In2O3 Surface Research Articles

Carbon coated In2O3 hollow tubes embedded with ultra-low content ZnO quantum dots as catalysts for CO2 hydrogenation to methanol

CO2 hydrogenation coupled with renewable energy to produce methanol is of great interest. Carbon coated In2O3 hollow tube catalysts embedded with ultra-low content ZnO quantum dots (QDs) were synthesized for CO2 hydrogenation to methanol. ZnO-In2O3-II catalyst had the highest CO2 and H2 adsorption capacity, which demonstrated the highest methanol formation rate. When CO2 conversion was 8.9%, methanol selectivity still exceeded 86% at 3.0 MPa and 320 °C, and STY of methanol reached 0.98 gMeOHh−1gcat−1 at 350 °C. The ZnO/In2O3 QDs heterojunctions were formed at the interface between ZnO and In2O3(222). The ZnO/In2O3 heterojunctions, as a key structure to promote the CO2 hydrogenation to methanol, not only enhanced the interaction between ZnO and In2O3 as well as CO2 adsorption capacity, but also accelerated the electron transfer from In3+ to Zn2+. ZnO QDs boosted the dissociation and activation of H2. The carbon layer coated on In2O3 surface played a role of hydrogen spillover medium, and the dissociated H atoms were transferred to the CO2 adsorption sites on the In2O3 surface through the carbon layer, promoting the reaction of H atoms with CO2 more effectively. In addition, the conductivity of carbon enhanced the electron transfer from In3+ to Zn2+. The combination of the ZnO/In2O3 QDs heterojunctions and carbon layer greatly improved the methanol generation activity.

DFT-based microkinetic studies on methanol synthesis from CO2 hydrogenation over In2O3 and Zr-In2O3 catalysts.

Density functional theory (DFT) calculations and microkinetic simulations were performed to study the structure-performance relationship of In2O3 and Zr-doped In2O3 catalysts for methanol synthesis, focusing on the In2O3(110) and Zr-doped In2O3(110) surfaces. These surfaces are expected to follow the oxygen vacancy-based mechanism via the HCOO route for CO2 hydronation to methanol. Our DFT calcualtions show that the Zr-In2O3(110) surface is more favorable for CO2 adsorption than the In2O3(110) surface, and although the energy barriers are not lowered, most intermediates in the HCOO route are stablized with the introduction of the Zr dopant. Microkinetic simulations suggest that the CH3OH formation rate is improved by ∼10 times and CH3OH selectivity increased significantly from 10% on In2O3(110) to 100% on the Zr1-In2O3(110) catalyst model at 550 K. We find that the higher CH3OH formation rate and CH3OH selectivity on the Zr1-In2O3(110) surface than those on the In2O3(110) surface can be attributed to the slightly increased OV formation energy and the stablization of the reaction intermediates, whereas the much lower CH3OH formation rate on the Zr3-In2O3(110) surface is due to the much higher OV formation energy and the over binding of the H2O at the OV site.

Unusual catalytic hydrogenation caused by photoinduced solid frustrated Lewis pairs

Most homogeneously FLP-catalyzed hydrogenation reactions that follow cleavage of H2 occur via protonation of substrates followed by hydride transfer. This order of activated H-transfer unavoidably limits the application scope of currently FLP-catalyzed hydrogenation to nucleophilic substrates. Herein, we report an unusual inverse H-transfer order in which photoinduced solid In2O3-FLPs catalyze the hydrogenated dehalogenation of aryl halides with H2. After the generation of active FLPs of In-OH+ and In-[Ov]H- via H2 splitting on In2O3 surface upon irradiation, a series of aryl halides were readily activated and initiated at the In-[Ov]H- sites and then dehalogenated with high yields. By combining this work with detailed studies on H/D kinetic isotope effects and activation energies of hydrogenated dehalogenation, we demonstrate that initial hydride transfer mediated by photoinduced solid FLPs is more effective than common proton transfer to initiate hydrogenation of these substrates.

