Biosynthetic modulation of carbon-doped ZnO for rapid photocatalytic endocrine disruptive remediation and hydrogen evolution

Abstract

Pharmaceuticals and industry effluents such as dyes, and organic contaminants in wastewater are being identified among the top endocrine disruptive compounds with inherent recalcitrant and hazardous effects. Herein, microwave-induced coconut shell-activated carbon-doped-zinc-oxide (CSAC-ZnO) nanocomposites at various calcined temperatures were synthesized by hydrothermal techniques, characterized and applied towards photocatalytic degradation of endocrine disruptive compounds (EDC) and green energy generation via photocatalytic hydrogen production. The surface area, structural crystallinity, optical properties, thermal stability, functional group and morphological properties were accessed via Powdered X-ray diffraction, UV-Diffuse Reflectance Spectroscopy, Fourier Transform Infrared, Thermal Gravimetric Analysis, Brunauer-Emmett-Teller, X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy, and Transmission Electron Microscopy. An extremely high surface area of 320.65 m2g-1 was observed from the as-prepared carbon decorated (CSAC-ZnO) and excellent light absorption was shown by all the photocatalysts. The exceptional photo-degradation efficiencies of CSAC-ZnO on methylene blue (MB) cationic dye as well as ibuprofen (IBP) pharmaceutical are reported. Very rapid 91% MB and 94% IBP pharmaceutical degradation efficiency obtained within 60 min and 30 min, respectively were observed. The kinetics of the photocatalytic activities at different pH followed pseudo-first-order kinetics. The Liquid Chromatography-Mass Spectrometry analysis on MB and IBP before and after photodegradation confirmed the formation of intermediate products. The modulated CSAC-ZnO@600 exhibits hydrogen production of 18947μmolg−1h−1. The photocatalysts showed current densities ranging from 0.03 to 0.05 mA/cm2. The Fast charge transfer is supported by electrochemical impedance spectroscopy and −0.3 and −0.49 V versus Ag/AgCl flat band potentials. The relation between the electronic and catalytic properties is revealed from the calculation of density functional theory (DFT). The study revealed the impact of calcination on the properties of the biomass carbon-doped-photocatalysts, excellent photocatalytic degradation efficiency and efficient hydrogen production from water-splitting giving relevance to biomass carbon-doped CSAC-ZnO in environmental remediation and green energy production.