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An investigation of the adsorptive property of hydrated cement particle system for sulfur dioxide (SO 2 ) removal was conducted. In situ and ex situ experiments using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and X-ray Absorption Near Edge Spectroscopy (XANES) characterization techniques were employed to identify surface species formed during the exposure to SO 2 . Oxidation of SO 2 to sulfate and sulfite species observed during these experiments indicated dominant reaction pathways for SO 2 reaction with concrete constituents, such as calcium hydroxide, which were also moderated by adsorption on porous surfaces of crushed aggregates. The impact of variable composition of concrete on its adsorption capacity and reaction mechanisms was also proposed in this work. [ABSTRACT FROM AUTHOR]

In this paper, the in situ DRIFTS technology was employed to study the adsorption and reaction behavior of propylene oxide on different substances at different temperatures. And the adsorption behavior of the products at a certain temperature was also studied. The studies shows that the propylene oxide rearrangement involves thermal and catalytic transformation above 200 °C. In the first case, two main reaction pathways are involved: gradual rearrangement to the final products and pyrolysis leading to the formation of different products. In the former situation, the epoxy ring of propylene oxide first adsorbs on the basic lithium phosphate catalyst. Then it forms an intermediate with the bond between C O and C–O. The intermediate is finally converted to the final products, i.e., allyl alcohol at 300 °C. When the products (propyl aldehyde and acetone) adsorb on the catalyst, a conjugated structure consisting of basic lithium phosphate and α-H generates. [ABSTRACT FROM AUTHOR]

In this article, α-MnO 2 and β-MnO 2 nanorods, and urchin-like γ-MnO 2 catalysts with different tunnel structures were synthesized by a hydrothermal synthesis method and evaluated for the catalytic oxidation of nitric oxide (NO). The experimental results showed the γ-MnO 2 catalyst has the best catalytic activity among the three catalysts, with more than 80% NO conversion at 250 °C. The catalytic oxidation activities decreased in the order: γ- > β- ≈ α-MnO 2 . The XPS results implied that main manganese in all the catalysts was Mn 4+ and the activity was in close correlation with the surface concentration of O α species. The BET results showed that the surface area was not the suppression factor for NO oxidation. O 2 -TPO/TPD and In-situ DRIFTS experiments showed the catalytic activity of α-MnO 2 with [2 × 2] tunnels was benefit from the chemisorbed oxygen species while not the lattice oxygens or Mn cations. For β-MnO 2 with [1 × 1] tunnels and γ-MnO 2 with [2 × 1] tunnels, both chemisorbed oxygen and lattice oxygen or Mn cations were the influencing factors on the catalytic oxidation activity, and the chemisorbed oxygens were the major. The main intermediate active species were monodentate nitrites at low temperature, while were bridged nitrates mainly profited from chemisorbed oxygen over three catalysts at high temperature, and further decomposed to NO 2 and produced new Mn-O-Mn. The stacking faults of γ-MnO 2 with the random intergrowth of ramsdellite and pyrolusite structures resulted in the main sources of active oxygen species, which were beneficial to the catalytic activity. The reaction pathways over α-, β-, and γ-MnO 2 catalysts for NO oxidation were proposed. [ABSTRACT FROM AUTHOR]

Abstract: We have developed the next generation of photocatalytic testing to observe the gas-phase photocatalytic reactions in situ. It is based on modified Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) unit equipped with the Smart Collector system. We have employed UV diode coupled with fiber optics to illuminate the sample while simultaneous collecting the diffuse reflectance spectra. This method was applied to study the NO2 photocatalytic conversion on nanosize gold modified TiO2 samples. We have successfully demonstrated that both gas phase and surface adsorbed species can be identified and used to compare activities of various catalysts. We have found that gold nanoparticles have significantly increased the activity of the catalysts for both gas phase and liquid phase oxidation, resulting in more than quadrupling the NO2 photocatalytic conversion in the gas phase. [Copyright &y& Elsevier]

