Surface Of In2O3 Research Articles

Catalytic hydrogenation of CO2 to aromatics over indium-zirconium solid solution and sheet HZSM-5 tandem catalysts

The presence of acids and bases, coupled with its exceptional CO2 adsorption capacity and thermal stability, has established zirconia as a highly esteemed promoter and carrier. Researchers have found that the In2O3 supported ZrO2 exhibits high activity and remarkable stability. Therefore, xIn-yZr(T) solid solutions were prepared with different calcination temperatures and In/Zr molar ratios. The solid solutions were then combined with sheet HZSM-5 zeolite from tandem catalysts, which were investigated for their catalytic performance in converting CO2 to aromatics. The X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, NH3 temperature-programmed desorption, pyridine infrared radiation, X-ray photoelectron spectroscopy, electron paramagnetic resonance, CO2 temperature-programmed desorption and H2 temperature-programmed reduction characterization methods were used to investigate the physicochemical properties of catalysts. Density Functional Theory calculations were used to investigate the energy of thermal desorption and H2 reduction to generate oxygen vacancies on the surface of In2O3(111) and Zr/In2O3(111). Additionally, the influence of oxygen vacancies on CO2 adsorption energies was simulated. It was found that the incorporation of a moderate amount of zirconium carriers promoted the generation of oxygen vacancies and provided better metal-carrier interactions. The 4In-1Zr(500 °C)/HZSM-5 tandem catalyst exhibits excellent catalytic stability, achieving a CO2 conversion of 24.3 % and aromatics selectivity of 37.3 %.

DFT modeling of reaction of H2 with O2 pre-adsorbed on In2O3(011) surface

The DFT approach is used for the first time to model the reaction of hydrogen with oxygen molecule adsorbed on the defective surface of In2O3(011). This reaction is crucial for hydrogen detection by In2O3 sensor. The activation energies are calculated using two mechanisms involving the formation of both an adsorbed water molecule and hydroxyl groups on the In2O3(011) surface. One hydroxyl group is formed due to the bonding of OH with the surface metal atom, and the other due to the bonding of hydrogen with oxygen of the lattice. Both reactions are characterized by the presence of a potential barrier and are exothermic. The activation energies of the two reactions are calculated by the climbing-image nudged elastic band method to be 0.99 eV and 0.98 eV. The results of the calculations are compared with available experimental data. It is also shown that the presence of a surface neutral oxygen vacancy leads to the formation of a vacancy state below the Fermi level, and the electron density is concentrated on the fourfold coordinated indium atom.

Dual enhancement in response and anti-humidity properties of a triethylamine sensor based on trimethoxypropylsilane self-assembled functionalized In2O3

The anti-humidity properties of metal oxide semiconductors have become an important performance index requirement for the commercialization of gas sensors since ambient humidity is inescapable in many situations which changes rapidly depending on the region and climate. Herein, functionalized In2O3 nanospheres with enhanced response value and anti-humidity properties to triethylamine (TEA) were prepared by self-assembly of trimethoxypropylsilane (PTES) on the surface of In2O3. The effect of different levels of PTES functionalization on gas sensing properties was investigated in detail. Furthermore, the PTES-In2O3 sensor exhibited a high response (9.3–100 ppm TEA at 80 RH%), a remarkable relative response (95.6 %), a low theoretical detection limit (920 ppb), and long-term stability. The superior gas sensing properties can be attributed to the hydrophobicity of the alkyl chains in the PTES molecule, and the PTES captures free electrons from In2O3 which widens the electron depletion layer. Therefore, the strategy can be widely applied to construct metal oxide gas sensors with excellent humidity resistance and high gas response properties.

Synthesis of Pr doped In2O3 nanoparticles and their enhanced ethanol gas-sensing performance

Rare earth doping was an effective method to upgrade the gas-sensing performance of sensors based on oxide semiconductors. In this paper, Pr was successfully doped into In2O3 nanomaterials with a facile co-precipitation approach through a hydrothermal strategy. The as-obtained series of Pr doped In2O3 nanocomposites were analyzed by some technical characterization. The gas-sensing tests were performed by using series of Pr/In2O3 nanocomposites as sensitive materials. The results illustrated that the doping of Pr not only reduced the particle size of Pr/In2O3 nanocomposites but also produced more active oxygen on the surface of In2O3, thus, the responses of Pr/In2O3-based sensors towards ethanol gas (112.40–50 ppm) were enhanced. A possible mechanism for the improved gas-sensing property of Pr decorated In2O3 sensors was proposed.

