4)2F3 shows a high initial capacity of 119.85 mAhg−1 at 0.1C and maintains a capacity retention of 88.58 % after 500 cycles at 1C. Increase in the size of the saddle point, planes of monocapped trigonal prisms and the hexagonal cavities help in decreasing the ion diffusion activation energy, thus improving the diffusivity of the doped material. The improved electrochemical performances can be attributed to the increase in the electronic conductivity of the material. Besides, vanadium reduction in the cathode aids in manufacturing cost reduction. Our work demonstrates that carbon coated Na3V1.9Fe0.095Cr0.005(PO4)2F3 can be considered as a potential cathode candidate for practical applications in SIBs.

High performance Mn/Mg co-modified calcium-based material via EDTA chelating agent for effective solar energy storage

Calcium-based material is a very promising candidate energy storage material for next generation concentrated solar power (CSP) plants with operation temperatures above 700 °C. However, performance decay and poor solar absorption capacity limit the large utilization of calcium-based material. Here, ethylene diamine tetraacetic acid (EDTA)-assisted sol–gel method is first employed to modify CaO with magnesium (Mg) and manganese (Mn) elements. MgO and Ca2MnO4 nanoparticles are attached to the surface of CaO particles to separate grains spatially to inhibit sintering. In addition to the external separation effect, Mn elements are found to be doped successfully into CaO crystal lattice rather than simply mixed, which restrains atomic diffusion and agglomeration inside CaO and thus further inhibits sintering more efficiently. The Mg and Mn co-doped sample (Ca:Mn:Mg = 9:1:2) synthesized by EDTA demonstrates exceptional thermal stability at 800 °C. The performance decay is only 6.3 % after 100 cycles and mainly manifests in the first ten cycles (4 %). Furthermore, by combining two-step calcination to avoid agglomeration and uneven doping, we also obtain the co-doped sample (Ca:Mn:Mg = 9:1:1) with nearly no performance decay in 100 cycles. The proposed materials possess an average solar absorptance of 67 %, about 4 times that of pure calcium material. This work not only designs energy storage materials with excellent performance expected to be applied in the next generation CSP plant but also provides a lattice doping route for calcium-based material modification.

Stable cycling performance of lituium-doping Na3−xLixV2(PO4)3/C (0 ≤ x ≤ 0.4) cathode materials by Na-site manipulation strategy

Na3V2(PO4)3 (NVP) has become a hot material in the research field of sodium-ion batteries (SIBs) as a result of its unique structural advantages. Unfortunately, the poor electronic conductivity and ion diffusion ability fundamentally limit the practical development of NVP. Considering the above defects, a series of Li+ doped Na3−xLixV2(PO4)3/C cathode materials for SIBs are synthesized through hydrothermal assisted sol–gel method. The cell volume steadily decline with the raise of Li+ doping amount, which is consistent with the usual doping effect. Moreover, with the increase of lithium doping amount, Li+ preferentially occupies Na(2) site and then occupies Na(1) site. Through the first principles calculation, it is clear that the introduction of Li+ can significantly reinforce the conductivity of the material system and diminish the electron localization phenomenon. The analysis of (116) crystal plane by TEM shows that Li doping will reduce the interplanar spacing. The change of V valence during the charge–discharge process of Na2.8Li0.2V2(PO4)3/C is consistent with that of NVP by V element XANES characterization. There is no conventional phase transition phenomenon in the ex-situ XRD high-voltage charging state. The above facts indicate that lithium doping obtains a stable solid solution NVP. The electrochemical test results show that Na2.8Li0.2V2(PO4)3/C can provide an amazing reversible capacity of 116.9 mAh/g (theoretical capacity of 117 mAh/g) and capacity retention rate of 99.82 % after 500 cycles. GITT results show that Li+ can significantly increase the Na+ diffusion coefficient of the material. Such excellent electrochemical performance is attributed to the fact that the doping of Li+ activates the activity of Na+ in Na(2) site and improves the reaction efficiency.

Purple-blue luminescence and magnetic properties of visible-light active novel BiMn2O5 photocatalyst by ultrasonication assisted sol–gel method

Purple-blue luminescence and magnetic properties of visible-light active novel BiMn2O5 photocatalyst by ultrasonication assisted sol–gel method

Synthesis and Electrocatalytic Performance of TiO2 Supported on Carbon Nanoparticles Towards Positive Half-Cell Reaction of Hydrogen-1,4p-benzoquinone Flow-Battery

