Photoinduced synthesis of ultrafine Pt nanoparticles loaded on the surface of metal-organic frameworks-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 light at a wavelength of 395 nm and visible light at 450 and 550 nm without adding any reducing and stabilizing agents using metal-organic frameworks-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, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy, 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 5 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.