Correlation between the structural characteristics, oxygen storage capacities and catalytic activities of dual-phase Zn-modified ceria nanocrystals

Lin Fangjian; Delmelle Renaud; Vinodkumar ThalladaReddy Benjaram M.Wokaun AlexanderAlxneit Ivo

摘要

Doping ceria with heterocations is a commonly applied strategy to alter its structural and chemical properties including its key feature oxygen storage capacity (OSC). Although a few papers have been published on the structural properties and chemical reactivity of Zn-doped ceria, one lacks a comprehensive investigation on the effect of zinc incorporation in the ceria lattice on its structural properties, and how it could be correlated to the changes in its chemical reactivity including OSC and catalytic activities. Here, we have established an interesting correlation between the structural properties of dual-phase Zn-modified ceria nanocrystals, their OSCs, and their catalytic performance for the reverse water-gas shift (RWGS) reaction and soot oxidation. Upon incorporation of zinc in the ceria lattice, the degree of crystallinity is decreased according to XRD. Raman spectroscopy reveals a concomitant increase of oxygen vacancy concentrations within the Zn-modified ceria samples in comparison to pure ceria. The incorporation of zinc increases the reducibility of ceria according to H-2-TPR and doubles the OSC as revealed by thermogravimetric studies. When the variations of the degree of crystallinity, the oxygen vacancy concentrations and the OSCs within the Zn-modified ceria samples are compared, an excellent correlation is established. Catalytic testing shows that Zn-modified ceria exhibits higher activities for the RWGS reaction, especially at the lower temperatures of 400 degrees C and 600 degrees C, while at 800 degrees C the catalyst deactivates rapidly. Such deactivation at high temperature can be totally eliminated by impregnating additional cobalt oxide on the ceria support. Some improvement in the soot oxidation activity is achieved with Zn-modified ceria, attributed to enhanced OSCs of the materials. Within the set of Zn-modified ceria samples, the activities are essentially identical, which is again correlated to their nearly identical OSCs, irrespective of the zinc concentration. Upon impregnation of additional cobalt oxide, the materials' activities for soot oxidation are markedly enhanced, as observed with the RWGS reaction. Pure ceria and Zn-modified ceria samples perform significantly better for soot oxidation after being leached with citric acid. Such enhancement is more pronounced with CZ10 (10 mol% zinc) in comparison to pure ceria. This observation suggests that the removal of non-incorporated ZnO increases the activity for soot oxidation.

机译：具有异位的掺杂陶瓷是一种通常应用的策略，以改变其结构和化学性质，包括其关键特征氧储存能力（OSC）。尽管已经发表了一些有关Zn掺杂陶瓷的结构特性和化学反应性的论文，但缺乏对二氧化碳掺入二氧化碳晶格对其结构特性的影响的全面研究，以及如何与它与它的变化相关。它的化学反应性包括OSC和催化活性。在这里，我们建立了双相Zn修饰的二氧化碳纳米晶体的结构特性，其OSC与反向水气（RWGS）反应（RWGS）反应的催化性能与催化性能。在将锌掺入陶瓷晶格中后，根据XRD，结晶度降低。拉曼光谱法揭示了与纯陶瓷相比，Zn修饰的陶瓷样品中氧空位浓度的增加。锌的掺入可提高根据H-2-TPR的陶瓷的可还原性，并增加了OSC的一倍，如热重研究所示。当结晶度的变化，比较Zn修饰的陶瓷样品中的氧空位浓度和OSC时，建立了极好的相关性。催化测试表明，Zn修饰的陶瓷表现出较高的RWGS反应活性，尤其是在400摄氏度和600摄氏度的较低温度下，而在800摄氏度为800摄氏度，催化剂会迅速失活。通过在二氧化碳载体上浸入额外的氧化钴，可以完全消除在高温下的这种失活。通过Zn修饰的二氧化碳可实现烟灰氧化活性的一些改善，这归因于增强的材料OSC。在Zn修饰的陶瓷样品集中，这些活性基本相同，这再次与它们几乎相同的OSC相关，而与锌浓度无关。在浸入其他氧化钴的情况下，如RWGS反应所观察到的那样，材料的烟灰氧化活性显着增强。用柠檬酸浸出后，纯陶瓷和Zn修饰的陶瓷样品对烟灰氧化的性能明显更好。与纯陶瓷相比，CZ10（10 mol％锌）更为明显。该观察结果表明，去除非注册ZnO会增加烟灰氧化活性。

Correlation between the structural characteristics, oxygen storage capacities and catalytic activities of dual-phase Zn-modified ceria nanocrystals

摘要

著录项

相似文献

相关主题

期刊订阅