催化学报 ›› 2022, Vol. 43 ›› Issue (11): 2898-2905.DOI: 10.1016/S1872-2067(21)64044-5

• 论文 • 上一篇    下一篇

Cu表面应变效应调控电催化CO二聚反应活性的第一性原理分子动力学模拟

刘宏a,b, 刘健a, 杨波a,*()   

  1. a上海科技大学物质科学与技术学院, 上海 201210
    b中国科学院上海微系统与信息技术研究所, 信息功能材料国家重点实验室, 2020前沿实验室, 上海 200050
  • 收稿日期:2022-05-30 接受日期:2022-08-07 出版日期:2022-10-20 发布日期:2022-10-20
  • 通讯作者: 杨波
  • 基金资助:
    国家自然科学基金重大项目(21991152);国家自然科学基金重大项目(21991150);国家自然科学基金青年科学基金项目(21902102)

Tunable activity of electrocatalytic CO dimerization on strained Cu surfaces: Insights from ab initio molecular dynamics simulations

Hong Liua,b, Jian Liua, Bo Yanga,*()   

  1. aSchool of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
    bState Key Laboratory of Information Functional Materials, 2020 X-Lab, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
  • Received:2022-05-30 Accepted:2022-08-07 Online:2022-10-20 Published:2022-10-20
  • Contact: Bo Yang
  • Supported by:
    Major Program of National Natural Science Foundation of China(21991152);Major Program of National Natural Science Foundation of China(21991150);National Natural Science Foundation for Young Scientists of China(21902102)

摘要:

实验和理论计算研究发现, 随着Cu纳米颗粒逐渐变小, 表面低配位数Cu原子所占比例逐渐增加. 同时有理论研究表明, 在Cu纳米颗粒中, Cu-Cu键的平均加权长度随着Cu团簇原子数的减少而变短, 此时会体现出一定的应变效应, 而该效应可以打破催化作用中的线性关系限制, 从而使催化反应体现出不一样的性质. 实验发现, Cu-Ag合金表面产生了压缩应变, 并且提高了CO2还原反应对多碳含羰基产物的选择性; 并且, 通过铂族和第一副族金属表面原子之间的相互作用可以调整二维金属纳米片的厚度来实现10%的可调表面应变, 实现对析氧和析氢反应催化活性的调节. 因此我们认为, 应变效应对金属Cu催化剂用于电化学还原CO2的反应活性也会存在相应影响.

尽管有研究报道了晶格应变对Cu表面电化学CO2还原反应的影响, 但利用第一性原理分子动力学(AIMD)研究在电极-电解质界面处晶格应变效应对CO2还原反应中C2产物选择性的促进机制的报道仍然很少. 由于Cu(100)表面对C2产物的选择性明显高于其他表面, 因此本文选取Cu(100)表面, 结合自由能采样技术, 固定C‒C距离从4.0到1.4 Å, 每一个固定的C-C距离下都进行AIMD模拟, 在显式水溶液模型中研究了应变效应对产生C2物种的速率决定步骤, 即CO二聚反应形成OCCO*过程的影响. 结果表明, 随着Cu晶格从拉伸应变到压缩应变进行变化, CO二聚的自由能垒逐渐降低, 表明CO二聚反应的活性增加. 此外, 当压缩应变达到一定程度时, Cu(100)表面会发生重构. 研究还发现, 某些不稳定的清洁重构表面具有更低的自由能势垒, 但这些重构表面在有氧或一氧化碳分子吸附的情况下会变成最稳定的表面. 对表面铜原子电荷的定量分析发现, 自由能垒与OCCO中间体吸附位置附近的Cu原子上的电荷相关. 当Cu(100)的表面结构在压缩应变下发生变化时, 表面Cu原子的电子结构也随之变化, 从而调节其电催化CO二聚反应的活性. 综上, 本文为晶格应变效应调控Cu表面电化学还原CO2生成C2物种的活性提供了理论支持, 对后续开发高性能催化剂具有借鉴意义.

关键词: 电催化一氧化碳二聚, 表面应变, 铜, 表面重构, 从头算分子动力学

Abstract:

Controlling catalytic activities through surface strain engineering remains a hot topic in electrocatalysis studies. Herein, ab initio molecular dynamics (AIMD) simulation associated with free energy sampling technology were performed to study the energetics of the key step of producing C2 products in electrocatalytic reduction of CO or CO2, i.e. CO dimerization, on strained Cu(100) with an explicit aqueous solvent model. It is worth mentioning that when compressive strain reaches a certain extent, the surface of Cu(100) will undergo reconstruction. We showed that, from tensile to compressive strain, the free energy barrier of CO dimerization decreased, suggesting that the activity of CO dimerization increases. It was also found that some of the reconstructed surfaces showing the lowest free energy barriers but might be less stable can be stabilized in the presence of adsorbed O or CO. Upon detailed quantitative analysis on the charges of surface Cu atoms, we found that the free energy barriers were strongly correlated with the charge of Cu atoms where the OCCO intermediate adsorbs. When the surfaces structures of Cu(100) were altered under compressive strain, the electronic structure of surface Cu atoms was monitored and thus the activity of electrocatalytic CO dimerization can be tuned.

Key words: Electrocatalytic CO dimerization, Surface strain, Cu, Surface reconstruction, Ab initio molecular dynamics