Fast and Sensitive Detection of CO by Bi-MOF-Derived Porous In2O3/Fe2O3 Core-Shell Nanotubes.

In2O3 is an optimal material for sensitive detection of carbon monoxide (CO) gas due to its low resistivity and high catalytic activity. Yet, the gas response dynamics between the CO gas molecules and the surface of In2O3 is limited by its solid structure, resulting in a weak gas response value and sluggish electron transport. Herein, we report a strategy to synthesize porous In2O3/Fe2O3 core-shell nanotubes derived from In/Fe bimetallic organic frameworks. The fabricated porous In2O3/Fe2O3-4 core-shell nanotubes present outstanding gas sensitivities, including a response value 3.8 times (33.7 to 200 ppm CO at 260 °C) higher than that of monometallic-derived In2O3 (8.7), ultrashort response and recovery times (23/76 s) to 200 ppm CO, low detection limit (1 ppm), promising selectivity, and long-term stability. The enhanced sensing mechanisms are clarified by the combination of experiment and first-principles calculations, showing that the synergetic strategy of higher adsorption energy, increased electrical conductivity, higher electron transfer numbers, and larger specific surface area of porous core-shell structures promotes the surface activity and charge transfer efficiency. The present work paves a way to tune gas-sensing materials with special morphologies for the development of high-performance CO sensors.

Platinum Nanoclusters-Modified Porous In2O3 Nanocubes for Highly Sensitive and Selective Formaldehyde Gas Sensing at Room Temperature

The detection of formaldehyde gas generally requires a relatively high temperature. It is still challenging to simultaneously possess high sensitivity and strong selectivity for the detection of low-concentration formaldehyde at room temperature. The activation energy of the reaction can be reduced by introducing oxygen vacancies or loading the metal clusters on the surface of metal oxide-based semiconductors, leading to an improvement in the performance and detection limit of the sensor. However, this approach may lead to an increased cross-sensitivity to other gases and a reduction in the selectivity of the sensors. In this study, In2O3 can capture a significant amount of adsorbed oxygen by increasing the oxygen vacancies and introducing platinum nanoclusters on the surface of In2O3 synthesized with a specific morphology, leading to high sensitivity and selectivity for the detection of formaldehyde gas at room temperature. The Pt-In2O3 sensor exhibits a response value of approximately 38 to a concentration of 1 ppm formaldehyde gas at 20 °C. Moreover, the developed sensor demonstrates excellent performance in a complex atmosphere and exhibits good long-term stability. The achieved high sensitivity and selectivity for the detection of formaldehyde gas at low temperatures hold significant implications for research and practical applications in the field of sensors.

MOF-decorated sea urchin-like In2O3 gas sensor with higher gas sensitivity to formaldehyde

The sea urchin-like In2O3 material was successfully synthesized through a simple hydrothermal method. Furthermore, the material underwent surface decoration without adding extra indium ions, resulting in the formation of a thin MIL-68(In) layer on the surface of In2O3. The obtained In2O3@MIL-68(In) retains the sea urchin-like morphology while acquiring an additional porous structure. Compared to pure In2O3, the composite exhibits a significant increase in specific surface area, leading to enhanced gas sensitivity. Notably, it demonstrates exceptional sensitivity towards formaldehyde gas, with a response of 18 at 100 ppm at 300 °C, up to six times more than pure In2O3. Moreover, In2O3@MIL-68(In) showcases remarkable selectivity and stability. These findings suggest that surface-modified MOF can enhance gas-sensitive properties.

Effective degradation of doxycycline hydrochloride in simulated and real water by S-scheme heterojunction 2D/1D Bi4O5I2/In2O3 under visible light: DFT calculation, mechanism, degradation pathway and toxicity analysis

To effectively enhance the response to visible light, suppress the recombination of electron-hole pairs and enhance the degradation performance towards organic pollutants in water, a novel S-scheme heterojunction Bi4O5I2/In2O3 was synthesized by in situ solvothermal loading of Bi4O5I2 on the surface of In2O3, and employed to investigate its photocatalytic performance towards doxycycline hydrochloride. The prepared optimal photocatalyst Bi4O5I2/In2O3 shows excellent photo-degradation capability under visible light (94.1 %). The transfer pathway of photogenerated carriers in the Bi4O5I2/In2O3 heterojunction follows the S-scheme process, demonstrated by various characterizations and Density Functional Theory calculation. The internal electric field formed inside the Bi4O5I2/In2O3 S-scheme heterojunction impels the direct transmission of photogenerated carriers from the CB of In2O3 to the VB of Bi4O5I2, which produces the accumulation of e- and h+ on the CB of Bi4O5I2 and VB of In2O3, severally. Meanwhile, the formed internal electric field reduces the recombination rate of e-/h+. Superoxide and hydroxyl radicals contribute a major role. Degradation pathway was explored and toxicity evaluation of intermediates was also performed. The present results demonstrate that the construction of the Bi4O5I2/In2O3 heterojunction can be a feasible route to effectively degrade antibiotic under visible light irradiation.