Oxidation of nitric oxide is one of the main steps in the Ostwald process for industrial nitric acid production. This work summarises the use of γ - Al 2 O 3 supported Ru catalyst to study the oxidation of NO to NO 2 at ambient and 4 bar pressure with a feed of 10% NO, 6% O 2 , 15% H 2 O, and rest Ar. The catalyst was synthesised using wet impregnation and characterised by BET, CO chemisorption, H 2 -TPR, XPS, XRD, in-situ XAS-XRD and DRIFTS. We report the activity and kinetics of supported ruthenium catalyst for NO oxidation under realistic nitric acid plant conditions. The catalyst exhibited a promising low-temperature activity of 72% at 340 °C in complete nitric acid condition and 37% at 420 °C in partial nitric acid condition. An apparent activation energy of 152 kJ/mol was observed and the overall rate was determined to be r = k f. K G. P N O 2. P O 2 P N O 2 , where k f and K G represents forward rate and equilibrium rate constants respectively. The reaction was found to be second order with respect to NO, first order with respect to O 2 and inversely dependent on NO 2 partial pressure. The stability of the catalyst was also tested during 45 h of isothermal NO oxidation at ambient pressure. From in-situ XAS-XRD and DRIFTS experiments it was revealed that during isothermal NO oxidation the reaction oscillates as the ruthenium surface goes through redox cycles. A plausible reaction mechanism that fits with our experimental observations and the oxidative nature of ruthenium is proposed. This study demonstrates and explains the capacity of supported ruthenium catalysts to oxidise NO to NO 2 in industrial nitric acid production conditions. [Display omitted] • Ru/ γ -Al 2 O 3 catalyst exhibited an activity of 72% at 340 °C in industrial condition. • An apparent E a 152 kJ/mol was observed and reaction orders were determined. • In-situ XAS-XRD revealed surface redox cycles on ruthenium during NO oxidation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Defective LaNi 0.5 M 0.5 O 3 perovskites are synthesized by improved sol–gel method. • Doping M ions into LaNiO 3 leads to modified activity of NO + CO reaction. • The LaNi 0.5 Cu 0.5 O 3 catalyst exhibits optimized N 2 selectivity. • The improvement is attributed to surface amorphous CuO and oxygen vacancy. • The catalytic mechanism of LaNi 0.5 Cu 0.5 O 3 conforms to L-H mechanism. Abstract Catalytic removal of NO by CO has been studied over a series of LaNi 0.5 M 0.5 O 3 (M = Co, Mn, Cu) perovskite oxide catalysts were synthetized via an improved sol–gel method. The effects of M-doped on physicochemical properties of LaNiO 3 were systemic characterized by XRD, BET, SEM, ICP-AES, XPS, H 2 -TPR and O 2 -TPD techniques. The possible catalytic mechanism for NO + CO model reaction was also tentatively proposed with the help of the in situ DRIFTS technique. The M-doped samples remained pure perovskite structure and exhibited modified activity, among which the LaNi 0.5 Cu 0.5 O 3 possessed optimized catalytic performance, especially superior N 2 selectivity. It is confirmed that the amorphous CuO highly dispersed on Cu-doped defective perovskite oxide, the reduction of Cu2+ to Cu+ is vital for the chemisorption of CO, a large amount of oxygen vacancies accelerated the dissociation of NO and N 2 O. Hence, adsorbed CO can fast react with N and O at lower temperature, afterwards N 2 O was converted to N 2 fleetly, leading the improvement of activity/selectivity toward NO + CO reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ir/TiO 2 catalyst is prepared and studied CH 4 activation and its steam reforming. • 2 wt% Ir/TiO 2 catalyst exhibits low activation barrier and high TOF. • DFT results support the low-temperature activity of small Ir clusters for SRM. • Predicted product temperature with microkinetics agrees well with the experiment. Hydrogen production via low-temperature (<550 °C) steam reforming of methane (SRM) has attracted increasing research attention due to its importance as an alternative, efficient, and environmentally benign energy carrier. The thermodynamic limitation of low-temperature SRM can be eased by process design such as using a membrane reactor or an adsorption-enhanced reforming process, and an active low-temperature SRM catalyst with high stability would be indispensable. Herein, we report a 