In2O3 Phase Research Articles

Activity of bimetallic PdIn/CeO2 catalysts tuned by thermal reduction for improving methanol synthesis via CO2 hydrogenation

AbstractSynergistic Pd–In2O3 catalysts are promising candidates for producing methanol via CO2 hydrogenation, and the metal phases in them can be tuned by thermal reduction treatment affecting the catalytic activity significantly. This work presents a comprehensive investigation to gain an insight into the effect of thermal reduction temperature on the variation and interaction of Pd and In2O3 phases supported on CeO2 (viz., PdIn/CeO2) and their correlations with CO2 hydrogenation toward methanol synthesis. The findings show that Pd/In‐rich PdIn alloys and In2O3 with relatively strong interaction are key phases (by reducing the PdIn/CeO2 at 300°C) for promoting methanol formation, leading to a high selectivity to methanol at 78.9% and space–time yield (STY) of 3.6 gCH3OH gPdIn−1 h−1. A further increase in reduction temperature (from 300 to 500°C) promoted the formation of homogenized PdIn intermetallic alloys with significantly poor ability for H2 dissociation and CO2 activation, and hence poor methanol yield.

Grain refinement for indium zinc oxide ceramic targets by praseodymium doped induced blocked boundary migration

How to refine the grain has been a difficult problem in the preparation of high-performance ceramic targets. In this work, the doping-induced grain refinement strategy was proposed, indium zinc oxide doped with different concentrations of Pr (Pr-doped IZO, PrIZO) targets were obtained by optimizing the sintering time and holding temperature. Effects of Pr doping content on the density, phase microevolution, grain size and resistivity during the densification process as well as the kinetics of the grain growth and the mechanism of grain refinement of PrIZO targets were investigated in detail. The results demonstrated that PrIZO targets with the atomic ratios of Pr:In:Zn=0.01-0.03:1:1 all exhibited the excellent performance with high densification (>99.10%) and mere average grain size (<3.0 μm) at low sintering temperature of 1350 °C. Additionally, XRD and EDS analysis indicated that PrIZO targets were composed of In2O3 and Zn3In2O6 with slight PrInO3, which formed by the limited solid solubility of Pr element. Combined with theoretical calculations, it inferred that the mechanism of grain refinement was attributed to the solute transformation and fine PrInO3 distributed at the grain boundaries of In2O3 phases, which produced the drag effect of grain boundary migration, then hindering the further growth of grains.

P‐2: Investigation of high mobility crystalline IGO TFT with top‐gate structure for LCD display application

The present paper reports the study of electrical characteristics and bias temperature stress (BT) stability of crystalline Indium‐Gallium oxide (IGO) dual‐gate thin film transistor (TFT) with top‐gate structure. TFT with normalized Ion over 100εA and PBTS/NBTIS of 0.35/‐2.85V was successfully fabricated. By adjusting oxygen partial pressure (O2%) and substrate temperature, we can control the wet etching rate (WER) of as‐deposited IGO film. After post annealing, crystalline IGO containing In2O3 phase with preferred orientation of (222) has been formed. The TFT characteristics uniformity and BT stability were found to depend on parameters of gate insulator (GI) deposition and pre‐treatment before GI. Based on experimental results, we propose high GI deposition temperature associated with low N2O plasma treatment power as the optimal condition for industrial production of crystalline IGO TFT.

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.

Insights into direct/synergetic processes for high-efficiency steam reforming of methanol over Pt-In2O3/CeO2 catalysts: The effect of support structural properties