Construction of hexagonal hollow rod-shaped NiCo2O4–In2O3 p-n heterojunction for low concentration formaldehyde detection

The construction of p-n heterostructures using n-type and p-type semiconductor is a very important way to enhance gas sensing performance. In this work, hexagonal rod-shaped NiCo2O4/In2O3 with larger surface area was prepared via a simple water bath approach and subsequent calcination process. The microscopic morphology characterization results show that the NiCo2O4/In2O3 composite has a hexagonal hollow rod-shaped structure, where NiCo2O4 grows in situ on the surface of In2O3, forming p-n heterojunctions. Notably, the NiCo2O4/In2O3 composites formed with 6% NiCo2O4 addition (In-NC6) at 200 °C showed the best gas sensing performance for 1 ppm formaldehyde with a response value of 9.11 and a theoretical detection limit as low as 10.83 ppb. The rich oxygen vacancies, active site and p-n heterojunction are conducive to the adsorption of formaldehyde and electron transfer. This in situ growth approach provides novel ideas and promising prospects to synthesize other p-n heterojunction materials for applying to toxic gas detection.

Oxygen Plasma Treatment to Enable Indium Oxide MESFET Devices

AbstractMetal‐semiconductor field‐effect transistor (MESFET) devices based on pulsed laser deposition (PLD) grown In2O3 thin films with on–off ratios exceeding 6 orders of magnitude and low sub‐threshold swing values close to the thermodynamic limit are reported. Oxygen plasma treatment and compensation doping with Mg are utilized to suppress the accumulation of electrons at the surface of In2O3, which is a major obstacle for its use as an active material in electronic devices. The influence of both methods is investigated on the electrical properties of thin films as determined by Hall effect measurements on samples of varying film thickness. Using the performance of vertical Schottky barrier diodes as a benchmark, fundamental plasma parameters such as input power and background gas pressure are optimized.

Highly hydrogen generation and delivery path of In2O3(ZnO)4 photocatalyst via theoretical calculation and experimental investigation

Insight into the hydrogen production pathway and mechanism of catalysts is crucial to enhance the development of green hydrogen technology. Herein, In2O3(ZnO)4 catalysts with layered structure were synthesized, and the process and efficiency of hydrogen production were specifically analyzed by theoretical calculations and experimental studies for the first time. The density functional theory (DFT) results indicated that the crystalline surface energy arrangement: (012) > (101) > (106) > (111), the (111) crystal surface of In2O3(ZnO)4 was the final exposed crystal surface during the natural growth process, and there are stable Zn sites on the (111) crystal surface, which are favorable for H atom adsorption, then H2 escape is achieved through charge transfer between Zn and adjacent O atoms. The efficiency of In2O3(ZnO)4 reached 818.72 μmol⋅g−1·h−1 in visible light hydrogen production application. Moreover, the response surface methodology (RSM) was used to investigate the effect of pH, sacrificial agent, and catalyst addition on the efficiency exactly. This work provides an effective method to develop photocatalytic systems for applications related to hydrogen production and environmental pollution.

Nanowatt-Level Photoactivated Gas Sensor Based on Fully-Integrated Visible MicroLED and Plasmonic Nanomaterials.

Photoactivated gas sensors that are fully integrated with micro light-emitting diodes (µLED) have shown great potential to substitute conventional micro/nano-electromechanical (M/NEMS) gas sensors owing to their low power consumption, high mechanical stability, and mass-producibility. Previous photoactivated gas sensors mostly have utilized ultra-violet (UV) light (250-400nm) for activating high-bandgap metal oxides, although energy conversion efficiencies of gallium nitride (GaN)LEDs are maximized in the blue range (430-470nm). This study presents a more advanced monolithic photoactivated gas sensor based on a nanowatt-level, ultra-low-power blue (λpeak = 435 nm) µLED platform (µLP). To promote the blue light absorbance of the sensing material, plasmonic silver (Ag) nanoparticles (NPs) are uniformly coated on porous indium oxide (In2 O3 ) thin films. By the plasmonic effect, Ag NPs absorb the blue light and spontaneously transfer excited hot electrons to the surface of In2 O3 . Consequently, high external quantum efficiency (EQE, ≈17.3%) and sensor response (ΔR/R0 (%) = 1319%) to 1ppm NO2 gas can be achieved with a small power consumption of 63nW. Therefore, it is highly expected to realize various practical applications of mobile gas sensors such as personal environmental monitoring devices, smart factories, farms, and home appliances.