2 wt% Ir/TiO 2 catalyst that exhibits high methane conversion activity in low-temperature SRM with a relatively high turnover frequency (TOF) and a low activation energy in comparison with the literature. Long-term catalyst stability test demonstrates a good resistance to coking and sintering during low-temperature SRM reactions. In situ spectroscopy analyses and density functional theory (DFT) calculations reveal that the small Ir clusters and Ir single atoms (SAs) are both active for methane conversion, while the clusters exhibit higher activity than SAs for low-temperature SRM reaction. Microkinetic simulation based on DFT calculations shows consistent product formation temperatures and the simulation nicely reproduces the product distribution observed in experimental analysis, which confirms the superior SRM activity of the TiO 2 -supported Ir clusters in this work. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt NPs promoted the thermal decomposition process of MOFs in air atmosphere. • Pt NPs facilitated the formation of UMCs by the removal of coordinated solvent. • The E a change in air was determined by both LMCT effect and O 2 adsorption capacity. • Overflow effect of atomic H accelerated the decomposition rate of MOFs. • Ligand hydrogenation led to the enhanced thermostability of MOFs with higher E a. Metal-organic frameworks (MOFs) have been utilized as an important precursor/template to prepare diverse metal or metal oxide nanomaterials. Herein, we studied the thermal decomposition behaviors of M−BTC (M = Cu, Co, Zn, and Ce; BTC = benzene-1, 3, 5-tricarboxylate) and the Pt-supported M−BTC nanocomposites (M−BTC/Pt) in different atmospheres by using thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), in-situ X-ray diffractometer (in-situ XRD), and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). The results indicated that the presence of Pt promoted the decomposition of the Cu-BTC, Co-BTC, and Zn-BTC under air atmosphere with lower activation energies. For instance, the E a values of the decomposition process of Cu-BTC and Cu-BTC/Pt were 231 and 133 kJ/mol, respectively, which can be attributed to the enhanced ligand-to-metal charge transfer effect and higher oxygen adsorption capacity after the immobilization of Pt. However, the thermal decomposition of Ce-BTC showed a different trend with a larger E a value in the presence of Pt (167 vs 105 kJ/mol). In-situ DRIFTS showed that the introduction of Pt would change the thermal decomposition modes of MOFs by the strong hydrogen overflow effect. However, the improved thermostability of Cu-BTC, Co-BTC, and Zn-BTC in the hydrogen atmosphere is owing to the hydrogenation of the carboxylate on the organic linkers. For instance, the E a values of the decomposition process of Co-BTC and Co-BTC/Pt were 197 and 237 kJ/mol, respectively. Such findings could provide reference and guidance for further understanding of the effects of metal nanoparticles on the thermal decomposition of MOFs for controlling the physicochemical properties of the MOF-derived metal oxide nanomaterials. [ABSTRACT FROM AUTHOR]

[Display omitted] • First experimental-theoretical study of CO oxidation on AuCu/TiO 2. • Enhanced stability of Au NPs due to migration of Cu species to the surface. • In-situ Raman highlights TiO 2 reducibility during the reaction. • DFT calculations confirmed the close interaction between metals and support. • Restructuration of the catalysts due to the CO interaction was unveiled. Bimetallic AuCu/TiO 2 catalysts were thoroughly studied during the CO oxidation reaction via three in-situ spectroscopic techniques (FTIR, UV–Vis and Raman) and density functional theory (DFT) calculations. Samples were synthesized through the deposition–precipitation with urea (DPU) method, and ex-situ characterized by several techniques. The superior catalytic activity displayed by the AuCu/TiO 2 sample was associated with the presence of nanoparticles in the form of heterodimers composed of the Au and Cu X O phases in close interaction with the TiO 2 support. In-situ DRIFTS results indicated that gold nanoparticles (NPs) presented some restructuration in the monometallic sample, while this event did not occur in the bimetallic one. The better stability on the AuCu/TiO 2 catalyst was related to the partial migration of Cu X O species to the surface of the NPs, also confirmed through in-situ UV–Vis spectroscopy. The favorable role played by the TiO 2 reducibility was established through in-situ Raman spectroscopy. Moreover, findings obtained by DFT confirmed the experimentally evidenced structural modifications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel porous MnCoO x sphere catalyst was fabricated for NH 3 -SCR of NO x. • MnCoO x sphere exhibits high low-temperature activity and strong H 2 O/SO 2 resistance. • MnSO 4 but not NH 4 HSO 4 /(NH 4) 2 SO 4 formed led to the poisoning of Mn-based catalysts. • The strong tolerance of MnCoO x catalyst to SO 2 poisoning is due to the less formation of MnSO 4. For the effectively removal of NO x emissions in the practical flue gas, a highly active NH 3 -SCR catalyst with remarkable SO 2 tolerance is desirable. Herein a novel MnCoO x sphere catalyst has been developed, which not only exhibited high low-temperature activity for the NH 3 -SCR of NO x but also significantly enhanced SO 2 resistance. XPS analysis and in-situ DRIFTs revealed that the formation of abundant bulk MnSO 4 species due to the present SO 2 led to the irreversible poisoning of pure MnO x catalyst, which could change the Langmuir-Hinshelwood (L-H) mechanism of NH 3 -SCR reaction into the Eley-Rideal (E-R) mechanism and inhibit the low-temperature activity. While over MnCoO x sphere catalyst the formation of MnSO 4 is significantly inhibited in the presence of SO 2 , so that the reaction over the SO 2 -poisoned Mn(5)Co(5)O x catalyst can still proceed by the L-H mechanism and maintain its high catalytic performance. This work unravels the mechanistic promoting effect of Co on the SO 2 tolerance of MnCoO x catalyst from sulfates as well as the reaction mechanism perspectives, which would guide an ingenious design of SO 2 tolerant Mn-based NH 3 -SCR catalysts. [ABSTRACT FROM AUTHOR]

The Cu/ZnO catalyst prepared by supercritical phase CO 2 drying (denoted as CZS catalyst) and the conventional Cu/ZnO catalyst prepared by heating dry process (denoted as CZO catalyst) were comparatively investigated. The low-temperature methanol synthesis reaction from CO + CO 2 + H 2 using 2-butanol as solvent was conducted over the CZS and CZO catalysts at 443 K and 5.0 MPa for continuous 20 h in a flow-type reactor. It was found that the total carbon conversion of the CZS catalyst was increased from 35.1% to 46.4% and the methanol yield of the CZS catalyst was enhanced from 33.8% to 44.8%, comparing with those of the CZO catalyst. The results of kinetic analysis by in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) revealed that the reaction rate of the low-temperature methanol synthesis on CZS catalyst was faster than that on CZO catalyst at 443 K, in good accordance to the catalytic reaction performances. It was indicated that the supercritical fluid CO 2 , which was used to dry the catalyst precursor, suppressed the sintering of the Cu and ZnO particles and increased both the BET surface area of the catalysts and metallic surface area of Cu 0 , which further improved the reaction activity of the catalyst for the low temperature methanol synthesis. [ABSTRACT FROM AUTHOR]

A series of WO 3 -doped Mn–Zr mixed oxide catalysts were investigated for the selective catalytic reduction of NO x by NH 3 (NH 3 –SCR). It was found that the added WO 3 significantly enhanced the catalytic performance of Mn–Zr mixed oxide catalyst for NH 3 –SCR of NO x . In situ diffuse reflectance infrared transform spectroscopy (DRIFTS) studies revealed that the highly dispersed WO 3 not only resulted in more acid sites formed on the catalyst surface, but also inhibited the adsorption of the inactive nitrate specie, leaving more active sites available for the adsorption of NH 3 . In addition, the synergetic effect between W and Mn contributes to improving the redox property of the catalyst. Therefore, the high catalytic deNO x performance was obtained over WO 3 -promoted Mn–Zr mixed oxide catalyst. [ABSTRACT FROM AUTHOR]

