Abundant Oxygen Vacancies Research Articles

Novel sulfur-doped ZnSn(OH)6 nanocubes with induced oxygen vacancies for enhanced humidity sensing

The introduction of defect engineering may increase materials surface redox activity, thereby their sensing properties. Herein, surface defect modulation was achieved by introducing sulfur to induce abundant oxygen vacancies on the surface of ZnSn(OH)6 cubes, which in turn enhanced their humidity sensing performance. Three orders of magnitude in impedance of the S5-ZnSn(OH)6-based humidity sensor was recorded over a relative ambient humidity range of 11 %-95 %, with a response time of 8 s. The sensor also exhibited good linearity, small humidity hysteresis (4.1 %), and long-term stability. The water molecules contact angle of S5-ZnSn(OH)6 sample rapidly decreased to 0°, indicating its stronger excellent hydrophilicity. The adsorption energy of water molecules for S5-ZnSn(OH)6 (−0.827 eV) is more negative than that of the pure one (−0.708 eV), as calculated by using the density functional theory (DFT), revealing a better humidity sensitivity performance of S5-ZnSn(OH)6, which is in agreement with the experimental results. Overall, the proposed sulfur-doped ZnSn(OH)6 humidity sensor was advantageous in terms of simple preparation, low material cost, and good stability performance, thereby promising for future applications.

Transforming Plain LaMnO3 Perovskite into a Powerful Ozonation Catalyst: Elucidating the Mechanisms of Simultaneous A and B Sites Modulation for Enhanced Toluene Degradation.

Herein, we propose preferential dissolution paired with Cu-doping as an effective method for synergistically modulating the A- and B-sites of LaMnO3 perovskite. Through Cu-doping into the B-sites of LaMnO3, specifically modifying the B-sites, the double perovskite La2CuMnO6 was created. Subsequently, partial La from the A-sites of La2CuMnO6 was etched using HNO3, forming novel La2CuMnO6/MnO2 (LCMO/MnO2) catalysts. The optimized catalyst, featuring an ideal Mn:Cu ratio of 4.5:1 (LCMO/MnO2-4.5), exhibited exceptional catalytic ozonation performance. It achieved approximately 90% toluene degradation with 56% selectivity toward CO2, even under ambient temperature (35 °C) and a relatively humid environment (45%). Modulation of A-sites induced the elongation of Mn-O bonds and decrease in the coordination number of Mn-O (from 6 to 4.3) in LCMO/MnO2-4.5, resulting in the creation of abundant multivalent Mn and oxygen vacancies. Doping Cu into B-sites led to the preferential chemisorption of toluene on multivalent Cu (Cu(I)/Cu(II)), consistent with theoretical predictions. Effective electronic supplementary interactions enabled the cycling of multiple oxidation states of Mn for ozone decomposition, facilitating the production of reactive oxygen species and the regeneration of oxygen vacancies. This study establishes high-performance perovskites for the synergistic regulation of O3 and toluene, contributing to cleaner and safer industrial activities.

Modulate synthesis of CeMn solid solution using various alcohols for toluene catalytic oxidation: synergistic effect of Ce-Mn and reaction mechanism

A redox co-precipitation method was employed to synthesize CeMn homogeneous solid solutions, utilizing various alcohols as activating agents. Ethanol effectively orchestrated the precipitation of CeO2 and MnOx, promoting their co-growth. As a result, the CeMn-EA achieved 90 % toluene conversion at 218 ℃ (T90 =218 ℃) with a weight hourly space velocity (WHSV) of 48000 ml/(g·h). It also demonstrated high adaptability to increased WHSV, suggesting its potential for industrial-scale applications. The uniform dispersion of Ce and Mn accelerated the coupling between Ce3+/Ce4+ and Mn4+/Mn3+, engineering numerous oxygen vacancies, which enhanced the activation of gas-phase oxygen and the mobility of lattice oxygen. In situ DRIFTS confirmed that toluene oxidation accommodated both Langmuir-Hinshelwood (L-H) and Mars-van Krevelen (MvK) mechanisms, with benzoate identified as a pivotal intermediate. Enhanced oxygen mobility facilitated the cleavage of the benzene ring, which was the rate-determining step. Additionally, the introduction of H2O significantly enhanced the dissociation and adsorption of toluene and facilitated the activation of gas-phase oxygen. At higher temperatures, H2O could further activate lattice oxygen engaging in toluene oxidation. Environmental ImplicationVolatile organic compounds (VOCs) have emerged as major air pollutants due to the changes in air pollution patterns. They can act as precursors to near-surface ozone and haze. Toluene, a typical VOC, is primarily released from anthropogenic sources and poses significant risks to human health and the environment. Ce-based catalysts have been demonstrated efficiency in toluene oxidation due to their excellent oxygen storage and release properties. This study synthesized CeMn homogeneous solid solutions utilizing various alcohols as activating agents, which possessed abundant oxygen vacancies and optimum oxygen activation capacity to oxidize toluene in time.

