In2O3 Particles Research Articles

Cr as a promoter for the In2O3-catalyzed hydrogenation of CO2 to methanol

The utility of Cr as a promoter for In2O3 catalysts in the hydrogenation of CO2 to methanol is investigated. Uniform precursors to binary CrOx-In2O3 and ternary NiO-CrOx-In2O3 catalysts are prepared by flame spray pyrolysis. For the CrOx-In2O3 samples, the highest methanol rate is obtained at a Cr content of 2 mol%, exceeding the methanol rate of In2O3 by 55 %. With increasing Cr content, the CO2 conversion rate does not increase, albeit the methanol selectivity decreases. Characterization of the samples supported by density functional theory calculations provides insight into the role of Cr. At low content, Cr is mainly doped into the lattice of In2O3, which leads to more oxygen vacancy (Ov) sites. The In2O3 surface sites close to Cr-oxide clusters present on the surface are also activated towards Ov formation, offsetting the decrease in Ov due to coverage of the In2O3 surface by Cr-oxide with increasing Cr content. Cr2O3 dispersed on the surface of the In2O3 particles suppresses sintering of In2O3 under reducing conditions, which is especially evident at a Cr content above 2 mol% and higher reaction temperatures. Introducing Ni to the CrOx-In2O3 catalysts results in a higher methanol formation rate compared to CrOx-In2O3. The methanol rate increases with the Ni content with the highest activity obtained at Ni and Cr contents of 22 mol% and 8 mol%, respectively. The optimum Ni(22)-Cr(8)-In2O3 catalyst displays twice the methanol rate of a Ni(22)-In2O3 reference. Ni and Cr play different promoting roles in achieving an increased and more stable rate of methanol formation compared to In2O3: Ni promotes the hydrogenation of formate and methoxy surface intermediates to methanol, while Cr results in more Ov sites and suppresses sintering of In2O3.

Ultrafast-response H2S MEMS gas sensor based on double phase In2O3 monolayer particle film

The regulation of crystal structure plays a crucial role in gas sensing. In this work, by precisely controlling the annealing temperature, we first synthesized rhombohedral corundum-type In2O3 (h-In2O3), cubic bixbyite-type In2O3 (c-In2O3) and double phase In2O3 (c/h-In2O3). The c/h-In2O3 possesses the heterostructures of double phases, the abundant oxygen vacancies (61.1 %), and the more adsorbed oxygen (35.9 %). Subsequently, by self-assembly method, the sensors with one monolayer In2O3 particle film were successfully fabricated. The c/h-In2O3 sensor shows excellent H2S sensing performances with high response of 54.4 (50 ppm), extremely fast response time of 3.3 s and low limit of detection (LOD) of 20 ppb at 160 °C. The reasons for the ultrafast response of the sensor were unveiled through the comparison experiment of 4 layers particle film sensor and the theoretical analysis. Additionally, the outstanding sensing performance could be attributed to the abundant oxygen vacancies, the double phase heterojunction and the monolayer particle film. This work provides a new idea for designing micro-electro-mechanical system (MEMS) gas sensors with high sensitivity, extremely fast response, low power consumption and high level of integration.

Enhanced acetone detection for non-invasive diabetes monitoring by atomic layer deposited WO3 nanoparticle on hierarchical In2O3 particles

This study addressed the critical need for non-invasive monitoring of diabetes by proposing an acetone gas sensor based on hierarchical In2O3 with atomic layer deposition (ALD)-deposited WO3 nanoparticles. The sensor fabrication involved a carefully designed process, leveraging ALD to control WO3 deposition, ensuring uniform distribution, and mitigating agglomeration. The resulting composite exhibited enhanced sensitivity, making it promising for detecting acetone, a key biomarker for diabetes. Material synthesis, including hydrothermal formation of In2O3 hierarchy particles and ALD of WO3, was meticulously conducted. Comprehensive characterizations, involving SEM, TEM, EDX, XRD, XPS, and BET, validated the successful synthesis and deposition. The sensor’s response to varying acetone concentrations (50–2000 ppb) was systematically investigated, revealing a positive correlation. The In2O3/WO3–2 sensor exhibited the highest sensitivity, attributed to the catalytic properties of WO3. The proposed sensor presented a cost-effective, sensitive, and selective solution, paving the way for non-invasive diabetes monitoring.

