CuPd Bimetallic Nanoparticles Supported on Magnesium Oxide as an Active and Stable Catalyst for the Reduction of 4-Nitrophenol to 4-Aminophenol

Abstract

Abstract:In this work, we report the synthesis and characterization of a catalyst based on bimetallic CuPd nanostructures generated over a magnesium oxide support. Its catalytic activity and reusability have been tested in the reduction of 4-nitrophenol as a model reaction using NaBH4 as the source of hydrogen for the reduction of the nitro-group. The structure, composition and morphology of the catalysts were studied by N2 physisorption, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The reaction kinetics of reduction of 4-nitrophenol to 4-aminophenol has been followed by UV-visible spectrophotometry, and its apparent rate constant has been determined and compared with its monometallic counterparts. All the tested catalysts exhibited remarkable high activity and excellent stability upon reuse for multiple consecutive cycles. We found out that a small loading addition of Pd to Cu catalyst greatly improved the catalytic activity in comparison with the monometallic samples. Our characterization results pointed out a higher metallic dispersion degree as the main explanation for this enhanced performance. CuPd/MgO is highly competitive or outperforms the catalytic activity of other bimetallic systems reported in literature.

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“…47 Nevertheless, Cu 1+ is assumed to be present in the Li(HEO)F compound. The peak at 1303.8 eV in the Mg 1s spectrum can be attributed to Mg 2+ , 48,49 and the Zn 2p 3/2 at 1021.3 eV and Zn LMM at 988.6 eV are indicative of Zn 2+ . [50][51][52] 'NaCl' has also been successfully added to the HEO structure through an identical ball-milling approach.…”

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“…Additionally, an extra peak is observed at 646.3 eV, representing the satellite peak of the Mn 2p 3/2 main peak. Figure d displays the Mg 1s XPS spectrum. − The peak at 1303.7 eV is associated with the chemical environment of Mg(1) in Mg(1)­(OH) 6 coordination. From the XPS diffraction patterns, it can be observed that there is only one environment for Mn and Mg throughout the entire crystal structure.…”

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“… 36 The Mg XPS spectrum generally uses Mg 1s to analyze the oxidation state, which is located between 1302 and 1305 eV. 37 However, the binding energy of Mg 1s is out of the scan range of the equipment we used in this study. Therefore, Mg 2p was used for the Mg oxidation state analysis.…”