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Supported metal nanoparticle catalysts have become increasingly crucial for many catalytic applications. However, long‐term catalyst stability remains a problem due to catalyst deactivation caused by coke formation and sintering. The deposition of a thin overcoating via atomic layer deposition (ALD) onto metal‐supported nanoparticles has shown to greatly inhibit catalyst deactivation. This work utilizes a model catalyst system comprised of Pt nanoparticles supported on Al₂O₃to demonstrate the effect of an atomically thin overcoating on supported metal nanoparticles. Continuous operando small‐angle X‐ray scattering (SAXS) and X‐ray absorption near edge spectroscopy (XANES) monitor structural and electronic changes to the catalyst and overcoating during calcination. SAXS data fitting reveals the formation of nanopores in the overcoating at high temperatures, while XANES monitors the oxidation state of the Pt catalyst. Herein, the usefulness of combined X‐ray techniques is demonstrated to characterize supported metal catalysts to further understanding of the synergistic effects of the ALD overcoating to aid in the design of new catalyst materials.

 

In this work, a Pt catalyst supported on an equimolar Al 2 O 3 –CeO 2 binary oxide (Pt–Al–Ce) was prepared and applied in photo-thermo-chemical dry reforming of methane (DRM) driven by concentrated solar irradiation. It was found that the Pt–Al–Ce catalyst showed good stability in DRM reactions and significant enhancements in H 2 and CO production rates compared with Pt/CeO 2 (Pt–Ce) and Pt/Al 2 O 3 (Pt–Al) catalysts. At a reaction temperature of 700 °C under 30-sun equivalent solar irradiation, the Pt–Al–Ce catalyst exhibits a stable DRM catalytic performance at a H 2 production rate of 657 mmol g −1 h −1 and a CO production rate of 666 mmol g −1 h −1 , with the H 2 /CO ratio almost equal to unity. These production rates and the H 2 /CO ratio were significantly higher than those obtained in the dark at the same temperature. The light irradiation was found to induce photocatalytic activities on Pt–Al–Ce and reduce the reaction activation energy. In situ diffuse reflectance infrared Fourier transform spectroscopy ( in situ DRIFTS) was applied to identify the active intermediates in the photo-thermo-chemical DRM process, which were bidentate/monodentate carbonate, absorbed CO on Pt, and formate. The benefits of the binary Al 2 O 3 –CeO 2 substrate could be ascribed to Al 2 O 3 promoting methane dissociation while CeO 2 stabilized and eliminated possible coke formation, leading to high catalytic DRM activity and stability.