The addition of Pt (1 %) and In2O3 (7 %) phases into CeO2 supports exhibited an interaction, resulting in the formation of bifunctional Pt2+-In2O3-CeO2, Ptδ+-CeO2 (0 < δ < 2), In2O3-CeO2, and inactive In2O3 macroparticles., Low CO selectivity was achieved in methanol steam reforming (MSR) by sacrificing methanol conversion/catalytic stability. Two distinct reaction paths were identified, viz., the direct process over bifunctional Pt2+-In2O3-CeO2 and the synergetic process between Ptδ+-CeO2 and In2O3-CeO2. The relative ratio of these two processes played a decisive role in determining the product distribution. The direct process improved methanol conversion while maintaining low CO selectivity. However, a decrease in catalytic stability was attributed to the agglomeration and sintering of the In2O3 phase, leading to the conversion of Pt2+-In2O3-CeO2 into Ptδ+-CeO2. To address the challenge of balancing methanol conversion/catalytic stability and CO selectivity, it was crucial to enhance Pt2+-In2O3-CeO2 sites and preserve their stability. Furthermore, the structural properties of the support played a significant role in governing the distributions and states of Pt and In2O3 phases. Specifically, the use of CeO2 (0.5 °C min−1) support resulted in a substantial increase in Pt2+-In2O3-CeO2 and effectively mitigated the sintering of In2O3 phases, ensuring the stability of Pt2+-In2O3-CeO2. In conclusion, our work elucidated the intricate relationships among the structural properties of CeO2 supports, the distributions and states of Pt and In2O3 phases, and MSR performance over Pt-In2O3/CeO2 catalysts, which hold promise for advancing the development of high-performance MSR catalysts.

Independent and simultaneous photocatalytic decontamination and disinfection of water over In2O3/TiO2 heterojunctions

We have explored the application of In2O3/TiO2 heterojunctions to the photocatalytic removal of a substance classified as a pollutant of emerging concern, such as the anti-inflammatory drug sodium diclofenac (DCF), from aqueous solutions. In addition, the study of water disinfection by means of photocatalysis, simultaneously with the elimination of DCF, has been carried out with the same catalysts, by using bacterial populations of the genus Enterococcus faecalis. The In2O3/TiO2 catalysts with different indium amounts consist of bi-phasic samples with anatase TiO2 and In2O3 phases, without evidence in In doping into the titania structure, and show, according to UV–vis and time-resolved fluorescence spectra, light absorption into the visible range and interfacial charge transfer from the conduction band of In2O3 to that of TiO2. Complete photocatalytic removal of DCF was achieved by using all catalysts after 120 min of irradiation, being the most active the catalyst with 5% of In2O3, in agreement with its highest efficiency of interfacial charge transfer revealed by fluorescence lifetime. In contrast, in terms of DCF mineralization, the 5In2O3/TiO2 catalyst did not outperform the pristine TiO2, the higher mineralization percentage being achieved with 1% In. Simultaneous decontamination and disinfection experiments show that the 5% In2O3/TiO2 heterojunction outperforms the activity of titania for DFC removal in the presence of Enterococcus faecalis, but not for the inactivation of bacteria.

Interface engineering of a GaN/In2O3 heterostructure for highly efficient electrocatalytic CO2 reduction to formate

Electrocatalytic CO2 reduction reaction (eCO2RR) to obtain formate is a promising method to consume CO2 and alleviate the energy crisis. Indium-based electrocatalysts have demonstrated considerable potential to produce formate. However, their unsatisfactory long-term stability and selectivity restrict their widespread application. In this study, a heterostructure of GaN- and In2O3-encapsulated porous carbon nanofibers was constructed via electrospinning and the phase transition of eutectic gallium-indium during calcination. The GaN and In2O3 nanoparticle-encapsulated porous carbon nanofibers, when used as electrocatalysts for eCO2RR, displayed high formate selectivity with a faradaic efficiency of 87% and maximum partial current density of 29.7 mA cm−2 in a 0.5 mol L−1 KHCO3 aqueous solution. The existence of the interface can cause a positive shift in the In 3d binding energy, leading to electronic redistribution. Moreover, the GaN component induced a higher proportion of O-vacancy sites in the In2O3 phase, resulting in improved selectivity for CO2-to-formate. In-situ Raman experiments and density functional theory calculations revealed that the interface between GaN and In2O3 could lower the adsorption energy of the key intermediates for formate production, thus providing superior eCO2RR performance. In addition, the framework of the porous carbon nanofibers exhibited a large electrochemically active surface area, which enabled the full exposure of the active sites. This study highlights the cooperation between GaN and In2O3 components and provides new insights into the rational design of catalysts with high CO2-to-formate conversion efficiencies.

