In situ Tracking the Constrained Reconstruction of Cu3Pd@SiO2 Nanoparticles Driven by Redox Atmospheres

The microstructural constructions of bare Cu₃Pd particle and Cu₃Pd@SiO₂ particle under the stimuli of oxidizing and reducing environments were in situ studied in ETEM. Distinctive confinement of porous SiO₂ shell prevents phase separation in oxidization atmosphere and facilitates the formation of series of restructured Cu₃Pd architectures. It offers efficient way to tailor surface microstructures of bimetallic particles via well-controlled pretreatments in reactive atmospheres.

Abstract

Endowed with flexible surface coordination and synergetic electronic status, bimetallic particles serve as promising heterogeneous catalysts as their microstructures evolved sensitively to the treatment atmospheres, whereas knowledge of dynamic manners is less. Herein, utilizing environmental transmission electron microscopy (ETEM), the reconstructions of Cu₃Pd particles in oxidization/reduction atmospheres were explored at atomic scale. Specifically, bare Cu₃Pd particles went through a phase separation of CuO_x and PdO_x during in situ oxidation, and subsequent agglomeration after H₂ reduction. While protected in a silica shell, the confined Cu₃Pd particles were oxidized into Cu_1.5Pd_0.5O₂ phase after air calcination and subsequently restructured into versatile configurations during H₂ reduction. Specifically, hollow Cu₃Pd alloy architecture with Pd enriched layer near surface as reduced at 200 °C. Further rising 400 to 600 °C, it yielded disordered Cu₃Pd alloys with slightly Pd atoms enrichment at outmost surface. The dynamical behaviors of single Cu_1.5Pd_0.5O₂ particle during in situ reduction have been visualized in ETEM, wherein a series of deformation, elongation and rotation is involved during the hollow architecture firstly formation, and then vanished into a Cu₃Pd solid solution nanoparticle. The tunable microstructures of Cu₃Pd@SiO₂ driven by redox atmospheres demonstrate efficient approach for precisely regulating the chemical environments of constrained bimetallic nanocatalysts.

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