Pd-based nanoflowers catalysts: controlling size, composition, and structures for the 4-nitrophenol reduction and BTX oxidation reactions

Abstract

We describe herein the synthesis of solid Au@Pd and hollow AgPd nanoflowers displaying controlled sizes and compositions in order to investigate how their size, composition, and the presence of Au in the core of the nanoparticles influence their catalytic performance toward both liquid and gas-phase transformations. While the size and composition of Au@Pd and AgPd the nanoflowers could be controlled as function of growth time, their structure (solid or hollow) was dependent on the nature of the seeds employed for the synthesis, i.e., Au or Ag nanoparticles. Moreover, Au@Pd and AgPd nanoflowers were successfully supported onto commercial silica displaying truly uniform dispersion. The catalytic activities of Au@Pd and AgPd nanoflowers were investigated toward the 4-nitrophenol reduction and the benzene, toluene, and o-xylene (BTX) oxidation. The catalytic activities for the reduction of 4-nitrophenol decreased as follows: Au58@Pd42 > Au27@Pd73 > Ag20Pd80 and Ag8Pd92 > Au12@Pd88 > Ag38Pd62, suggesting that the Au core enhanced the catalytic activity relative to the hollow material when for Pd at.% was up to 80. Regarding the BTX oxidation, supported Au@Pd displayed higher catalytic activities than AgPd nanoflowers, also illustrating the role of the Au cores in the nanoflowers for improving catalytic performance. We believe these results may serve as a platform for the synthesis of Pd-based bimetallic nanomaterials that enable the correlation between these physical/chemical parameters and properties and thus optimized catalytic activities.