Preparation of WO3/In2O3 heterojunctions and their performance on the CO2 photocatalytic conversion in a continuous flow reactor

This study investigated the CO2 conversion in the gas phase using the WO3/In2O3 photocatalysts synthesized by the solvothermal method at different WO3 content (5, 10, and 15 wt%). The experimental results in a continuous flow reactor demonstrated that carbon monoxide was the main product obtained from the photocatalytic reduction of CO2 using the coupled oxides and the individual semiconductors. However, in addition to CO, the WO3/In2O3 catalyst also produced CH4 and C3H6 hydrocarbons. The incorporation of WO3 into In2O3 inhibits the crystal growth and changes the preferentially formed cubic phase of In2O3 to the hexagonal phase structure, promoting the generation of hydrocarbons. The W15%/In coupled catalyst exhibited the best performance on methane and propylene production. This behavior was attributed to the enhanced interaction between the gas and the catalyst surface, and the improved charge separation promoted by the direct Z-scheme mechanism in the W15%/In heterojunction.

Effect of the Type of the Crystal Phase of In2O3 On Its Conductivity and Sensor Properties in Hydrogen Detection

Effect of the Type of the Crystal Phase of In2O3 On Its Conductivity and Sensor Properties in Hydrogen Detection

Zn-In-O electrocatalysts with co-existing ZnO and In2O3 phases for efficient reduction of CO2 to formate through sacrificial mechanism

Electrochemical CO2 reduction reaction (eCO2RR) is considered an efficient approach to produce value-added chemicals and fuels. In this paper, a series of MOF-derived composite catalysts with coexisting In2O3 and ZnO are fabricated using a simple process for eCO2RR to produce formate. The Zn-In-O/800 catalyst achieves a formate Faradaic efficiency (FEHCOO−) of 94.25 % at −1.16 V vs. RHE, which can maintain over 89 % after 30 h in a stability test. The electrochemical evidence and density functional theory analysis show that the strong interface effect between In2O3 and ZnO can enhance the CO2 adsorption and activation, and promote the conversion of CO2 to formate. In addition, the ZnO phase can protect In2O3, as the main active site, from being reduced to a certain extent for a long time under negative potential, which ensures the high stability of the composite catalyst.

Silicalite-1 Layer Secures the Bifunctional Nature of a CO2 Hydrogenation Catalyst.

Close proximity usually shortens the travel distance of reaction intermediates, thus able to promote the catalytic performance of CO2 hydrogenation by a bifunctional catalyst, such as the widely reported In2O3/H-ZSM-5. However, nanoscale proximity (e.g., powder mixing, PM) more likely causes the fast deactivation of the catalyst, probably due to the migration of metals (e.g., In) that not only neutralizes the acid sites of zeolites but also leads to the reconstruction of the In2O3 surface, thus resulting in catalyst deactivation. Additionally, zeolite coking is another potential deactivation factor when dealing with this methanol-mediated CO2 hydrogenation process. Herein, we reported a facile approach to overcome these three challenges by coating a layer of silicalite-1 (S-1) shell outside a zeolite H-ZSM-5 crystal for the In2O3/H-ZSM-5-catalyzed CO2 hydrogenation. More specifically, the S-1 layer (1) restrains the migration of indium that preserved the acidity of H-ZSM-5 and at the same time (2) prevents the over-reduction of the In2O3 phase and (3) improves the catalyst lifetime by suppressing the aromatic cycle in a methanol-to-hydrocarbon conversion step. As such, the activity for the synthesis of C2 + hydrocarbons under nanoscale proximity (PM) was successfully obtained. Moreover, an enhanced performance was observed for the S-1-coated catalyst under microscale proximity (e.g., granule mixing, GM) in comparison to the S-1-coating-free counterpart. This work highlights an effective shielding strategy to secure the bifunctional nature of a CO2 hydrogenation catalyst.

