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Herein, two CeO2 samples dominantly decorated with surface and bulk sulfates were constructed and their distinct effects on high-temperature NH3-SCR were investigated by strictly controlling the sulfate content at a comparable level. The obtainment of surface and bulk sulfates was revealed using a designed leaching experiment, and further evidenced by the characterization results from XPS and H2-TPR. In comparison with CeO2 modified with bulk sulfates (B-CeS), sufficient acid sites with strong intensity were generated on CeO2 modified with surface sulfates (S-CeS). In addition, due to electron-withdrawing effect from S=O in sulfate species, NH3 oxidation over S-CeS was greatly suppressed, providing an additional contribution to enhanced performance in high-temperature NH3-SCR. [ABSTRACT FROM AUTHOR]

Ceria-based solid solutions were synthesized and used as supports to prepare MnO x /Ce 0.8 Ti 0.2 O 2 and MnO x /Ce 0.8 Sn 0.2 O 2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH 3 . The effects of Ti or Sn doping on the catalytic performance of MnO x /CeO 2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnO x /CeO 2 . The NO conversion of Mn/CeTi catalyst is more than 90% at temperature window of 175–300 °C under a gas hour space velocity of 60,000 mL g −1 h −1 . Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. Characterization results indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity. X-ray photoelectron spectroscopy (XPS) analysis of spent catalysts following SCR reaction in the presence of SO 2 verify that the loss of surface Mn species was inhibited by doping of Ti, which contributes to extend the sulfur durability. The SCR activity is considered as well to be promoted by the dual redox cycles in Mn/CeTi (Mn 4+ + Ce 3+ ↔ Mn 3+ + Ce 4+ , Ce 4+ + Ti 3+ ↔ Ce 3+ + Ti 4+ ) and Mn/CeSn (Mn 4+ + Ce 3+ ↔ Mn 3+ + Ce 4+ , 2Ce 4+ + Sn 2+ ↔ 2Ce 3+ + Sn 4+ ) catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] CuO-CeO2/SBA-15 catalysts were prepared by a novel solid state impregnation method. [•] Both copper species and ceria can be well dispersed. [•] In comparison with wet impregnation, the solid state impregnation derived catalyst owns increased interfacial CuO-CeO2 entities and enhanced interfacial interactions. [•] CuO-CeO2/SBA-15 catalyst from solid state impregnation shows enhanced CO-PROX activity and good tolerance to CO2 and H2O. [Copyright &y& Elsevier]

Abstract: A family of metal oxides (Co3O4, NiO and CeO2) confined in SBA-15 with high loadings (≥20wt%) was prepared through a solvent-free method. Characterizations of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aggregation-free nanoparticles were obtained and N2 physisorption confirmed they were studded in mesopores. It was proposed that the intermediate molten salt phases ensured successful encapsulation and homogeneous dispersion of metal oxides. Lastly, the importance of the strategy was exemplified by NiO, and the high thermal stability together with superior performance in hydrodechlorination of chlorobenzene suggested great potential of these samples in heterogeneous catalysis. [Copyright &y& Elsevier]

Monolithic Mn-Fe-Ce-Al-O catalyst with honeycomb cordierite ceramic as a carrier was reported for the first time for low temperature deNOx application. In the reaction of selective catalytic reduction (SCR) of NO with NH3, a NO conversion of above 80% at 100 °C was obtained. Notably, the catalyst also showed excellent resistance against SO2 and H2O. About 60% NO conversion was maintained after successive operation in the mixed stream of SO2 and H2O for 168 h. The Brunner−Emmet−Teller (BET) measurement, SEM, EDS, thermogravimetric analysis (TG), FT-IR, and XPS results of the used catalysts indicated that certain amounts of ammonium sulfate was formed on the surface of the catalyst. XPS results revealed that partial of Fe2+ was oxidized to Fe3+ during the reaction process, and Fe2+ species have strong redox ability, which can explain the decrease in activity after reaction. In addition, SO2 and H2O induced a transformation of Ce from Ce4+ to Ce3+ on the surface of the catalyst, which increased the amount of chemisorbed oxygen. Owing to these factors, the addition of Ce and Fe species contributes to excellent resistance of the catalyst to SO2 and H2O. [ABSTRACT FROM AUTHOR]

A series of ceria modified CuO/γ-Al 2 O 3 (CuO-CeO 2 /γ-Al 2 O 3 ) catalysts were prepared via stepwise impregnation (CuCeAl-SI) and co-impregnation (CuCeAl-CI) method and tested in the model reaction of NO reduction by CO. It was found that the influence of impregnation modes on the catalytic properties of CuCeAl samples mainly lies on the control of ceria particle sizes and modulation of the distribution of various copper species. In both impregnation modes, ceria was mainly spread on γ-Al 2 O 3 as small particles while copper species were highly dispersed. A quantitative estimation of copper species was tentatively provided via a combined surface acid leaching experiment and H 2 -TPR characterization for the first time. The results showed that for CuCeAl-CI catalyst, about 55% and 25% copper species were dispersed on γ-Al 2 O 3 and nanosized ceria, respectively, while about 20% was migrated into ceria lattice during the calcination process. In contrast, in CuCeAl-SI sample, the corresponding values changed to about 25%, 70% and 5%, respectively. The synergistic effect between copper species and ceria can promote the improvement of catalytic performance, which results in higher activity of CuCeAl-SI than that of CuCeAl-CI catalyst. [ABSTRACT FROM AUTHOR]