Efficient Ozone Elimination Over MnO2 via Double Moisture-Resistance Protection of Active Carbon and CeO2.

The widespread ozone (O3) pollution is extremely hazardous to human health and ecosystems. Catalytic decomposition into O2 is the most promising method to eliminate ambient O3, while the fast deactivation of catalysts under humid conditions remains the primary challenge for their application. Herein, we elaborately developed a splendidly active and stable Mn-based catalyst with double hydrophobic protection of active carbon (AC) and CeO2 (CeMn@AC), which possessed abundant interfacial oxygen vacancies and excellent desorption of peroxide intermediates (O22-). Under extremely humid (RH = 90%) conditions and a high space velocity of 1200 L h-1 g-1, the optimized CeMn@AC achieved nearly 100% O3 conversion (140 h) at 5 ppm, showing unprecedented catalytic activity and moisture resistance toward O3 decomposition. In situ DRIFTS and theory calculations confirmed that the exceptional moisture resistance of CeMn@AC was ascribed to the double protection effect of AC and CeO2, which cooperatively prevented the competitive adsorption of H2O molecules and their accumulation on the active sites of MnO2. AC provided a hydrophobic reaction environment, and CeO2 further alleviated moisture deterioration of the MnO2 particles exposed on the catalyst surface via the moisture-resistant oxygen vacancies of MnO2-CeO2 crystal boundaries. This work offers a simple and efficient strategy for designing moisture-resistant materials and facilitates the practical application of the O3 decomposition catalysts in various environments.

Comparing the abiotic removal of glyphosate by β-MnO2 and δ-MnO2 colloids: Insights into kinetics and mechanisms

Glyphosate as an effective broad-spectrum herbicide is frequently detected in various water and soil resources. Given the ubiquity of β-MnO2 and δ-MnO2 colloids in groundwater and soil, the abiotic removal of glyphosate by MnO2 colloids was investigated. β-MnO2 colloids exhibited superior glyphosate removal efficiency, up to 37%, compared to 21% for δ-MnO2 colloids at a pH of 4.0. Glyphosate removal involved simultaneous adsorption and oxidation process, identified by HRTEM, NH3-TPD, XPS, LC-MS, FTIR analyses and the occurrence of aminomethylphosphonic acid (AMPA) and Mn2+. Moreover, adsorption dominated the removal of glyphosate by two MnO2 colloids. The solution pH had a substantial effect on glyphosate removal. Co-existing ions in the solution, such as carbonate (CO32−), phosphate (Na2HPO4, NaH2PO4) and humic acid (HA), were also found to impede glyphosate removal. Phosphate, in particular, exhibited a strong competitive effect for adsorption sites on both MnO2 colloids. Of them, the removal of glyphosate by β-MnO2 colloids was more prone to occur due to its higher specific surface area, abundant oxygen vacancies, and moderate acid sites. However, δ-MnO2 colloids presented a stronger oxidation capacity than that of β-MnO2 colloids due to the quicker generation rate of Mn2+. Finally, AMPA was the same products by two MnO2 colloids in the oxidation process, revealing the degradation pathway based on the cleavage of C–N bond. Therefore, by comparing kinetics and mechanisms of glyphosate removal by β- and δ-MnO2 colloids, this study improves us better understanding for the behavior of glyphosate in the environment.

