Ultrafine PtRu nanoparticles confined in hierarchically porous carbon derived from micro-mesoporous zeolite for enhanced nitroarenes reduction performance

Abstract

The fabrication of ultrafine PtRu alloy nanoparticles (NPs) confined in mesoporous carbon (MCN) remains a great challenge due to its high carbonization temperature, and the mechanism of ultrafine PtRu alloy NPs for hydrogenation reaction is still ambiguous. We report herein, for the first time, a general synthesis of ultrafine PtRu alloy NPs (less than 1.5 nm) encapsulated in MCN derived from micro-mesoporous zeolite under microwave-assisted heating. The ultrafine PtRu NPs are well dispersed in the structure of mesoporous carbon, and exhibit excellent stability. The reductive Pt2Ru NPs supported on MCN (Pt2Ru/MCN-R, R denotes reduction) exhibit the highest reaction rate constant k (0.894 min−1) and TOF (0.317 s−1) for 4-nitrophenol (4-NP) reduction, and have an excellent reduction ability for other nitroarenes. In-depth investigation of the structure–property relationship by high resolution transmission electron microscopy, X-ray absorption near edge structure analysis, X-ray photoelectron spectroscopy, and density functional theory calculation revealed that the Pt atoms as the active sites exhibit higher reduction ability for 4-NP, while the Ru atoms as the active sites have higher adsorption ability towards 4-NP. Therefore, the bifunctional mechanism and/or electronic synergistic effects of Pt and Ru play an important role in the reduction of 4-NP, and a good balance between the amount of Ru and Pt with Pt/Ru mole ratio of 2.0 has been demonstrated to be well suitable for 4-NP reduction.