Different mechanisms of FLP-catalyzed photocatalytic dehalogenation of BDE47 in polar/non-polar solvents: Insight into the vital role of solvents

Recently, the hydrogenation reactions of heterogeneous frustrated Lewis pairs (FLP) catalysis based on metal oxides and corresponding reaction mechanisms were extensively studied. Generally, the hydrogenation performance of metal oxides in FLP catalysis was considered to be mainly related to the physicochemical properties of oxygen defects while the effect of solvents was ignored. Thus, the development of strategies for increasing the performances of catalysts is restricted to the regulation of oxygen defects. Herein, we reported different mechanisms for the FLP-catalyzed photocatalytic dehalogenation of 2,2′,4,4′-tetrabromodiphenyl ether (BDE47) by In2O3 in polar/non-polar solvents. Namely, in polar solvents, the Lewis basic sites of FLP transferred to the solvent molecules bonded with oxygen defects while it remains at the In2O3 surface in non-polar solvents. Thus, in different non-polar solvents, the photocatalytic activities for the dehalogenation of BDE47 remained almost unchanged. On the contrary, in reactions with polar solvents, because of the inactivation of original Lewis basic sites, the photocatalytic performances were largely determined by charge densities of the Lewis basic sites in solvent molecules. The above fundamental insight into the different mechanisms of FLP-catalyzed dehalogenation in polar/non-polar solvents could provide a new strategy for the improvement of heterogeneous FLP catalysts for hydrogenation reactions.

Hybrid MOF Template-Directed Construction of Hollow-Structured In2 O3 @ZrO2 Heterostructure for Enhancing Hydrogenation of CO2 to Methanol.

Direct hydrogenation of CO2 to methanol using green hydrogen has emerged as a promising method for carbon neutrality, but qualifying catalysts represent a grand challenge. In2 O3 /ZrO2 catalyst has been extensively applied in methanol synthesis due to its superior activity; however, the electronic effect by strong oxides-support interactions between In2 O3 and ZrO2 at the In2 O3 /ZrO2 interface is poorly understood. In this work, abundant In2 O3 /ZrO2 heterointerfaces are engineered in a hollow-structured In2 O3 @ZrO2 heterostructure through a facile pyrolysis of a hybrid metal-organic framework precursor MIL-68@UiO-66. Owing to well-defined In2 O3 /ZrO2 heterointerfaces, the resultant In2 O3 @ZrO2 exhibits superior activity and stability toward CO2 hydrogenation to methanol, which can afford a high methanol selectivity of 84.6% at a conversion of 10.4% at 290°C, and 3.0MPa with a methanol space-time yield of up to 0.29gMeOH gcat -1 h-1 . Extensive characterization demonstrates that there is a strong correlation between the strong electronic In2 O3 -ZrO2 interaction and catalytic selectivity. At In2 O3 /ZrO2 heterointerfaces, the electron tends to transfer from ZrO2 to In2 O3 surface, which facilitates H2 dissociation and the hydrogenation of formate (HCOO*) andmethoxy (CH3 O*) species to methanol. This study provides an insight into the In2 O3 -based catalysts and offers appealing opportunities for developing heterostructured CO2 hydrogenation catalysts with excellent activity.

CO2 Hydrogenation to Methanol on Indium Oxide-Supported Rhenium Catalysts: The Effects of Size

In this work, CO2 hydrogenation over In2O3-supported rhenium (Re) catalysts was found to be highly size-dependent. When the Re loading was less than 1 wt %, the strong interaction between Re and In2O3 caused atomically dispersed Re species with a positive charge, resulting in high activity for CO2 hydrogenation to methanol with enhanced stability at elevated temperatures. The space–time yield of methanol over the 1 wt % Re/In2O3 catalyst reached 0.54 gMeOH gcat–1 h–1 with a methanol selectivity of 72.1% at 5 MPa and 573 K. With increasing Re loading, the In2O3 supported Re catalysts become more favored for CO2 methanation. Under the same experimental conditions, the methane selectivity is close to 100.0% over the 10 wt % Re/In2O3 catalyst. Catalyst characterizations and density functional theoretical (DFT) calculations further confirm that the size of the Re/In2O3 catalyst has a significant effect on hydrogen activation and the selectivity of the CO2 hydrogenation reaction. Due to the strong Re–In2O3 interaction, the atomically dispersed Re in the In2O3 surface lattice not only stabilizes oxygen vacancies but also results in Hδ+ formation upon hydrogen adsorption. This significantly promotes methanol synthesis from CO2 hydrogenation. Meanwhile, the 10 wt % Re/In2O3 catalyst with supported Re nanoclusters induces Hδ- formation, which eventually leads to more methane production. The present study demonstrates the atomically dispersed Re/In2O3 catalyst is promising for CO2 hydrogenation to methanol.

