Simple Sol-gel Method Research Articles

Improved ppb level SnO2@In2O3 sensor induced by In2O3 nanoparticles embedded on SnO2 nanoflower for superior NO2 sensing performance

The current study, accurately designed and created a two-dimensional (2D) structure of SnO2 nano-flowers and In2O3 nanoparticles using a simple hydrothermal technique and sol-gel method, respectively. On the outer surface of SnO2 nanoflowers the In2O3 nanoparticles were uniformly growing, clearly revealed by field emission scanning electron microscopic. Besides, crystal phase structure, surface area and elementals composition were characterized by XRD, BET, TEM, EDS, XPS and the gas sensing properties of In2O3@SnO2 NFs. The results exhibited that 2 wt% In2O3@SnO2 NFs sensor is highly sensitive to NO2, the response (Rg/Ra) to 30 ppm NO2 is 94.5, and at 50 ppb the response measured 0.61 at 150 °C, the response time is 32 and 51s, respectively, along with good moisture resistance. Besides along with excellent selectivity, long-term stability, and relative humidity (RH) in high-humidity environment, the 2 wt% In2O3@SnO2 NFs still maintain high response 91 at 30 ppm. More importantly, at room temperature the response was (Rg/Ra = 1.01) at detection limit 300 ppb towards NO2, which could use be for trace NO2 gas detection. The large specific surface areas of SnO2, the abundance of oxygen species adsorbed on the surface, the distinctive electron transformation between heterojunction materials, and high electron transmission channel of SnO2 and In2O3 transition layer were all considered to have a synergistic effect thatin2 contributed to excellent sensing properties of In2O3@SnO2 NFs.

Novel TiO2 nanoparticle-based sensor for xanthate quantification in mineral flotation samples

A voltammetric method for xanthate quantification was developed by fabricating a new electrode based on TiO2 nanoparticles (TiO2 NPs). The nanomaterial in the anatase phase was synthesized by a simple sol-gel method followed by a thermal treatment (9 h at 500 °C). The nanoparticles have a spheroidal morphology with an average size of 20.61 ± 6.01 nm. The band gap energy (3.7 eV) was determined by means of UV–visible spectroscopy from the absorption band at 335 nm. The TiO2 based sensor was employed as working electrode (electroactive area: 0.02248 cm2) in a cyclic voltammetry study, and a greater peak current was observed for the electrooxidation of isopropyl xanthate at pH 10 as compared to the unmodified electrode. The electrode optimization showed that the percentage of TiO2 and the amount of mineral oil in the electrode have a significant influence on the electrochemical response, with 18.4 % of TiO2 NPs, 0.74 mL of mineral oil, and 18 h of electrode rest before the first use as optimal conditions. In the polarization studies, the charge transfer reaction occurred through a lower overpotential with respect to the open circuit potential. The exchange current density was three times higher for the modified electrode. Electrochemical impedance spectroscopy indicated the detection of xanthate with lower charge transfer resistance than when the unmodified electrode was used. The electrochemical sensor allows the quantification of xanthate from 5 μmol/L to 10 mmol/L by cyclic voltammetry and the square wave technique. For the cyclic voltammetry calibration, the limits of detection and quantification were 40.6 μmol/L and 135 μmol/L, respectively. The limit of detection by square wave voltammetry was 2.4 μmol/L, and the limit of quantification was 7.9 μmol/L. The repeatability of the method showed a relative dispersion of 3.1 % at 0.51 mmol/L. The electroanalytical response of the sensor was reproducible up to 30 days. The recoveries of xanthate in real flotation samples were 91.9 % and 94.6 % for concentrations of 0.55 and 1.1 mmol/L, respectively. No statistically significant differences were found between the quantification using the sensor and the UV spectrophotometric method. Dicresyl dithiophosphate showed statistically significant interference with the xanthate oxidation signal.

