期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 144, 期 33, 页码 15132-15142出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.2c04871
关键词
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资金
- Integrated Mesoscale Architecture for Sustainable Catalysis (IMASC)
- Energy Frontier Research Center (EFRC) - US Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0012573]
- ACS PRF [61059-ND5]
- Department of Energy Office of Science User Facility [DE-AC02-05CH11231]
- US Department of Energy, Office of Basic Energy Sciences [DE-SC0012704]
Dynamic restructuring of bimetallic catalysts is crucial for their catalytic activity and selectivity. The authors use CO as a probe and agent to induce surface restructuring in Pd/Au(111) catalysts, uncovering the kinetics and timescale of in situ restructuring. This minute-timescale dynamics provides insights into the fluxional nature of alloy catalysts and the opportunity for surface fine-tuning under moderate conditions.
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 similar to 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.
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