Amount Of Surface Oxygen Vacancies Research Articles

Facile fabrication of carbon supported Bi2O3-BiOCl-Bi heterostructure to boost ammonia under visible light

In this paper, carbon supported Bi2O3-BiOCl-Bi heterostructures were successfully synthesized via a facile and simple hydrothermal method. A series of structure and morphology testing clearly showed that carbon and metallic Bi were deposited on the surface margin of Bi2O3-BiOCl, which benefited the rapid transfer of internal photogenerated electrons. Photophysical experiments including electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) indicated that the amount of surface oxygen vacancies (OVs) was significantly increased, which act as reactive active sites and therefore effectively enhance the photocatalytic performance. The photocatalytic N2 reduction yield of C@Bi2O3-BiOCl-Bi was remarkably improved to 400 μg·L−1, which was 3.63 times higher than that of BiOCl. This research demonstrated a feasible strategy to construct advanced photocatalyst by incorporating defect-rich structures and surface engineering.

Morphological effect of MnO2 promoter on iron-based Fischer-Tropsch synthesis catalysts

In this work, flower-like spherical, sea urchin-like and tubular MnO2 are prepared via hydrothermal synthesis and used as promoters of iron-based Fischer-Tropsch synthesis (FTS) catalysts to investigate their morphological effects. It is found that the different morphology of MnO2 exhibits observably distinct promotion functions on iron-based FTS catalysts. Tubular MnO2 contains moderate amount of surface oxygen vacancies accompany with weak Fe-Mn electronical interaction, as a result, tubular MnO2 promotes the formation of long-chain hydrocarbon and olefins, and restrains the generation of CH4. Flower-like spherical MnO2 presents negative roles in the CO conversion and formation of long-chain hydrocarbon, due to its insufficient oxygen vacancies and moderate Fe-Mn electronical interaction. With the most abundance of oxygen vacancies and strongest Fe-Mn interaction, sea urchin-like MnO2 modified catalysts exhibits the highest initial CO conversion, but deactivates rapidly. Besides, the sea urchin-like MnO2 enhances the formation of long-chain paraffins. This work presents new insights of the promotion roles of Mn additive, which is beneficial for the rational design of efficient iron-based FTS catalysts.

Atomically dispersed SrOx species on exposed {2 2 2} facets of pyrochlore La2Zr2O7 nanocrystals for boosting low-temperature oxidative coupling of methane

The efficient catalysts of strontium oxide (SrOx) supported on exposed {222} facets of pyrochlore La2Zr2O7 nanocrystals (SrOx/LZO-Y) were elaborately synthesized by incipient wetness impregnation method. The introduction of atomically dispersed SrOx species on La2Zr2O7 surface can increase the amount of surface oxygen vacancies induced by Sr2+ substitution of La3+ cations, and the increasing of moderate surface alkaline sites are beneficial to enhance catalytic performance for oxidative coupling of methane (OCM). The SrOx/LZO-Y catalysts have super catalytic performance during low-temperature OCM reaction. SrOx/LZO-12 catalyst with the highest concentrations of O2– species exhibits the highest activity and the lowest apparent activation energy (84 kJ mol−1) during low-temperature OCM into C2H4 and C2H6 (C2) products, i.e., its CH4 conversion, selectivity and yield of C2 products at 600 °C are 30.5 %, 47.4 % and 14.5 %, respectively, and its ratio of C2H4/C2H6 products is 0.77. Based on the results of multiple experimental characterizations, the mechanism of SrOx/LZO-Y catalysts for OCM reaction is proposed: the surface alkaline active centers (O2–) induced by doping of Sr ions can promote the critical step of CH4 activation significantly during low-temperature OCM reaction. It is a new strategy to develop the low-temperature and high-activity catalysts for OCM in practical application.

Silver-modified NiCo2O4 nanosheets monolithic catalysts used for catalytic soot elimination