SYNTHESIS OF NANO-SILICA FROM LOA KULU RICE HUSK USING THE SOL-GEL METHOD

Silica is a material that is widely found in nature and is able to withstand corrosion attacks from corrosive environments. However, this natural material must be extracted to obtain high purity silica. Simple sol-gel method is used to solve the extraction problem (nano-silica with high purity). The natural materials used in this research come from organic materials, namely rice husks from the local area (Loa Kulu area). The main objective of this experiment is studying the effect concentration of HCl for crystalline size. The synthesis of silica was carried out with the preparation of ashes, then mixed with NaOH 7M until a solution of sodium silicate was produced. Silicate sodium solution was pressed with HCl 2M to form a silica gel with pH 7, 5, and 3 then was dried to produce silica powder. Silica powder was then burned at a temperature of 1000°C to produce silica with a crystalline phase. Based on the experiment, silica powder before calcination has amorphous phase and at any pH variation, the crystallite size calculated with the Debye Scherrer approach does not show any change the crystallite size by the variation of the silica gel’s pH. In addition, silica powder calcinated at 1000°C has amorphous and cristobalite phases and showed changes in crystal size after calculated with Debye Scherrer’s approach.

Effect of clay on TiO2 embedded PMMA nanocomposite for high-performance energy storage application

Present work deals with the dielectric and electrochemical properties of PMMA/TiO2 and PMMA/TiO2@Clay nanocomposite prepared via a simple sol-gel method followed by ultrasonication. With pore diameters of 16.657 Å, ternary nanocomposites have an increased specific surface area of 28.88 m2/g. The significant dielectric properties are observed for PMMA/TiO2 and PMMA/TiO2@Clay nanocomposite with the highest dielectric constant ε′ of 3.66 × 103 and 1.45 × 103 and maximum dielectric loss ε″ of 1.7 and 1.9 at 1 kHz respectively. The PMMA/TiO2 nanocomposite exhibits the highest σac conductivity of 1.29 × 10−4 S/m and 6.85 × 10−2 S/m, whereas; the PMMA/TiO2@Clay nanocomposite demonstrates the highest σac conductivity of 1.47 × 10−4 S/m and 1.84 × 10−2 S/m at 1 kHz and 3 MHz, respectively. The manufactured device's highest specific capacitance is 364.13 F/g, which corresponds to an energy density of 129.26 Wh/kg and a power density of 2913.04 W/kg. Even after 5000 CV cycles, a 97 % capacitance retention is reported in the cyclic stability. The present work proves its virtue and competency towards superior energy storage applications.

Facile green synthesis route for new ecofriendly photo catalyst for degradation acid red 8 dye and nitrogen recovery

This study novelty is that new photo catalyst prepared from sustainability low cost precursors. Dark red color hydrogel composites have been easily prepared from gelatin biopolymer using a simple sol–gel method. Gelatin doped by cobalt chloride, and silver nanoparticles (SNPs) in the presence of traces amount of sodium dodecyl sulfate surfactant and calcium chloride. Water-insoluble Gelatin composites are thermally stable photocatalysts for the degradation of toxic anionic acid red 8 dye. Promising photodynamic activity confirmed by fluorescence emission at λmax 650 nm. Optical absorption in Vis. light enhanced photo catalytic activity. Silver nanoparticles enhanced crystallinity, and improved optical properties and porosity. Dopants by CoCl2 and silver nanoparticles increased band gap of gelatin composites from (1.82 to 1.95) indicating interfacial charge separation. Low band gaps improved photo catalytic activity. Optical band gaps (Eg) lower than 2.0 eV indicates high catalytic activity in the photo degradation acid red 8 dye using Vis. light, wavelength 650 nm. Percent removal efficiency (%Re) of the dye at 500 ppm initial concentration, pH 1, contact time 30 min., and 0.20 g L−1 dose photo catalyst reached 95%. pH not affects removal efficiency. So, gelatin composites removed AR8 dye by photodegradation mechanism rather than adsorption due to photodynamic activity. Kinetics of photodegradation followed pseudo first order kinetic with rate constant k1 5.13 × 10−2 min.−1 Good electrical conductivity and magnetic properties (effective magnetic moment (µeff 4.11 B.M) improved dye degradation into simple inorganic species. Nutrients NH4+, and NO3− degradation products recovered by using alumina silicate clay via a cation exchange mechanism.

