研究目的
To compare the reactivities of g-ZnO nanostructures and thin films on Au(111) with w-ZnO(0001) single crystal towards CO and H2 activation, and to understand the mechanisms using experimental and computational methods.
研究成果
The w-ZnO(0001) surface exhibits higher reactivity towards CO and H2 compared to g-ZnO on Au(111), with reactivity trends explained by differences in oxygen vacancy formation energy and surface polarity. This provides insights into the catalytic properties of ZnO and suggests surface polarity as a descriptor for reactivity.
研究不足
The study is limited to model systems (g-ZnO on Au(111) and w-ZnO(0001)), which may not fully represent industrial catalysts. The reactivity comparisons are based on specific experimental conditions, and the findings might not generalize to other ZnO structures or supports. The DFT calculations involve approximations that could affect accuracy.
1：Experimental Design and Method Selection:
The study used near-ambient-pressure scanning tunneling microscopy (NAP-STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations to investigate the interaction and reaction between CO/H2 and ZnO surfaces.
2：Sample Selection and Data Sources:
Samples included g-ZnO nanostructures and thin films grown on Au(111) and w-ZnO(0001) single crystals.
3：List of Experimental Equipment and Materials:
Equipment included UHV systems with NAP-STM, XPS, NAP-XPS, mass spectroscopy, and cleaning facilities. Materials included Au(111) and w-ZnO(0001) single crystals, Zn atoms, NO2 gas, CO gas, H2 gas.
4：Experimental Procedures and Operational Workflow:
ZnO layers were prepared by evaporating Zn atoms in NO2 atmosphere on Au(111) at various temperatures. Surfaces were cleaned by Ar ion sputtering and annealing. CO and H2 exposures were done by backfilling the chamber. STM and XPS measurements were performed before and after exposures.
5：Data Analysis Methods:
STM images were processed with SPIP software. XPS spectra were analyzed using CasaXPS with Shirley background subtraction and Gaussian-Lorentzian fits. DFT calculations were performed using VASP with PBE functional, PAW pseudopotentials, and vdW corrections.
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NAP-STM
SPECS
Used for near-ambient-pressure scanning tunneling microscopy to study surface structures and reactions.
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XPS
SPECS
Used for X-ray photoelectron spectroscopy to analyze surface composition and chemical states.
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NAP-XPS
SPECS
Used for near-ambient-pressure X-ray photoelectron spectroscopy to study surfaces under reaction conditions.
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Mass Spectrometer
Hiden
Used for mass spectroscopy to monitor gases.
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STM Tips
Pt/Ir tips
Used for scanning tunneling microscopy imaging.
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SPIP Software
Image Metrology
Used for processing STM images.
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CasaXPS Software
Used for analyzing XPS spectra with Shirley background subtraction and Gaussian-Lorentzian fits.
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VASP
5.4
Vienna Ab-initio Simulation Package
Used for density functional theory calculations.
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w-ZnO(0001) Single Crystal
MTI
Used as a model catalyst surface for reactivity studies.
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