In2O3-SnO2 Hedgehog-Like nanostructured heterojunction for acetone detection

The In2O3-SnO2 heterojunction nanostructures resembling hedgehogs were synthesized through hydrothermal method and physical stirring for acetone detection. SEM and TEM characterization showed that the composites were SnO2 nanosheets (NSs) assembled into a flower-like morphology with In2O3 particles grown in situ on the NSs. The In2O3-SnO2 sensor has excellent vapor sensitivity compared to pure SnO2. At an optimal temperature of 260 ℃, the In2O3-SnO2 sensor achieves a response value of 19.4 for acetone vapors at a concentration of 100 ppm. The composites still exhibit excellent gas-sensitized performance at low concentration (100 ppb). The improved gas-sensitized performance of In2O3-SnO2 composites is attributed to the sea urchin-like nanoflower morphology enriched with oxygen vacancies and the formation of n-n heterojunctions. To further substantiate its enhancing mechanism, the adsorption behavior of acetone molecules on the fabricated composite material was investigated through the utilization of density functional theory (DFT). This study confirms the enhanced gas sensing performance of In2O3-SnO2 heterojunction composites towards acetone and elucidates the enhancement mechanism by DFT calculations.

Interfacial Electronic Interaction in In2O3/Poly(3,4-ethylenedioxythiophene)-Modified Carbon Heterostructures for Enhanced Electroreduction of CO2 to Formate.

Formate, as an important chemical raw material, is considered to be one of the most promising products for industrialization among CO2 electroreduction reaction (CO2RR) products, but it still suffers from poor selectivity and a low formation rate at a high current density on account of the competitory hydrogen evolution reaction. Herein, the heterogeneous nanostructure was constructed by anchoring In2O3 nanoparticles on poly(3,4-ethylenedioxythiophene) (PEDOT)-modified carbon black (In2O3/PC), in which the PEDOT polymer interface layer could immobilize In2O3 nanoparticles and obtain a notable reduction in electron transfer resistance among the In2O3 particles, showing a 27% increase in the total electron transfer rate. The optimized In2O3/PC with rich heterogeneous interfaces selectively reduced CO2 to formate with a high FE of 95.4% and a current density of 251.4 mA cm-2 under -1.18 V vs RHE. Also, the formate production rate for In2O3/PC was up to 7025.1 μmol h-1 cm-2, surpassing most previously reported CO2RR catalysts. The in situ XRD results revealed that In2O3 particles were reduced to metallic indium (In) as catalytic active sites during CO2RR. DFT calculations verified that a strong interface interaction between In sites and PC induced electron transfer from In sites to PC, which could optimize the charge distribution of active sites, accelerate electron transfer, and elevate the p-band center of In sites toward the Fermi level, thereby lowering the adsorption energy of *OCHO intermediates for CO2 conversion to formate.

Efficient low-loaded ternary Pd-In2O3-Al2O3 catalysts for methanol production

Pd-In2O3 catalysts are among the most promising alternatives to Cu-ZnO-Al2O3 for synthesis of CH3OH from CO2. However, the intrinsic activity and stability of In2O3 per unit mass should be increased to reduce the content of this scarcely available element and to enhance the catalyst lifetime. Herein, we propose and demonstrate a strategy for obtaining highly dispersed Pd and In2O3 nanoparticles onto an Al2O3 matrix by a one-step coprecipitation followed by calcination and activation. The activity of this catalyst is comparable with that of a Pd-In2O3 catalyst (0.52 vs 0.55 gMeOH h−1 gcat-1 at 300 °C, 30 bar, 40,800 mL h−1 gcat-1) but the In2O3 loading decreases from 98 to 12 wt% while improving the long-term stability by threefold at 30 bar. In the new Pd-In2O3-Al2O3 system, the intrinsic activity of In2O3 is highly increased both in terms of STY normalized to In specific surface area and In2O3 mass (4.32 vs 0.56 g gMeOH h−1 gIn2O3-1 of a Pd- In2O3 catalyst operating at 300 °C, 30 bar, 40,800 mL h−1 gcat-1).The combination of ex situ and in situ catalyst characterizations during reduction provides insights into the interaction between Pd and In and with the support. The enhanced activity is likely related to the close proximity of Pd and In2O3, wherein the H2 splitting activity of Pd promotes, in combination with CO2 activation over highly dispersed In2O3 particles, facile formation of CH3OH.

