Oxygen vacancy enhanced catalytic activity in a Pt nanoparticle decorated GO–CexOy catalyst for the efficient synthesis of pyran based derivatives

Abstract

Decoration of metal nanoparticles on a GO supported nanorod-based catalyst resulted in enhanced catalytic activity. The generation of a greater number of oxygen defects and the change in redox potential value could be some of the factors responsible behind such activity. Hence, a detailed study was required to understand these effects. With this in mind, in this work, a detailed study on the role of such factors in the synthesis of pyran and its derivatives was carried out with a GO–Ce_xO_y–Pt catalyst. The ternary nanocatalyst was utilized for the synthesis of pyran and its derivatives under solventless conditions. The prepared nanocomposite was thoroughly characterised using different instrumental techniques such as X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS), N₂-adsorption desorption Brunauer–Emmett–Teller (BET) isotherms, electron paramagnetic resonance (EPR) spectroscopy and inductively coupled plasma-optical emission spectrometry (ICP-OES). The detailed structural and morphological analysis revealed that the nanocomposite possessed a rod morphology with a length of 30–80 nm and was crystalline in nature. Also, the XPS results showcased the +3 and +4 oxidation states of Ce and the metallic state of platinum. The O1s spectra confirmed the creation of more oxygen vacancies on the Ce_xO_y surface after Pt decoration and the ICP-OES results also exhibited the stability and reusability up to five continuous cycles with a minimal loss in activity. Different parameters such as the amount of catalyst, catalyst loading, solvent effect, and temperature were varied to optimize the most preferable reaction conditions.