云计算-衬底缺陷和应力对高效单原子CO催化氧化的协同调控作用的第一性原理计算研究.pdf

摘要

I

摘要

近年来，由于孤立金属原子作为催化剂具有较多的活性位点和较高的原料

利用率，将金属原子分散和稳定在合适的衬底上作为高效单原子催化剂（SACs）

的研究已经成为多相催化领域的热点。然而，SACs 化学反应烧结和活性位点不

稳定的特性极大地阻碍了其开发和利用。本文采用第一性原理计算方法，以沉积

是，当同一个 WTe

衬底上存在 Te 原子缺陷（D-WTe

2

）时，这些贵金属原子的

行为发生了很大变化，衬底缺陷具有稳定单原子相的趋势。在对衬底施加拉应力

时，相对于具有电子闭壳层结构的 Au

2

二聚体，具有电子开壳层的单个 Au 原子

占据 Te 空位处（V

Te

），后者从 WTe

2

衬底上获得更多电荷，从而产生更强的 EMSI。

然而，对于具有电子开壳层的 PdAu（Pd

2

）二聚体而言，对衬底施加压应力时，

的研究结果证明了衬底工程在稳定 SACs 方面的重要性，以及提供了一种有效的

方法用来制造 SACs。

第一章，绪论，简要介绍了催化领域的背景知识。探讨了纳米/亚纳米团簇

催化剂和单原子催化剂催化性能的差异，并介绍了单原子催化剂的独特特性、以

及如何表征和制备。同时，针对单原子催化剂的瓶颈问题，本论文提出了切实可

行的解决办法来调控单原子催化剂的催化活性。

第二章，理论与方法，简单介绍了计算物理学中的密度泛函理论、计算模拟

中采用的第一性原理计算方法、模型构建、以及单个原子结合能（缺陷形成能）

的计算方法。

摘要

中发现缺陷使沉积的原子 Pd（Au）与衬底之间的结合作用显著增强。并且，计

算结果显示对缺陷衬底施加外部应力时（分别为−5%，−2%，0%和+2%）， 费米

能级附近的 DOS 显著增加，这些都促进孤立活性位点的产生，从而有助于构造

单原子催化剂。

第四章，针对第三章调控出的单原子催化剂，考虑到 O

2

的活化激发是 CO

催化氧化的关键一步，本论文系统的研究了 Pd--Au@D-WTe

2

和 Au--Au@D-WTe

催化剂 O

2

的吸附构型。基于此通过 Langmuir–Hinshelwood (L–H)和 Eley–Rideal

催化氧化；反应势垒；SACs 催化性能调控

Abstract

III

Developing highly efficient single-atom catalysts (SACs) containing isolated

metal atom monomers dispersed on appropriate substrates has surged to the forefront

of heterogeneous catalysis in recent years, driven by both specificity of the unique

active site and cost-effectiveness of the approach. Nevertheless, the instability of the

the electronic metal-substrate interactions (EMSI) via a synergetic effect of strain

engineering and substrate defect to prevent clustering at the initial stage of the SACs.

It is noted that on the perfect WTe

2

(P-WTe

2

), both Au and Pd adatoms prefer

dimerization to separation. However, when a defect exists on the same WTe

2

substrate

2

), the situation changes considerably, and substrate defect have a tendency to

2

distances, therefore the increased Coulomb repulsive interactions (CRI) separates them

to be stable SACs. Importantly, we find that strain can effectively strengthen the

pinning effect of single atom on defect site. So the stabilities of these noble metal single

atoms on the defect substrate are significantly enhanced which make them difficult

diffusion and reduce the possibility of nucleation. Moreover, strain can further regulate

activation of energy barriers (E

a

) of SACs for CO oxidation. Our results demonstrate

the importance of substrate engineering in stabilizing the SACs and offer a valid

approach in fabricating SACs systems.

Chapter 1, introduction. We briefly describe the background knowledge of

Abstract

Chapter 2, theory and methods. The density functional theory in computational

physics, first-principles calculation method used in computational simulation,

reasonable construction model and the calculation of the binding energy (formation

energy) are presented.

Chapter 3, we systematically study the adsorption and diffusion behaviors of

monoatomic and diatomic systems on perfect and defect substrates, respectively. For

the diatomic system, taking electronically close-shelled Au

2

and open-shelled Pd

2

significantly increases. These engineering strategies promote the production of isolated

active sites, which will help us to synthesize the SACs.

Chapter 4, combining with the SACs regulated in Chapter 3, considering the key

we further extensively investigate the CO oxidation processes by examining both

Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) reaction mechanisms. Further,

we examine the synergy of the strain and defect effects on the catalysis of the Pd (Au)

active sites in SACs. It is shown that the strain effect and zero-point energy (ZPE)

correction can further reduce the values of the activation energy barrier in the rate-

limiting steps.

Chapter 5, conclusions and outlook.

Abstract

V