Synthesis, Structural and Sensor Properties of Nanosized Mixed Oxides Based on In2O3 Particles.

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO2, SnO2, ZnO), and the type of conductivity of metal oxides (Co3O4, ZrO2) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO2-In2O3 on the structure of the resulting composites, as well as their conductive and sensor properties.

Stability of In2O3 nanoparticles in PTFE-containing gas diffusion electrodes for CO2 electroreduction to formate

Electrocatalytic conversion of CO2 to fuels and chemicals can help mitigate climate change by reuse of the greenhouse gas. Formic acid is an interesting product of electrochemical CO2 reduction, because it can serve as a liquid hydrogen carrier. Indium-based electrodes show promising activity and selectivity towards formic acid formation during CO2 electroreduction. However, the low stability of such electrodes at high current density limits their implementation in industry. Herein, we optimize a gas diffusion electrode (GDE) containing ∼6 nm In2O3 nanoparticles obtained by flame spray pyrolysis. The catalyst exhibits high initial faradaic efficiency towards formate (> 80%) at current densities up to 200 mA/cm2. In situ Raman spectroscopy reveals that the In2O3 particles rapidly reduce under reaction conditions, demonstrating that metallic indium is the active phase for CO2 reduction. Degradation mechanisms of the catalyst during 50 h at high current density were studied using XPS, in situ Raman, TEM and SEM, and elemental analysis of the electrolyte. Catalyst reduction, sintering of the active phase and dissolution of indium could be excluded as a cause of the declining FE. Adding carbon and hydrophobic PTFE particles to the catalyst in the GDE improves CO2 supply and prevents early saturation of the GDE by liquid electrolyte. The optimized GDE configuration inhibits hydrogen evolution and demonstrates increased stability during 50 h of CO2 electroreduction.

Theoretical and experimental studies on the size- and morphology-dependent thermodynamics of nanoparticle electrodes

The morphology and size of nanoparticles have a significant effect on the thermodynamics of nanoparticle electrodes due to the nanometer effect. However, the influencing mechanism and regularity of morphology and particle size on electrochemical thermodynamics of nanometer electrodes are still unclear. Herein, the universal thermodynamics equations of nanometer electrodes which consisting of nanoparticles with different morphologies and particle sizes are deduced theoretically and we discuss the influencing mechanism and regularity of morphology and size on electrochemical thermodynamics. Experimentally, we adopt a hydrothermal method to prepare nanometer In2O3 particles with different particle sizes and morphologies and make them into nanometer electrodes. The electrode potentials at different temperatures are measured by a potentiometer, the standard electrode potentials, temperature coefficients of electrode potential, reaction equilibrium constants, reaction thermodynamic properties, and reversible reaction heats are obtained for the nanometer electrode with diverse particle morphologies and sizes. The effects of particle size and morphology on these thermodynamic properties are discussed and we find that the experimental results conform to the corresponding theoretical relations. The electrochemical thermodynamics theory of nanoparticle electrodes can quantitatively describe the electrochemical thermodynamic behavior of nanometer electrodes with different morphologies and particle sizes, explain relevant experimental phenomena, and provide theoretical guidance and support reference to design, research, and apply various nanometer electrode.

