Synthesis of p-n NiO-ZnO heterojunction for photodegradation of crystal violet dye

Abstract

Photocatalytic treatment of wastewater utilizing oxides of metals as photocatalysts has merged a subject of major concern. The photocatalytic efficiency can be increased by the separation of electrons and holes formed by the absorption of photons. The development of heterojunction between two semiconductors is one of the methods used for the separation of photo-induced electrons and holes. Herein, we report a p-n NiO-ZnO heterojunction photocatalyst for efficient photodegradation of crystal violet dye. The homogeneous precipitation method was used for the synthesis of p-n NiO-ZnO in this study. The synthesized heterojunction was characterized by XRD, SEM, EDX, and TGA techniques. The aqueous solution of crystal violet dye was used as model wastewater for the evaluation of the photocatalytic efficiency of as-synthesized material. The photocatalytic performance of p-n NiO-ZnO for photodegradation of crystal violet dye was significantly higher than pristine NiO and ZnO. The photocatalytic activities of NiO, ZnO and NiO-ZnO were found in the ratio of 1: 3.8: 7.8, respectively. Similarly, the ratio of photocatalytic activities of 5% NiO-ZnO, 10% NiO-ZnO, and 15% NiO-ZnO was 1: 1.2: 0.8, respectively. The degradation data was analyzed for kinetics analyses using the Langmuir-Hinshelwood mechanism.

Keywords

• p-n NiO-ZnO
• Heterojunction
• Electron-hole pair
• Crystal violet dye
• Langmuir-Hinshelwood mechanism