Synthesis and characterization of NiO/TiO2 porous films and their photocurrent-enhanced mechanism in gas phase

• The photocurrent of NiO/TiO2 porous films in methanol is much higher than usual.
• A quantitative formula confirms the synergistic effect between the p–n junction and methanol.
• A new insight into gas molecule photooxidation on the coupling catalyst is provided.

In this work, the NiO/TiO2 porous films with different weight-ratios were prepared by the screen-printing technique. To uncover the roles of gas molecules and the junction on the carrier migration, the photocurrent measurements in methanol were employed. The corresponding experiments were performed in a high-throughput platform where the concentration of target gas and the applied bias voltage were both precisely controlled. Our results revealed that not only the p–n junction but also methanol had a distinct enhancement effect on the photocurrent. Furthermore, the synergistic effect was further confirmed by a quantitative formula of multi-factor effect (ME) based on the carrier density. In addition, a new insight into gas molecule photooxidation on the coupling catalyst was provided, which was of great significance for potential application to photocatalytic degradation and gas sensing.