Highly active spinel-derived monolithic catalysts loading Ag (xAg/NiCo-NS) have been successfully designed and synthesized and used to catalytic soot elimination. The crossed macro-porous of NiCo2O4 nanosheets and the three-dimensional porous structure of Ni foam not only provides a convenient gas mass transfer channel, but also provides a large number of contact points between soot and catalyst. After loading Ag on the NiCo-NS, the catalytic performance for soot oxidation is improved remarkably. Among the xAg/NiCo-NS catalysts, the 4.5Ag/NiCo-NS sample has the highest catalytic performance with the lowest T50 (333 °C), which is 50 °C lower than that of the NiCo-NS catalyst and lower than that of other prove metal catalysts (Pt/Pd/Au) in the atmosphere of 500 ppm NO/10 % O2/N2. The metal-support interaction between Ag and NiCo-NS weakens the Co-O bond, increases the amount of surface oxygen vacancies and improves the intrinsic activity determined by turnover frequency (TOF) of the catalyst. Moreover, Ag can also adsorb and activate gaseous oxygen to produce the low-temperature active oxygen species (O2−), which can promote the soot combustion in the low temperatures. Based on the catalytic performance for soot oxidation and activation Energy (Ea), the reaction paths for the catalytic combustion of soot on Ag/NiCo-NS are identified.

Tuning oxygen vacancy in Bi2WO6 by heteroatom doping for enhanced photooxidation-reduction properties

Heteroatom doping was recently regarded as an effective method to tune the band gap and improve the separation and transfer of photogenerated electron-hole pairs in semiconductor photocatalysts. Herein, a novel S,F-codoped Bi2WO6 (S,F-Bi2WO6) with suitable oxygen vacancies was synthesized via the hydrothermal-calcination and post-sulfurization, for efficient Cr(VI) reduction and methyl orange (MO) degradation under visible light. The amount of surface oxygen vacancies could be controlled by adjusting the S/F ratio during the doping process, which modulated the band structure and photogenerated charge behavior of Bi2WO6. The optimal S0.10F-Bi2WO6 exhibited an excellent photooxidation-reduction performance, which Cr(VI) reduction and MO degradation efficiencies were 1.6 and 2.6 times than those of the pristine Bi2WO6 without oxygen vacancy under visible-light, respectively. The enhanced photooxidation-reduction performance was because the right amount of oxygen vacancies could effectively narrow the bandgap and improve the separation efficiency of electron-hole pairs. Thus, this work offered a mild and simply approach for preparing heteroatom doped Bi2WO6 and a potential to be extended to the synthesis of other doped materials for environmental remediation.

Enhancing the photocatalytic activity of Ruddlesden-Popper Sr2TiO4 for hydrogen evolution through synergistic silver doping and moderate reducing pretreatment

The photocatalytic hydrogen (H2) generation relies heavily on the properties of photocatalysts, including their light absorption, charge transport, and oxygen vacancy of photocatalysts. In this work, we have successfully synthesized Ruddlesden-Popper perovskite Sr2TiO4 as photocatalysts for H2 evolution reaction. Importantly, we adopted a facile and effective strategy of Ag doping and reducing pretreatment to tailor the properties of Sr2TiO4 photocatalysts. The synergistic effect of Ag doping and moderate reducing pretreatment confers Sr2TiO4 photocatalyst with improved morphological characteristics, increased specific surface area, optimized light absorption capability, and bandgap, suppressed charge carrier recombination, as well as an increased amount of surface oxygen vacancies. Benefiting from these merits, r-Ag0.05Sr1.95TiO4 with a suitable amount of Ag doping and moderate reducing pretreatment displays an excellent photocatalytic performance for H2 generation, which presents average H2 production rates of 1695 μmol h−1 g−1 and 541 μmol h−1 g−1 under full-range light irradiation (λ ≥ 250 nm) and visible light irradiation (λ ≥ 400 nm), respectively.

Preparation of supported In2O3/Pd nanocatalysts using natural pollen as bio-templates for CO2 hydrogenation to methanol: Effect of acid-etching on template