PH dependent synthesis of ceria nanoparticles for efficient sunlight-driven photocatalysis of methyl orange containing wastewater

In this study, cerium nitrate hexahydrate was used as a precursor to create nanocrystalline ceria nanoparticles, which were then created utilizing a simple and economical sol-gel method by adjusting the pH of the reactants between 6 and 12. Under direct sun radiation, wastewater containing methyl orange (MO) was photodegraded using the produced CeO2 NPs. For recent photocatalysis experiments, the degree of crystallinity, shape, dimensions, and degree of MO photodegradation were characterized and analyzed using XRD, FTIR, SEM, and UV–Vis spectrometry. According to the results, the pH of the synthesis solutions had a significant impact on the ceria-based photocatalysis of MO. Ceria NPs synthesized at a pH of 8 demonstrated optimal photocatalytic activity. Moreover, the results showed that variation in catalyst loading, initial concentration of MO, pH of MO-wastewater as well as exposure time have significantly impacted on photocatalytic performance of optimized CeO2. The optimum percentage degradation of around 75 % of MO was achieved in 80 min exposure of sunlight. Optimized low-cost ceria NPs prepared herein may be employed for dyes containing industrial wastewater treatment throughout the year using ordinary sunlight.

Tuning the Magnetic Behavior of Zinc Ferrite via Cobalt Substitution: A Structural Analysis.

Cobalt-doped zinc ferrite is a contemporary material with significant structural and magnetic characteristics. Our study explores the magnetic properties of cobalt-substituted zinc ferrite (ZnxCo1-xFe2O4), synthesized via a simple sol-gel method. By varying the cobalt ratio from 0 to 0.5, we found that zinc substitution impacts both the magnetization and lattice parameters. FTIR analysis suggested the presence of functional groups, particularly depicting an M-O stretching band, within octahedral and tetrahedral clusters. X-ray diffraction analysis confirmed the phase purity and cubic structure. The synthesized materials exhibited an average particle size of 24-75 nm. Scanning electron microscopy revealed the morphological properties, confirming the formation of truncated octahedral particles. In order to determine the stability, mass loss (%), and thermal behavior, a thermal analysis (thermogravimetric analysis (TGA)/differential thermal analysis (DTA)) was performed. The magnetic properties of the synthesized ferrites were confirmed via a vibrating sample magnetometer (VSM). Finally, the highest saturated magnetization and lowest coercivity values were observed with higher concentrations of the cobalt dopant substituting zinc. The synthesized nanomaterials have good stability as compared to other such materials and can be used for magnetization in the near future.

Confined synthesis of edge-rich V-doped MoSe2 nanosheets on carbon black for advanced hydrogen evolution reaction

V-MoSe2 nanosheets produced by space-confined growth on carbon black with an ultrathin structure were synthesized by a simple sol–gel method and exhibited excellent catalytic activity for the hydrogen evolution reaction.

Amorphous bismuth and GO co-doped WO3 electrochromic film with fast-switching time and long-term stability.

The sol-gel process for fabricating electrochromic thin films is straightforward, offering advantages such as low cost and ease of compositional control. Herein we prepared GO-Bi-WO3 films with improved electrochromic performance using a simple sol-gel spin-coating method. The sample shows a fast-switching time (1.8 s for coloring and 1.8 s for bleaching), large optical modulation (85% at 630 nm), excellent stability (86.4% retention after 10 200 cycles), and high coloration efficiency (65.9 cm2 C-1). This work indicates the electrochromic performance of WO3-based films can be enhanced by incorporating GO, which provides an effective strategy for the rapid, safe, and efficient fabrication of electrochromic thin films.

