Photoinduced synthesis of ultrafine Pt nanoparticles loaded on the surface of MOFs-modified carbon materials for efficient catalytic reduction reactions

Abstract In this paper, ultrafine platinum nanoparticles (Pt/Co-N-C) were prepared by irradiating the mixture of Co-N-C and K2[PtCl4] with near-ultraviolet (UV) light at a wavelength of 395 nm and visible light at 450 and 550 nm without adding any reducing and stabilizing agents using MOFs-modified carbon materials (Co-N-C) as the carrier. The composition and morphology of the Pt/Co-N-C catalysts were investigated using characterization tools such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM), etc. The results showed that the Pt nanoparticles were well dispersed on the surface of the Co-N-C, with average particle sizes of about 2.39, 2.86, and 3.53 nm, respectively. In the catalytic 4-NP reduction experiments, the catalyst (Pt/Co-N-C-1) prepared under near-ultraviolet light (395 nm) irradiation showed the highest catalytic activity with a rate constant k=0.64 min-1. After five cycles, the conversion rate was still maintained at about 90%, which was highly reusable. It was demonstrated that 395 nm near-ultraviolet light was more favorable for the modulation of the distribution of the species during the hydrolysis and reduction of platinum in this reaction to form smaller-sized platinum nanocrystals, which was conducive to the catalyst to exhibit higher activity.