氧化铈在生物分析与传感检测中的应用研究进展

铈是镧系元素中活性最高的一种稀土元素,氧化铈已广泛应用于抛光剂、脱色剂、催化剂、发光增强剂等领域。Ce3+/Ce4+之间自发的氧化还原循环可在氧化铈晶面上产生许多氧空位（V?）,加快反应中的电荷转移,使氧化铈具有很高的催化活性和储放氧能力。混合价态自发的氧化还原循环以及由此产生的氧空位对氧化铈的性质有着重大影响,使其表现出独特的抗菌、抗炎、抗肿瘤和模拟酶等生物医学活性,可用于多种疾病的诊疗。此外,氧化铈还可单独使用或与其他材料掺杂、复合来构建灵敏的传感材料,应用于多种物质的分析与检测,并已成为国内外研究的热点。该文首先阐明了氧化铈作为传感材料的理论基础,然后分别从电化学传感、比色传感、荧光传感和化学发光传感四个方面对国内外氧化铈传感检测领域的应用进展进行了归纳,最后对氧化铈传感器的研发现状进行总结并对未来发展进行了展望,为高性能传感器的研发提供了参考。     

Interaction of Hydrogen with Ceria: Hydroxylation,Reduction, and Hydride Formation on the Surface and in the Bulk

The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO₂) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO₂(111) thin films and CeO₂ powders, and theoretical calculations of CeO₂(111) surfaces with oxygen vacancies (O_v) at the surface and in the bulk. We show that, on a stoichiometric CeO₂(111) surface, H₂ dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO_2−x samples, both films and powders, hydroxyls and hydrides (Ce−H) are formed on the surface as well as in the bulk, accompanied by the Ce³⁺ ↔ Ce⁴⁺ redox reaction. As the O_v concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H₂/CeO₂ interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere.     

In Situ Investigation of Methane Dry Reforming on Metal/Ceria(111) Surfaces: Metal–Support Interactions and C−H Bond Activation at Low Temperature

Studies with a series of metal/ceria(111) (metal=Co, Ni, Cu; ceria=CeO₂) surfaces indicate that metal–oxide interactions can play a very important role for the activation of methane and its reforming with CO₂ at relatively low temperatures (600–700 K). Among the systems examined, Co/CeO₂(111) exhibits the best performance and Cu/CeO₂(111) has negligible activity. Experiments using ambient pressure X‐ray photoelectron spectroscopy indicate that methane dissociates on Co/CeO₂(111) at temperatures as low as 300 K—generating CH_x and CO_x species on the catalyst surface. The results of density functional calculations show a reduction in the methane activation barrier from 1.07 eV on Co(0001) to 0.87 eV on Co²⁺/CeO₂(111), and to only 0.05 eV on Co⁰/CeO_2−x (111). At 700 K, under methane dry reforming conditions, CO₂ dissociates on the oxide surface and a catalytic cycle is established without coke deposition. A significant part of the CH_x formed on the Co⁰/CeO_2−x (111) catalyst recombines to yield ethane or ethylene.     

Density functional theory study of formaldehyde adsorption and decomposition on Co-doped defective CeO_2(110) surface

Formaldehyde as an air pollutant to adverse health effects for humanity has been getting attention. The adsorption and dissociation of formaldehyde(HCHO) on the Co_xCe_(1-x_O_(2-δ)(110) surface were investigated by the density functional theory(DFT) calculations. We calculated the oxygen vacancy formation energy as the function of its site around dopant Co in detail. The results showed that Co doping was accompanied by compensating oxygen hole spontaneous formation.The adsorption configurations and bindings of HCHO at different locations on the Co_xCe_(1-x)O_2(110) were presented.Four possible pathways of oxidation of formaldehyde on the catalytic surface were explored. The results suggested that formaldehyde dissociation at different adsorption sites on the doped CeO_2(110) — first forming dioxymethylene(CH_2O_2)intermediate, and then decomposing into H_2O, H_2, CO_2, and CO molecules. It was found that the presence of cobalt and oxygen vacancy significantly prompted the surface activity of CeO_2.     

