Preparation of CdS-g-C3N4/C composites via hollyhock stem biotemplate and its photocatalytic property

Abstract

Bio-templated porous CdS-g-C3N4/C composite with controllable morphology and energy band structure was successfully prepared by simple thermal condensation and hydro-thermal method using dicyandiamide and cadmium chloride as precursor, Hollyhock stem as biological template and in-situ carbon dopant. The structure and property of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, fluorescence spectroscopy (PL), UV–visible spectroscopy and diffuse reflectance ultraviolet spectroscopy (DRS). The results indicated that, compared with pure g-C3N4, g-C3N4/C had a porous structure, higher specific surface area and better photogenerated carrier separation efficiency. In addition, compared with g-C3N4/C, the light response of the three-phase composite anchored with 2D CdS expanded from ultraviolet to visible and even near infrared regions. The n-n heterojunction formed between CdS and g-C3N4 reduces the energy required for electron transition and makes the photogenerated electron hole pairs easier to be separated. The highest photocatalytic efficiency for RhB of CdS-g-C3N4/C is 86.96%, which is 3.23 times that of pure g-C3N4. In the photo-catalytic process, the main photocatalytic reactive substance is ·O2−, followed by h+. Therefore, the CdS-g-C3N4/C synthesized by stem induction and multi-phase heterojunction has a more stable microstructure, and the charge separation efficiency is greatly improved, which is suitable for practical photocatalytic environmental protection.