Design of Ag2O/In2O3 heterostructure composites with hollow fish basket-like structures for detecting petroleum volatile gases

In this study, Ag2O/In2O3 composites with hollow fish basket-like structure were synthesized by facile one-step hydrothermal method involving the modification of In2O3 by doping with Ag2O, which effectively enhanced the performance of gas-sensitive materials. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to analyze the structure, morphology, and content of the samples. The results showed that the synthesized product was polycrystalline with hollow fish basket-like microsphere structure; moreover, XRD and TEM results demonstrated the formation of p–n heterojunction structure between Ag2O and In2O3. Based on this, the gas-sensitive performance study of Ag2O/In2O3 composites for C3H8-based petroleum volatile gases was carried out by static experimental methods, including the study of operating temperature, humidity, sensitivity response, response-recovery time, selectivity, and stability. The results showed that the composite exhibited the best sensing performance when the Ag2O doping was 0.6%. The maximum sensitivity was obtained for C3H8 at an operating temperature of 140 °C, with a response value of 210.3. This value is roughly 2.52 times greater than the sensitivity of undoped In2O3 (84.1 at 180 °C). Moreover, Ag2O/In2O3 composites exhibited high reaction sensitivity, good selectivity, and excellent stability when the doping amount of Ag2O was 0.6%. The experimental results clearly indicate that adding Ag2O improves the gas-sensitive performance compared to pure In2O3. This is attributed to presence of more adsorbed oxygen and oxygen vacancies on the surface of In2O3, the catalytic effect of Ag2O, and the formation of p–n type heterojunctions.

Photoactivated Processes on the Surface of Metal Oxides and Gas Sensitivity to Oxygen.

Photoactivation by UV and visible radiation is a promising approach for the development of semiconductor gas sensors with reduced power consumption, high sensitivity, and stability. Although many hopeful results were achieved in this direction, the theoretical basis for the processes responsible for the photoactivated gas sensitivity still needs to be clarified. In this work, we investigated the mechanisms of UV-activated processes on the surface of nanocrystalline ZnO, In2O3, and SnO2 by in situ mass spectrometry and compared the obtained results with the gas sensitivity to oxygen in the dark and at UV irradiation. The results revealed a correlation between the photoactivated oxygen isotopic exchange activity and UV-activated oxygen gas sensitivity of the studied metal oxides. To interpret the data obtained, a model was proposed based on the idea of the generation of additional oxygen vacancies under UV irradiation due to the interaction with photoexcited holes.

Glucose sensing by field-effect transistors based on interfacial hydrogelation of self-assembled peptide

Interfacial hydrogelation of peptides gated on the semiconductor channel has yet to be explored in surface chemistry and field-effect transistor-based biosensors (bio-FETs). This work reports the first example of peptidic hydrogel gated bio-FET by surface assisted self-assembly for label-free and real-time monitoring of the glucose with low limit of detection, excellent sensitivity, and good stability in mouse serum. The boric acid-containing peptide forms a hydrogel layer on the surface of In2O3, which interacts with glucose reversibly and generates boronate anions to influence the semiconductor's conductivity. The results also indicate the superiority of hydrogel gated bio-FET for real-time monitoring of glucose in complex environments and serve as a wearable device. This work illustrates a simple and fundamental strategy for integrating peptidic hydrogel with bio-FET for the real-time detection of analytes.

Highly Sensitive MEMS Sensor Using Bimetallic Pd-Ag Nanoparticles as Catalyst for Acetylene Detection.

Acetylene detection plays an important role in fault diagnosis of power transformers. However, the available dissolved gas analysis (DGA) techniques have always relied on bulky instruments and are time-consuming. Herein, a high-performance acetylene sensor was fabricated on a microhotplate chip using In2O3 as the sensing material. To achieve high sensing response to acetylene, Pd–Ag core-shell nanoparticles were synthesized and used as catalysts. The transmission electron microscopy (TEM) image clearly shows that the Ag shell is deposited on one face of the cubic Pd nanoseeds. By loading the Pd–Ag bimetallic catalyst onto the surface of In2O3 sensing material, the acetylene sensor has been fabricated for acetylene detection. Due to the high catalytic performance of Pd–Ag bimetallic nanoparticles, the microhotplate sensor has a high response to acetylene gas, with a limit of detection (LOD) of 10 ppb. In addition to high sensitivity, the fabricated microhotplate sensor exhibits satisfactory selectivity, good repeatability, and fast response to acetylene. The high performance of the microhotplate sensor for acetylene gas indicates the application potential of trace acetylene detection in power transformer fault diagnosis.

