Dependence of β-Co(OH)<inf>2</inf>/ZnO heterostructural composite prepared by one-pot hydrothermal method on visible-light-driven photocatalytic degradation of organic dye

Abstract

A β-Co(OH)2/ZnO heterostructural composite was successfully prepared via a simple one-pot hydrothermal method. The β-Co(OH)2/ZnO heterostructural composite was utilized as the photocatalyst in the photocatalytic degradation of aqueous methylene blue (MB) solution under visible light irradiation. The calcined β-Co(OH)2/ZnO heterostructural composite was characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), Brunauer–Emmett–Teller (BET) analysis, UV–Vis diffused reflectance spectroscopy (UV–Vis DRS), and photoluminescence (PL) spectroscopy. In the absence of β-Co(OH)2, ZnO particles formed as nanoplatelets but in the composite, they formed as nanorods, and in response to increased Co2+ ion concentration, as flower-like structures. The particle shape of β-Co(OH)2 did not alter. The optical band gap energy of ZnO powder prepared without β-Co(OH)2 was 3.220 eV, and Urbach energy was 0.0712 eV. In 10 mol%β-Co(OH)2/ZnO composite, the optical band gap energy decreased to 2.775 eV and Urbach energy increased to 0.542 eV. Under visible light irradiation, the highest photocatalytic degradation of aqueous MB solution (93.69%) was obtained on a 10 mol%β-Co(OH)2/ZnO heterostructural composite photocatalyst, which also exhibited excellent stability and reusability.