The Hydrogen- 1,4 p-Benzoquinone redox flow battery (H2—BQ RFB) is simple and economic to use with a cell potential of 0.714 V. Carbon-based electrodes are extensively used as electrode materials due to their comprehensive properties but possess poor hydrophilic nature and low electrochemical activity. It is essential to modify carbon-based materials before employing them in battery applications. Because of its low-cost and enhanced catalytic activity, Titanium dioxide (TiO2) is chosen to modify the carbon material. In the present work, TiO2 supported on carbon nanoparticles (TiO2@CNP) electrocatalyst was synthesized by using the ultra-sound assisted sol-gel method for the positive half-cell of H2—BQ RFB. The composition of the sol is optimized by using cyclic voltammetry (CV) analysis. Surface morphology TiO2@CNP coated on carbon paper was carried out using Scanning Electron Microscope (SEM). The TiO2 and carbon interaction bonds were identified using Fourier transform infrared spectroscopy (FTIR). The phase and crystalline nature were identified by using X-ray diffraction (XRD). The activity of the electrode was assessed by CV and Tafel analysis. The electrocatalyst was tested in H2—BQ RFB positive half-cell by galvanostatic charge-discharge and obtained energy efficiency up to 73%.

The critical role of Ga doped Cu/Al2O3 aerogels in carbon monoxide suppression during steam reforming of methanol

Steam reforming of methanol is an effective method for providing high-purity hydrogen to polymer electrolyte membrane fuel cells, however, this technology still faces the challenge of high CO selectivity. Herein, a series of Ga2O3/Cu/Al2O3 aerogels with different Ga doping (0–50 wt%) were synthesized through freeze-drying assisted sol-gel method. Experimental studies verify that 20GaCuAl exhibits the best performance, which achieves 100% methanol conversion with no CO production. It is demonstrated that Ga doping facilitates the formation of smaller Cu crystalline size, which improves the affinity of catalyst to CO, thus inhibiting CO formation. Results also indicate that the aerogel materials have larger specific surface area and porosity, which is conducive to the homogeneous distribution of the active sites, the intensified diffusion of reactant molecules, and the suppression of their sintering and agglomeration. The methanol reforming performance, especially for CO suppression capability and long-term durability, can be comprehensively promoted, attributing to the synergy of Ga doping and aerogel material fabrication. In situ DRIFTS results illustrate that SRM on Ga2O3/Cu/Al2O3 aerogel undergoes the following process: CH3OH → CH3O* → HCHO→ monodentate HCOOH→ H2 and CO2. The strong absorbed monodentate formate is to the benefit of water-gas shift reaction, thus hindering the generation of CO.

Pearl-Structure-Enhanced NASICON Cathode toward Ultrastable Sodium-Ion Batteries.

Based on the favorable ionic conductivity and structural stability, sodium superionic conductor (NASICON) materials especially utilizing multivalent redox reaction of vanadium are one of the most promising cathodes in sodium-ion batteries (SIBs). To further boost their application in large-scale energy storage production, a rational strategy is to tailor vanadium with earth-abundant and cheap elements (such as Fe, Mn), reducing the cost and toxicity of vanadium-based NASICON materials. Here, the Na3.05 V1.03 Fe0.97 (PO4 )3 (NVFP) is synthesized with highly conductive Ketjen Black (KB) by ball-milling assisted sol-gel method. The pearl-like KB branch chains encircle the NVFP (p-NVFP), the segregated particles possess promoted overall conductivity, balanced charge, and modulated crystal structure during electrochemical progress. The p-NVFP obtains significantly enhanced ion diffusion ability and low volume change (2.99%). Meanwhile, it delivers a durable cycling performance (87.7% capacity retention over 5000 cycles at 5 C) in half cells. Surprisingly, the full cells of p-NVFP reveal a remarkable capability of 84.9 mAh g-1 at 20 C with good cycling performance (capacity decay rate is 0.016% per cycle at 2 C). The structure modulation of the p-NVFP provides a rational design on the superiority of others to be put into practice.

Reversible cationic-anionic redox in disordered rocksalt cathodes enabled by fluorination-induced integrated structure design

Cation-disordered rocksalt oxides (DRX) have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity. However, their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O2/CO2 evolution, which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling. To address these issues, a micron-sized DRX cathode Li1.2Ni1/3Ti1/3W2/15O1.85F0.15 (SLNTWOF) with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol–gel method. Within this fluorination-induced integrated structure design (FISD) strategy, in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction, while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism. Attributed to the multiple modifications and size effect in the FISD strategy, the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g−1 at 0.05C (1C = 200 mA g−1), improved cycling stability of 78.5% capacity retention after 50 cycles at 0.5 C, and modified rate capability of 102.8 mA h g−1 at 2 C. This work reveals that the synergistic effects between bulk structure modification, surface regulation, and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.