The synergistic effect of surface decorated and intrinsic O-vacancies through an oxygen replenishment-migration pathway is the key to boost the remarkable catalytic activity for deep toluene oxidation. [Display omitted] • The Pt-CeO 2 /MnO 2 hetero-nanostructures can be fine-manipulated via a novel synthesis method. • The synergistic effect of dual O-vacancies is the key to enhance the deep toluene oxidation. • The Pt-CeO 2 /MnO 2 exhibited more O-vacancies, well redox ability and well dispersion of Pt. • DRIFTS study revealed that toluene was adsorbed directly on surface adsorbed oxygen species. Oxygen vacancy engineering has been verified as an important approach to achieve the efficient degradation of VOCs in nanomaterials. Herein, a synthetic strategy of Pt-CeO 2 /MnO 2 hetero-catalysts is developed to fine-manipulate the surface oxygen vacancies and catalytic activities through surface CeO 2 decoration as a surface O-vacancy donor. Among these Pt-based catalysts, the optimal Pt-0.15Ce-Mn catalyst exhibits the greatest catalytic activity for toluene oxidation (T 99 = 155 °C), which is attributed to more oxygen vacancies, outstanding redox ability and well dispersion of Pt. Combined with experiments and DFT calculations, it has been demonstrated that the special role of introducing CeO 2 NPs is to induce the generation of more O-vacancies, new structure defects (Mn3+ and Ce3+ species), and the lower formation energy of oxygen vacancy. Furthermore, the synergistic effect of dual O-vacancies (surface decorated and intrinsic O-vacancies) via an oxygen replenishment-migration pathway is the key to boost the remarkable catalytic activity for deep toluene oxidation. Finally, in situ DRIFTS reveals that partial toluene molecules can be adsorbed directly on surface adsorbed oxygen species replenished by gas-phase oxygen, and these catalysts with richer O-vacancies can effectively reduce the accumulation of by-product (phenolate, C 6 H 5 –OH). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MnNi x oxides with irregular pits were synthesized via hydrothermal method. • The addition of Ni into MnO 2 promoted the catalytic activity for propane oxidation. • The MnNi 0.09 sample could convert 90% propane at 220 °C. • The MnNi 0.09 sample with pits exhibited the lowest apparent activation energy (33.6 kJ mol−1). Abstract Series of nickel doping MnO 2 with irregular surface pits were synthesized and employed for propane deep oxidation. The partial substitution of Ni for Mn resulted in the formation of structural defects, which could be observed by high-resolution transmission electron microscopy. The MnNi 0.09 sample exhibited the best catalytic activity for propane oxidation with the conversion of 90% at 220 °C. The presence of pits on the MnNi 0.09 sample could facilitate the dissociation of propane and mobility of oxygen along the conduction channels of surface pits, thus promoting the catalytic efficiency. Moreover, the in situ studies found that different intermediates were formed on the MnO 2 and MnNi 0.09 catalysts during the propane oxidation process. The propane was oxidized to propanoyl species on the surface of MnO 2 catalyst, while it was oxidized to hydrogen carbonates and carbonates on the surface of MnNi 0.09 sample, which were thermally less stable and converted into CO 2 at lower temperature. The finding provides a new perspective on understanding the effect of cation doping. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photocatalytic degradation of toluene was promoted by oxygen vacancy on InOOH. • OVs also facilitated methyl oxidation with the enhanced selectivity for ring opening. • In situ DRIFTS dynamically tracked the formation of primary reaction intermediates. • The reaction mechanism involved in photocatalysis of toluene is elucidated. The potential of oxygen vacancies (OVs) has been demonstrated in controlling photocatalytic activities by altering the electronic and/or band structures of photocatalysts. The effects of oxygen vacancies on photocatalytic reaction processes are yet unclear. In this work, indium oxyhydroxide (InOOH), well known as a wide band p-block metal compound with OVs, was synthesized through a one-pot solvothermal method to explore the roles of OVs in photocatalytic oxidation and ring opening of toluene. The defect level introduced by OVs enhanced light absorption and charge carrier separation, while promoting the activation of reactants to generate active oxygen species. As such, the modified InOOH was validated to enhance the photocatalytic performance by lowering the reaction energy barrier of the key intermediates during toluene oxidation (relative to the pristine InOOH). More strikingly, the energy barrier for the formation of benzoic acid was reduced with the increasing number of OVs on InOOH (accompanied by the