Oxygen storage capacity and thermal stability of the CuMnO<sub>2</sub>–CeO<sub>2</sub> composite system

Huang, Xiubing; Ni, Chengsheng; Zhao, Guixia; Irvine, John T. S.

doi:10.1039/c5ta01361e

Cited by 42 publications

(31 citation statements)

References 43 publications

(71 reference statements)

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“…The proposed mechanism requires fast O-transport, which would have been assured by very mobile oxygen vacancies in CeO2. Similar phase cooperation has been observed between CeO2 and: CuMnO2 [25], Mn2O3, MnxFe1-xOy (both in [26]); CuO [27,28], La2O2SO4 [29] and tungstophosphoric acid HPW [30].…”

Section: Discussionsupporting

confidence: 75%

High selectivity epoxidation of ethylene in chemical looping setup

Marek

Gabra

Dennis

et al. 2020

Applied Catalysis B: Environmental

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We describe the remarkable performance of a new catalyst for the chemical looping (CL-) epoxidation of ethylene, performed at atmospheric pressure and without any promoters added to either the catalyst or the feed gas. To undertake the CL-epoxidation of ethylene, silver was used as the catalyst, supported on either the perovskite SrFeO3 or Ce-modified SrFeO3. Here, the oxygen for the reaction is supplied to the silver catalyst from the active solid support, not from the gas stream. When the support has been reduced and depleted of oxygen, it is regenerated in a separate step with air, which makes the process cyclic and closes a chemical loop. Thus, there is no need to co-feed gaseous oxygen along with the ethylene feed, an important improvement in safety. Two methods were used to synthesise Ce-modified materials, employing either (i) the mechanical mixing of powdered CeO2 and the solid precursors of the perovskite, or (ii) the impregnation of a solution of cerium nitrate into solid particles of SrFeO3. In both cases, the materials were calcined to produce a mixture of CeO2 and SrFeO3. Both CeO2-SrFeO3 materials surpassed the unmodified SrFeO3 for CL-epoxidation. For the CeO2-SrFeO3 prepared by mechanical mixing, the production of ethylene oxide was stable over 15 cycles, giving 60% selectivity at 10% conversion of C2H4. In contrast, the material prepared by impregnation gave up to 85% selectivity but only in the first cycle of reduction, with the performance degrading over subsequent cycles. The reported results are better than the 50% selectivity achieved for the classical epoxidation using pure silver as the catalyst and feeds of gaseous ethylene and oxygen, without reaction promoters.

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Section: Discussionsupporting

confidence: 75%

High selectivity epoxidation of ethylene in chemical looping setup

Marek

Gabra

Dennis

et al. 2020

Applied Catalysis B: Environmental

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“…Delafossite type oxides Cu I M III O 2 with M = (Fe, Al, Ga, Cr…) due to their large range of properties and the abundance of their constituent elements in the nature, have been studied for several applications such as transparent p-type conducting oxides (TCO) [10,11,12,13,14,15,16,17], transparent electronic devices [18,19,20,21,22,23,24,25], dye-sensitized solar cells [26,27,28,29], and photoelectrodes [30] but also for outstanding catalysis [31] and photo-catalysis [31,32,33,34,35,36,37,38,39,40,41], antibacterial [42], luminescence [43,44,45], gas and temperature sensing [46,47,48,49], magnetic and electric [50,51,52,53,54], energy storage [55], oxygen storage [56], water reduction [57], thermoelectricity and superconductivity [58] properties. In the oxide family, the cation Cu I is a monovalent metal and the cation M III is a trivalent metal.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric and Transport Properties of Delafossite CuCrO2:Mg Thin Films Prepared by RF Magnetron Sputtering