Composite heterojunction of BiFeO3 and CdS: A photocathode for promoting efficient decomposition of water using piezoelectric photoelectrocatalysis

BiFeO3 has excellent potential as a narrow band gap semiconductor and piezoelectric material for photoelectrochemical decomposition of water (PEC) applications. However, because of its susceptibility to impurities and oxygen vacancy defects during preparation and its high complexation rate of photogenerated carriers, relevant applications are greatly limited. In this paper, BiFeO3/CdS heterojunction films were prepared on FTO conductive glass by a very simple and feasible sol-gel and chemical bath method to improve the efficiency of the photoelectrochemical decomposition of water. It was shown based on a series of PEC tests. The photocurrent density of the pure BiFeO3 thin film photocathode reached −85 μA/cm2 after giving ultrasonic stress conditions. Furthermore, the BiFeO3/CdS heterojunction photocathode achieved a photocurrent density of about −230 μA/cm2 at 0 V vs. RHE under the synergistic effect of piezoelectric polarization and the built-in electric field built in the heterostructure. In summary, semiconductor modification approaches using the construction of suitable heterojunction structures can effectively promote the separation and transfer of carriers between interfaces. The use of piezoelectric polarization and the search for appropriate energy level-matched semiconductors to construct heterojunctions can synergistically improve the efficiency of piezoelectric photocatalysis.

Synthesis of LiNi1/3Mn1/3Fe1/3O2 as an Intended Cathode Material for Li-Ion Battery

In the present work, we report the synthesis and characterization of LiNi1/3Mn1/3Fe1/3O2 as cathode material for Li-ion batteries. LiNi1/3Mn1/3Fe1/3O2 was synthesized using a very simple and low-cost sol-gel method and subsequent annealing treatment. The Structural, morphological, and electrochemical performance of the synthesized materials is investigated using X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron microscopy (FE-SEM), Cyclic voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance spectroscopy (EIS), respectively. The XRD results revealed the formation of layer structure with a pure α-NaFeO2 hexagonal phase, space group R3¯m. Moreover, these results show negligible cation mixing, which suggests well order layer structure. Raman spectrum of the synthesized sample shows structural fingerprints at 609 and 503 cm-1, which also confirms the R3¯m space group. Raman results support the XRD results. The non-uniform microsphere-like morphology with an average particle size of around 200-300 nm was revealed using FE-SEM. The electrochemical properties of the synthesized products were evaluated in rechargeable Li-ion half cells using a non-aqueous organic electrolyte (1 M LiPO4). The cyclic voltammetry shows that redox reactions occur at the surface of the electrode, which is attributed to Mn3+/Mn4+ and Fe3+/Fe4+. The EIS of LiNi1/3Mn1/3Fe1/3O2 exhibits a lower charge transfer resistance, which indicates a shorter path to move the ions. Further, the electrochemical performance of the synthesized material will be discussed in detail.

Synthesis, structural, magnetic property, and Cd(II) adsorption behavior of Ca-substituted MgFe2O4 nanomaterials in aqueous solutions.

In the present study, magnetic nanomaterials (Mg1-xCaxFe2O4, 0.0 ≤ x ≤ 0.8) were prepared via a simple sol-gel method. The samples were characterized using XRD, TEM, SEM, EDX, FTIR, BET, and VSM. The structural and magnetic properties of prepared nanomaterials (NMs) were investigated, and the adsorption capacity of Cd2+ from aqueous solution was evaluated via flame atomic absorption spectroscopy (AAS). The impact of several factors on Cd2+ adsorption such as contact time (1-60 min), pH (3-8), dose (0.003-0.03 g), and initial concentration of Cd2+ (5-60 mg L-1) has been assessed. The adsorption capacity of Cd2+ for the prepared NMs followed the pseudo-second order. Several isotherm models were analyzed, and the Langmuir model was found to be the best fit for NMs. Among as-prepared NMs, Mg0.8Ca0.2Fe2O4 (MCF2, cubic 97%, orthorhombic 3%, qe 100 mg g-1) and Mg0.2Ca0.8Fe2O4 (MCF8, cubic 18%, orthorhombic 83%, qe 90 mg g-1) samples exhibited the highest adsorption performance at conditions, viz., contact time 20 min, pH 7, NM dosage 3 mg, and ions at a concentration 60 mg l-1. Cd removal percentages were achieved 93 and 75 for MCF2 and MCF8, respectively. Overall, the prepared MCF2 and MCF8 NMs could be used as effective adsorbents to eliminate toxic Cd2+ from polluted aqueous solution.