Abstract: The present work focuses on the combination of ceria with another oxide of different ionic valences from period 3 (Mg2+, Al3+, and Si4+) using coprecipitation method, followed by calcination at 450 and 750°C, respectively. The textural, structural, morphological and redox properties of nanosized ceria–magnesia, ceria–alumina and ceria–silica mixed oxides have been investigated by means of N2 physisorption, XRD, Raman, HRTEM, DRS, FT-IR, and H2-TPR technologies. XRD results of these mixed oxides reveal that only nanocrystalline ceria (ca. 3–6nm for the 450°C calcined samples) could be observed. The grain size of ceria increases with the increasing calcination temperature from 450 to 750°C due to sintering effect. The highest specific surface area is obtained at CeO2–Al2O3 mixed oxides when calcination temperature reaches 750°C. Raman spectra display the cubic fluorite structure of ceria and the existence of oxygen vacancies, and displacement of oxygen ions from their normal lattice positions in the ceria-based mixed oxides. DRS measurements confirm that the smaller the grain size of the ceria, the higher indirect band gap energy. H2-TPR results suggest that the reductions of surface and bulk oxygen of ceria were predominant at low and high calcination temperature, respectively. Finally, CO oxidation were performed over these ceria-based mixed oxides, and the combination of CeO2–Al2O3 exhibited highest activity irrespective of calcination temperature, which may due to excellent textural/structural properties, good homogeneity, and redox abilities. [Copyright &y& Elsevier]

Graphical abstract Highlights • Sm doped CeO 2 -TiO 2 catalyst presents excellent NH 3 -SCR activity in range of 250–425 °C. • The acidity and redox property are adjusted with appropriate balance by Sm doping. • Redox cycle of Ce4++Sm2+⇌Ce3++Sm3+ is responsible for the good SO 2 tolerance. Abstract The Sm doped CeO 2 -TiO 2 mixed oxide catalyst, which exhibited excellent activity and tolerance to H 2 O and SO 2 in the NH 3 -SCR reaction, was synthesized. The reasons for the high activity and SO 2 resistance of the catalyst were investigated by a series of characterization. The H 2 -TPR and O 2 -TPD results suggested that the reducibility and oxygen storage capacity (OSC) of CeTi catalyst were promoted by the addition of Sm species, which was beneficial for improving the activity of catalyst. The in situ DRIFTS results revealed that the adsorptive ability of NO x species and activation ability of NH 3 were enhanced by Sm doping, which was also propitious to enhance the activity. XPS combined with DFT calculated results confirmed that the transfer of electron by Sm2++Ce4+⇌Sm3++Ce3+ circles occurred in the SmCeTi catalyst. The redox circles may be the reason of the good SO 2 tolerance of the SmCeTi catalyst, for which suppressed the electron transferring from adsorbed SO 2 to Ce4+. Through in situ DRIFTS and TG-DSC results, it can be concluded that the sulphation of catalyst was lowered by samarium doping into CeTi catalyst. Consequently, the SmCeTi catalyst exhibited significant SO 2 tolerance ability. [ABSTRACT FROM AUTHOR]

• Three MnOx-CeO 2 catalysts with controlled surface and interfacial properties are prepared for investigation. • Strong interface between dispersed MnOx and CeO 2 does not show the best NH 3 -SCR performance. • The unique role of crystalline Mn 3 O 4 in promoting NH 3 activation is revealed. • The catalytic performance can be considerably improved by the synergistic interaction between crystalline Mn 3 O 4 and CeO 2. MnOx-CeO 2 catalysts have been widely investigated in the reaction of selective catalytic reduction of NO with NH 3 (NH 3 -SCR). However, the existence of diverse Mn species together with multiple interfaces between MnOx and CeO 2 precludes clear understanding of the synergy. Herein, by constructing MnOx-CeO 2 catalysts with controlled dispersion and interface properties, the significant promotion effect of interfacial contact between CeO 2 and crystalline Mn 3 O 4 in NH 3 -SCR was revealed. Although dispersed MnOx exhibited the combined merits of strong interaction with CeO 2 , improved textural property and abundant adsorption sites for NO/NH 3 , the catalytic performance was still not superior. With advent of Mn 3 O 4 crystallites, the NO conversion was much enhanced, demonstrating essential role of crystalline MnOx. Notably, loss of activity was also observed when apparent phase segregation between ceria and crystalline Mn 3 O 4 occurred, emphasizing the importance of Mn 3 O 4 /CeO 2 boundary. Further mechanism analyses from in situ NH 3 -DRIFTS, quantitative titration of surface NOx with NH 3 and kinetics measurement disclosed the crucial role of crystalline Mn 3 O 4 in activating NH 3 for reaction with NOx anchored on ceria, greatly boosting the catalytic performance. The result of present study enriches our understanding on the synergism between MnOx and ceria in NH 3 -SCR. [ABSTRACT FROM AUTHOR]

