Photochemical Freeze Synthesis of Ultrafine Platinum Nanocatalysts

Here, well-dispersed and ordered ultrafine Pt nanocatalysts (Pt/SWCNTs) were synthesized by ice-photochemical method on single-walled carbon nanotubes (SWCNTs) without stabilizers and reducing agents. The catalytic performance of Pt/SWCNTs was studied in the reduction of 4-nitrophenol (4-NP). The morphology and crystal structure of as-synthesized materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The prepared samples all contained diffraction peaks of C and Pt with small size and good dispersion by XRD analysis. HR-TEM images displayed that the average particle sizes of the three samples were 1.2 ± 0.2 nm, 1.0 ± 0.2 nm and 1.1 ± 0.1 nm, respectively. The XPS analysis results confirmed the existence of Pt0. The catalytic performance test results showed that the prepared Pt/SWCNTs could effectively catalyze the reduction of 4-NP to 4-aminophenol (4-AP) with the apparent rate constants of 0.36 min−1, 0.28 min−1, and 0.35 min−1, respectively. Compared with literatures, they all had better catalytic activity. Though after seven cycles, the high catalytic activity was maintained with no significant deactivation and indicating high stability. The experimental results showed that Pt nano-rectangular array catalysts with uniform distribution and ultrasmall particle size were synthesized by a simple freezing method under the irradiation of visible (Vis)/ultraviolet (UV) light. It was demonstrated that the dispersion of Pt(II) reaction intermediates was effectively limited by light induction, carrier-substrate interaction and the use of the natural domain limitation of the ice lattice. Thus controlling the aggregation of Pt(0) to a certain extent and obtaining ordered dispersed ultrafine Pt nanoparticles. This method not only provides a method for the synthesis of ultrafine nanoparticles, but also provides a new idea for single-atom dispersed nanoparticles.Graphical Abstract