Rare earth metals ion intercalated hydrated vanadium oxides for high-performance aqueous zinc-ion batteries

Hydrated vanadium oxide (V2O5·nH2O) is promising cathode candidates for aqueous rechargeable Zn-ion batteries (ZIBs) owing to its high theoretical specific capacity, abundant resources and environmentally friendly. However, the higher charge density of Zn2+ lead to its structural instability, cyclic degradation and sluggish Zn2+ diffusion kinetics. Herein, rare earth metal ions intercalated into the interlayer of V2O5·nH2O materials (abbreviated as RE-VOH) are successfully synthesized to expand interlayer spacing and stabilize the layered structure via a simple sol-gel method, among, the yttrium ion intercalated V2O5·nH2O (Y–VOH) exhibits a honeycomb porous microstructure and a remarkably enlarged interlayer distance (13.6 Å), which can not only increase the contact area between the electrode material and the electrolyte but also offer rapid diffusion channel for Zn2+. Meanwhile, the problem of vanadium dissolution of cathode materials is inhibited by the electrolyte additive strategy through adding suitable vanadium oxide sol to aqueous electrolyte, furthermore, the zinc anode modification strategy in electroplating process inhibits the formation of zinc dendrites. Benefitting from the synergistic effect of modification design for the ZIBs systems of cathode, electrolyte and anode, the overall electrochemical performance of Y–VOH electrode is significantly improved, delivering a large specific capacity of 337 mAh g−1 at the current density of 500 mA g−1 and excellent rate capability of 170 mAh g−1 at 10 A g−1, along with an outstanding capacity retention of 90 % over 3000 cycles. Additionally, systematical ex situ characterizations prove the (de)intercalation reversibility of Zn2+ storage mechanism for the Y–VOH cathode. This research may provide a new way for exploiting high performance vanadium-based materials for aqueous ZIBs.

An intelligent instantaneous selective method, through compacted ZnO nanoparticle pellets, based on the concept of a virtual electronic nose, for different volatile organic compounds

This paper exercises a novel procedure with virtual e-nose (VEN) systems using a single compacted nanoparticle ZnO chemical sensor. The pellets are formed by a nano-powders synthesized via a simple sol–gel method. Furthermore, in this paper task we show the transient differences in the dynamic response curves for ZnO pellet when exposed to volatile organic compounds (VOCs) namely ethanol, methanol, isopropanol, acetone and toluene. VOCs are categorized using the transient response of a single sensor at four different operating temperatures, offering diverse features that came from the reaction mechanism of the target molecule. The relevant attributes of responses were run through Ascending Hierarchical Classification integrated with Principal Component Analysis. Three clusters classified for three specific features subsets were distinguished. A new mathematical iteration of this hybrid process was performed and leads to good HAC output stability. The result is delivered automatically with three-digit sorts in a specified order after thorough implementation.

Enhancing the carbon dioxide sensing performance of LaFeO3 by Co doping

Owing to the poor oxidizing and reducing properties of carbon dioxide (CO2), there are few materials suitable for developing CO2 semiconductor gas sensors, among which LaFeO3 (LFO) has been proven to have CO2 sensing properties. To enhance the CO2 sensing performance of LFO, a Co doping strategy is proposed in this work. Specifically, the LFO and LaCo0.1Fe0.9O3 (LCFO) nanoparticles were prepared via a simple sol-gel method, and the corresponding LFO and LCFO sensors were fabricated. The test results showed that the LCFO sensor exhibited wide detection range (25–10,000 ppm CO2), fast response/recovery time (6/42 s), and higher response (6.69% to 1% CO2) than that of LFO sensor at the optimal working temperature of 220 °C (51.9% relative humidity (RH)). In addition, the LCFO sensor showed good resistance to wide humidity range of 0–86.7% RH. Finally, the reasons for the enhanced CO2 sensing performance of LCFO were analyzed combining characterization and theoretical calculation, which could mainly be attributed to the enhancement of oxygen vacancy and large adsorption energy caused by Co doping. This work provides a useful strategy to develop high-performance semiconductor CO2 gas sensor.