The conversion of CO2 into value-added chemicals is an effective way to mitigate the environmental problems caused by huge anthropogenic CO2 emissions. Although In2O3/Pd catalyst possesses excellent catalytic performance in CO2 hydrogenation to methanol, the formation of Pd-In alloy on the catalyst surface greatly reduces the yield of methanol. Herein, we adopt a natural biomaterial (viz., rape pollen) as a template to synthesize hierarchically structured bio-In2O3 and bio-In2O3/Pd catalysts. In particular, we found that the pretreatment of pollen using hydrochloric acid (HCl) played a critical role in determining catalytic performance. A series of bio-In2O3 were prepared by using the pollen templates with different etching degrees, and then the bio-In2O3-x/Pd catalysts (x denoted as the amount of HCl, mL) were prepared using an impregnation-reduction method. It was surprising that the CO2 conversion of bio-In2O3–15/Pd catalyst was 8.2% with methanol selectivity of 74.7%, which was much better than the bio-In2O3–0/Pd (2.6% and 54.6%, respectively). The dramatic enhancement was due to that the acid-etched pollen template owns a hollow cage-like structure and abundant surface functional groups (-NH2 and -COOH), which is beneficial to the growth of In2O3 with a high amount of surface oxygen vacancies. Also, the bio-In2O3/Pd catalyst (prepared with untreated pollen template) was more prone to form Pd-In alloys as a result of the strong interaction between Pd with In2O3. In contrast, the In2O3 spatial distribution of bio-In2O3–15/Pd was more uniform with an appropriate interaction of Pd with In2O3 that inhibited the formation of Pd-In alloys. Even Pd loaded on commercial In2O3 exhibited inferior performance (3.4% CO2 conversion and 81% methanol selectivity) to bio-In2O3–15/Pd catalyst. Accordingly, the present work offers a green and efficient method to prepare supported In2O3/Pd catalysts by using the acid-etched pollen as a template.

Exploring the activation pathway of photo-induced electrons in facets-dependent I− doped BiOCl nanosheets for PCPNa degradation

Electrons can degrade pentachlorphenate sodium (PCPNa) directly or activate molecular oxygen to produce and ·OH for its degradation. However, less work has been performed to control such two kinds of reaction pathway by modifying BiOCl. Herein, we firstly regulated the reaction pathway between electrons and PCPNa by adjusting the amount of surface oxygen vacancies (OVs) and surface adsorbed hydroxyl groups in I− doped BiOCl exposed with different facets. OVs on (001) facets-exposed I− doped BiOCl enabled large amount of PCPNa to adsorb on its surface and facilitated the direct reaction between electrons and PCPNa. In contrary, more surface adsorbed hydroxyl groups and oxygen on (010) facets-exposed I− doped BiOCl can retard the direct reaction between electrons and PCPNa via lowering the adsorption of PCPNa and increasing the activation of molecular oxygen by electrons. Although more and ·OH generated in I− doped (010)-facets exposed BiOCl, I− doped (001)-facets exposed BiOCl exhibited better photocatalytic activity. We proposed that the direct reaction between electrons and PCPNa can enhance the utilization efficiency of photogenerated electrons and improve photocatalytic degradation efficiency of PCPNa.

Promotional Effect of Manganese on Selective Catalytic Reduction of NO by CO in the Presence of Excess O2 over M@La–Fe/AC (M = Mn, Ce) Catalyst

The catalytic performance of a series of La-Fe/AC catalysts was studied for the selective catalytic reduction (SCR) of NO by CO. With the increase in La content, the Fe2+/Fe3+ ratio and amount of surface oxygen vacancies (SOV) in the catalysts increased; thus the catalytic activity improved. Incorporating the promoters to La3-Fe1/active carbon (AC) catalyst could affect the catalyst activity by changing the electronic structure. The increase in Fe2+/Fe3+ ratio after the promoter addition is possibly due to the extra synergistic interaction of M (Mn and Ce) and Fe through the redox equilibrium of M3+ + Fe3+ ↔ M4+ + Fe2+. This phenomenon could have improved the redox cycle, enhanced the SOV formation, facilitated NO decomposition, and accelerated the CO-SCR process. The presence of O2 enhanced the formation of the C(O) complex and improved the activation of the metal site. Mn@La3-Fe1/AC catalyst revealed an excellent NO conversion of 93.8% at 400 °C in the presence of 10% oxygen. The high catalytic performance of MnOx and double exchange behavior of Mn3+ and Mn4+ can increase the number of SOV and improve the catalytic redox properties.

Understanding the Structure-Performance Relationship of Lithium-Rich Cathode Materials from an Oxygen-Vacancy Perspective.