et al. 2017

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P-type Mg doped CuCrO2 thin films have been deposited on fused silica substrates by Radio-Frequency (RF) magnetron sputtering. The as-deposited CuCrO2:Mg thin films have been annealed at different temperatures (from 450 to 650 °C) under primary vacuum to obtain the delafossite phase. The annealed samples exhibit 3R delafossite structure. Electrical conductivity σ and Seebeck coefficient S of all annealed films have been measured from 40 to 220 °C. The optimized properties have been obtained for CuCrO2:Mg thin film annealed at 550 °C. At a measurement temperature of 40 °C, this sample exhibited the highest electrical conductivity of 0.60 S·cm−1 with a Seebeck coefficient of +329 µV·K−1. The calculated power factor (PF = σS²) was 6 µW·m−1·K−2 at 40 °C and due to the constant Seebeck coefficient and the increasing electrical conductivity with measurement temperature, it reached 38 µW·m−1·K−2 at 220 °C. Moreover, according to measurement of the Seebeck coefficient and electrical conductivity in temperature, we confirmed that CuCrO2:Mg exhibits hopping conduction and degenerates semiconductor behavior. Carrier concentration, Fermi level, and hole effective mass have been discussed.

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“…[19][20][21][22][23] Therefore, it can be imagined that modifying MnO 2 nanomaterials with CeO 2-δ could be an effective strategy to enhance the oxygen transferring by utilizing CeO 2-δ as a possible mediator. [18,24,25] Even though the enhanced catalytic performance in CO, C 3 H 8 , NO, Hg 0 and soot oxidation on Ce-Mn mixed oxides has been contributed to the synergistic effect between Ce and Mn, [24,[26][27][28][29][30] the exact mechanism of synergistic effect between CeO 2-δ and MnO 2 , as well as the relationship with surrounding atmospheres is still not clear enough, and needs further exploring.…”

Section: Introductionmentioning

confidence: 99%

Nanocrystalline CeO2−δ coated β-MnO2 nanorods with enhanced oxygen transfer property

Huang

Zhao

Chang

et al. 2018

Applied Surface Science

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In this research, β-MnO 2 nanorods were synthesized by a hydrothermal method, followed by a facile precipitation method to obtain nanocrystalline CeO 2-δ coated β-MnO 2 nanorods. The as-prepared samples were characterized by XRD, HRTEM, FESEM, XPS and in-situ high-temperature XRD. The HRTEM results show that well dispersed CeO 2-δ nanocrystals sized about 5 nm were coated on the surface of β-MnO 2 nanorods. The oxygen storage and transfer property of as-synthesized materials were evaluated using TGA under various atmospheres (air, pure N 2 , and 5%H 2 /95%Ar). The TGA results indicate that CeO 2-δ modification could favour the reduction of Mn 4+ to Mn 3+ and/or Mn 2+ at lower temperature as compared with pure β-MnO 2 nanorods and the physically mixed CeO 2-δ-β-MnO 2 under low oxygen partial pressure conditions (i.e., pure N 2 , 5%H 2 /95%Ar). Specifically, CeO 2-δ @β-MnO 2 sample can exhibit 7.5 wt% weight loss between 100 and 400 o C under flowing N 2 and 11.4 wt% weight loss between 100 and 350 o C under flowing 5%H 2 /95%Ar. During the reduction process under pure N 2 or 5%H 2 /95%Ar condition, the oxygen ions in β-MnO 2 nanorods are expected to be released to the surroundings in the form of O 2 or H 2 O with the coated CeO 2-δ nanocrystals acting as mediator as inferred from the synergistic effect between the well-interacted CeO 2-δ nanocrystals and β-MnO 2 nanorods.

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Oxygen storage capacity and thermal stability of the CuMnO₂–CeO₂ composite system

Cited by 42 publications

References 43 publications

High selectivity epoxidation of ethylene in chemical looping setup

High selectivity epoxidation of ethylene in chemical looping setup

Thermoelectric and Transport Properties of Delafossite CuCrO2:Mg Thin Films Prepared by RF Magnetron Sputtering

Nanocrystalline CeO2−δ coated β-MnO2 nanorods with enhanced oxygen transfer property

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Oxygen storage capacity and thermal stability of the CuMnO2–CeO2 composite system

Cited by 42 publications

References 43 publications

High selectivity epoxidation of ethylene in chemical looping setup

High selectivity epoxidation of ethylene in chemical looping setup

Thermoelectric and Transport Properties of Delafossite CuCrO2:Mg Thin Films Prepared by RF Magnetron Sputtering

Nanocrystalline CeO2−δ coated β-MnO2 nanorods with enhanced oxygen transfer property

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Oxygen storage capacity and thermal stability of the CuMnO₂–CeO₂ composite system