Strain effect on adsorption and reactions of AHx (A = C, N, O, x ≤ 3) on In2O3(110), TiO2(110), and ZrO2(101) surfaces.

More and more attention has been paid to strain-based regulation of catalytic activity. To guide regulation of catalytic performance via strain engineering, adsorption and reactions of AHx (A = C, N, O, x ≤ 3) were investigated on uniformly strained In2O3 (110), rutile TiO2 (110), and tetragonal ZrO2 (101) from -2% to 4%. The results show that adsorption energies vary linearly with strain; expansive strain enhances the adsorption of most adsorbates. Unlike the adsorbate scaling relations that are central atom dependent, the adsorbate scaling relations on strained surfaces are central atom independent. C-H/O-H bonds are elongated/shortened with expansive strain, and adsorption energies of CHx generally change more than those of OHx and NHx, which can be rationalized with effective medium theory and pertinent bond energies. Thermodynamically, In2O3(110)/ZrO2(101) is the most active/inactive. The estimated variation of rate constants at 300K from 0% to 2% strain based on the Brønsted-Evans-Polanyi relationship demonstrates great strain regulation potential of catalytic performance on these oxide surfaces. Finally, it is demonstrated that strain tends to facilitate the reactions whose sum of the stoichiometric number is positive, which can be used as a rule to guide strain engineering for heterogeneous catalysis.

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Morphology controlled synthesis of Fe and Mn co-doped In2O3 nanocubes and their Dopant-Atom effects on electronic structure and magnetic properties

Fe and Mn co-doped In2O3 single-phase cubic crystal structure nanocubes of uniform size and control over dopant concentration (In1.96Fe0.02Mn0.02O3, In1.94Fe0.02Mn0.04O3, In1.92Fe0.02Mn0.06O3 and In1.90Fe0.02Mn0.08O3) and microstructure were prepared using the hydrothermal-annealing technique. On a wider vision, we systematically investigated the influence of Fe and Mn co-doping in In2O3 through complementary experimental techniques and density functional theoretical (DFT) calculations to reveal the physical mechanisms involved in the origin of observed ferromagnetism. DFT calculations demonstrated that the substitution of surface indium atom by iron (FeIn) leads to impurity states on the top of In2O3 valence band maximum (VBM). Conversely, incorporation of interstitial (Mni) impurities in the host matrix without oxygen vacancies (VO) slightly shifts the top of the valence band and incorporation of interstitial Mn-impurity in the In2O3 (111) surface with oxygen vacancy does not provide noticeable changes in the electronic structure of the defective surface. High-resolution transmission electron microscopy measurements showed the formation of regular nanocubes in shape with 36.9–37.6 nm in average edge length. X-ray photoelectron spectroscopy investigations revealed that valence state of Fe mostly as Fe2+ and Fe3+ and Mn2+ for Mn atom in the In1.96Fe0.02Mn0.02O3, In1.94Fe0.02Mn0.04O3, In1.92Fe0.02Mn0.06O3 and In1.90Fe0.02Mn0.08O3. Magnetic studies exhibited room temperature ferromagnetism (RTFM) in the investigated samples with the high coercivity and saturation magnetization of 145.48 Oe and 0.023 emu/g, respectively for the In1.94Fe0.02Mn0.04O3. The origin of observed RTFM was described based on the bound magnetic polaron (BMP) model mechanism. DFT investigations demonstrated the clusters of impurities (FeIn-nMni) robust magnetic interactions within the cluster and between the clusters. Interestingly, only FeIn-nMni clusters contribute ferromagnetism observed in the investigated co-doped systems. Therefore, increasing the concentration of defects leads to the improvement of ferromagnetism. The comprehensive experimental and DFT investigations present new evidence to the observed ferromagnetism and electronic structure of Fe,Mn co-doped In2O3 nanocubes.

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.

