Methylene Blue Sensitization by Enriched Oxygen Vacancy ZnO

Metal oxide photocatalysts have gained special attention as a green technology for environmental remediation. Zinc oxide is a popular semiconductor photocatalyst due to its electronic properties, low cost and toxicity, and the ability to mineralize organic pollutants completely. However, disadvantages such as a high rate of electron-hole recombination, and a wide bandgap for harvesting visible light, limit the application of ZnO [1]. One of the possible methods to overcome the metal oxide limitations is providing oxygen vacancies (OV) at the surface of the nanoparticles. OVs can trap the photo-generated electrons and they can act as an adsorption site, where the excited electron can transfer to the adsorbed compound. Hence, the presence of OVs will enhance photocatalytic degradation by reducing the electron-hole recombination [2]. In this study, the enriched OVs ZnO were provided by a temperature-programmed reduction (TPR) method. To this aim, commercial ZnO was heated by a ramp rate of 10°C/min to 500°C in a flow of 10% H 2 /Ar. The formation of OVs was investigated by several characterization analyses such as TPR, TPO, PCO, XPS, XRD, PL, EPR, FE-SEM, TEM, BET, and Tauc plot. The adsorption capacity and photocatalytic activity of commercial ZnO (C-ZnO