Preparation of defect-enriched Cu-doped FeOCl/g-C3N4Z-scheme composites for efficient photo-Fenton-like performance

In this study, a Z-scheme heterojunction with abundant oxygen vacancies (OVs) formed by Cu-doped FeOCl (Cu-FeOCl) and graphitic carbon nitride nanosheets (CNNS) was successfully synthesized for the removal of tetracycline hydrochloride (TC). The prepared Cu-FeOCl/CNNS had excellent catalytic properties under hydrogen peroxide and light illumination, and the maximum reaction rate was nearly 156 and 48 times higher than that of FeOCl and CNNS, respectively. The enhancement of catalytic performance was due to the synergistic effect of Cu species, Fe species and Ovs, which effectively promoted the adsorption and activation of H2O2, and inhibited the recombination of photogenerated carriers. We further studied the effects of different reaction conditions (catalyst dosage, H2O2 dosage, initial pH, TC concentration, and coexisting substances) on the degradation reaction. 1O2, h+, •O2−, and •OH were active species participating in the reaction, and a possible TC degradation mechanism was studied. This work provided insights into the synergetic action of interface engineering, ion doping, and oxygen defects in the photo-Fenton-like system.

Reinforcing built-in electric field via weakening metal–oxygen covalency within MOFs-based heterointerface for robust oxygen evolution reaction

Achieving enhanced built-in electric field (BEF) is highly desirable for accelerating charge transfer and boosting catalytic activity towards oxygen evolution reaction (OER) but still remains a huge challenge. Herein, we constructed the heterointerface composed of FeCo2S4 and CoFe-MOF with abundant oxygen vacancies on Ni foam substrate (named as FeCo2S4@Ov-CoFe-MOF/NF). Experimental and theoretical findings proposed that the introduction of abundant oxygen vacancies into the heterointerface could increase the energy level difference of the two components and reduce electron clouds overlap between metal Co/Fe and oxygen for increased BEF. Such enhanced BEF could accelerate the electronic migration for optimizing the d-band center and adsorption/desorption capacity of reaction intermediates. As expected, the target FeCo2S4@Ov-CoFe-MOF/NF with high BEF intensity displayed splendid OER activity and durability in the alkaline and neutral medium. The present work provides precise guidance for designing other advanced catalysts through deliberately manipulating the BEF.

In Situ Growth of Mn-Co3O4 on Mesoporous ZSM-5 Zeolite for Boosting Lean Methane Catalytic Oxidation

The low-temperature oxidation of methane gas in coal mine exhaust gas is important for reducing the greenhouse effect and protecting the environment. Unfortunately, the carbon–hydrogen bonds in methane molecules are highly stable, requiring higher reaction temperatures to achieve effective catalytic oxidation. However, metal oxide-based catalysts face the problem of easy sintering and the deactivation of active components at high temperatures, which is an important challenge that catalysts need to overcome in practical applications. In this work, a series of Mn-Co3O4 active components were grown in situ on ZSM-5 zeolite with mesoporous pore structures treated with an alkaline solution via a hydrothermal synthesis method. Due to the presence of polyethylene glycol as a structure-directing agent, manganese can be uniformly doped into the Co3O4 lattice. The large specific surface area of ZSM-5 zeolite allows the active component Mn-Co3O4 to be uniformly dispersed, effectively preventing the sintering and growth of active component particles during the catalytic reaction process. It is worth mentioning that the Mn-Co3O4/meso-ZSM-5-6.67 catalyst has a methane conversion rate of up to 90% at a space velocity of 36,000 mL·g−1·h−1 and a reaction temperature of 363 °C. This is mainly due to the mesoporous ZSM-5 carrier with a high specific surface area, which is conducive to the adsorption and mass transfer of reaction molecules. The active component has an abundance of oxygen vacancies, which is conducive to the activation of reaction molecules and enhances its catalytic activity, which is even higher than that of noble metal-based catalysts. The new ideas for the preparation of metal oxide-based low-temperature methane oxidation catalysts proposed in this work are expected to provide new solutions for low-temperature methane oxidation reactions and promote technological progress in related fields.

Strong Electronic Interaction in High-Entropy Oxide Enhances Oxygen Evolution Reaction.

