Homojunction TiO2 thin film-based room-temperature working H2 sensors with non-noble metal electrodes

An Ultrasensitive Room-Temperature H2 Sensor Based on a TiO2 Rutile–Anatase Homojunction

“…There are two main factors that affect the height o effective barrier in this series of sensors. First, H2 reacts with the topmost Pt electro form PtHx, which decreases the height of the Schottky barrier [44][45][46]. Second, the ch in the charge concentration in the anatase-phase TiO2 layer also changes the barrier he Therefore, the potential barrier of the TiO2(R/A-X) sample in air showed a trend of increasing and then decreasing with increasing anatase TiO2 content.…”

“…There are two main factors that affect the height of the effective barrier in this series of sensors. First, H 2 reacts with the topmost Pt electrode to form PtHx, which decreases the height of the Schottky barrier [44][45][46]. Second, the change in the charge concentration in the anatase-phase TiO 2 layer also changes the barrier height.…”

“…When H 2 enters the test chamber, H 2 reacts with O 2 − on the surface of the sensor so that the released electrons return to the rutile-phase TiO 2 nanorods, the depletion layer becomes smaller, and the resistance of the system decreases (Figure 8d). The associated reaction can be represented as follows [44][45][46].…”

“…When the sensor was exposed to NH 3 and C 2 H 6 atmospheres, the initial resistance of the sensor did not change, reflecting that the sensor was not responsive to these two gases. Because these two gas molecules show high stability at room temperature, they are less likely to break the chemical bond and cause a change in the resistance of the TiO 2 [45]. As shown in Figure 9b, at the same concentration of 2500 ppm, the response of the TiO 2 (R/A-25 mL) sensor to hydrogen was 109 times greater than that of NO, 230 times more than that of SO 2 , and 503 times greater than that of NO 2 , indicating that the TiO 2 (R/A-25 mL) sensor has excellent selectivity to H 2 .…”