Defect Chemistry of Singly and Doubly Doped Ceria: Correlation between Ion Transport and Energetics

Earlier studies have shown a strong correlation between the enthalpy of formation, ΔH_f,ox, and the ionic conductivity, σ_i, near room temperature in doped ceria systems, which are promising solid electrolytes for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). The present work demonstrates that this correlation holds at the operating temperature of IT‐SOFCs, 600–700 °C. Solid solutions of Ce_1?xNd_xO_2?0.5x, Ce_1?xSm_xO_2?0.5x, and Ce_1?xSm_0.5xNd_0.5xO_2?0.5x are studied. The ΔH_f,ox at 702 °C is determined by considering the excess heat content between 25 and 702 °C combined with the value of ΔH_f,ox at 25 °C. Both σ_i and ΔH_f,ox show maxima at x=0.15 and 0.20 for the singly and doubly doped ceria, respectively, suggesting that the number of mobile oxygen vacancies in these solid solutions reaches a maximum near those compositions. An increase in temperature results in a shift of the maximum in both ΔH_f,ox and σ_i towards higher concentrations. This shift results from a gradual increase in dissociation of the defect associates.     

铈铝复合载体对钼基催化剂耐硫甲烷化催化性能的研究

采用共沉淀法、浸渍法和沉积沉淀法制备了CeO₂-Al₂O₃复合载体,比较了不同复合载体浸渍钴钼后的耐硫甲烷化催化性能,并优化了复合载体中CeO₂的含量。结合N₂物理吸附、XRD、H₂-TPR等表征手段对复合载体及其负载的钴钼催化剂进行物相和结构分析发现,在Al₂O₃中添加CeO₂可以明显提高合成气的耐硫甲烷化活性,其中,沉积沉淀法制备的25% CeO₂-Al₂O₃复合载体负载钴钼后具有最佳催化活性。     

Ce0.8Nd0.2O1.9-La0.95Sr0.05Ga0.9Mg0.1O3-δ固体复合电解质的结构和电性能

采用溶胶-凝胶法分别制备La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-δ (LSGM)和Ce_0.8Nd_0.2O_1.9 (NDC)电解质,并在NDC溶胶中加入0-15% (w,质量分数)的LSGM预烧粉体制得NDC-LSGM复合电解质,研究不同质量比复合电解质的结构和电性能. 采用X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)和X能量色散谱仪(EDS)对样品进行结构表征,交流(AC)阻抗谱测试样品导电性能. 结果表明：NDC-LSGM复合体系主要由立方萤石结构相、钙钛矿结构相和杂质相组成;LSGM的添加可促进晶粒的生长,产生大量相界面,清除或降低SiO₂有害影响,明显提高晶界导电性;LSGM质量分数为10%的样品NL10 具有最高晶界电导率和总电导率,400 ℃时NL10 的晶界电导率σ_gb和总电导率σ_t分别为12.15×10^-4和3.49×10^-4 S·cm^-1,与NDC的σ_gb (1.41×10^-4 S·cm^-1)和σ_t (1.20×10^-4 S·cm^-1)相比分别提高了7.62和1.91倍,总电导率的提高主要归因于晶界电导率的影响.     

用于质子交换膜燃料电池抗CO的Pt-CeO2/C催化剂的制备和表征

采用一步沉淀法,制备了纳米级Pt-CeO2/C电催化剂.透射电镜和X射线衍射表征结果表明,制备的催化剂Pt颗粒均匀分散于碳载体表面,其粒径主要分布于1.5～2.5 nm.将Pt-CeO2/C催化剂制备成质子交换膜燃料电池膜电极,经循环伏安和单电池极化曲线测试发现,Pt-CeO2/C催化剂性能与Pt/C催化剂的相当.一氧...     

双模板法制备具有介孔孔壁的三维有序大孔二氧化铈及其改善的低温还原性能

以聚甲基丙烯酸甲酯(PMMA)为硬模板,三嵌段共聚物F127、十六烷基三甲基溴化铵(CTAB)或聚乙二醇(PEG)为软模板剂(表面活性剂),柠檬酸为络合剂,硝酸铈为金属前驱体,采用双模板法成功地合成出具有介孔孔壁的三维有序大孔(3DOM)结构的立方相CeO2样品CeO2-F127,CeO2-CTAB和CeO2-PEG,...