High-entropy oxides are a new type of material with significant application potential. However, the lack of a universal HEO preparation method severely limits the property study and application of HEOs. Herein, we report a universal approach of spray pyrolysis for the preparation of various HEOs and study the electrocatalytic performance of HEOs toward the oxygen evolution reaction. FeCoNiMoWOx HEO exhibits an overpotential of 281 mV at 10 mA cm-2 and a Tafel slope of 34.5 mV dec-1, which are far superior to those of the corresponding medium-entropy oxide and low-entropy oxide. It is found that the high entropy of the HEO greatly strengthens the interaction between Fe and Mo/W and produces abundant oxygen vacancies (OVs) around Mo and W. This work not only provides a universal preparation method for HEOs but also deepens our understanding of OER catalytic activity of HEOs.

Highly responsive double-shell ZnO hollow microspheres based gas sensor for acetic acid detection in vinegar

Acetic acid sensing materials for environmental and related food quality control requiring high sensitivity and selectivity, and ppb-level detection limit, remain challenging. Double-shell ZnO hollow microspheres were prepared by a surfactant assisted template method, and the resultant gas sensor showed excellent acetic acid sensing performance. The sensor response reached 116 to 100 ppm acetic acid at 270°C with a short response time of 3.2 s. The relationship between acetic acid concentration and the response was established, and the detection limit reached 100 ppb. DFT theory computational results demonstrated the highest adsorption energy of the ZnO gas sensor to acetic acid among all tested gases, proving its high selectivity to acetic acid. Besides, the unique double-shell hollow structure with abundant oxygen vacancy and large surface area might be the other factors that gave rise to its excellent acetic acid gas sensing performance. Based on the gas sensor, a method for fast quantitative detection of acetic acid content in vinegar was developed. The linear relationship between sensor response and acetic acid gas concentration of vaporized white vinegar was established, and the acetic acid content in the vinegar can be quickly determined. The result proved our acetic acid sensor to be a promising candidate for practical applications.

Boosting CO2 methanation activity by tuning Ni crystal plane and oxygen vacancy in Ni/CeO2 catalyst

It is challenging to boost CO2 methanation activity over Ni-based catalysts, and new findings that decipher the relationship between the essential laws of catalysts and their catalytic performance will be transformative. Herein, three kinds of Ni/CeO2 catalysts with different Ni crystal facets and oxygen vacancy are developed by varied preparation methods, which show significant differences in catalytic performance for CO2 methanation, and these catalysts are taken as a case study for the investigation of the crystal plane and oxygen vacancy effects in CO2 methanation as well. It is observed that the activity of Ni/CeO2-SG catalyst with abundant oxygen vacancies and principally exposed Ni (111) crystal facet is highly active for CO2 methanation reaction, which is 1–3 times than that of Ni/CeO2 catalysts with poor oxygen vacancy and/or Ni (111) crystal face. In addition, the former one cannot suffer from deactivation even in operation 130 h at 300 °C. Both structural investigations and catalytic evaluations indicate that the adsorption and activating ability of H2 and CO2 can be controlled by adjusting the Ni-exposed crystal face and oxygen vacancy concentration, respectively. It is also verified that the synergistic contribution of the Ni crystal facets and the oxygen vacancy play a crucial role in boosting the catalytic activity of the Ni/CeO2 catalysts by affecting the adsorption and activation of reactants. The Ni/CeO2 catalysts exposed Ni (111) crystal plane facilitate the catalytic activity by strengthing the H2 adsorption/dissociation capacity, while the abundantly available oxygen vacancies maximize the activity via acting as CO2 activation sites. Furthermore, the in situ DRIFT experiments reveal that the direct formate hydrogenation pathway is involved in the CO2 methanation process over the Ni/CeO2-SG catalyst.