Li-rich layered oxide cathode materials are regarded as an attractive candidate of next-generation Li-ion batteries (LIBs) to realize an energy density of >300 Wh kg-1. However, challenges such as capacity fade, cycle life, oxygen release, and structural transformation still restrain its practical application. Micro/nanotechnology is one of the effective strategies to enhance its structural stability and electrochemical performance. An in-depth understanding of the relationship between micro/nanostructures and the electrochemical performance of Li-rich layered oxides is undoubtedly important for developing high-performance cathode materials. Herein, Li1.2Ni0.13Co0.13Mn0.54O2 with different micro/nanostructures including irregular particles, microspheres, microrods, and orthogonal particles are synthesized. Starting from the amount of surface oxygen vacancies in the different structures, the influence of oxygen vacancies on every step during the charge-discharge processes is analyzed by experimental characterizations and theoretical calculations. It is indicated that intrinsic oxygen vacancies can enhance the electrical conductivity and decrease the energy barrier for ion migration, which exerts a significant influence on promoting the kinetics and capacity. Among the different micro/nanostructures, microrods with abundant oxygen vacancies can not only promote lithium ion transport but also stabilize a cathode electrolyte interface (CEI) film by adjusting the distribution of surface elements with lower nickel content. The microrods deliver an initial discharge capacity of up to 306.1 mAh g-1 at 0.1C rate and a superior cycle performance with a capacity retention of 91.0% after 200 cycles at 0.2C rate.

Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria: Soot-ceria contact and interfacial oxygen evolution

Ceria is widely used as a catalyst for soot combustion, but effects of Zr substitution on the reaction mechanism is ambiguous. The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria. The nanostructured CeO2, Ce0.92Zr0.08O2, and Ce0.84Zr0.16O2 composed of 5–6 nm crystallites display Tm-CO2 (the temperature at maximum CO2 yield) at 383, 355, and 375°C under 10 vol.% O2/N2, respectively. The size of agglomerate decreases from 165.5 to 51.9–57.3 nm, which is beneficial for the soot-ceria contact. Moreover, Zr increases the amount of surface oxygen vacancies, generating more active oxygen (O2− and O−) for soot oxidation. Thus, the activities of Ce0.92Zr0.08O2 and Ce0.84Zr0.16O2 in soot combustion are better than that of CeO2. Although oxygen vacancies promote the migration of lattice O2−, the enriched surface Zr also inhibits the mobility of lattice O2−. Therefore, the Tm-CO2 of Ce0.84Zr0.16O2 is higher than that of Ce0.92Zr0.08O2. Based on reaction kinetic study, soot in direct contact with ceria preferentially decomposes with low activation energy, while the oxidation of isolated soot occurs through diffusion with high activation energy. The obtained findings provide new understanding on the soot combustion over nanoceria.

Ag/Ag2S Nanoparticle-Induced Sensitization of Recovered Sulfur-Doped SnO2 Nanoparticles for SO2 Detection

Sulfur dioxide is one of the most hazardous and toxic air pollutants. Herein, S-doped SnO2 material (S-SnO2) was successfully recovered from tin sludge that is an important secondary tin resources with a tremendous output and high tin oxide content. After dispersion and Ag modification of the recovered S-SnO2, the as-prepared Ag/Ag2S-doped S-SnO2 (Ag/Ag2S/S-SnO2) showed an excellent sensing performance toward SO2. The morphology, structure, and surface state of the as-prepared materials were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), photoluminescence (PL), and N2 adsorption–desorption. The recovered S-SnO2 dispersed by titanate coupling agents (CT-201) showed enhanced particle dispersion and an enlarged active surface area and exhibited a high response toward SO2. Ag/Ag2S modification of the dispersed S-SnO2 obtained a markedly increased response of 10.1 and a lower operating temperature of 180 °C by increasing the amount of surface oxygen vacancies and by facilitating SO2 dissociation by further reacting between SO2 oxidation products and Ag2S. This work demonstrated the enhancement mechanism of the reaction between multiple valence sulfides on SO2-sensitive properties of SnO2-based catalysts. Furthermore, this work realized high-value-added recovery of a secondary tin resource and contributed to the alleviation of the scarcity of tin resources and reduction in the burden on the environment.

Highly efficient Cu/CeO2-hollow nanospheres catalyst for the reverse water-gas shift reaction: Investigation on the role of oxygen vacancies through in situ UV-Raman and DRIFTS

Self-assembled CeO2 with 3D hollow nanosphere, nanoparticle and nanocube morphologies were prepared and used to support Cu particles. The obtained samples (denoted as Cu/CeO2-hs, Cu/CeO2-np and Cu/CeO2-nc, respectively) were tested for the reverse water-gas shift (RWGS) reaction. Under the reaction conditions, V(H2):V(CO2) = 3:1 and weight hourly space velocity (WHSV) = 300,000 mL g−1 h−1, the Cu/CeO2-hs sample exhibited the best catalytic performance among the as-prepared catalysts. In order to reveal the key factors affecting the catalytic performance, the physicochemical properties of the catalysts were analyzed by XRD, BET, SEM, TEM, H2-TPR, quasi in-situ XPS and in situ UV-Raman techniques. The results point out that the particle size of Cu is not the rate-determining factor while the amount of surface oxygen vacancies is highly correlated with the catalytic reaction rate. In situ UV-Raman and in situ DRIFTS experiments indicate the formation of bidentate carbonate and formate species on oxygen vacancy sites which is thought to be the key intermediates for the RWGS reaction. These findings unravel the crucial roles of surface oxygen vacancies on CO2 adsorption and activation and also highlight a feasible way for the design of highly efficient catalysts for the important RWGS reaction in chemical industry.

