Photogenerated charges transfer across the interface between NiO and TiO2 nanotube arrays for photocatalytic degradation: A surface photovoltage study.

To better understand the behavior of photogenerated charges in the composite photocatalyst interface is beneficial to the designing of effective photocatalyst for photocatalytic reaction. In our work, the separation and transfer process of photogenerated charges in NiO/TiO2 nanotube arrays (NiO/TiO2 NTAs) has been studied by surface photovoltage (SPV) spectroscopy and transient photovoltage (TPV) measurement. Through the experimental results analysis, we find that an interfacial electric field is formed at NiO/TiO2 NTAs interface, which is attributed to the work function difference between NiO and TiO2 NTAs. The photogenerated holes in TiO2 can transfer to the NiO layer along the interface electric field under the ultraviolet irradiation. A large amount of photogenerated holes can be separated effectively and then prolonged the holes lifetime to participate in the photocatalytic oxidation reaction. The above results show that the favorable hole-collecting process of NiO in the surface of TiO2 NTAs is the main factor being responsible for the increase the photocatalytic efficiency.