Role of reduced graphene oxide in improving interfacial charge transfer of hybridized rGO/silica/zirconia for enhanced Bisphenol A photodegradation

Abstract

An effective photocatalyst for environmental rehabilitation, reduced graphene oxide (rGO) supported on silica-zirconia (Si/Zr) was synthesized by simple microwave and sonication methods after varying rGO loading (1, 5 and 10 wt%), and denoted as 1, 5 and 10 rGO/Si/Zr. The catalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption, Fourier-transform infrared (FTIR), electron spin resonance (ESR), and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) analyses. Catalytic activity towards photodegradation of Bisphenol A (BPA) was ranked in the following order: 5 rGO/Si/Zr (87%) > 1 rGO/Si/Zr (81%) > 10 rGO/Si/Zr (71%). The highest photoactivity of 5 rGO/Si/Zr was found to be due to the excess unpaired electrons in Si/Zr, induced by the rGO, which resulted in a remarkable excitation of electrons and, subsequently, accelerated the photocatalytic activity. In addition, optimum carbon–support interactions possessed by the 5 rGO/Si/Zr improved the interfacial charge transfer at a strategic energy level of rGO and efficiently suppressed the electron–hole recombination. The photokinetics of degradation followed the pseudo-first-order Langmuir-Hinshelwood model. The ESR trapping and scavenger experiments further confirmed that the photogenerated electron played a crucial role in mediating the degradation of BPA. The 5 rGO/Si/Zr was still active after 5 runs, indicating its potential for degradation of BPA in wastewater from the plastics industry. The 5 rGO/Si/Zr also demonstrated lower energy consumption and cost estimation towards the photodegradation of BPA.