Facile green synthesis of highly efficient carbon nanospheres@g-C3N4 catalysts for photodegradation of Bisphenol A

Abstract

Novel Carbon nanospheres@graphitic-carbon nitride nanocomposites were successfully synthesized by a simple, inexpensive and ecofriendly chemical method (hydrothermal). The as-prepared materials Carbon nanospheres (CNS), pure g-C₃N₄, CNS@g-C₃N₄ and heat treated (HT)CNS@g-C₃N₄ were characterized by FTIR, Raman spectroscopy, XPS, XRD, TEM, EDX and N₂-adsorption desorption, UV-Visible DRS, and Photoluminescence (PL). The photodegradation of bisphenol A (a typical endocrine disruptor) using photocatalysts was followed by HPLC-UV technique. The results show that (HT)CNS@g-C₃N₄ exhibits high photocatalytic efficiency for BPA degradation (99 %), which is 45 and 8.5 times greater than that of pure g-C₃N₄ and CNS@g-C₃N₄, respectively. Additionally, the (HT)CNS@g-C₃N₄ photocatalyst displays a high constant rate of apparent pseudo-first-order (k_app = 94.78 × 10⁻³ min^–1) and low electrical energy per order consumption (EEO = 0.24 kWh/m³). These excellent abilities of (HT)CNS@g-C₃N₄ were attributed to its excellent morphological, structural and optical properties induced during the heat treatment: (i) The presence of CNS reduces the bad gap and consequently enhances the absorption of visible light and promotes the charge carriers separation, (ii) the high specific surface area and porosity and therefore availability of a high number of active sites to interact with BPA, (iii) high presence of different functional groups on the catalyst surface that enhance the interaction between the surface and BPA molecules, and (iv) The heterojunction interface created between CNS and g-C₃N₄ constitutes an efficient structure that enhances interfacial charge transfer and prevents direct recombination of charge carriers originating from g-C₃N₄. Based on the identification of the products and intermediates of the BPA photodegradation reaction, by HPLC−MS, a plausible mechanism of photocatalytic degradation of BPA using the prepared photocatalysts was proposed.