Visible-light-driven photocatalysis for methylene blue degradation and hydrogen evolution reaction: a case of black TiO2 nanotube arrays

Abstract

In this study, black TiO2 nanotube arrays (TNAs) were synthesized by hydrothermal process which indicate the presence of substantial Ti3+ and oxygen vacancies (OVs). The formation of Ti3+ and OVs contributed to the reduced bandgap of TNAs and improved the efficiency of methylene blue (MB) photocatalytic degradation and hydrogen evolution reaction (HER). In this study, the black TNAs synthesized by the anodization method. The current density for hydrogen evolution reaction (HER) of the black TNAs was over − 2 mA/cm2 at just − 1.4 V vs. Ag/AgCl and the photocurrent density of the black TNAs is about 25% higher than that of the pristine TNAs. In addition, MB photocatalytic degradation of the black TNAs reached nearly 60% after 150 min under visible light. This study inspired the next studies in the use of materials to both treat polluted water and generate renewable energy.