CeO2基氧化物储氧材料研究 (Ⅰ) 制备、储氧性能研究

用共沉淀法制备了CZO和CZYO复合气化物,对在750,900,1050℃老化的样品进行XRD,BET和OSC的测试和分析。在高温条件下纯CeO2样品的比表面积和OSC迅速下降,晶粒尺寸快速增大;所制备的CZO复合氧化物由立方相和四方相两种结构的固溶体组成,在高温老化后氧化物晶粒的尺寸增大较快;CZYO复合氧化物中的Y含量增至0.15mol时形成均相的固溶体,且氧化物的晶粒尺寸增长较慢,Y起到了高温条件下稳定氧化物性能的作用;CZYO复合氧化物具有BET表面积大、OSC高等优良的耐高温性能,是适用于开发新一代TWO、的储氧材料。     

Frontispiece: Activating Lattice Oxygen in Spinel ZnCo2O4 through Filling Oxygen Vacancies with Fluorine for Electrocatalytic Oxygen Evolution

The development of productive catalysts for the oxygen evolution reaction (OER) remains a major challenge requiring significant progress in both mechanism and material design. Conventionally, the thermodynamic barrier of lattice oxidation mechanism (LOM) is lower than that of absorbate evolution mechanism (AEM) because the former can overcome certain limitations. However, controlling the OER pathway from the AEM to the LOM by exploiting the intrinsic properties of the catalyst remains challenging. Herein, we incorporated F anions into the oxygen vacancies of spinel ZnCo₂O₄ and established a link between the electronic structure and the OER catalytic mechanism. Theoretical density calculations revealed that F upshifts the O 2p center and activates the redox capability of lattice O, successfully triggering the LOM pathway. Moreover, the high electronegativity of F anions is favourable for balancing the residual protonation, which can stabilize the structure of the catalyst.     

Imaging of Oxygen Diffusion in Individual Platinum/Ce2Zr2Ox Catalyst Particles During Oxygen Storage and Release

The spatial distribution of Ce³⁺ and Ce⁴⁺ in each particle of Ce₂Zr₂O_x in a three‐way conversion catalyst system was successfully imaged during an oxygen storage/release cycle by scanning X‐ray absorption fine structure (XAFS) using hard X‐ray nanobeams. For the first time, nano‐XAFS imaging visualized and identified the modes of non‐uniform oxygen diffusion from the interface of Pt catalyst and Ce₂Zr₂O_x support and the active parts in individual catalyst particles.     

Superconductivity Induced by Oxygen Doping in Y2O2Bi

When doped with oxygen, the layered Y₂O₂Bi phase becomes a superconductor. This finding raises questions about the sites for doped oxygen, the mechanism of superconductivity, and practical guidelines for discovering new superconductors. We probed these questions in terms of first‐principles calculations for undoped and O‐doped Y₂O₂Bi. The preferred sites for doped O atoms are the centers of Bi₄ squares in the Bi square net. Several Bi 6p x /y bands of Y₂O₂Bi are raised in energy by oxygen doping because the 2p x /y orbitals of the doped oxygen make antibonding possible with the 6p x /y orbitals of surrounding Bi atoms. Consequently, the condition necessary for the “flat/steep” band model for superconductivity is satisfied in O‐doped Y₂O₂Bi.     

CeO_2-ZrO_2-Al_2O_3稀土储氧材料制备工艺的研究

采用化学沉淀法制备了系列CeO2-ZrO2-Al2O3稀土储氧材料,并用BET,XRD和储氧性能测定等表征手段考察了陈化时间、La2O3含量、反应pH和沉淀方式等工艺因素对CeO2-ZrO2-Al2O3比表面积、储氧性能和结构的影响。结果表明:当陈化时间为12 h,反应pH=10时,掺杂2%(质量分数)La2O3的CeO2-ZrO2-Al2O3样品在老化前后均具有很高比表面积和良好的储氧性能,并且pH为影响样品比表面积及热稳定性能的主要因素。与一步法沉淀相比,二步法制得的CeO2-ZrO2-Al2O3样品具有很高的热稳定性能,1050℃老化5 h后的样品比表面积高达46.4 m2.g-1,但储氧性能略差,这与Al2O3对CeO2-ZrO2的结构影响程度有关。     

