Synthesis and characterization of thiol-functionalized MCM-41 nanofibers and its application as photocatalyst

Abstract

In this paper, the simple fabrication of MCM-41 mesoporous material nanofibers (NFs) by an electrospinning technique was suggested. The morphology of the MCM-41nanofibers (MCM-41NFs) depended on spinning voltages. Tetraethylorthosilicate (TEOS) and polyvinyl alcohol (PVA) were used as a silica source and fiber forming polymer for MCM-41NFs synthesis, respectively. MCM-41NFs were modified with organic silicanes (3-mercaptopropyltrimethoxysilane). Thiol–functionalized MCM-41 nanofibers (MCM-41-SHNFs) prepared has been used for dispersing of AgBr nanoparticles (NPs) by precipitation method. The MCM-41 and AgBr/MCM-41-SHNFs photocatalyst were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) and nitrogen adsorption–desorption measurements. The smooth and long MCM-41NFs were observed in voltages less than 16 kV. TEM and SEM images showed synthesis of MCM-41NFs with a diameter of 200 nm. The BET results indicated that the pore diameter and surface area of calcined MCM-41NFs were reduced in thiol - functionalized MCM-41 and AgBr/MCM-41-SHNF nanocomposite. Silver bromide, with different weight percentage (30%, 40% and 50%) was coupled into MCM-41-SH nanofibers. The images displayed presence of AgBr NPs with particle size ∼35 nm over nanofibers support. The AgBr/MCM-41-SH nanofibers were used for the photocatalytic degradation of methyl blue (MB) under visible light. The results showed that for the various AgBr loadings in the composites, MB photocatalytic degradation efficiency arrived at the maximum of 60% at 40% loading, or with 40AgBr/MCM-41-SHNFs photocatalyst. The MB removal reached 87% at 0.25 g/L of the 40AgBr/MCM-41-SHNFs dosage, 3.2 ppm of initial MB concentration, and 6.5 of unadjusted initial pH. The cycle experiments on the AgBr/MCM-41-SHNFs photocatalyst indicated that NFs enhance photoinduced stability of photosensitive silver compounds in all cycles. The MCM-41-SHNFs reduced photocorrosion of AgBr NPs. On the basis of the experimental results, a possible mechanism for the enhanced photocatalytic activity and photoinduced stability of AgBr/MCM-41-SHNFs photocatalyst was proposed. The enhancement of photocatalytic activity was attributed to the increase of separation efficiency of electrons and holes in AgBr. The MCM-41-SHNF played an important role in decreasing recombination of photogenerated electrons-holes and increasing MB absorption.