In2O3 surface modification of a Li-rich layered cathode material for boosting electrochemical performance

Lithium-rich layered cathode materials have high specific capacities. However, some drawbacks such as low initial Coulombic efficiency (ICE) and severe capacity/voltage decay during repeated cycling hinder their practical applications. Herein, a pristine Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) material is synthesized by the carbonate coprecipitation method and then the In2O3 surface modified LMNCO materials with different amounts of In2O3 are prepared by the facile solvent evaporation and calcination method. The In2O3-modified LMNCO material with 2 wt% In2O3 demonstrates the highest ICE and the best rate capability and cycle stability, which are much superior to those of the pristine LMNCO. This surface modified material exhibits the specific capacities of 268.2 and 109.1 mAh g−1 at the current rates of 0.1C and 5C, respectively. After cycling at 1C rate for 200 cycles, the discharge specific capacity is declined from 176.2 to 140.9 mAh g−1, giving capacity retention of 80.0%. The improved electrochemical performance is ascribed to the surface modification of a moderate amount of In2O3. This surface modification can enhance the electrical conduction and hence the electrochemical reaction activity of the active material without hindering the lithium ion transport through the electrode surface. Moreover, it can suppress the undesirable increasing growing of the solid electrolyte interphase film during the repeated charge/discharge cycling due to the surface side reactions between the active material and the electrolyte.

Pristine and Ag decorated In2O3 (110): A gas-sensitive material to selective detect NO2 based on DFT study

High-performance sensors for toxic gases have been the goal of research in the industry. In this paper, the adsorption of seven toxic target gases, NO, NO2, NH3, H2S, CO, CH4 and HCHO, on the intrinsic and modified In2O3 (110) surface is investigated based on Density functional theory (DFT). Relevant parameters such as adsorption energy, charge transfer, adsorption distance and band gap are calculated and a combination of density of states (DOS), deformation charge density (DCD) and frontier molecular orbital theory are employed to investigate the application of In2O3 (110) in gas sensing. Theoretical recovery times were also calculated to provide a basis for the reusability of In2O3 (110) gas sensors. Our calculations show that the intrinsic In2O3 (110) surface responds to several toxic gases, while the Ag dopant enhances the adsorption of In2O3 on NO2 while suppressing its response to HCHO and H2S gases, making Ag-doped In2O3 (110) a promising candidate for a highly selective sensor for NO2.

Adsorption configurations of Co-phthalocyanine on In2O3(111)

Indium oxide offers optical transparency paired with electrical conductivity, a combination required in many optoelectronic applications. The most-stable In2O3(111) surface has a large unit cell (1.43 nm lattice constant). It contains a mixture of both bulk-like and undercoordinated O and In atoms and provides an ideal playground to explore the interaction of surfaces with organic molecules of similar size as the unit cell. Non-contact atomic force microscopy (nc-AFM), scanning tunneling microscopy (STM), and density functional theory (DFT) were used to study the adsorption of Co-phthalocyanine (CoPc) on In2O3(111). Isolated CoPc molecules adsorb at two adsorption sites in a ∼7:3 ratio. The Co atom sits either on top of a surface oxygen (‘F configuration’) or indium atom (‘S configuration’). This subtle change in adsorption site induces different bending of the molecules and differences in their electronic structure. According to DFT, the lowest unoccupied molecular orbital of the undistorted gas-phase CoPc remains mostly unaffected in the F configuration but is filled by one electron in S configuration. At coverages up to one CoPc molecule per substrate unit cell, a mixture of domains with molecules in F and S configuration are found. Molecules in F configuration first condense into a poorly ordered F-(2 × 2) structure and finally rearrange into an F-(1 × 1) structure in which the molecules partially overlap. The only ordered structure of molecules adsorbed in S configuration is an S-(1 × 1) superstructure at full monolayer coverage.

Low-temperature n-type doping of insulating ultrathin amorphous indium oxide using H plasma-assisted annealing

Low-temperature process compatibility is a key factor in successfully constructing additional functional circuits on top of pre-existing circuitry without corrupting characteristics thereof, a technique that typically requires die-to-die (wafer-to-wafer) stacking and interconnecting. And against thermal annealing, which is mandatory and is possible only globally for activating amorphous oxide semiconductors, the selective control of electrical characteristics of the oxide thin-films for integrated circuit applications is challenging. Here, a low-temperature process that enables n-type doping of the designed region of insulating In2O3 thin-film is demonstrated. A short hydrogen plasma treatment followed by low-temperature annealing is used to increase interstitial and substitutional hydrogen associated bond states creating shallow donor levels in the insulating In2O3 surface to transform the thin-film into an n-type semiconductor. As a result, an In2O3 thin-film transistor with a high on/off current ratio (>108), a field-effect mobility of 3.8 cm2 V−1 s−1, and a threshold voltage of ∼3.0 V has been developed. Compared to performing just thermal annealing, the H-plasma assisted annealing process resulted in an n-type In2O3 thin-film transistor showing similar characteristics, while the processing time was reduced by ∼1/3 and the plasma-untreated area still remained insulating. With further development, the hydrogen plasma doping process may make possible a monolithic planar process technology for amorphous oxide semiconductors.