Optimization of BiVO4 photoelectrodes made by electrodeposition for sun-driven water oxidation

In this work, the synthesis of cheap BiVO4 photoanodes for the photoelectrochemical water splitting reaction was optimized via the scalable thin film electrodeposition method. Factors affecting the photoelectrochemical activity, such as the electrodeposition time, the ratio of the Bi-KI to benzoquinone-EtOH in the deposition bath, and the calcination temperature, have been investigated by using the Central Composite Design of Experiments. Pristine monoclinic scheelite BiVO4 photoanodes having a photocurrent density of 0.45 ± 0.05 mA/cm2 at 1.23 V vs RHE have been obtained. It was shown that a high photocurrent density is generally dictated by the following physico-chemical properties: a higher crystallite size, optimal thickness and a porous morphology, which give rise to a low charge transfer resistance, low onset potential and a high donor density. Moreover, to the best of our knowledge, this is the first report on the depth profile XPS analysis performed in BiVO4 photoanodes made by electrodeposition technique, from which it was concluded that the surface V species exist as V4+ while the bulk V species are V5+. The V4+ induces a higher amount of surface oxygen vacancies, which was found to be beneficial for the photoactivity.

Hydrogenated LaFeO3 with oxygen vacancies for Enhanced Visible light photocatalytic performance

A novel hydrogenated LaFeO3 was fabricated and firstly used as photocatalyst in the application of visible-light photocatalytic decomposition of organic contaminant. Through the adjusting of annealing atmosphere and temperature, a series of treated LaFeO3 with oxygen vacancies were obtained. Compared with untreated LaFeO3 and argon treated LaFeO3, hydrogenated LaFeO3 photocatalysts exhibited higher catalytic ability. This notably improved catalytic ability was mainly assigned to the formation of disordered layer on the surface of hydrogenated LaFeO3. The surface oxygen vacancies of LaFeO3 caused by hydrogenation were beneficial to light absorption and separation of photogenerated carriers. In this system, we found the amount of surface oxygen vacancies had a direct impact on the catalyst ability of hydrogenated LaFeO3 photocatalysts. In addition, the magnetic hydrogenated LaFeO3 photocatalysts were stable, and reused after five times without obvious decrease of catalytic ability.

Activated carbon supported MnO nanoparticles for efficient ozone decomposition at room temperature

Abstract MnO nanoparticles supported on coal-based activated carbon (AC) were facilely fabricated via incipient wetness impregnation method by calcination of manganese acetate in nitrogen. The as-prepared catalysts were characterized by N2 adsorption-desorption, XRD, TEM, and XPS. It is demonstrated that calcination under inert atmosphere can facilely obtain well dispersed MnO nanoparticles on AC, and the particle size, as well as the surface oxygen species of the catalysts strongly depended on the calcination temperature. The AC supported MnO nanoparticles all exhibited high catalytic activity toward ozone decomposition at room temperature, and an optimal one was displayed as the calcination temperature of 700 °C. The smallest particle size of MnO nanoparticles and the most amount of surface oxygen vacancies, were mainly responsible for the highest activity of MnO/AC-700. Moreover, lower loading of Mn was found to be more favorable for stable catalytic performance. This work reported a series of MnO based catalysts for efficient removal of ozone at room temperature for the first time, and may shed new lights on the design of manganese oxides with lower oxidation state for efficient ozone decomposition.

