Improvement of photocatalytic activity of BiOBr and BiOBr/ZnO under visible-light irradiation by short-time low temperature plasma treatment

In this work, BiOBr and BiOBr/ZnO were produced by using a simple hydrothermal method, and then were modified by a short-time low temperature plasma treatment using the gas of argon mixed with 3% hydrogen in pulsed mode with the fixed cycle discharge times. The related morphological, crystal, chemical, optical and photocatalytic properties were investigated. A three-dimensional flower-like structure of pure BiOBr and layered ultrathin nanosheets structure of BiOBr/ZnO can be observed. And the plasma treatment process at the discharge power of 100 W would not affect their basic morphologies. However, the changes in the surface chemical bonding has been identified, which indicates the presence of strong electronic interactions and strong chemical bonds caused by the plasma modification. The photodegradation rate has been greatly improved by mixing BiOBr with ZnO since the heterojunction structure was built during the hydrothermal process. Moreover, the photocatalytic activity can be further improved after the plasma treatment, it is attributed to the higher photogenerated carrier separation rate and narrow band gap due to the defects generated by the surface plasma effects.