JOURNAL OF ALLOYS AND COMPOUNDS
·
2021
·
IF 5.316
Sara Adeeba Ismail,Lulu Jiang,Peng Zhong,Truls Norby,Donglin Han
La 2 Ce 2 O 7 is known to be a disordered fluorite, i.e., 50% La-doped CeO 2 , exhibiting oxide ion conduction with contributions from protons in wet atmospheres and minority electrons under reducing conditions. Here, we report the effect of additional doping by partial substitution of La 3+ with divalent alkaline earth cations A 2+ ( A = Ca, Sr, Ba) on the hydration behavior and electrical conductivity of La 2 Ce 2 O 7 . A single-phase cubic fluorite structure was obtained for La 2 Ce 2 O 7 , (La 1- x Ca x ) 2 Ce 2 O 7-δ ( x = 0–0.3), (La 1- x Sr x ) 2 Ce 2 O 7-δ ( x = 0–0.2), and (La 1- x Ba x ) 2 Ce 2 O 7-δ ( x = 0–0.05). Substitution by A 2+ enhanced the degree of hydration, which may be attributed to increased concentration of hydratable oxygen vacancies and coordination of oxide ions by A 2+ in addition to La 3+ , while the basicity of the different A 2+ seemed unimportant. The doping increased ionic conductivity slightly, while the n-type electronic conductivity under reducing atmospheres increased considerably. XPS analyses indicated that the concentration and binding energy of Ce 3d electrons decreased with increasing doping level of Ca, implying an enhanced mobility of electrons which may be attributed to an observed decrease in lattice parameter .
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2019
·
IF 2.846
Wenfeng Han,Zhi Li,Huazhang Liu
La 2 Ce 2 O 7 nanoparticles were prepared by citric acid complexation method followed by calcination at varied temperatures. Then, supported with 4 wt% Ru, they were evaluated as the catalysts for ammonia synthesis under conditions similar with industry. With La 2 Ce 2 O 7 being calcinated at 700 or 800 °C, the experimental results indicate that the Ru/La 2 Ce 2 O 7 catalyst exhibits much higher ammonia concentration or ammonia synthesis rate than that of Ru/CeO 2 and Ru/La 2 O 3 . In addition, Ru/La 2 Ce 2 O 7 possesses high stability under over-heating test. In the absence of any promotor, ammonia concentration of Ru/La 2 Ce 2 O 7 catalyst approaches 14% at 450 °C, GHSV of 10000 h −1 and pressure of 10 MPa. The rate-determining step of ammonia synthesis, dissociation of N 2 is significantly facilitated by the strong metal–support interaction (SMSI) between Ru and La 2 Ce 2 O 7 . Due to the interaction, La 2 Ce 2 O 7 tends to donate electrons to Ru, resulting in the high electron density over the surface of Ru active sites which is favorable for the dissociation of N 2 . Consequently, high activity is achieved.
研究领域:
催化化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2022
·Vol. 105
·期 12
·7548-7557
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IF 4.186
Sara Adeeba Ismail,Donglin Han
La 2 Ce 2 O 7 is a fluorite-type oxide, showing almost pure oxide ion conduction in dry oxygen atmosphere. Under wet oxygen atmosphere, protons are introduced into La 2 Ce 2 O 7 through hydration reaction, making the material proton-conducting. However, compared with the oxide ion conductivity, the proton conductivity is negligibly small in La 2 Ce 2 O 7 . Here we report the effect of doping trivalent rare earth cations R 3+ ( R = Y, Ho, Er, Yb, or Tm) and elevating partial pressure of water vapor on the proton concentration and conductivity of La 2 Ce 2 O 7 . The samples show single fluorite phases with the doping level up to 0.2, and the solubilities of these dopants were within 0.2–0.3 in La 2 Ce 2 O 7 . The proton concentration increased by doping, due to higher amount of hydratable oxygen vacancies, and statistical coordination of oxide ions surrounded by R 3+ in addition to La 3+ . The sample with the Y content ( x ) of 0.05 showed the highest conductivity at 600°C among La 2 (Ce 1− x Y x ) 2 O 7− δ ( x = 0–0.3) samples, possibly due to the balance between the improved hydration ability and decreased mobility of protons with the increasing Y doping level. Then, the dopant content was fixed to 0.05, and La 2 (Ce 0.95 R 0.05 ) 2 O 7− δ ( R = Y, Ho, Er, Tm, or Yb) was prepared. It was found that as the water vapor partial pressure increased, the proton concentration and conductivity increased regardless of the dopants. Y-doped La 2 Ce 2 O 7− δ ha the highest proton concentration and conductivity.
研究领域:
材料科学
·
化学
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产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2023
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IF 6.2
Xiaowei Chen,Zhongqin Li,Jiancheng Zhou,Shi Chen,Yi Huang,Weiwei Wang,Wuyou Wang,Qi Xu,Xinguo Xi
It is an effective strategy to improve photocatalytic degradation performance by constructing step scheme (S-scheme) heterojunction photocatalysts with superior photo-redox capacity and high charge transfer efficiency. In this study, a series of two-dimensional/two-dimensional (2D/2D) La 2 Ce 2 O 7 /g-C 3 N 4 (LCO/CN) S-scheme heterojunction photocatalysts were synthesized via in-situ solid-phase sintering by regulating the mass ratio of raw materials. The large junction area between La 2 Ce 2 O 7 nanosheets and ultra-thin graphitic carbon nitride (g-C 3 N 4 ) endows the composite with significantly enhanced separation and transfer efficiency of photogenerated carriers within a satisfactory light response region. The LCO/CN-2 composite not only shows the highest photocatalytic activity with a reaction rate constant of 0.02701 min −1 to degrade Rhodamine B (RhB) under visible light irradiation for 90 min but also demonstrates stable reusability after four runs. Moreover, based on the Mott-Schottky calculations, radical trapping experiments, and ESR analysis,·O 2- and·OH are identified as the main active species, and an S-scheme charge transfer mechanism is suggested to explain the enhanced photocatalytic activity. This work inspires the application of fluorite-type photocatalysts to wastewater purification and environmental restoration.
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
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