Synthesis and Characterization of Metal-Chalcogenide Nanoparticles Decorated over N-rGO with their Enhanced Photocatalytic Activity

Abstract

Ascribed to increasing energy demands and environmental pollution, development of eco-friendly technologies is direly needed. Nanocomposite based photocatalysis seems a promising option to coup these major issues. Most photo active materials exhibit absorbance in UV region which constitute only 3% of solar spectrum. Visible light active photocatalysts are deemed inefficient due to small diffusion length of carriers, which evolve to inept charge transport and incompetent photo harnessing. Zinc selenide (ZnSe) and Cobalt telluride (CoTe) nanoparticles (NPs) are two photo active materials that manifest broad absorbance of visible frequencies but also linger due to fast recombination and ineffective charge transfer. Nitrogen doped reduced graphene oxide (N-rGO) has vastly been explored for its inherent and intrinsic conductivity, carrier density and diverse active sites. It is therefore a better option against reduced graphene oxide (rGO) for a base material in photocatalytic composites. In this exertion, the chosen photosensitizers ZnSe & CoTe have been synthesized via simple inexpensive hydrothermal routes. N-rGO has been prepared via simultaneous N incorporation and reduction of graphene oxide (GO) using Urea as an inexpensive, green and N rich source. rGO was obtained through conventional reduction of GO by hydrazine for comparative study. Fabrication of five nanocomposites by ultrasonic blending has been described; composites being ZnSe@N-rGO, ZnSe@rGO, ZnSe/CoTe, CoTe@rGO and CoTe@N-rGO. Bare ZnSe, CoTe NPs, pristine N-rGO & rGO along with their nano blends were characterized by FTIR-ATR, UV-Visible-DRS, pXRD, SEM-EDS, XPS and Raman spectroscopy for the assessment of structural, morphological, crystal phase, elemental composition, purity and optical features. Elemental composition and phase purity was established by SEM-EDS, pXRD and XPS information. EDS of N-rGO indicated nitrogen enrichment in graphene plane with novel N content of 11%. Raman supported slightly better restoration of π-conjugation network in N-rGO w.r.t rGO. Band gaps of involved nanomaterials were evaluated by DRS, valence band maxima (VBM) of NPs were obtained from XPS study while conduction band minima of graphenes were determined by Mott-Schottky plots. Based upon Anderson’s Rule, band alignment diagrams were thus constructed for each nanocomposite by which each blend encompass surface potential to generate reactive oxygen species (i.e. -•O2) from adsorbed oxygen and hydroxyl radicals (•OH) for photocatalytic degradation of organic