increases in the ring opening reaction rates), in line with the results derived from the in situ DRIFTS investigation and theoretical calculation. Accordingly, it is possible to explain the mechanism regulating the photocatalytic oxidation of toluene on defective InOOH. This work could provide an electronic insight into oxygen vacancy engineering as a new strategy to enhance the photocatalytic selectivity and activity for VOC degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Monolayer NiAl-LDH was prepared by a facile two-step process. • Carrier density and carrier separation abilities were improved. • The possible reaction mechanism on LDHs surface was proposed. • HCO 3 – and c-CO 3 2- were key intermediates to transform to •CO 2 – active species. • More active species were more competitive to adsorb onto NiAl-UT. CO 2 conversion into valuable products by utilizing solar energy is one of the most sustainable approaches to simultaneously address looming energy and environmental issues. Herein, through a facile two-step process, including in-situ inhibiting layer growth and the following 10-min exfoliation process, monolayer NiAl-LDH nanosheet was successfully prepared, which demonstrated electron yield of 18.32 μmol g-1h−1 and quantum efficiency of 0.09 % in absence of sacrificial agent. The atomic-level dispersed nanosheets enabled the significantly increased carrier density and accelerated carrier separation abilities. In-situ DRIFTS characterization affirmed that the thickness regulation strategy had not only promoted the CO 2 adsorption and activation capacity but also altered the adsorption and activation modes of CO 2 upon photocatalysts. The ultrathin sample exposed more active sites that were available for binding and activating reactant molecules. More HCO 3 – and c-CO 3 2- species, the key intermediates to transform into •CO 2 – active species, were more competitively adsorbed on the ultrathin nanosheets, thus more markedly enhanced photoactivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZrO 2 coated with highly dispersed Pt nanoclusters was obtained by one-pot method without using surfactant. • Ethanol can promote the formation of terminal hydroxyl in ZrO 2 , thus facilitating the dispersion of Pt nanoclusters. • ZrO 2 @Pt presented high catalytic efficiency in nitrobenzene hydrogenation at room temperature and ambient pressure. • DRIFTS spectra and DFT calculation verified that the hydrogenation of nitrobenzene proceeds along the condensation route on ZrO 2 @Pt. High dispersion of active metal is an inevitable requirement to improve the catalytic performance of supported metal catalysts and achieving this goal always requires the support with a large specific surface area. Here we innovatively prepared a ZrO 2 @Pt catalyst using ZrO 2 with a small specific surface area as the core which is coated with highly dispersed Pt nanoclusters (<2 nm). In this process, the surface of ZrO 2 was firstly functionalized to increase the number of hydroxyl group, Pt nanoclusters were formed simultaneously and uniformly coated on the ZrO 2 surface. In this work, much attention was paid to the role of 2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesulfonic acid (HEPES) and ethanol in the one-pot preparation process. The results showed that HEPES acted as a reductant, while treatment with ethanol promoted both the generation of hydroxyl groups on ZrO 2 surface and the reduction of Pt precursor under mild conditions. As-prepared ZrO 2 @Pt catalyst showed excellent catalytic performance in the selective hydrogenation of nitrobenzene; nitrobenzene was completely converted to aniline with 100 % selectivity at room temperature and 8 bar H 2 pressure within 30 min, and the TOF reached as high as 3304 h−1. Moreover, ZrO 2 @Pt also exhibited a good reusability and a broad substrate applicability. The results of both DRIFTS analysis and DFT calculation demonstrated that the hydrogenation of nitrobenzene on ZrO 2 @Pt catalyst followed the condensation reaction pathway. Our findings can provide a new approach to obtaining highly dispersed metal nanoparticles on the support with a small specific surface area. [ABSTRACT FROM AUTHOR]