Exploiting Two-Dimensional Bi2O2Se for Trace Oxygen Detection

We exploit a high-performing resistive-type trace oxygen sensor based on 2D high-mobility semiconducting Bi₂O₂Se nanoplates. Scanning tunneling microscopy combined with first-principle calculations confirms an amorphous Se atomic layer formed on the surface of 2D Bi₂O₂Se exposed to oxygen, which contributes to larger specific surface area and abundant active adsorption sites. Such 2D Bi₂O₂Se oxygen sensors have remarkable oxygen-adsorption induced variations of carrier density/mobility, and exhibit an ultrahigh sensitivity featuring minimum detection limit of 0.25 ppm, long-term stability, high durativity, and wide-range response to concentration up to 400 ppm at room temperature. 2D Bi₂O₂Se arrayed sensors integrated in parallel form are found to possess an oxygen detection minimum of sub-0.25 ppm ascribed to an enhanced signal-to-noise ratio. These advanced sensor characteristics involving ease integration show 2D Bi₂O₂Se is an ideal candidate for trace oxygen detection.     

Oxygen sensitivity of algal H2- production

Applied Biochemistry and Biotechnology - Photoproduction of H2 by green algae utilizes electrons originating from the photosynthetic oxidation of water and does not require metabolic intermediates....     

Oxygen intercalation of two polymorphs of CuScO2

Both the 2H and 3R forms of CuScO₂ have been intercalated with oxygen to yield CuScO_2+x, phases where x has been observed to range from 0.0 to 0.12 and 0.44 to 0.5. The position of the interstitial oxygen in the CuScO_2.5 phases was determined from powder neutron diffraction data. In both cases the interstitial oxygen resides in triangular sites in the Cu layer. However, in the 3R form the oxygen is displaced 0.3 Å toward a Sc atom above or below the Cu plane. When heating the 2H form of CuScO₂ under oxygen, the oxygen initially absorbed is released at about 440 °C. The 3R form does not lose oxygen under these conditions but it does lose oxygen around 580 °C when heated in air. These are exceptionally low temperatures for the thermal reduction of Cu²⁺ to Cu¹⁺ in an oxide system, but it is consistent with the low calculated bond valence sum of 1.7 for interstitial oxygen compared to 2.0 calculated for the network oxygen. The weak bond formed between the interstitial oxygen and Sc in 3R CuScO₂ is presumably the reason why this oxygen is more strongly held in the 3R form relative to the 2H form. On oxygen intercalation there is a 1.46% increase of the hexagonal a cell edge the 2H form and a 1.61% increase for the 3R form. The c cell edge expands by 0.23% on oxidation of the 2H form, but contracts by 0.30% on oxidation of the 3R form. This contraction of c and greater expansion for a for the 3R form can be attributed to the weak bond formed between Sc and the interstitial oxygen. Most synthesis routes to CuScO₂ give a mixture of the 2H and 3R forms, and this mixing can extend to the atomic level in the form of stacking faults.     

纳米CeO2包覆TiO2氧传感器材料氧敏性能的机理研究

在用溶胶-凝胶方法成功制备纳米TiO2、纳米CeO2包覆纳米TiO2材料的基础上,进行了氧敏性能、阻抗谱的测试和对比,并且通过热力学和活化能计算对实验结果进行了分析.实验结果表明:纳米CeO2包覆纳米TiO2材料的氧敏性能优于纯TiO2材料,.当包覆4.9mol?O2时材料的氧敏性能最好.热力学计算证明:CeO2对TiO2起到催化作用,从而改善TiO2的氧敏性能.对材料活化能计算表明:包覆纳米CeO2后材料的晶粒、晶界活化能显著降低,TiO2的活性得到提高:并且随着CeO2包覆量降低活化能降低,说明活化能存在极小值,CeO2包覆量有最优值,从而解释了实验结果中出现极值的现象.     

CeO2基氧化物储氧材料研究(Ⅱ)添加贵金属改进储氧能力

在高温老化的复合氧化物CZO和CZYO体系中,添加微量贵金属(Pt,Pd,Rh)明显提高还原速度并增加OSC.含贵金属的CZO或CZYO的OSC与其组成和贵金属的种类有关.较长时间(10 h)老化后含Pd的CZO3样品的OSC明显下降,CZYO2样品的OSC略有下降.含Pt/Rh,10 h老化后CZO3和CZY02样品的OSC均高于相应同条件老化的含Pd样品的OSC.     