Electron Regulation of Single Indium Atoms at the Active Oxygen Vacancy of In2 O3 (110) for Production of Acetic Acid and Acetone through Direct Coupling of CH4 with CO2.

The production of acetic acid and acetone from the direct coupling of CO2 and CH4 on the doped In2 O3 (110) surface has been studied by extensive first-principles calculations, and the Ga or Al substitution for the single In atom at the active oxygen vacancy of In2 O3 (110) can stabilize the reaction species and reduce the free energy barrier of the rate-limiting C-H activation for the conversion of CO2 and CH4 to acetic acid. Herein, the metal doping lowers the energy level of partially empty s and p orbitals of In1 at the oxygen vacancy site and manipulates its electronic properties, resulting in the activity improvement. The stable intermediate with the newly-formed CH3 COO* has the available In1 site for subsequent CH4 activation, which may initiate the direct C-C coupling of CH3 COO* and CH3 * to yield C3 species on the doped In2 O3 (110). These findings suggest that the metal doping of the active oxygen vacancy opens an avenue for the carbon-chain growth through heterogeneously catalytic coupling of CO2 and CH4 .

Acetone sensing mechanism of Ar/O2 plasma modified indium oxide electrospun fibers: A combined DFT and experimental study

Surface adsorbed oxygen plays a crucial role in the redox reactions of semiconductor gas sensors. A novel, radio frequency plasma modification method, using mixed Ar/O2, was applied to surface treatment of In2O3 electrospun nanofibers to form an oxide-rich structure. Acetone adsorption behavior on the In2O3 (110) surface was investigated using density functional theory (DFT). With the injection of high-energy Ar/O2 plasma, an unoccupied electronic state was formed in the valence band electronic structure of In2O3. The adsorption energy of acetone on In2O3 after modification was 0.136 eV higher than before plasma modification. The adsorption ability of acetone was greatly improved after modification of Ar/O2 plasma. In2O3 sensors were fabricated before and after plasma modification, and the acetone sensing performances were measured. Gas sensing measurement showed that the Ar/O2 mixed plasma modification caused a unique improvement in the acetone sensing performance of the In2O3 sensors.

Efficient removal of PFOA with an In2O3/persulfate system under solar light via the combined process of surface radicals and photogenerated holes

The environmental persistence, high toxicity and wide spread presence of perfluorooctanoic acid (PFOA) in aquatic environment urgently necessitate the development of advanced technologies to eliminate PFOA. Here, the simultaneous application of a heterogeneous In2O3 photocatalyst and homogeneous persulfate oxidation (In2O3/PS) was demonstrated for PFOA degradation under solar light irradiation. The synergistic effect of direct hole oxidation and in-situ generated radicals, especially surface radicals, was found to contribute significantly to PFOA defluorination. Fourier infrared transform (FTIR) spectroscopy, Raman, electrochemical scanning microscope (SECM) tests and density functional theory (DFT) calculation showed that the pre-adsorption of PFOA and PS onto In2O3 surface were dramatically critical steps, which could efficiently facilitate the direct hole oxidation of PFOA, and boost PS activation to yield high surface−confined radicals, thus prompting PFOA degradation. Response surface methodology (RSM) was applied to regulate the operation parameters for PFOA defluorination. Outstanding PFOA decomposition (98.6%) and near-stoichiometric equivalents of fluorides release were achieved within illumination 10 h. An underlying mechanism for PFOA destruction was proposed via a stepwise losing CF2 unit. The In2O3/PS remediation system under solar light provides an economical, sustainable and environmentally friendly approach for complete mineralization of PFOA, displaying a promising potential for treatment of PFOA-containing water.

