A novel core–shell Pd(0)@enSiO2–Ni–TiO2 nanocomposite with a synergistic effect for efficient hydrogenations

Abstract

Bimetallic core–shell nano-structured catalysis has sparked great interest due to the multiple possibilities relating to morphology, atomic arrangement, and composition. In the present study, three bimetallic core–shell-based nanocatalysts, viz. Pd(0)@enSiO₂–TiO₂–Ni, Pd(0)@enSiO₂–Ni–TiO₂, and Pd(0)@Ni–enSiO₂–TiO₂, were synthesized via an economical and facile method using Pd(0) and amine-functionalized silica–titania Ni(II) in the shell and core, respectively. The arrangement of Ni(II) was varied in the three nanocatalysts and their catalytic activities were studied for hydrogenation reactions. The best results were obtained in the case of Pd(0)@enSiO₂–Ni–TiO₂ among all the catalysts. The enhanced catalytic activity of Pd(0)@enSiO₂–Ni–TiO₂ was demonstrated via surface characterization techniques. Brunauer–Emmett–Teller (BET) analysis depicted the highest surface area in the case of Pd(0)@enSiO₂–Ni–TiO₂; X-ray photoelectron spectroscopy (XPS) analysis supported the results, as an additional peak from Ni(III) was observed in the spectrum of the reused catalyst, which suggested the presence of electronic interactions between Ni(II) in the core and Pd(0) in the shell. Moreover, Pd(0)@enSiO₂–Ni–TiO₂ was found to be highly active for carrying out hydrogenation reactions under mild reaction conditions with good yields and high selectivity, and it can be reused for up to five runs.