Fabrication of In2O3 doped PbO2 anode and its application for electrochemical degradation of norfloxacin in aqueous solutions

To improve the electrochemical activity and stability of PbO2 electrode, In2O3 particles were doped into β-PbO2 active layer by composite electrodeposition technology. When the In2O3 concentration in electrodeposition solution was 2 mM, the In2O3-PbO2 electrode had larger specific surface area, tighter crystal structure, higher oxygen evolution potential (2.09 V vs. SCE), smaller charge transfer resistance (64.32 Ω/cm2), stronger ability to generate hydroxyl radicals (0.213 μM/min) and thereby the better electrocatalytic activity and stability. In electrochemical oxidation of norfloxacin (NOR), the NOR removal rate at the In2O3-PbO2 anode was 1.388 times faster than that at pristine PbO2 electrode. Additionally, the effects of current density, initial pH, initial NOR concentration and electrolyte concentration on NOR removal efficiency were investigated by the principle of single variable. With the increase of current density and the decrease of initial NOR concentration, the NOR removal efficiency increased significantly; the better degradation effect was obtained under pH 3 and Na2SO4 concentration of 0.2 M. Finally, the degradation mechanism of NOR was discussed and five possible degradation pathways were proposed.

Effect of In2O3 particle size on CO2 hydrogenation to lower olefins over bifunctional catalysts

A reaction-coupling strategy is often employed for CO2 hydrogenation to produce fuels and chemicals using oxide/zeolite bifunctional catalysts. Because the oxide components are responsible for CO2 activation, understanding the structural effects of these oxides is crucial, however, these effects still remain unclear. In this study, we combined In2O3, with varying particle sizes, and SAPO-34 as bifunctional catalysts for CO2 hydrogenation. The CO2 conversion and selectivity of the lower olefins increased as the average In2O3 crystallite size decreased from 29 to 19 nm; this trend mainly due to the increasing number of oxygen vacancies responsible for CO2 and H2 activation. However, In2O3 particles smaller than 19 nm are more prone to sintering than those with other sizes. The results suggest that 19 nm is the optimal size of In2O3 for CO2 hydrogenation to lower olefins and that the oxide particle size is crucial for designing catalysts with high activity, high selectivity, and high stability.

Influences of silica additive on sintering and Hall effect of novel transparent In2O3 semiconductive ceramics

Polycrystalline transparent In2O3 semiconductive ceramics are successfully fabricated by oxygen atmosphere sintering for the first time. The starting rounded In2O3 particles are obtained via pyrolyzing the nanoplate-like hydrated basic sulfate precursor prepared by a chemical precipitation route using hexamethylenetetramine as the precipitant. The silica additive dissolves into the In2O3 lattice to form an interstitial solid solution, which promotes the diffusion rate during high-temperature densification process and thus helps to achieve good optical quality for In2O3 ceramics. The created interstitial oxygen further compensates the oxygen vacancy in the ceramic body to result in a higher resistivity and lower carrier concentration / carrier mobility. The optical qualities of In2O3 ceramics are also found to have slight effects on the resistivity, carrier mobility, carrier concentration, and Hall coefficient.

Effects of In2O3 nanoparticles addition on microstructures and thermoelectric properties of Ca3Co4O9 compounds

The (x) In2O3/(1-x) Ca3Co4O9 (x = 0-15 wt%) composites were prepared using the solid reaction method followed by a spark plasma sintering process. There is no reaction occurring, and the natural c-axis grain-oriented structure is observed in all samples by XRD measurements. Scanning electron microscopy and Energy dispersive spectroscopy observations indicate that the In2O3 nanoparticles are present as the ultrafine particles/clusters secondary phase in Ca3Co4O9. Electric properties measurement shows that the electrical conductivity reduced by adding In2O3 particles, while the seebeck coefficient is virtually unaffected, which leads to the low power factor PF value of Ca3Co4O9. Significantly, however, there is an obvious recovery in the electrical conductivity of S15 sample compared to that of S5 and S10 samples, which also results in a rise again in PF of S15. This result may be of significance for further increase In2O3 secondary phase content (x > 15 wt%) to enhance the thermoelectric property of Ca3Co4O9.

Organs Distribution and Injury After Repeated Intratracheal Instillations of Nano-In₂O₃ Particles into the Lungs of Wistar Rats.