Electrochemical behavior of V/Ce co-doped carbon shell-coated NiO nanocomposite for alkaline OER and supercapacitor applications

Developing highly efficient, versatile, durable, and non-precious electrode materials for sustainable electrochemical energy storage and conversion technologies is still a long-term challenge in the energy sector for researchers. Herein, we developed a sustainable and bifunctional electrode, based on V/Ce co-doped NiO coated with carbon grown on Ni foam substrate through a simple and cost-effective sol-gel method. OER activity and supercapacitance characteristics have been validated by coupling contact and morphological porous features (unique core-shell) and also demonstrated satisfying electronic structural attributes for grown material. The formation of defective lattice and oxygen vacancies in NiO by co-doping along with varying oxidation states of V, Ce, and Ni was confirmed by XPS. The modified material as a supercapacitor electrode, manifested superior specific capacitance of 1719 F g−1 at 2 A g−1 current density and outstanding cycling stability performance with 98.21 % retention after 5000th cycles. This highly efficient cycling is due to abundant redox states and surface redox functionalities of carbon, providing an easy pathway to transfer ions. The redox behavior of the composite catalyst also contributes toward high conductivity and the electrochemically active surface area thus showed a small Tafel slope of 35.4 mV dec−1. The current density of 10 mA cm−2 showed a low overpotential of 238 mV. In a practical system, it also revealed significant stability for OER over 100 h of continuous electrolysis, tested by chronoamperometry. The influence of co-doping and carbon support highlights the remarkable advantages of electrochemical performance and enriches its application prospect for efficient electrolysis and storage technology.

Fenton-like degradation of methyl orange by alumina-supported Cu–Co catalysts at neutral pH: Optimization by the Taguchi method

Fenton oxidation is considered to be an effective method for removing non-biodegradable organic materials from industrial wastewater. However, several challenges need to be overcome for its utilization in industrial-scale applications. A series of alumina-supported Cu–Co samples were prepared via a simple sol–gel method, and their utility for Fenton-like degradation of methyl orange (MO) at neutral pH was assessed. In addition, various catalyst synthesis parameters, namely (Cu + Co)/Al molar ratio, Cu/Co molar ratio, water content, and treatment conditions, were optimized by the Taguchi method. The parameters were selected in three levels, and L9 from the orthogonal array design was used. The optimum synthesis parameters for the catalyst included a (Co + Cu)/Al molar ratio of 0.08, a Co/Cu molar ratio of 1/3, an H2O/Al molar ratio of 6, a calcination temperature of 400°C, and a calcination time of 8 h. Furthermore, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction were employed to characterize the physical and chemical properties of the samples. The results revealed that the optimized catalyst achieved a 94% removal efficiency of MO and a 75% removal efficiency of total organic carbon. Compared to the data reported in similar previous studies, the catalyst prepared herein demonstrated promising development potential.

A simple sol–gel method for the synthesis of Pt co-catalyzed spinel-type CuFe2O4 for hydrogen production; the role of crystallinity and band gap energy

In this investigation, spinel-type copper ferrites (CuFe2O4) at different calcination temperatures (600–900 °C) were produced using a facile citric acid-assisted sol–gel method. The crystal structure, morphology, optical, and electrical properties of the as synthesized photocatalysts were comprehensively characterized. XRD and UV–vis diffuse reflectance spectra (UV–vis (DRS)) showed that the phase structure and the band gap energy of the copper ferrite are strongly correlated to the applied calcination temperature. TEM results investigated that the copper ferrites calcined at higher temperatures presented large particle sizes and crystallized very well. In addition, the photocatalytic activity was tested for hydrogen production in the presence of methanol, with and without Pt nanoparticles as a cocatalyst. The results indicated that the CuFe2O4 annealed at 900 °C (CuF-900) has higher hydrogen production activity than photocatalysts calcined at lower temperatures in the presence and absence of Pt, which is mainly assigned to the higher crystallinity, and narrower bandgap energy. Moreover, this study explained in more detail the role of Pt nanoparticles in enhancing the photocatalytic activity of CuF-900. This work introduces a new direction of thinking for the tetragonal phase structure as an efficient photocatalyst for hydrogen production.

