The influence of Au and Pt electrodes on the stability of TiO2 under UV light activation for sensing formaldehyde in moisture circumstances

The structural stability of TiO2 thick films on Au and Pt electrodes was investigated under UV light activation for sensing formaldehyde in moisture circumstances. A chameleon phenomenon of TiO2 on the anode was found on the Au electrode samples, while no color changed on the Pt samples. The discolored (puce) TiO2 powders were characterized by X-ray photoelectron spectroscopy, where the generation of Ti3+ was verified. Different mechanisms that caused the disparities between the Au and Pt ones were discussed in detail. With the purpose of further evaluating the gas sensing performance stability, four test circles were performed. The Au electrode samples emerged an irreversible drift, while the Pt samples perfectly recovered to initial state undergoing a transitory 300 °C thermal cycle. The results in this paper show that Pt electrode is a suitable choice for TiO2 sensing formaldehyde in moisture circumstances.