[1]ZHI Cuimei,ZHANG Riguang,WANG Baojun.CO Methanation on La/Ni(111) Surface: Effect of La Electron Delocalization on Activity and Selectivity[J].中国材料进展,2020,(09):670-680.[doi:10.7502/j.issn.1674-3962.201909017]
　,La/Ni(111)表面CO甲烷化：助剂La对活性和选择性的影响[J].MATERIALS CHINA,2020,(09):670-680.[doi:10.7502/j.issn.1674-3962.201909017]
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CO Methanation on La/Ni(111) Surface: Effect of La Electron Delocalization on Activity and Selectivity()
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中国材料进展[ISSN:1674-3962/CN:61-1473/TG]

卷:
期数:
2020年第09期
页码:
670-680
栏目:
出版日期:
2020-09-30

文章信息/Info

Title:
La/Ni(111)表面CO甲烷化：助剂La对活性和选择性的影响
文章编号:
1674-3962(2020)09-0670-11
作者:
ZHI Cuimei1;  ZHANG Riguang2;  WANG Baojun2
(1. College of Chemistry and bioengineering, Taiyuan University of Science and Technology, Taiyuan 030021，China) (2. Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024，China)
Author(s):
智翠梅1; 章日光2; 王宝俊2
（1. 太原科技大学化学与生物工程学院，山西 太原 030021）（2. 太原理工大学 煤科学与技术教育部和山西省重点实验室，山西 太原 030024）
关键词:
DFT;  microkinetic modeling;  differential charge density;  synergistic effect
Keywords:
密度泛函理论; microkinetic modeling; 差分电荷密度; 协同催化
分类号:
O641.12+1
DOI:
10.7502/j.issn.1674-3962.201909017
文献标志码:
A
摘要:
In attempting to promote the activity and selectivity of CO conversion to CH4 and simultaneously suppress CH3OH formation, density functional theory (DFT) calculation has been employed to insight into the reaction mechanism and the effect of the promoter La on CO conversion to CH4 on La/Ni(111). Our results indicate that the promoter La could enrich the outer layer valence electron density of Ni, make the d-band center of La/Ni(111) upward, and thereby lead to a significant increase of the reactivity. Accordingly, the enhanced activity and selectivity to CH4 as well as CH3OH resistance are mainly originated from the electronic effect of the promoter La on La/Ni(111), where the synergistic effect between La and Ni plays an important role. Meanwhile, the microkinetic modeling is used to estimate the production rates of CH4 and CH3OH under the experimental conditions, and the result shows that r(CH4) is larger than r(CH3OH) at the same temperature, and the relative selectivity of CH4 reaches almost as high as 100% in the temperature range of 550 to 750 K, and thereby no CH3OH is formed when La is doped. Further, to clarify the effect of La promoter on CH4 formation at electron level, Bader charges and the projected density of states (PDOS) have been examined for CO,HCO,COH and CH2O, which are the key intermediates of Path1, Path2, Path3, and Path4 for CH4 formation, respectively. The results indicate that it is electron transfer from La to Ni and the strong interaction between La and O that weaken the C—O bond and promote the cleavage of C—O bond, and thereby lead to no CH3OH yield, which controls the selectivity to CH4. Through analyzing the differential charge density of La atom and its surrounding Ni atoms over La/Ni(111), the result of the direction along La→Ni of charge transfer, has been shed light on furtherly. Conclusively, La/Ni(111) shows a significant increase in the activity and selectivity to CH4 compared to Ni(111), which is mainly originated from the synergistic effect between La and Ni.
Abstract:
针对Ni(111)表面上因副产物CH3OH形成而导致CH4选择性低的问题，采用量子化学密度泛函理论（density functional theory, DFT）计算的方法，通过添加富电子的助剂La调节表面Ni原子的电子状态，增大Ni的d电子平均能以增加La/Ni(111)表面的反应性，实现La与Ni的协同催化，从而提高CO甲烷化活性和CH4生成选择性。同时，基于DFT结果，以Microkinetic modeling模拟实验条件下CH4和CH3OH的生成速率，结果表明，反应速率r随着温度升高而增大；在同一温度下，CH4生成速率r(CH4)远大于CH3OH的生成速率r(CH3OH)，且SCH4在反应温度550~750 K内高达100%，表明在La/Ni(111)表面上的CO甲烷化过程中没有副产物CH3OH的生成。究其原因，在电子水平上通过对CH4形成路径Path1、Path4、Path9和Path10所对应的关键中间体CO、HCO、CH2O和COH进行Bader电荷和pDOS分析，发现C—O键明显弱化，C—O断键能垒显著降低，因而无CH3OH生成的微观机理是La→Ni电子离域和La与O强相互作用而产生的“给电子诱导”效应。进一步通过La与邻近Ni原子的三维差分电荷密度分析得知，La原子的电荷损耗是沿着“La→Ni”方向，这就给出了助剂La与Ni协同催化CO甲烷化并高活性高选择性地生成CH4的微观解释。

备注/Memo

备注/Memo:
Received date：2019-09-18 Revised date：2019-12-20 Foundation item：National Natural Science Foundation of China （21736007）；Research Start up Fund of Tai yuan University of Science and Technology（20 182003, 20182016） First author：ZHI Cuimei，Female，Born in 1975, Lecturer，Master tutor,Email:zhicuimei@tyust.edu.cn Corresponding author：WANG Baojun，Male，Born in 1964, Professor，PhD supervisor, Email: wangbaojun@tyut.edu.cn
更新日期/Last Update: 2020-11-24