Unravelling the Synergy between Oxygen Vacancies and Oxygen Substitution in BiO2−x for Efficient Molecular‐Oxygen Activation

Defects in nanomaterials often lead to properties that are absent in their pristine counterparts. To date, most studies have focused on the effect of single defects, while ignoring the synergy of multiple defects. In this study, a model of photocatalytic O₂ activation was selected to unravel the role of dual defects by decorating bismuth oxide with surface O vacancies and bulk O substitution simultaneously. The introduction of dual defects led to a spatial and electronic synergistic process: i) O substitution induced a local electric field in the bulk of BiO_2?x, which promoted bulk separation of electrons and holes immediately after their generation; ii) O vacancies efficiently lowered the conduction band, served as the capture center for electrons, and thus facilitated the adsorption and activation of O₂. This effect was greatly promoted by the coexistence of bulk O substitution, and DFT calculations showed that only O substitution near an O vacancy could have this effect.     

单层含氧缺陷δ-MnO2用于二氧化碳还原

电催化还原二氧化碳成多碳燃料一直是研究的热点. 而找到活性高,选择性优,稳定性好的催化剂一直是研究者们奋斗的目标. 二氧化锰因其独特的物理和化学性质被广泛的应用于电催化领域,而缺陷的调控可以改变催化剂的电子性质,在此次工作中作者系统地研究了在有氧缺陷和没有氧缺陷的二维二氧化锰上的电催化二氧化碳还原反应. 通过利用自旋极化密度泛函理论,作者分别计算了他们的电子性质和分子在吸附过程中的能量值. 结果显示,缺陷的引入改变了二氧化锰的特性,使其从半导体性质变为半金属性质,从而提高催化剂的导电性. 同时,分析能量图也很容易发现对应产品的选择性也发生了变化. 二氧化锰有利于甲酸的产生,而氧缺陷的二氧化锰更有利于一氧化碳的生成. 本研究将为二氧化碳还原的其他非贵金属氧化物催化剂的结构设计和优化提供一定的指导.     

氧在镧钼阴极中的作用

利用脉冲激光沉积在不同真空度下制备了不同La／O的La-Mo薄膜阴极，测量其发射性能并进行了原位AES分析，讨论了氧在镧钼阴极热电子发射中的作用。过多的氧易形成稳定的氧化镧，不利于电子发射；适当比例的氧可以减缓镧的蒸发，有助于阴极的稳定工作。La-O化合物中氧空位的形成有利于阴极的电子发射，氧缺位增强了镧氧化合物的半导体性。     

GNs-MnO2复合催化剂的制备及催化氧还原性能

石墨烯由单层碳原子组成,具有大的比表面积和超高的导电性,广泛应用于催化与储能领域.本工作结合石墨烯独特的物理化学性质和结构特性,采用原位氧化还原法,以KMnO4和石墨烯(GNs)为原料合成GNs-MnO2氧还原催化剂,通过X射线衍射(XRD)、拉曼光谱(Raman)、透射电镜(TEM)、热重(TG)、BET等分析测试技术研究了纳米GNs-MnO2复合材料的微观结构特征.结果表明,合成的MnO2纳米线直接生长在石墨烯的表面,增加了MnO2的比表面积,提高了催化剂的活性位点.电化学测试表明,合成的GNs-MnO2催化剂在碱性介质中电催化氧还原电位比纯MnO2的氧还原电位正移80 mV,电流提高了1.3倍,在燃料电池氧还原电催化中有一定的应用前景.     

氧在Ni-MnO2电极上的电催化还原

采用喷雾热解法合成了超细二氧化锰, 通过喷涂制作成Ni-MnO2薄膜电极, 结合SEM、AFM和电化学测试技术, 研究了碱性介质中氧在Ni-MnO2薄膜电极上的电催化还原过程. 发现二氧化锰颗粒呈片状, 是由球形前驱体烧结后碎裂而成; 通过快速循环伏安法检测到了MnO2电极上存在着中间态粒子的还原过程, 该粒子浓度可累积, 并逐渐消耗直至消失, 寿命可持续约200周循环; 结果表明, 该粒子对氧的还原具有特殊的电催化活性.     

CeO2基氧化物储氧材料研究(Ⅱ)添加贵金属改进储氧能力

在高温老化的复合氧化物CZO和CZYO体系中,添加微量贵金属(Pt,Pd,Rh)明显提高还原速度并增加OSC.含贵金属的CZO或CZYO的OSC与其组成和贵金属的种类有关.较长时间(10 h)老化后含Pd的CZO3样品的OSC明显下降,CZYO2样品的OSC略有下降.含Pt/Rh,10 h老化后CZO3和CZY02样品的OSC均高于相应同条件老化的含Pd样品的OSC.