• A series of Au-modified hollow Ni–Mn spinel decorated on GA catalysts is developed. • The hollow structure leads to a larger surface area and more active sites. • Au and GO strengthens the reducibility and adsorption capacity for toluene. • The catalyst shows great stability, moisture tolerance and compressibility. • An in-situ DRIFTS study and a modified MVK catalytic mechanism was proposed. The development of a highly efficient oxide catalyst is crucial for thermal and environmental catalytic reactions. Herein, a facile and eco-friendly strategy is developed to synthesize a series of Au-modified hollow Ni–Mn spinel nanospheres decorated on graphene aerogels (GAs) (termed Au y -hNi x Mn 3−x /GA z) composite catalysts for deep catalytic oxidation of Volatile organic compounds (VOCs). The introduction of hollow structure leads to a larger specific surface area and more accessible active sites. The subsequent cooperation of Au further strengthens the low-temperature reducibility along with more active surface oxygen species. After being embedded into the graphene network, the composite catalyst shows an improvement in electron transfer and accessibility to active metal sites. The adsorption capacity of the catalyst for toluene is greatly improved by the above steps, thus facilitating the catalytic performance. The resulting Au 1 -hNi 1 Mn 2 /GA 0.5 composite catalyst exhibits optical activity for VOCs removal, reaching 100 % toluene and benzene (500 ppm) oxidation at 155 °C and 148 °C, respectively. Meanwhile, the catalyst shows extraordinary catalytic stability, selectivity, moisture tolerance and compressibility making it a promising catalyst for industrial thermal catalysis. Moreover, an in situ DRIFTS study is carried out for the exploration of the reaction pathway and a modified Mars van Krevelen (MVK) catalytic mechanism was proposed as well. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photodeposition of Ni enhances the confinement effect of TiO 2 nanotubes. • Ni embedding in the surface lattice of TiO 2 nanotubes replaced Ti4+ to form Ni3+. • Ni emplacement enhance the CO 2 low-temperature methanation performance. • Ru@TiO 2 NTs-Ni catalysts exhibit excellent durability. Transforming CO 2 into valuable chemicals and fuels via hydrogenation receives excellent concern, considering the severe environmental problems caused by CO 2 emissions. However, the development of catalytic materials for low-temperature CO 2 hydrogenation remains challenging. Herein, we construct a nanotube (NT) catalyst system, where Ru is confined in TiO 2 nanotubes (Ru@TiO 2 NTs), which are further modified by Ni photodeposition (Ru@TiO 2 NTs–Ni). This system aims to enhance CO 2 methanation by modulating the confinement effect. Ru@TiO 2 NTs–Ni exhibits better low-temperature catalytic activity than Ru@TiO 2 NTs. Approximately 86 % CO 2 conversion and 100 % CH 4 selectivity are achieved at 220 °C, and no decrease in catalyst activity is observed in 110 h. The interactions between Ni, Ru, and TiO 2 NTs are investigated in depth using characterization techniques, such as extended X-ray absorption fine structure and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results indicate that part of Ni is embedded in the surface lattice of the TiO 2 NTs, resulting in a large amount of Ni3+. The presence of Ni3+ causes oxygen vacancies on the surface of the nanotube and enhances the electron-deficient state inside the nanotube, thereby improving the performance of low-temperature CO 2 methanation. In situ DRIFTS results indicate that the presence of Ni considerably enhances the ability of Ru to dissociate CO 2 and improves CO 2 methanation performance at low temperatures. This study advances the understanding of the confinement effect of TiO 2 NTs and presents an approach to design efficient catalysts by modifying their electronic state, thereby providing novel insights into CO 2 utilization. [ABSTRACT FROM AUTHOR]