Design and Implementation of Three-Layer Mesoporous Silica Coating for Tri-wavelength Broadband Antireflection by Block Copolymer Assisted Sol–Gel Method

A three-layer tri-wavelength broadband antireflective (AR) coating has been successfully fabricated on quartz substrate via a sol–gel route using acid-catalyzed silica sols. An ethylene oxide-propylene oxide-ethylene oxide triblock copolymer is used as a template to prepare ordered mesoporous SiO2 films. Assisted by Filmstar thin film design software, film thickness for each layer is optimized based on actual optical constants of the three mesoporous silica films. The three layers generate a reasonable refractive index gradient from the air, and thus the obtained AR coating possesses high transmittance of 99.24%, 99.66%, and 99.64% at 351 nm, 527 nm, and 1053 nm, respectively. The mesoporous SiO2 films with tough skeletons despite different porosity endow the coating with good abrasion-resistance, and 1H, 1H, 2H, 2H-Perfluorodecyltriethoxysilane is further used to modify the surface of the AR coating, which can improve the experimental stability of the coating. This work provides beneficial references for AR coating production of the sol–gel technique.

Preparation of ZrO2 aerogels by L-malic acid and L-tartaric acid assistant sol–gel method

Preparation of ZrO2 aerogels by L-malic acid and L-tartaric acid assistant sol–gel method

Synthesis and Characterization of Li2Mn0.8Ni0.2SiO4/Mn3O4 Nanocomposite for Photocatalytic Degradation of Reactive Blue (RB5) Dye

This study successfully synthesized Li2MnSiO4/Mn3O4 (LMS/M3) and Li2Mn0.8Ni0.2SiO4/Mn3O4 (LMNS/M3) nanocomposites in a two-step method first, by preparing Mn3O4 (M3) nanoparticles through a hydrothermal method and second, by synthesizing Li2MnSiO4 (LMS) and Li2Mn0.8Ni0.2SiO4 (LMNS) by ethylene diamine tetra-acetic assisted sol–gel method. In the last method, the two nanoparticles are mixed by hand-milling to form nanocomposites. Synthesized nanoparticles were characterized using X-ray diffraction, Fourier-transform infrared, Raman spectra, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area, pL and UV–vis spectra measurements. The nanocomposite presents a well-developed orthorhombic crystal structure with a Pmn21 space group. BET surface area measurements indicate that all the prepared materials are mesoporous. The photocatalytic activity of M3, LMS, LMNS, (LMS/M3), and (LMNS/M3) was investigated by the photocatalytic degradation of reactive blue 5 (RB5) under UV light irradiation using a homemade photoreactor. The maximum photodegradation was achieved at optimal pH 4 and photocatalyst dose 0.005 g/50 ml dye. Higher stability for dye degradation efficiency was attained for the LMS and LMNS nanomaterials and LMS/M3 and LMNS/M3 nanocomposites than M3 to photocatalytic activity. The photocatalyst is readily recoverable and shows excellent stability even after three cycles. The photocatalytic degradation for RB5 followed first-order kinetics.Graphical

Synthesis, characterization and electrochemical investigation on Nickel Manganese Oxide - Polybutylene Sebacate composite electrode of biodegradable nature for micro capacitor applications

Synthesis, characterization, surface morphology and electrochemical properties of non-stochiometric Nickel–Manganese oxide nanoparticles were carried out by urea assisted sol gel method. The Ni1-xMnxO (0.15≤ X ≤ 0.50) nanoparticle synthesized was found to be cubic and the existence of Mn3O4 and MnO2 phases were established and confirmed by X-ray Diffraction (XRD) studies. Thermo Gravimetric-Differential Thermal Analysis (TG-DTA) studies provided the calcination temperature of the xerogel at 600 °C, wherein the lattice strain and the size of the nanoparticles were determined through Williamson Hall (WH) Plot. The surface morphology characteristics of these nanoclusters were authenticated by Scanning Electron Microscope (SEM) techniques. Further, electroanalytical techniques were employed as a tool in establishing the nanocomposite as an intriguing material to act as a capacitor at enhanced efficiency compared to that of conventional capacitors. The electrochemical competence of the electrode was established through cyclic voltammogram, (CV) and Electrochemical Impedance Spectral (EIS) studies. The values of capacitance for Ni1-xMnxO, (0.15≤ X ≤ 0.5) nanoparticles varied from 7000 to 8000 mFg−1, measured at 20 mVs−1scan rate in 1.0 M Na2SO4and the temperature dependent conductance property for Ni0.85Mn0.15O electrode verified the Arrhenius Equation. The synthesis of a biodegradable polymer, Poly Butylene Sebacate (PBS) employed as conducting polymer for ultra capacitor applications is comparatively superior and definitely provides an edge over other capacitors in existence which is predominanantly attributed to its biodegradability nature. Further, the specific capacitance of PBS- Ni0.85Mn0.15O composite electrode was found to be 5180 mFg−1 which clearly illustrates that these composites are potential candidates of the type biodegradable supercapacitors that are evolving transient sources of power in the future and the biodegradability of the polymer-metal oxide composite electrode fetches more significance in terms of disposal of electronic and electrical wares.