Indium Oxide–Graphene Composites Prepared by the Sol–Gel Process and Single-Electrode Gas Sensors on Their Base

Indium oxide–graphene composites (containing 0–6.0 wt % graphene) were manufactured by the sol–gel process. The phase composition, microstructure, and gas-sensitive properties of the prepared materials were studied. The composites consist of isolated In2O3 and graphene phases, where graphene is predominantly adsorbed on the surfaces of indium oxide grains (the indium oxide grain sizes are 8–11 nm). The nanocomposites are distinguished by an enhanced sensitivity to both reducing gases (CH4, acetone) and oxidative gases (NO2). A far greater enhancement is in the sensory response to oxidative gases. Presumably, the major factors influencing the sensory properties of the composite are the high defectiveness of In2O3 and graphene phases, higher specific surface areas of composites compared to those of individual In2O3, and the likely formation of p–n junctions in the indium oxide and graphene contact zone. Graphene additives to indium oxide can improve the main performances (sensory response, response time, and recovery time) of single-electrode semiconductor sensors.

Rhombohedral/Cubic In2O3 Phase Junction Hybridized with Polymeric Carbon Nitride for Photodegradation of Organic Pollutants.

In recent studies, phase junctions constructed as photocatalysts have been found to possess great prospects for organic degradation with visible light. In this study, we designed an elaborate rhombohedral corundum/cubic In2O3 phase junction (named MIO) combined with polymeric carbon nitride (PCN) via an in situ calcination method. The performance of the MIO/PCN composites was measured by photodegradation of Rhodamine B under LED light (λ = 420 nm) irradiation. The excellent performance of MIO/PCN could be attributed to the intimate interface contact between MIO and PCN, which provides a reliable charge transmission channel, thereby improving the separation efficiency of charge carriers. Photocatalytic degradation experiments with different quenchers were also executed. The results suggest that the superoxide anion radicals (O2-) and hydroxyl radicals (·OH) played the main roles in the reaction, as opposed to the other scavengers. Moreover, the stability of the MIO/PCN composites was particularly good in the four cycling photocatalytic reactions. This work illustrates that MOF-modified materials have great potential for solving environmental pollution without creating secondary pollution.

The effect of indium–tin oxide coatings on the formation of craters on glass surfaces under the impact of high-velocity microparticles

This article considers the problem of improved mechanical properties and protection of glass materials in optical systems of space vehicles. One the possible methods to solve the problem is the formation of multi-phase nanocomposite shock-resistant transparent coatings on the surface of glass plates. Considerable attention is paid to the application of indium–tin oxide (ITO) coatings on the surface of quartz glass pieces deposited by the method of pulsed magnetron sputtering. Such coatings demonstrate the highest properties. The optical characteristics of ITO coatings were studied in a range of wavelengths of 200–1100 nm. It was shown that in the visible spectrum they remain transparent. The structure and phase composition of indium tin oxide coating, basically, contains nanocrystalline In2O3 phase, which is indicated by the diffraction reflexes on obtained electron diffraction patterns and X-ray diagrams.It was unveiled that the deposited ITO-based coatings possess resistance to the shock impact of hyper-velocity iron microparticles. They can appreciably reduce surface density of the craters formed on the surface of glass plates under the impacts of solid microparticles due to increased strength and cracking resistance of the glass specimens. The character of alteration of the crater density of the glass surface with the coating is explained by the superposition of two mechanisms: reinforcement of the surface layer of glass due to deposited nanocomposite coating and supplementary dissipation of the energy of the normal shock wave that excites generation and propagation of secondary surface waves at the interface of heterogeneous layers of the ceramic coating and quartz.

