物理化学学报 >> 2018, Vol. 34 >> Issue (12): 1334-1357.doi: 10.3866/PKU.WHXB201804201

所属专题: 表面物理化学

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原子层沉积:一种多相催化剂“自下而上”气相制备新策略

王恒伟1,路军岭1,2,*()   

  1. 1 中国科学技术大学化学物理系,合肥微尺度物质科学国家研究中心,能源材料化学协同创新中心,合肥 230026
    2 中国科学技术大学,中国科学院能量转换重点实验室,合肥 230026
  • 收稿日期:2018-03-27 发布日期:2018-04-27
  • 通讯作者: 路军岭 E-mail:junling@ustc.edu.cn
  • 作者简介:Prof. LU Junling received his PhD degree from Institute of Physics, Chinese Academy of Sciences under the supervision of Prof. Hongjun Gao in 2007. During his PhD studies, he visited Prof. Hans-Joachim Freund group at Chemical Physics Department, Fritz-Haber-Institute, Max Planck Society as an exchange student in 2004-2006. After graduation, he spent three years in Prof. Peter C Stair's group at Northwestern University and then about two and a half years in Dr. Jeffrey W. Elam's group at Argonne National Laboratory as a Postdoc. In March. 2013, he became a professor at University of Science and Technology of China. His current research interest is atomically-precise design of new catalytic materials using a combined wet-chemistry and atomic layer deposition (ALD) approach for advanced catalysis
  • 基金资助:
    国家自然科学基金(21673215);国家自然科学基金(21473169);国家自然科学基金(51402283);中央高校基本科研业务费(WK2060030029);中央高校基本科研业务费(WK6030000015);Max-Planck伙伴小组资助项目

Atomic Layer Deposition: A Gas Phase Route to Bottom-up Precise Synthesis of Heterogeneous Catalyst

Hengwei WANG1,Junling LU1,2,*()   

  1. 1 Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, University of Science and Technology of China, Hefei 230026, P. R. China
    2 CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei 230026, P. R. China
  • Received:2018-03-27 Published:2018-04-27
  • Contact: Junling LU E-mail:junling@ustc.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21673215);the National Natural Science Foundation of China(21473169);the National Natural Science Foundation of China(51402283);the Fundamental Research Funds for the Central Universities, China(WK2060030029);the Fundamental Research Funds for the Central Universities, China(WK6030000015);the Max-Planck Partner Group

摘要:

多相催化剂是极为重要的一类催化剂,在许多重要工业反应中扮演关键角色。然而,传统的湿化学合成手段在很多情况下难以做到对催化剂活性位点的结构、组成以及其周围局部环境的原子级精细调控,继而给优化催化剂性能、理解多相催化机理带来较大的挑战。原子层沉积(ALD)是一种气相催化剂合成技术,其原理是基于两种前驱体蒸汽交替进样并在载体表面上发生分子层面上的“自限制”反应,实现目标材料在载体表面上的精准沉积。利用其分子层面上的“自限制”反应特性,并通过改变沉积周期数、次序和种类等方法可以实现对催化剂活性位结构的原子级精细控制,进而为人们提供了一种催化剂“自下而上”精细可控合成的新策略。在本文中,我们总结了利用ALD方法在负载型单金属和双金属催化剂精细设计方面的进展,讨论了ALD方法在设计高效催化剂方面的特点与优势。特别地,我们总结了利用ALD方法制备单原子和双原子结构金属催化剂的方法与策略。此外,我们总结了利用氧化物可控沉积精准调控金属催化活性中心周围的微环境,从而实现提升催化剂活性、选择性和稳定性的方法。最后我们展望了ALD技术在催化剂制备领域中应用的潜力。

关键词: 原子层沉积, 负载型金属催化剂, “自下而上”合成, 单原子催化剂, 双原子催化剂, 金属氧化物界面, 限域效应

Abstract:

Heterogeneous catalysts are usually synthesized by the conventional wet-chemistry methods, including wet-impregnation, ion exchange, and deposition-precipitation. With the development of catalyst synthesis, great progress has been made in many industrially important catalytic processes. However, these catalytic materials often have very complex structures along with poor uniformity of active sites. Such heterogeneity of active site structures significantly decreases catalytic performance, especially in terms of selectivity, and hinders atomic-level understanding of structure-activity relationships. Moreover, loss of exposed active components by sintering or leaching under harsh reaction conditions causes considerable catalyst deactivation. It is desirable to develop a facile method to tune catalyst active site structures, as well as their local chemical environments on the atomic level, thereby facilitating reaction mechanisms understanding and rational design of catalysts with high stability.

Atomic layer deposition (ALD), a gas-phase technique for thin film growth, has emerged as an alternative method to synthesize heterogeneous catalysts. Like chemical vapor deposition (CVD), ALD relies on a sequence of molecular-level, self-limiting surface reactions between the vapors of precursor molecules and a substrate. This unique character makes it possible to deposit various catalytic materials uniformly on a high-surface-area support with nearly atomic precision. By tuning the number, sequence, and types of ALD cycles, bottom-up precise construction of catalytic architectures on a support can be achieved.

In this review, we focus on the design and synthesis of supported metal catalysts using ALD. We first review strategies developed to precisely tailor the size, composition, and structures of metal nanoparticles (NPs) using ALD. Catalytic performances of these ALD metal catalysts are also discussed and compared to conventional catalysts. We highlight synthetic strategies for synthesis of metal single-atom catalysts and bottom-up precise synthesis of dimeric metal catalysts. Their impact on catalysis is discussed. We demonstrate that metal oxide ALD on metal NPs can enhance catalytic activity, selectivity, and especially stability. In particular, we show that site-selective blocking of metal NPs with an oxide overcoat improves selectivity and contributes to an understanding of the distinct functionalities of the low-and high-coordination sites in catalytic reactions on the atomic level. Next, we discuss an effective method to construct bifunctional catalysts via precisely-controlled addition of a secondary functionality using ALD. Finally, we summarize the advantages of ALD for the advanced design and synthesis of catalysts and discuss the challenges and opportunities of scaling up ALD catalyst synthesis for practical applications.

Key words: Atomic layer deposition, Supported metal catalyst, "Bottom-up" synthesis, Single-atom catalyst, Dimeric metal catalysts, Metal-oxide interfaces, Confinement effect

MSC2000: 

  • O643