Facile synthesis of porous Au-decorated SnO2 microflowers with abundant oxygen vacancies for trace VOCs detection

Hierarchical Au-decorated SnO2 (Au@SnO2) microflowers with a porous structure were successfully synthesized. The preparation process involves in a hydrothermal method, calcination treatment, as well as modification. The hierarchical structure consisted of a large number of porous, uniform nanosheets. Excellent gas-sensing performances were demonstrated by the gas sensors fabricated using Au@SnO2 microflowers, for detecting volatile organic compounds (VOCs). In particular, for the accurate and fast detection of formaldehyde, the 2%Au-decorated SnO2 microflowers sensors showed a strong sensing response (76.5) for formaldehyde (100 ppm) at 140 °C, approximately three times higher than that (28.2) observed for the pure porous SnO2 microflowers. The response and recovery times (10 s/16 s) were shorter than those (12 s/25 s) of the pure SnO2, respectively. The detection limit for the 2%Au@SnO2 sensor was 19.03 ppb. The sensing mechanism of Au@SnO2 sensors was also investigated. Favorable porous 3-dimensional structure, high catalytic activity, and electron sensitization effect of Au nanoparticles (NPs) improved the gas-sensing performance. Furthermore, the catalytic activity of Au NPs was maximized due to their uniform distribution on the surface of each porous SnO2 nanosheet. The Au-decorated SnO2 microflowers sensors have great potential for the accurate, fast, and highly sensitive response detection of formaldehyde gas.

A novel Fe2O3@CeO2 heterojunction substrate with high surface‐enhanced Raman scattering performance

AbstractSurface‐enhanced Raman scattering (SERS) has been applied in many fields due to its advantages of fast and nondestructive detection. For semiconductors, the large‐scale electron‐hole pair separation of heterojunction is conducive to efficient charge transfer, which is a promising SERS substrate. Here, we designed a Fe2O3@CeO2 heterojunction substrate by hydrothermal method and explored its enhancement mechanism in detail. α‐Fe2O3 is a promising semiconductor with a narrow bandgap, and CeO2 has adequate oxygen vacancies on the surface. Combing α‐Fe2O3 and CeO2 into a shell‐core structure, Fe2O3@CeO2 heterojunction presents higher SERS performance than pure Fe2O3 and CeO2 for methyl orange (MO) molecule with a limit of detection (LOD) of 5 × 10−8 mol/L. Under the excitation of 514 nm, Fe2O3 can produce an effective exciton resonance due to its narrow bandgap (2.01 eV). The oxygen vacancy in CeO2 acts as the active site to promote the adsorption of molecules and facilitate the photo‐induced charge transfer (PICT) between the substrate and MO molecules. Therefore, the high SERS performance of Fe2O3@CeO2 heterojunction is achieved due to the coupling effect of excitons resonance, molecular resonance, and PICT resonance. It is found that Fe2O3@CeO2 has good SERS performance and stability to organic pesticides, especially metamitron (LOD = 5 × 10−9 mol/L). This work combines the advantages of Fe2O3 being prone to producing photoelectrons and abundant oxygen vacancies of CeO2, providing a reference for designing semiconductor SERS.

Oxygen vacancy-enhanced Ni3FeN/NF nanoparticle catalysts for efficient and stable electrolytic water splitting

The highly effective and economical electrocatalysts hold great importance in the context of water electrolysis. In this work, a nanosheet catalyst (Ni3FeN/NF) composed of nanoparticles for comprehensive water splitting was synthesized through a facile hydrothermal technique followed by a subsequent nitridation process. This catalyst is endowed with an abundance of oxygen vacancies, thereby conferring a richer array of active sites. Therefore, the catalyst demonstrates a markedly low overpotential for the OER of 271 mV at 50 mA cm−2 and an equally low overpotential for the HER of 35 mV at 10 mA cm−2. Serving as a dual-function electrode, this electrocatalyst is employed in overall water splitting in alkaline environments, demonstrating impressive efficiency of 10 mA cm−2 at a cell voltage of 1.45 V. In-situ Raman spectroscopy was employed to elucidate the active phase and dynamic surface structure of the Ni3FeN/NF catalyst by conducting measurements at intervals of 0.1 V. At open circuit voltage (OCV), Ni3FeN/NF exhibited pronounced peaks at 532 and 702 cm−1. Notably, at potentials exceeding 1.40 V, distinct peaks were observed at 473 and 551 cm−1. The manifestation of these dual peaks indicates that γ-Ni(Fe)OOH serves as the predominant active species in the oxygen evolution reaction (OER) mechanism for Ni3FeN/NF.

