乙醇重整条件下钴对二氧化铈还原特性的影响：AP-XPS和XANES研究,The Journal of Physical Chemistry C

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乙醇重整条件下钴对二氧化铈还原特性的影响：AP-XPS和XANES研究
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2016-07-01 00:00:00 , DOI: 10.1021/acs.jpcc.6b02490
Hyuntae Sohn ₁ , I. Ilgaz Soykal ₁ , Shiran Zhang ₂ , Junjun Shan ₂ , Franklin Tao ₂ , Jeffrey T. Miller ₃ , Umit S. Ozkan ₁

Affiliation

使用AP-XPS和XANES技术在乙醇蒸汽重整条件下研究了裸露的二氧化铈和负载有钴纳米粒子的二氧化铈的表面和体积减少特性。制备二氧化铈颗粒，其具有两种不同的粒径，一种为纳米级，另一种为微米级（称为CeO ₂ -NP和CeO ₂ -MP），平均粒径分别为4 nm和120 nm。已经发现，粒径影响二氧化铈颗粒的表面还原性。较小的粒径导致较高的表面还原度。负载钴纳米颗粒对CeO ₂ -NP和CeO ₂的表面还原性都有显着影响-MP。与裸露的二氧化铈颗粒相比，由于氧化钴相（Co ₃ O ₄和CoO）的还原优先于二氧化铈，因此在二氧化铈载体表面上存在完全氧化的钴纳米颗粒会阻碍二氧化铈的表面还原性。乙醇蒸汽重整过程中钴相的还原程度决定了钴对二氧化铈还原过程的影响，即钴是否阻碍或促进了二氧化铈载体的还原。AP-XPS研究表明，钴纳米颗粒的表面由金属Co和CoOx组成。CoOx的表面区域还原为金属Co形成了金属Co基壳和CoOx基核。金属钴在CoOx上的锚固使金属钴壳良好地分散在CeO _2上没有烧结。另外，重整反应主要在金属Co和CeO ₂的界面处发生。Co / CeO ₂ -NP和Co / CeO ₂ -MP之间的差异比CeO ₂ -NP和CeO ₂ -MP之间的差异大得多，这表明金属Co在催化重整反应中的重要性，尽管裸露的二氧化铈载体表现出某些脱水作用。活动本身。

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Effect of Cobalt on Reduction Characteristics of Ceria under Ethanol Steam Reforming Conditions: AP-XPS and XANES Studies

The surface and bulk reduction characteristics of bare ceria and ceria with supported cobalt nanoparticles were investigated under ethanol steam reforming conditions using AP-XPS and XANES techniques. Ceria particles were prepared in two different particle sizes, one in nano and the other in micron size (termed CeO₂-NP and CeO₂-MP), with average particle sizes of 4 and 120 nm, respectively. It was found that particle size affects surface reducibility of ceria particles; smaller particle size leads to a higher extent of surface reduction. Supported cobalt nanoparticles have a significant effect on the surface reducibility of both CeO₂-NP and CeO₂-MP. Compared to bare ceria particles, the presence of fully oxidized cobalt nanoparticles on the surface of ceria support retards surface reducibility of ceria since reduction of the cobalt oxide phases (Co₃O₄ and CoO) takes precedence over that of ceria. The degree of reduction of the cobalt phase during ethanol steam reforming determines the effect of cobalt on the reduction process of ceria, i.e., whether it retards or facilitates the reduction of ceria support. AP-XPS studies show that the surface of cobalt nanoparticles consists of both metallic Co and CoOx. The reduction of the surface region of CoOx to metallic Co forms a metallic Co-based shell and CoOx-based core. The anchor of metallic Co on CoOx make metallic Co shell well dispersed on CeO₂ without sintering. In addition, the reforming reaction takes place primarily at the interface of metallic Co and CeO₂. The much larger difference between Co/CeO₂-NP and Co/CeO₂-MP than the difference between CeO₂-NP and CeO₂-MP suggests the significance of metallic Co in catalyzing the reforming reaction, although bare ceria support shows some dehydration activity in its own right.

更新日期：2016-07-01

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