Graphical abstract The hydrothermal stability of Cu-SAPO-34 was significantly enhanced by the addition of Ce or La. The introduction of Ce or La effectively mitigated the dealumination and restrained the aggregation of copper species. The hydrothermal treatment cut off the "E-R" reaction route over the Cu-SAPO-34 and opened the new reaction pathway ("L-H" mechanism) over the Cu/La-SAPO-34. Highlights • Adding Ce or La into Cu-SAPO-34 effectively enhanced the hydrothermal stability. • Cu2+ increased over Cu/La-SAPO-34 after aging and affected low-temperature activity. • The addition of Ce or La restrained the aggregation of Cu species and dealumination. • The introduction of Ce or La stabilized the surface acid sites of Cu-SAPO-34. • Hydrothermal aging changed SCR reaction route of Cu-SAPO-34 and Cu/La-SAPO-34. Abstract The effect of Ce or La on the hydrothermal stability of Cu-SAPO-34 catalyst was evaluated by the selective catalytic reduction of NO x by ammonia (NH 3 -SCR) reaction after hydrothermal aging at 700 °C in 10 vol% H 2 O/air for 10 h. The hydrothermal stability of Cu-SAPO-34 was dramatically enhanced by introducing small amount Ce or La into Cu-SAPO-34. More than 93% NO x conversion was maintained over the aged Ce or La modified Cu-SAPO-34 at 175–350 °C, while extremely poor NH 3 -SCR activity was obtained over the aged Cu-SAPO-34. In situ diffuse reflection infrared Fourier transform spectrum (DRIFTS) results illustrated that the hydrothermal treatment cut off the intrinsic "E-R" reaction route over the Cu-SAPO-34 and opened the new reaction pathway ("L-H" mechanism) over the La modified Cu-SAPO-34 catalyst. Additionally, the introduction of Ce or La effectively mitigated the dealumination progress and restrained the aggregation of copper species over Cu-SAPO-34 during the hydrothermal aging, further maintaining the relatively large specific surface area and uniform pore size distribution. Meanwhile, the incorporation of Ce or La enhanced the redox property and stabilized the surface acid sites of Cu-SAPO-34, further facilitating the adsorption and activation of reactants. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hierarchical honeycomb-like NiFe-layered double hydroxide (LDH)/rGO was obtained. • The NiFe-LDH/rGO was deposited with Pt to yield the Pt/NiFe-LDH/rGO composite. • HCHO oxidation activity of the Pt/NiFe-LDH/rGO composite was firstly investigated. • The Pt/NiFe-LDH/rGO composite displays excellent HCHO degradation performance. • The intermediates in HCHO decomposition process were detected by in situ DRIFTS. Abstract Formaldehyde (HCHO) is regarded as the most ubiquitous indoor pollutant, which causes severe health symptoms for humans. Catalytic oxidation at ambient temperature has been identified as the most promising technique for indoor HCHO removal. Herein, a hierarchical honeycomb-like nanocomposite of reduced graphene oxide (rGO) and nickel-iron layered double hydroxide (NiFe-LDH) was prepared via a hydrothermal method. After decoration of the NiFe-LDH/rGO with 0.34 wt% of platinum (Pt), the Pt/NiFe-LDH/rGO showed excellent catalytic performance for HCHO degradation at room temperature, which are due basically to the better dispersion of both NiFe-LDH and rGO in the composite. This structural characteristic endows Pt/NiFe-LDH/rGO with larger surface area, thus resulting in plentiful surface active sites and highly dispersed Pt nanoparticles, which are conducive to the activation of both surface oxygen atoms of NiFe-LDH and adsorbed oxygen molecules. Moreover, dioxymethylene and formate were major reaction intermediates, while surface hydroxyl groups and surface active oxygen atoms were the key species involved in the catalytic reaction, which shed light on the HCHO oxidation mechanism. This work demonstrates that introducing graphene materials into hierarchical catalysts can enhance the removal of gaseous HCHO and potentially other indoor pollutants. [ABSTRACT FROM AUTHOR]

Montmorillonite based porous clay heterostructures modified with Fe (Fe-PCH) catalysts were prepared by ion exchange and impregnation methods, respectively. The PCH samples were characterized by XRD, BET, UV-vis, HRTEM, XPS, H 2 -TPR, Py-FTIR, etc. The catalytic activity of the catalysts was evaluated for the selective catalytic reduction of NO with C 3 H 6 with a fixed-bed reactor and the in situ DRIFTS study was conducted to investigate the reaction mechanism. It was observed that the catalysts prepared by impregnation methods were more reactive for the SCR-C 3 H 6 , e.g., 96% of NO conversion to N 2 was tested at 400 °C when 8.4 wt% iron was supported on the PCH. The results of catalyst characterization indicated that α-Fe 2 O 3 nanorods formed in PCHs channels and (1 1 0) and (1 0 4) planes exposed. α-Fe 2 O 3 nanorods promoted the formation of the Lewis acid sites. With the study of DRIFTS, a reaction mechanism was proposed, where the reaction intermediates were mainly inorganic nitrates, acetates, organic nitrogen compounds and isocyanate species. [ABSTRACT FROM AUTHOR]