Magneto-transport and magneto-dielectric anomalies in Co doped iron oxide thin films – Microwave assisted sol-gel route

Use of microwave (MW) energy as an alternate to high temperature treatment during material synthesis is gaining much attention as it offers the advantages of being faster and economical than other heating methods. A comprehensive study of structure, magnetization, and polarization behaviour of Cobalt (Co) doped Fe3O4 thin films, prepared by means of microwave assisted sol–gel method is performed. Co doped (0-10 wt%) sols are prepared after irradiating them at MW power of 1000 W. Phase analysis is confirmed using XRD where Fe3O4 phase persisted with Co concentrations of 0-6 wt%. Higher concentration results in the appearance of cobalt oxide phase. Magnetic and transport properties are strongly affected by the presence of Co ions. Co doped Fe3O4 films show anisotropic behaviour with high saturation magnetization obtained for 6 wt% Co doped Fe3O4 thin films, i.e. ∼ 125 emu/g. Verwey transition is observed for thin films with low dopant concentration while no sharp transition in magnetization behaviour is observed for higher dopant concentration. High frequency anomaly in dielectric analysis is observed at high frequencies for Co doped Fe3O4 thin films. Negative values of magneto-dielectric coefficient show coupling of magnetic and dielectric behaviour at room temperature.

Preparation of Li3V2(PO4)3 as cathode material for aqueous zinc ion batteries by a hydrothermal assisted sol-gel method and its properties.

To alleviate the depletion of lithium resources and improve battery capacity and rate capacity, the development of aqueous zinc-ion batteries (AZIBs) is crucial. The open channels monoclinic structure Li3V2(PO4)3 is conducive to the transfer and diffusion of guest ions, making it a promising cathode material for AZIBs. Therefore, in this study, nanoneedles and particles Li3V2(PO4)3 cathode materials for AZIBs were prepared by a hydrothermal assisted sol-gel method, and the effect of synthesized pH values was studied. XRD results show that all samples had the monoclinic structure, and the Li3V2(PO4)3 sample prepared at pH = 7 exhibits (LVP-pH7) the highest peak tips and narrowest peak widths. SEM images demonstrate that all samples have the morphology character of randomly oriented needles and irregular particles, with the LVP-pH7 sample having more needle-like particles that contribute to ion diffusion. EDS results show uniform distribution of P, V, and O elements in the LVP-pH7 sample, and no obvious aggregation phenomenon is observed. Electrochemical tests have shown that the LVP-pH7 sample exhibits excellent cycling performance (97.37% after 50 cycles at 200 mA g-1) and rate ability compared to other samples. The CV test results showed that compared with other samples, the LVP-pH7 sample had the most excellent ionic diffusion coefficient (2.44 × 10-12 cm2 s-1). Additionally, the Rct of LVP-pH7 is the lowest (319.83 Ω) according to the findings of EIS and Nyquist plot fitting, showing a decreased charge transfer resistance and raising the kinetics of the reaction.

Modulation of Structure and Optical Property of Nitrogen-Incorporated VO2 (M1) Thin Films by Polyvinyl Pyrrolidone

VO2, as a promising material for smart windows, has attracted much attention, and researchers have been continuously striving to optimize the performance of VO2-based materials. Herein, nitrogen-incorporated VO2 (M1) thin films, using a polyvinylpyrrolidone (PVP)-assisted sol-gel method followed by heat treatment in NH3 atmosphere, were synthesized, which exhibited a good solar modulation efficiency (ΔTsol) of 4.99% and modulation efficiency of 37.6% at 2000 nm (ΔT2000 nm), while their visible integrated transmittance (Tlum) ranged from 52.19% to 56.79% after the phase transition. The crystallization, microstructure, and thickness of the film could be regulated by varying PVP concentrations. XPS results showed that, in addition to the NH3 atmosphere-N doped into VO2 lattice, the pyrrolidone-N introduced N-containing groups with N-N, N-O, or N-H bonds into the vicinity of the surface or void of the film in the form of molecular adsorption or atom (N, O, and H) filling. According to the Tauc plot, the estimated bandgap of N-incorporated VO2 thin films related to metal-to-insulator transition (Eg1) was 0.16-0.26 eV, while that associated with the visible transparency (Eg2) was 1.31-1.45 eV. The calculated Eg1 and Eg2 from the first-principles theory were 0.1-0.5 eV and 1.4-1.6 eV, respectively. The Tauc plot estimation and theoretical calculations suggested that the combined effect of N-doping and N-adsorption with the extra atom (H, N, and O) decreased the critical temperature (τc) due to the reduction in Eg1.