Elevated industrial production and broaden applications of indium oxide materials have increased concerns over the occupational exposure of industry workers. Respirable In₂O₃ particles have been identified in the workplaces and lung of indium-processing workers. The aim of this study was to assess the indium distribution in vivo and organs injury induced by nano-In₂O₃ particles. More than 50% of nano-In₂O₃ particles were accumulated in the lungs after 8-week exposure period and caused serious pulmonary alveolar proteinosis (PAP) and pneumonia. The migration of nano-In₂O₃ particles from lungs to the other organs was very low and dose not steadily increase the indium burden in those organs except kidney and liver. The repeated intratracheal instillations of nano-In₂O₃ particles into the lungs of Wistar rats were dose-dependent increased the concentrations of serum indium.

The effect of group IIIA oxides on the oxygen reduction reaction at cathodes for intermediate-temperature solid oxide fuel cells

This study investigates the effect of B2O3, Al2O3, Ga2O3 and In2O3, belonging to group IIIA, on the oxygen reduction reaction (ORR) at typical electrocatalysts, lanthanum strontium cobalt ferrite (LSCF) and lanthanum strontium ferrite (LSF), for intermediate temperature solid oxide fuel cells (SOFCs). Amongst these oxides, In2O3 significantly enhances the electrochemical performance by improving ORR as determined by AC impedance spectroscopy using symmetrical cells comprising samaria-doped ceria as the electrolyte. When 13.73 and 7.88 wt % In2O3 is impregnated into the porous LSCF and LSF electrodes, at 650 °C, the area specific interfacial polarization resistance (ASR) decreases from 0.41 to 0.27 Ω cm2 and from 0.99 to 0.39 Ω cm2, respectively. The distribution of relaxation time analysis suggests that In2O3 efficiently accelerates the charge transfer and oxygen incorporation processes. The chemical oxygen surface exchange coefficients are greatly increased by In2O3 deposition as demonstrated with the electrical conductivity relaxation technique. For example, at 800 °C, the deposition of 0.202 mg cm−2 In2O3 particles increases the coefficient from 4.53 × 10−5 to 2.81 × 10−4 cm s−1 and from 2.39 × 10−5 to 9.3 × 10−5 cm s−1 for LSCF and LSF, respectively.

High sensitivity and ultra-low detection limit of chlorine gas sensor based on In2O3 nanosheets by a simple template method

Chlorine (Cl2) gas sensors with outstanding gas response and ultra-low detection limit by an easy and economical fabrication are increasingly in demand in practical application. In this work, In2O3 nanosheets with excellent gas sensing properties for Cl2 have been successfully synthesized using melamine-formaldehyde (MF) sponge as the template via a simple soak-drying-calcination approach. The gas response (Rgas/Rair) of In2O3 nanosheets sensor is up to 2353.4 toward 3 ppm Cl2 at 200 °C, which is about 158 times compared with In2O3 particles (14.9). The selectivity to Cl2 reaches up to 254.3 against other interferential gases. Additionally, the sensor based on In2O3 nanosheets displays extremely low detection limit of 0.037 ppb. Such excellent gas sensing performance is primarily ascribed to the unique sheet structure and abundant oxygen vacancies which are formed during the removal of MF sponge template. Therefore, the In2O3 nanosheets sensor shows great potential in Cl2 detection.

Preparation of large In(OH)3 and In2O3 particles through a seed-mediated growth method in a microreactor

Indium hydroxide (In(OH)3) and indium oxide (In2O3) particles are typically synthesized through chemical precipitation methods. In this study, we used a seed-mediated growth method and microreactor-based synthesis process. We synthesized cubic In(OH)3 particles with a crystal size of 172 nm from an 5% (w/v) indium chloride solution. The In2O3 particles synthesized through the thermal decomposition of In(OH)3 particles featured crystals up to 90 nm in size with an average size of 73 nm, which were much larger than the 20–30 nm In2O3 particles synthesized by a traditional precipitation method. The concentrations of the seed and growth solutions were varied from 1% to 7% (w/v). The crystal size of the particles increased with the concentration of the seed and growth solutions; this tendency was the opposite to that observed for the precipitation method. Through the use of a 5% (w/v) seed solution, the flow rate of the growth solution was varied from 1 to 10mL/min, and the resulting crystal size decreased as the flow rate was increased. To understand the reasons for this trend, the growth rate of the crystals was determined at different flow rates (i.e., 1, 5, and 10mL/min). A growth model consistent with the experimental results was established, which demonstrated that slow addition of the growth solution was beneficial for preparing large indium hydroxide particles.

