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Dynamical Study of Adsorbate-Induced Restructuring Kinetics in Bimetallic Catalysts Using the PdAu(111) Model System
Journal of the American Chemical Society ( IF 15.0 ) Pub Date : 2022-08-11 , DOI: 10.1021/jacs.2c04871
Chen Zhou 1, 2 , Hio Tong Ngan 3 , Jin Soo Lim 4 , Zubin Darbari 1, 2 , Adrian Lewandowski 4 , Dario J Stacchiola 1 , Boris Kozinsky 5, 6 , Philippe Sautet 3, 7 , Jorge Anibal Boscoboinik 1
Affiliation  

Dynamic restructuring of bimetallic catalysts plays a crucial role in their catalytic activity and selectivity. In particular, catalyst pretreatment with species such as carbon monoxide and oxygen has been shown to be an effective strategy for tuning the surface composition and morphology. Mechanistic and kinetic understanding of such restructuring is fundamental to the chemistry and engineering of surface active sites but has remained challenging due to the large structural, chemical, and temporal degrees of freedom. Here, we combine time-resolved temperature-programmed infrared reflection absorption spectroscopy, ab initio thermodynamics, and machine-learning molecular dynamics to uncover previously unidentified timescale and kinetic parameters of in situ restructuring in Pd/Au(111), a highly relevant model system for dilute Pd-in-Au nanoparticle catalysts. The key innovation lies in utilizing CO not only as a chemically sensitive probe of surface Pd but also as an agent that induces restructuring of the surface. Upon annealing in vacuum, as-deposited Pd islands became encapsulated by Au and partially dissolved into the subsurface, leaving behind isolated Pd monomers on the surface. Subsequent exposure to 0.1 mbar CO enabled Pd monomers to repopulate the surface up to 373 K, above which complete Pd dissolution occurred by 473 K, with apparent activation energies of 0.14 and 0.48 eV, respectively. These restructuring processes occurred over the span of ∼1000 s at a given temperature. Such a minute-timescale dynamics not only elucidates the fluxional nature of alloy catalysts but also presents an opportunity to fine-tune the surface under moderate temperature and pressure conditions.

中文翻译:

使用 PdAu(111) 模型系统对双金属催化剂中吸附质诱导重组动力学的动力学研究

双金属催化剂的动态重组对其催化活性和选择性起着至关重要的作用。特别是,用一氧化碳和氧气等物质预处理催化剂已被证明是调整表面组成和形态的有效策略。对这种重组的机械和动力学理解是表面活性位点的化学和工程的基础,但由于结构、化学和时间自由度很大,仍然具有挑战性。在这里,我们结合时间分辨温度程序红外反射吸收光谱、从头算热力学和机器学习分子动力学来揭示以前未知的原位时间尺度和动力学参数在 Pd/Au(111) 中进行重组,这是一种用于稀释 Pd-in-Au 纳米颗粒催化剂的高度相关模型系统。关键的创新在于利用 CO 不仅作为表面 Pd 的化学敏感探针,而且作为诱导表面重组的试剂。在真空中退火后,沉积的 Pd 岛被 Au 包裹并部分溶解到地下,在表面上留下孤立的 Pd 单体。随后暴露于 0.1 mbar CO 使 Pd 单体能够重新填充表面,最高可达 373 K,高于此温度时 Pd 完全溶解发生在 473 K,表观活化能分别为 0.14 和 0.48 eV。这些重组过程在给定温度下发生在~1000 s 的跨度内。
更新日期:2022-08-11
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