Fe2TiO5 nanoparticle-based novel gas sensor with high response to ethanol and acetone

This paper presents a novel Fe2TiO5 sensing material for ethanol and acetone detection. Pure Fe2TiO5 nanomaterial was synthesized by a combined solvothermal and calcination method using ferrous sulfate as precursor and urea as a surfactant. The microstructure and surface morphology indicate that Fe2TiO5 belongs to the orthorhombic crystal structure with a Bbmm space group and is composed of loose aggregates of irregular nanoparticles (20–30nm) and abundant pores. X-ray photoelectron spectroscopy analysis indicates that the Fe2TiO5 aggregates contain mixed valence states of Fe2+ and Fe3+ and abundant oxygen vacancies. Examination of gas sensing properties suggests that Fe2TiO5 is an excellent gas-sensitive material. Particularly, at a low optimum operating temperature (240 °C), the gas response of the Fe2TiO5 aggregates to 100 ppm ethanol and acetone is as high as 84.1 and 220.9, respectively. The linear relationship between log(S-1) and logC indicates that Fe2TiO5 can accurately detect ethanol and acetone over a wide concentration range. The gas-sensing performance of the novel Fe2TiO5 nanomaterial can be explained based on the synergistic effect of oxygen vacancy defects and the characteristic surface morphology.

Zn promoted GaZrOx Ternary Solid Solution Oxide Combined with SAPO-34 Effectively Converts CO2 to Light Olefins with Low CO Selectivity.

We proposed a new strategy for CO2 hydrogenation to prepare light olefins by introducing Zn into GaZrOx to construct ZnGaZrOx ternary oxides, which was combined with SAPO-34 to prepare a high-performance ZnGaZrOx/SAPO-34 tandem catalyst for CO2 hydrogenation to light olefins. By optimizing the Zn doping content, the ratio and mode of the two-phase composite, and the process conditions, the 3.5 %ZnGaZrOx/SAPO-34 tandem catalyst showed excellent catalytic performance and good high-temperature inhibition of the reverse water-gas shift (RWGS) reaction. The catalyst achieved 26.6 % CO2 conversion, 82.1 % C2 =-C4 = selectivity and 11.8 % light olefins yield. The ZnGaZrOx formed by introducing an appropriate amount of Zn into GaZrOx significantly enhanced the spillover H2 effect and also induced the generation of abundant oxygen vacancies to effectively promote the activation of CO2. Importantly, the RWGS reaction was also significantly suppressed at high temperatures, with the CO selectivity being only 46.1 % at 390 °C.

Empowering green sustainable technologies: Frontier synthesis of oxygen vacancy-modified cobalt oxide

The electrocatalytic hydrogen production and supercapacitor technologies have positive impacts on the environment, promoting the production and utilization of clean and renewable energy sources, thus facilitating the reduction of greenhouse gas emissions. Among them, cobalt oxide (Co3O4) has emerged as an ideal choice for electrode materials in these technologies due to its low toxicity, affordability, and significant theoretical capacity. Nevertheless, practical applications are restricted by its low conductivity and sluggish reaction kinetics. Addressing these challenges, this study introduces a pioneering approach: the synthesis of oxygen vacancy-modified Co3O4/Co/NC small-sized nanoflower composite, which combines the advantages of abundant oxygen vacancies, small size effects, and nitrogen-doped porous carbon. The optimized Co3O4/Co/NC small-sized nanoflower exhibits high porosity and excellent conductivity, providing numerous active sites and effectively enhancing the ion and electron transport rates. As a consequence, optimized Co3O4/Co/NC shows a low Tafel slope and overpotential, highlighting its potential for catalytic application. Moreover, as an electrode for supercapacitors, optimized Co3O4/Co/NC demonstrates excellent long-term stability, maintaining 94.7% of its capacitance even after 5000 charge-discharge cycles. Additionally, it showed a significant specific capacity of 251.4 mAh g−1 when tested at 1 A g−1. In addition to addressing the pressing challenges associated with traditional Co3O4 electrodes, this work opens up exciting avenues for designing and fabricating transition metal oxide-based materials with unprecedented electrochemical performance.