Preparation of In2O3@TiO2 core-shell spherical nanocomposites with the enhanced photocatalytic activity under solar light irradiation

In this study, we demonstrate In2O3@TiO2 core-shell spherical nanocomposites prepared by hydrothermal method and sol-gel coating method. The In2O3 particles show quite a uniform part icle size (∼200 nm in diameter) and smooth surface. Porous TiO2 polycrystalline is coated on the surface of In2O3 nanospheres as a shell. The thickness of the shell can be controlled by adjusting the molar rat ios of In to Ti. UV-Vis spectra indicate that the adsorption peaks of pure In2O3 and TiO2 nanospheres are located at 323 and 319 nm, respectively. The surface coating of TiO2 canmake the adsorption of nanocomposites shift to the long wavelength to ∼340 nm. The photocatalytic activities of the pure In2O3, TiO2, and the nanocomposites obtained with different molar rat ios of In to Ti were evaluated by measurement of the degradation concentration of 30 ppm methylene blue (MB). The results show that the nanocomposites show higher photocatalytic performance than the pure oxides. The ratio at 1:10 exhibits the highest reaction rate constant (0.0152 min−1), similar to other nanocomposites but higher than pure In2O3 nanospheres (0.0069 min−1) and TiO2 (0.0058 min−1). This can be attributed to the large surface and tuned band energy structure for enhanced visible light absorption and the effective charge separation at the heterojunction of In 2O3 and TiO2. These findings may benefits to the new developed core-shell material as photocatalysts with enhanced efficiency for environmental applications.

Continuous and Ultrafast Preparation of In(OH)3, InOOH, and In2O3 Series in a Microreactor for Gas Sensors

In(OH)3 and InOOH were synthesized in a high-temperature continuous flow microreactor, which was much faster than the hydrothermal synthesis in a Teflon-lined autoclave. The phase transition interval of In(OH)3 and InOOH is measured, and the effect of aging temperatures on equilibrium compositions was also theoretically calculated. A transformation from nanorods to nanocubes was observed when the aging temperatures increased. In(OH)3 and InOOH were also synthesized with Sn dopant, which was proven to be beneficial for the transformation from In(OH)3 to InOOH. The sensors based on cubic and hexagonal In2O3 particles showed a fast response (4–5 s) and recovery speed (12–15 s) to acetone vapor at the optimum operating temperature of 290 °C. The sensor based on hexagonal In2O3 showed a higher response than that based on cubic In2O3. This work provided a rapid, continuous, and high-temperature synthesis method of an In(OH)3, InOOH, and In2O3 series.

Microwave Hydrothermal Synthesis of In2O3-ZnO Nanocomposites and Their Enhanced Photoelectrochemical Properties

Indium oxide (In2O3) doped zinc oxide (ZnO) nanocomposites were successfully synthesized through a facile microwave hydrothermal method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption isotherms (BET) and UV-Vis diffuse reflectance spectroscopy. The morphology of In2O3-ZnO composites was observed to be like flowers, and the diameter of particles constituting the porous petal was about 30 nm. The photoelectrocatalytic test results showed that the photoelectrocatalytic methylene blue (MB) degradation efficiency using In2O3-ZnO nanocomposites as photocatalysts under visible light irradiation and a certain voltage could reached above 95.3% after 60 min, much higher than that of In2O3 particles and ZnO particles. The enhanced photoelectrocatalytic activity was attributed to the doping of In2O3 and applied voltage, which beneficially reduced the recombination of electrons and holes in the photoelectrocatalytic process, therefore, it promoted the production of active species (•OH and •O−2).