Impact of annealing on the growth dynamics of indium sulphide buffer layers

Thin films of Indium sulphide are deposited on corning glass substrate by thermal evaporation at room temperature (300 K). The as-deposited films were annealed from 373 to 723 K under vacuum ∼1 × 10−3 mbar. An amorphous phase is obtained from 300 to 473 K; the polycrystalline β-In2S3 emerges at 523 K, and In2O3 is grown at 723 K. The intermediary phases of β-In2S3 and In2O3 are perceived from 573 to 673 K. A clear distinction between the morphology of β-In2S3 and In2O3 was observed in the micrographs of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The β-In2S3 dominated films provide absorption coefficient (α) from 18 to 25 × 104 cm−1, while α values of In2O3 layers lie within 1–5 × 104 cm−1. The bandgap (Eg) of β-In2S3 thin films is low (2.34 eV), and that of In2O3 is high (3.47 eV); however, the intermediary phases of β-In2S3 and In2O3 exhibit bandgap tunning from 2.30 to 3.14 eV. Moreover, the β-In2S3 shows the highest carrier concentration (Nd; 3.25 × 1018 cm−3), In2O3 provides the highest mobility (μ; 228 Cm2/V.s), and intermediary phases exhibit the lowest resistivity (ρ; 1.27 × 103 Ω/cm) within the existing forms. The thin films β-In2S3 phase grown at 523 and 573 K meet its stoichiometric ratio. In comparison, the In2O3 phase emerges under high oxygen and sulphur deficit conditions. The films are suitable for photo-conduction devices and in the buffer/window layer of PV solar cell design.

Texture evolution mechanism of pulsed laser deposited in-doped Ga2O3 film affected by laser fluence and its application in solar-blind photodetector

This work explored the crystal structural, optical bandgap, and morphological texture evolution of pulsed laser deposited In-doped Ga2O3 films grown on sapphire substrate at different laser fluence from 1.0 to 2.6 J/cm2. The in situ optical emission spectroscopy was carried out to monitor the plasma radicals generated during the deposition. All the deposited films were crystallized and some clusters were formed because of high deposition temperature and rapid surface diffusion of indium (In). The growth rate and the crystallinity of the film increased and then declined with increasing laser fluence. The texture evolution mechanism of the films has been proposed firstly. The rapid diffusion of In, the sputtering and reflection effect of plasma species exist in whole films’ deposition process, which has a significant impact on the texture characteristics of the films. The clusters emerging on film surface were the crystallized In-rich InGaOx nanoparticles consisting of β-Ga2O3 and cubic In2O3 phases. Metal-semiconductor-metal solar-blind photodetectors were also fabricated and analyzed to illustrate the effect of laser fluence. The elaboration of texture evolution mechanism and effect of laser fluence on the properties of the In-doped Ga2O3 films and photodetectors is very beneficial for its application in high performance photoelectric devices.

Catalytic roles of In2O3 in ZrO2-based binary oxides for CO2 hydrogenation to methanol

Four different compositing strategies were explored to synthesize In2O3/ZrO2 binary composite oxides with the goal of optimizing the interaction between the two phases and the degree of In2O3 surface exposure. The composite oxide prepared by the precipitation-coating method demonstrated the highest exposure area of In2O3 (SIn = 6.22 m2·g−1). In contrast, the composite oxide prepared by the co-precipitation method caused In2O3 to form a bulk dispersion structure with ZrO2, resulting in the lowest In2O3 exposure area (SIn = 1.56 m2·g−1). The incorporation of an In2O3 phase in ZrO2 inhibited the excessive formation of oxygen vacancies compared with pure In2O3, improving the catalytic performance for hydrogenation of CO2 to methanol. The 10% In2O3/m-ZrO2 composite prepared by the precipitation-coating method had excellent catalytic performance and stability: the CO2 conversion was 7.5%, the space-time yield (STY) of methanol reached 0.398 gMeOH·h−1·gcat−1, and the catalytic performance did not significantly decline after a reaction time of 120 h. The results of experimental and simulation calculation verify that In2O3 surface exposure contributes to CO2 adsorption and activation. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and DFT calculation were used to show that oxygen vacancy defects in the In2O3/m-ZrO2 composite oxides helped stabilize formate intermediates and that methanol synthesis followed a carbonate-formate-methoxy pathway.