Quantification and Tuning of Surface Oxygen Vacancies for the Hydrogenation of CO2 on Indium Oxide Catalysts

AbstractThe direct hydrogenation of CO2 to methanol is an attractive approach to employ the greenhouse gas as a chemical feedstock. However, the commercial copper catalyst, used for methanol synthesis from CO‐rich syngas, suffers from deactivation at elevated CO2 partial pressure. An emerging alternative is represented by In2O3 as it withstands the hydrothermal conditions induced by the reverse water‐gas shift reaction. The active sites for the adsorption of CO2 and the subsequent conversion into methanol were shown to be oxygen vacancies on the surface of In2O3. In this study, N2O was utilized as a probe molecule to quantify the number of vacancies on indium oxide catalysts. The number of inserted oxygen atoms could be correlated to the respective CO2 hydrogenation activity. Furthermore, the atomic efficiency of indium was enhanced by applying atomic layer deposition of indium oxide on ZrO2.

Anchoring Platinum Clusters onto Oxygen Vacancy-Modified In2O3 for Ultraefficient, Low-Temperature, Highly Sensitive, and Stable Detection of Formaldehyde.

To avoid carcinogenicity, formaldehyde gas, currently being only detected at higher operating temperatures, should be selectively detected in time with ppb concentration sensitivity in a room-temperature indoor environment. This is achieved in this work through introducing oxygen vacancies and Pt clusters on the surface of In2O3 to reduce the optimal operating temperature from 120 to 40 °C. Previous studies have shown that only water participates in the competitive adsorption on the sensor surface. Here, we experimentally confirm that the adsorbed water on the fabricated sensor surface is consumed via a chemical reaction due to the strong interaction between the oxygen vacancies and Pt clusters. Therefore, the long-term stability of formaldehyde gas detection is improved. The results of theoretical calculations in this work reveal that the excellent formaldehyde gas detection of Pt/In2O3-x originates from the electron enrichment due to the surface oxygen vacancies and the molecular adsorption and activation ability of Pt clusters on the surface. The developed Pt/In2O3-x sensor has potential use in the ultraefficient, low-temperature, highly sensitive, and stable detection of indoor formaldehyde at an operating temperature as low as room temperature.

G-C3N4/In2O3 composite for effective formaldehyde detection

This paper reports a new type of high-performance formaldehyde gas sensor using g-C3N4 nanosheets to modify the surface of In2O3 nanospheres as the sensing material. SEM and TEM results showed that g-C3N4 nanosheets were uniformly distributed on the surface of In2O3. The samples were characterized by XPS, and it was found that both oxygen defects (Ov) and chemically adsorbed oxygen (Oc) in the composite material were increased. The sensor performance under different loadings of g-C3N4 was systematically studied. Especially for 12 wt% loading the response of the sensor material with to 100 ppm formaldehyde reached 1405, which was 2 times bigger than that of pure In2O3. Importantly, it also had a low operating temperature of 119〬C and a short response time of 1 s. The enhancement of sensing performance could be attributed to the realization of rapid electron transfer and the exposure of high-density active center by constructing a unique n-n heterostructure. This research provides an effective method for preparing a formaldehyde sensor with fast response, high sensitivity and low power consumption.

Ag nanoparticles-functionalized dumbbell-shaped In2O3 derived from MIL-68(In) with excellent sensitivity to formaldehyde

Formaldehyde, as a pollutant gas produced by indoor home decoration, threatens human health to Tablea large extent, so it is necessary to detect formaldehyde gas at low concentrations. The dumbbell-shaped indium oxide (In2O3) prepared with MIL-68(In) as the precursor was modified by Ag nanoparticles, and a series of characterization and analysis were performed on it. Field-emission scanning electronic microscope (FESEM) and transmission electron microscope (TEM) results showed that the Ag nanoparticles are successfully grown on the surface of In2O3. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Ag nanoparticles. The gas-sensing results showed that to 20 ppm formaldehyde, In2O3/Ag showed the highest response (29.9) at 160 °C, and the sensor showed high and rapid response-recovery, good reproducibility, and remarkable stability. This work proves that loading Ag is a feasible method to improve the performance of In2O3 based gas sensor.