Enhanced Interface Charge Carrier Transport of SnO2/CeO2 via Oxygen Vacancy Synergized Heterojunction for Triethylamine Sensing Property.

Efficient charge carrier transport characteristics are critical to achieving the excellent performance of metal-oxide semiconductor gas sensors. Herein, SnO2/CeO2 heterojunction layered nanosheets with abundant oxygen vacancies were successfully synthesized through a simple solvothermal assisted high-temperature calcination method. The synergistic effect of oxygen vacancies and heterojunctions promoting the charge carrier transport properties at the SnO2/CeO2 interface for the enhanced sensing properties of triethylamine (TEA) was highlighted. As a result, the optimized SnO2/CeO2 exhibits improved gas sensing performance at 173 °C to 50 ppm of TEA. These include high response (205), excellent selectivity, low detection limit, and good long-term stability. This enhanced gas sensing property of SnO2/CeO2 is mainly attributed to the fact that the heterojunction and oxygen vacancies act as dual active sites synergistically inducing electron transfer, thereby effectively modulating the transport properties of the interfacial charge carriers, and thus facilitate the surface reactions efficiently. In this work, the dual-engineering strategy of synergistic interaction of heterojunction and oxygen vacancies can provide new perspectives for the design of advanced gas sensing materials.

Construction of hollow sphere MnOX with abundant oxygen vacancy for accelerating VOCs degradation: Investigation through operando spectroscopycombined with on-line mass spectrometry

To clarify the key role of oxygen vacancy defects on enhancing the oxidative activity of the catalysts, metal–organic frameworks (MOFs) derived MnOX catalysts with different morphologies and oxygen vacancy defects were successfully prepared using a facile in-situ self-assembly strategy with different alkali moderators. The obtained morphologies included three-dimensional (3D) triangular cone stacked MnOX hollow sphere (MnOX-H) and 3D nanoparticle stacked MnOX nanosphere (MnOX-N). Compared to MnOX-N, MnOX-H exhibited higher activity for the oxidation of toluene (T90 = 226 °C). This was mainly due to the large number of oxygen vacancy defects and Mn4+ species in the MnOX-H catalyst. In addition, the hollow structure of MnOX-H not only facilitated toluene adsorption and activation of toluene and also provided more active sites for toluene oxidation. Reaction mechanism studies showed that the conversion of toluene to benzoate could be realized over MnOX-H catalyst during toluene adsorption at room temperature. In addition, abundant oxygen vacancy defects can accelerate the activated oxidation of toluene and the formation of oxidation products during toluene oxidation.

Antimony-Doped Wide Bandgap Molybdenum Trioxide with Enhanced Localized Surface Plasmon Resonance for Nitrogen Photofixation.

Plasmonic metal oxides are promising photocatalysts for the artificial photosynthesis of green ammonia due to localized surface plasmon resonance (LSPR) enhanced photoconversion and rich surface oxygen vacancies improved chemisorption and activation of dinitrogen molecules. However, these oxygen vacancies are unstable during the photocatalytic process and could be oxidized by photogenerated holes, leading to the vanishing of the LSPR. Here, we fabricated antimony-doped molybdenum trioxide nanosheets with stable plasmonic absorption extending into the near-infrared (NIR) range, even after harsh treatment in oxidative atmospheric conditions at high temperatures. For undoped plasmonic MoO3-x nanosheets, the LSPR originates from the abundant oxygen vacancies that vanish after heat treatment at high temperatures in air, leading to the disappearance of the LSPR absorption. Sb doping does not significantly increase the concentration of oxygen vacancies while donating more free electrons because Sb can keep a lower oxidation state. Heat treatment diminished the oxygen vacancies while not affecting the low oxidation state of Sb. As a result, heat-treated Sb-doped MoO3-x nanosheets still show strong LSPR absorption in the NIR range. Both experimental results and theoretical calculations demonstrated that add-on states close to the Fermi level are formed due to the Sb doping and high concentration of oxygen vacancies. The prepared samples were used for photocatalytic nitrogen reduction and showed an LSPR-dependent photocatalytic performance. The present work has provided an effective strategy to stabilize the LSPR of plasmonic semiconductor photocatalysts.