The surface oxygen vacancy induced visible activity and enhanced UV activity of a ZnO1-x photocatalyst

A ZnO1-x photocatalyst with surface oxygen vacancies was fabricated by the controllable reduction of H-2. After surface oxygen vacancies were introduced into the ZnO photocatalyst, a high visible-light-driven activity and photocurrent was produced. The UV activity for the degradation of MB and the photocurrent was enhanced about 2.2 times and 2.5 times, respectively. The visible-light activity resulted from the narrowed band gap due to the overlap of the valance band (VB) of the surface oxygen vacancy with O2p. The main active species are photoinduced holes and MB can be mineralized completely under visible-light irradiation. The overlap of the VB of the surface oxygen vacancy with O2p also extended the width of the VB and resulted in the increase of the separation efficiency of the photoinduced electron-hole pairs and the enhancement of the UV photoactivity greatly. The surface oxygen vacancy only increased the separation efficiency and did not change the photocatalytic degradation process, and the main oxidative species was still the photoinduced holes. The bulk oxygen vacancy can be formed via depth reduction at 700 degrees C for 5 h and resulted in the loss of photoactivity due to bulk defects.