Ecofriendly-synthesized pro-microporous C-Co3O4 nanoparticles conjugated with controlled electropolymerization of pyrrole for high-efficient symmetric supercapacitors

High energy density and high power density supercapacitor electrode materials are prepared by a simple pseudo sol-gel method, followed by electrochemical polymerization for electrochemical energy storage. A thin graphitic carbon-film coated Co3O4 (C-Co3O4) is synthesized as an efficient energy storage material with the help of an aqueous phytochemical extract. The green-synthesized C-Co3O4 is pro-microporous with the maximum pore volume centered at 0.7 nm pore width with a distribution of >85 % pore volume with ≤4.5 nm pore width. A thin layer of conducting polypyrrole (PPy) is electropolymerized on a nickel foam/C-Co3O4 electrode (NF/C-Co3O4/PPy). Specific capacitance of NF/C-Co3O4 and NF/C-Co3O4/PPy electrodes are 320 F g−1 and 1176 F g−1, respectively, at 20 mV/s and 221 F g−1 and 695 F g−1, respectively, at 0.5 A g−1. The enhanced capacitance of NF/C-Co3O4/PPy could be ascribed to the synergistic effect between C-Co3O4 and the conducting PPy nanolayer. The energy density of the symmetric supercapacitor (SC) fabricated with NF/C-Co3O4 is 8.1 Wh kg−1 at 800 W kg−1 with a potential window of 0.8 V. The energy density of the symmetric SC fabricated with NF/C-Co3O4/PPy is enhanced ~5 times with the use of the PPy thin film and is 34.4 Wh kg−1 at 1100 W kg−1 with a potential window of 1.1 V. The capacitance retention of NF/C-Co3O4/PPy was 93.9 % over 8000 cycles while that of NF/C-Co3O4 was 79.6 % only. The symmetric SC exhibited a high power density of 35.2 kW kg−1 with an energy density of 4.2 Wh kg−1. The inexpensive green approach coupled with the promising superior capacitance characteristics made C-Co3O4/PPy nanocomposites excellent candidates for high energy density aqueous supercapacitors.

Pattern Recognition with Temperature Regulation: A Single YSZ-Based Mixed Potential Sensor Classifies Multiple Mixtures of Isoprene, n-Propanol, and Acetone.

Gas sensors integrated with machine learning algorithms have aroused keen interest in pattern recognition, which ameliorates the drawback of poor selectivity on a sensor. Among various kinds of gas sensors, the yttria-stabilized zirconia (YSZ)-based mixed potential-type sensor possesses advantages of low cost, simple structure, high sensitivity, and superior stability. However, as the number of sensors increases, the increased power consumption and more complicated integration technology may impede their extensive application. Herein, we focus on the development of a single YSZ-based mixed potential sensor from sensing material to machine learning for effective detection and discrimination of unary, binary, and ternary gas mixtures. The sensor that is sensitive to isoprene, n-propanol, and acetone is manufactured with the MgSb2O6 sensing electrode prepared by a simple sol-gel method. Unique response patterns for specific gas mixtures could be generated with temperature regulation. We chose seven algorithm models to be separately trained for discrimination. In order to realize more accurate discrimination, we further discuss the selection of suitable feature parameters and its reasons. With temperature regulation coefficients which are easily available as feature input to model, a single sensor is verified to achieve elevated accuracy rates of 95 and 99% for the discrimination of seven gases (three unary gases, three binary gas mixtures, and one ternary gas mixture) and redefined six gas mixtures. This article provides a potential new approach via a mixed potential sensor instead of a sensor array that could provide a wide application prospect in the field of electronic nose and artificial olfaction.