Fabrication of Bimetallic Cu-Ag Nanoparticle-Decorated Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) and Its Enhanced Catalytic Activity for the Reduction of 4-Nitrophenol

We reported a study on the preparation of bimetallic Ag-Cu nanoparticles (NPs) impregnated on PZS poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotubes via a facile and efficient reduction method. Herein, PZS nanotubes consisting of enriched hydroxyl groups are fabricated through an in situ template method, and then, fluctuating the amount ratios of Cu and Ag precursors, bimetallic NPs can be fabricated on readily prepared PZS nanotubes using NaBH₄ as a reductant, which results in a series of bimetallic catalysts having tunable catalytic activity. The characterization investigations of scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy results show that Ag-Cu bimetallic NPs are well-dispersed, ultrasmall in size, and well-anchored on the surface of PZS nanotubes. In addition, to examine the catalytic activity and reusability of these nanocomposites, reduction of 4-nitrophenol to 4-aminophenol is utilized as a prototype reaction. The optimized Ag-Cu NPs with a copper ratio of 0.3% are well-stabilized by the organic-inorganic poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotubes. The obtained results show that bimetallic NPs have remarkably higher catalytic ability than that of their monometallic counterparts with maximum catalytic activity. These results are even better than those of noble metal-based bimetallic catalysts and pave the avenue to utilize the polyphosphazene polymer as a substrate material for highly effective bimetallic catalysts.