Cu‐In intermetallic compounds as highly active catalysts for CH 3 OH formation from CO 2 hydrogenation

Converting CO2 into methanol, utilizing a reproducible hydrogen energy source, is one of the most prospective ways in solving the greenhouse effect and energy shortage. The main challenge is to develop highly efficient catalysts capable of achieving high catalytic activity and stability. Herein, we prepare bimetallic catalysts that can effectively catalytic methanol formation from CO2 hydrogenation with better performance compared to monometallic catalysts, which gives a selectivity close to 90% to methanol. The phase of Cu-In intermetallic catalysts changes significantly with the Cu:In molar ratio, but only two Cu11In9 and Cu7In3 intermetallic compounds emerge. The Cu-In intermetallic compounds and oxygen vacancies existed on In2O3 surface are the two active sites with different roles, and their synergistic catalysis results in the adsorption, activation, and further conversion of CO2 and H2. When the Cu:In molar ratio equals 1:2, a Cu11In9-In2O3 intermetallic catalyst is obtained by CuO-In2O3 reduction. Moreover, this catalyst possesses the highest Cu specific surface area (the highest Cu dispersion), the highest surface oxygen vacancy concentration (the highest CO2 adsorption capacity), and the optimal synergistic effect between Cu-In intermetallic compound and In2O3. It, therefore, displays the maximum catalytic performance. 10.3% CO2 conversion, 86.2% CH3OH selectivity, and 5.95 /h/g CH3OH space-time yield are obtained at 260°C, 3.0 MPa, and 7500 mL/gcat/h. CuIn(1:2) owns a good potential as a catalyst for CH3OH synthesis. Novelty Statement Controlled synthesis and catalytic properties of Cu-In intermetallic catalysts. Cu-In intermetallic compounds and In2O3 are the two different active sites. The optimal synergistic effect between Cu11In9 and In2O3 exists in Cu:In(1:2), and Cu:In(1:2) owns an extremely large potential as a catalyst for CH3OH formation from CO2 hydrogenation.

Molecular-Level Insights on the Facet-Dependent Degradation of Perfluorooctanoic Acid.

Perfluorooctanoic acid (PFOA) has raised significant health concerns due to its high ecotoxicological risks and difficulties in removal by conventional water treatment process. Previous studies have demonstrated that photocatalytic techniques exhibit great potential in PFOA removal. However, the underlying mechanism of the degradation process has not been fully understood, particularly the contribution of the facet effects of catalysts. In this study, a combination of experiments and first-principles calculations were conducted to shed light on the facet-dependence of the interfacial interactions and oxidation during the PFOA degradation process. We proved that the interfacial interaction was essential in initiating the hole-dominated degradation process, and the {110}R3̅c facet of hexagonal In2O3 features the strongest interaction with PFOA. The overall defluorination rate was mainly controlled by the hole-dominated oxidation processes under UV irradiation, which were further attributed to the electronic structures and reaction site distributions of different In2O3 surfaces. This study provides molecular-level insights on the facet-dependent PFOA catalytic degradation process, which can guide the rational design of photocatalysts to achieve superior decontamination efficiency.

Improved photocatalytic activity of ZnO via the modification of In2O3 and MoS2 surface species for the photoreduction of CO2

Herein, a series of In2O3 and MoS2 surface-bound active species co-modified using ZnO nanorods (ZnO–In2O3X%/MoS2Y%) were synthesized via a hydrothermal method. X-ray diffraction (XRD), High–resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–Vis absorption, and fluorescence spectroscopy, as well as time-resolved photoluminescence decay curves, have shown that In2O3 and MoS2 were the active species co-modified on the surface of ZnO. The band structure of the resulting photocatalysts was determined via characterization experiments combined with theoretical calculations, and the behavior of the photo-generated electrons and holes were investigated. We noted that the In2O3 and MoS2 surface-bound active species generated transfer channels for the holes and electrons, respectively. For the CO2 photoreduction reaction, the ZnO–In2O3X%/MoS2Y% photocatalysts exhibited improved performance due to the contribution of the surface species during the efficient separation of the photo-generated electrons and holes; this enhanced the visible light absorption capacity and, thus, the catalyst's band structure matching with the redox potential of CO2 photoreduction. This paper provides a new strategy for designing and preparing novel photocatalysts with surface-bound active sites and high photocatalytic performance.