In this work, CeO 2 nanocubes hybridized g-C 3 N 4 composites had been facilely synthesized to investigate the interfacial effects on photocatalytic water splitting. The c-CeO 2 /g-C 3 N 4 composites exhibited the superior photocatalytic hydrogen evolution under visible light irradiation. The optimal c-CeO 2 loading content was 5 wt%, with the H 2 evolution of 4300 μmol g −1 for 5 h illumination, higher than that of pristine CeO 2 , g-C 3 N 4 and irregular CeO 2 nanoparticles/g-C 3 N 4 . Moreover, UV–vis DRS, PL spectra and photoelectrochemical measurements demonstrated that 5 wt% c-CeO 2 /g-C 3 N 4 composite possessed more visible light adsorption and faster charge transfer, which was attributed to the stronger interfacial effects through the presence of the hydrogen bond and p-π hybrid between c-CeO 2 {100} and g-C 3 N 4 , revealed by the FT-IR and XPS results. The work suggested that engineering the structures of the CeO 2 and g-C 3 N 4 interface could be an effective strategy to obtain excellent photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hybrid strategy is employed to design catalysts with superior K resistance. • The main reason for CeMn deactivation is cut-off of L-H mechanism resulting from the formation of stable nitrates. • The addition of ZSM-5 can re-activate the inert nitrates. • Alkali metals poisoned catalysts can be regenerated by ZSM-5 hybridization. The application of cerium-manganese oxides (CeMn) in controlling exhaust gas from biomass combustion is greatly inhibited due to poor resistance to alkali metals. Herein, we report a smart strategy to circumvent the K poisoning problem of CeMn by physically coupling with ZSM-5, which exhibited almost no activity loss even under a high loading of 2 wt % K 2 O. Results showed that in contrast to the conventionally believed disturbance of redox property and reduction of acid sites, the dominant effect from K loading on the deactivation of CeMn catalysts lies on the formation of chemically inert nitrates, which significantly restrains the reaction cycle via Langmuir-Hinshelwood route. With ZSM-5 hybridization, the stable nitrates over CeMn can be facilely activated and consumed by NH 4 + species introduced by ZSM-5, thus transforming poisoning sites into active sites and ensuring superior catalytic performance. The study presenting here not only provides an efficient strategy for fabricating NH 3 -SCR catalysts with superior K resistance but also sheds new light on the deactivation mechanism of K over CeMn catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sn4+ can be incorporated into the lattice of CeO2 to form uniform Ce x Sn1–x O2 solid solution when the mole ratio of Ce:Sn is not less than 2:1. [•] The incorporation of Sn4+ into the lattice of CeO2 is conducive to the decrease of crystallite size, the increase of lattice strain and the improvement of reduction behavior, which further promote the enhancement of catalytic performance. [•] The catalytic domain (CD, -Ce3+-□-Sn2+- species) in these Ce x Sn1–x O2 mixed oxides plays a key role in NO reduction by CO model reaction. [ABSTRACT FROM AUTHOR]

Abstract: A series of ceria-based solid solutions (Ce0.67Zr0.33O2, Ce0.67Sn0.33O2, Ce0.67Ti0.33O2) were synthesized by inverse co-precipitation, and then used as supports to prepare CuO/Ce0.67M0.33O2 (M=Zr4+, Sn4+, Ti4+) catalysts through wetness impregnation method. The obtained samples were investigated in detail by means of XRD, LRS, N2-physisorption, H2-TPR, XRF, XPS and in situ FT-IR techniques. The catalytic reduction of NO by CO as a model reaction was chosen to evaluate the catalytic performance of these samples. These results suggest that: (1) the reduction of CuO/Ce0.67Zr0.33O2 is easier than CuO/Ce0.67Sn0.33O2 and CuO/Ce0.67Ti0.33O2 catalysts, which may be attributed to the difference in the electronegativity of dopant; (2) the reduced state Cu+ is present in CuO/Ce0.67Zr0.33O2 at ambient temperature due to the shifting of redox equilibrium (Cu2+ +Ce3+ ↔ Cu+ +Ce4+) to right; (3) the adsorbed NO species on CuO/Ce0.67Zr0.33O2 are more liable to desorb/transform/decompose than those on CuO/Ce0.67Sn0.33O2 and CuO/Ce0.67Ti0.33O2 samples. The results of catalytic performance show that Cu+/Cu0 species play a key role in NO reduction by CO, and the activity is mainly related to the electronegativity of dopant, the reduction and adsorption behaviors of these catalysts. Furthermore, a possible reaction mechanism (schematic diagram) is tentatively proposed to understand this reaction. [Copyright &y& Elsevier]