CO2 Hydrogenation to Higher Alcohols over K-Promoted Bimetallic Fe–In Catalysts on a Ce–ZrO2 Support

Novel K-promoted bimetallic Fe- and In-based catalysts on a Ce− ZrO2 support were prepared and tested for higher alcohol synthesis from CO2 and hydrogen. The FeIn/Ce−ZrO2 precursors with different Fe contents were characterized in detail, and well-dispersed Fe2O3 and In2O3 phases with oxygen vacancies were observed. The catalysts were tested in a continuous setup at extended times on stream (up to 100 h) at 300 °C, 10 MPa, a gas hourly space velocity of 4500 mL g−1 h−1, and a H2/CO2 ratio of 3. The effect of K loading, the pretreatment atmosphere, Fe/(Fe + In) molar ratios, and calcination temperature on CO2 conversion and product selectivity were studied. Best performance with a CO2 conversion of 29.6% and a higher alcohol selectivity of 28.7%, together with good stability, was obtained over a K-0.82-FeIn/Ce−ZrO2_900 catalyst after activation under a CO atmosphere. These findings were rationalized by considering the effects of the individual catalyst components (K, Fe, and In) on catalyst performance. Surprisingly, the presence of calcined SiC, used as a diluent in the packed bed reactor, was shown to have a positive effect on catalyst performance and as such also is catalytically active. The best performance in terms of higher alcohol yield (8.5%) obtained in this work ranks in the top three of reports on CO2 hydrogenation to higher alcohols in a continuous setup. Moreover, light olefins with 20.3% selectivity (6.0% yield) were coproduced over the optimized catalyst, which has a positive effect on the economic potential of the catalysts.

Sintering behavior of IZO ceramic targets prepared using hydrothermally synthesized Zn-doped In2O3 nanoparticles

Zn-doped In2O3 composite nanoparticles were synthesized by precipitation/hydrothermal processing in the pH range of 5–11 and at the reaction temperature of 180 °C. The precursor solution used to prepare these nanoparticles was composed of In(NO3)3 and ZnSO4·7H2O, mixed at the In:Zn atomic ratios of 1:1, 1.5:1, and 2.5:1. The effects of In:Zn atomic ratio and pH on the morphology and phase composition of the composite nanoparticles were investigated in detail using a scanning electron microscope (SEM), a transmission electron micrograph (TEM), and an X-ray diffraction (XRD) system. The obtained results show that under alkaline conditions (pH 9–11), the nanoparticles exhibit cubic morphology. However, at pH 7, the morphology is sheet-like. Based on XRD analyses, the Zn content in hydrothermally processed nanoparticles is highest when the pH of the precursor solution is 7. Assessments of sintering behavior demonstrate that the IZO ceramic targets sintered at 1550 °C for 20 h are composed of In2O3 and Zn3In2O6 phases, with uniform grain morphology and size distribution.

Indium Gallium Oxide Alloys: Electronic Structure, Optical Gap, Surface Space Charge, and Chemical Trends within Common-Cation Semiconductors.

The electronic and optical properties of (InxGa1-x)2O3 alloys are highly tunable, giving rise to a myriad of applications including transparent conductors, transparent electronics, and solar-blind ultraviolet photodetectors. Here, we investigate these properties for a high quality pulsed laser deposited film which possesses a lateral cation composition gradient (0.01 ≤ x ≤ 0.82) and three crystallographic phases (monoclinic, hexagonal, and bixbyite). The optical gaps over this composition range are determined, and only a weak optical gap bowing is found (b = 0.36 eV). The valence band edge evolution along with the change in the fundamental band gap over the composition gradient enables the surface space-charge properties to be probed. This is an important property when considering metal contact formation and heterojunctions for devices. A transition from surface electron accumulation to depletion occurs at x ∼ 0.35 as the film goes from the bixbyite In2O3 phase to the monoclinic β-Ga2O3 phase. The electronic structure of the different phases is investigated by using density functional theory calculations and compared to the valence band X-ray photoemission spectra. Finally, the properties of these alloys, such as the n-type dopability of In2O3 and use of Ga2O3 as a solar-blind UV detector, are understood with respect to other common-cation compound semiconductors in terms of simple chemical trends of the band edge positions and the hydrostatic volume deformation potential.