Soot oxidation over CeO2-ZrO2 based catalysts: The influence of external surface and low-temperature reducibility

Fresh CeO2-ZrO2-Y2O3-La2O3 (CZYL) catalyst was synthesized via calcining at 600 ºC of relative precipitates obtained by co-precipitation and then aged at 700–1000 ºC. Afterwards, 10wt% MnO2 was further loaded on the fresh and 800 ºC-aging sample, respectively. The oxidation activity tests illustrate that the catalytic performance of CZYL catalysts firstly remains stable and then decreases with increasing aging temperature. Systematical investigations suggest that the amount of surface oxygen vacancies and O2 desorption ability of all these Ceria-Zirconia (CZ) based catalysts may be high enough to make little difference on their catalytic activity. On the contrary, it is found that the external surface area and low-temperature reducibility (<500 ºC) are the two major factors to influence the soot oxidation activity. Interestingly, the external surface area will does no difference when its value is above a critical point. Furthermore, only relatively larger distinction in low-temperature reducibility among catalysts will contribute to apparently various catalytic activity.

Reduced TiO2 with tunable oxygen vacancies for catalytic oxidation of formaldehyde at room temperature

A series of reduced TiO2 were prepared using NaBH4 and the commercial Degussa P25 as the precursors by tuning the reaction time, and used for catalytic oxidation of HCHO at ambient conditions. Multiple techniques, i.e., UV–Vis, XRD, BET, SEM, TEM, Raman and XPS were used for catalyst characterization. The reduction time was found to remarkably affect the surface oxygen vacancies and surface disorder of the catalysts. Compared with P25, the reduced TiO2 were able to catalytic oxidation of formaldehyde at room temperature under dark condition since the rich surface oxygen vacancies, beneficial for the formation of surface hydroxyl groups and surface active chemisorbed oxygen (e.g., O2– and O−) which are useful to adsorb and/or oxidize formaldehyde. TiO2 reduced for 30 min was found most active for formaldehyde removal owing to the optimal amount of surface oxygen vacancies. A possible mechanism for formaldehyde degradation and catalyst deactivation were also proposed by using in situ DRIFTS study. Moreover, the reduced TiO2 supported low-loading Pd simultaneously exhibited superior activity toward CO2 and stability for formaldehyde oxidation in comparison with P25 supported Pd. This study sheds new light on the TiO2-based catalysts directly for formaldehyde degradation.

Improved NO x Reduction in the Presence of SO2 by Using Fe2O3-Promoted Halloysite-Supported CeO2-WO3 Catalysts.

Currently, selective catalytic reduction (SCR) of NO x with NH3 in the presence of SO2 by using vanadium-free catalysts is still an important issue for the removal of NO x for stationary sources. Developing high-performance catalysts for NO x reduction in the presence of SO2 is a significant challenge. In this work, a series of Fe2O3-promoted halloysite-supported CeO2-WO3 catalysts were synthesized by a molten salt treatment followed by the impregnation method and demonstrated improved NO x reduction in the presence of SO2. The obtained catalyst exhibits superior catalytic activity, high N2 selectivity over a wide temperature range from 270 to 420 °C, and excellent sulfur-poisoning resistance. It has been demonstrated that the Fe2O3-promoted halloysite-supported CeO2-WO3 catalyst increased the ratio of Ce3+ and the amount of surface oxygen vacancies and enhanced the interaction between active components. Moreover, the SCR reaction mechanism of the obtained catalyst was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy. It can be inferred that the number of Brønsted acid sites is significantly increased, and more active species could be produced by Fe2O3 promotion. Furthermore, in the presence of SO2, the Fe2O3-promoted halloysite-supported CeO2-WO3 catalyst can effectively prevent the irreversible bonding of SO2 with the active components, making the catalyst exhibit desirable sulfur resistance. The work paves the way for the development of high-performance SCR catalysts with improved NO x reduction in the presence of SO2.

Highly Active and Stable Pd−GaOx/Al2O3 Catalysts Derived from Intermetallic Pd5Ga3 Nanocrystals for Methane Combustion

AbstractCatalytic combustion of methane is widely used in industrial and transportation activities. The commonly used Pd‐based catalysts, however, are easily deactivated under hydrothermal conditions. In this work, we adopted a novel strategy to prepare a GaOx‐doped Pd/Al2O3 catalyst via the oxidative transformation of intermetallic Pd5Ga3 nanocrystals supported on γ‐Al2O3. We observed a synergistic effect between palladium and gallium oxide via formation of a bi‐functional active Pd−O−Ga phase, resulting in a highly active and exceptionally stable catalyst that could markedly suppress the sintering of noble metals under harsh conditions (hydrothermal treatment at 750 °C). Moreover, the presence of a large amount of surface oxygen vacancies and the surface Pd−O−Ga phase could promote methane combustion over the catalysts. It is believed that such a novel dual‐metal catalyst is promising in practical applications for methane combustion.