Application of TiO₂ to amperometric NO_x sensors based on NASICON

The work focused on improvement of the current response to NO and the reduction of response time of both NO and NO₂. By adding a layer of TiO₂ catalyst layer, the shortcoming of NO insensitivity of traditional NASICON based amperometric NO₂ sensor was solved. TiO₂ was known as an n-type semiconductor and a high-performance NO oxidation catalyst. We separately applied different types of TiO₂ (rutile and Degussa P25) on the device and compared the test results with the traditional type without a catalyst layer. The results showed that the TiO₂ attached device exhibited a significant improvement to NO response, and P25 was better than rutile TiO₂ on account of the higher activity of anatase TiO₂. In addition, TiO₂ also played a role of a semiconductor electrode, resulting in the increase of response to NO₂. The response time of NO and NO₂ was separately shrunk from 153 s, 70 s to 77 s, 43 s owing to the P25 layer. The current responses were found to be barely affected by the coexistence of CO₂.