A hydrogen sensor is an important part of any fuel cell. It detects the presence of hydrogen gas and triggers a reaction that causes a generator to produce electricity. This makes it possible for a vehicle to run on hydrogen, without the danger of a sudden explosion as would occur with combustible gases like oxygen or carbon monoxide.
The majority of hydrogen sensors are resistor-based (chemiresistors). They estimate the concentration of hydrogen based on changes in resistance, which are proportional to the concentration of hydrogen. This is because hydrogen interacts with the metal oxide semiconductor layer and reduces its resistance. Several research groups have worked on improving the performance of hydrogen sensors. However, resistance-type hydrogen sensors suffer from common-mode interference caused by variations in the gas thermal conductivity, which makes it difficult to isolate the signal from the noise.
Preventing Hazards: The Functionality of Hydrogen Leak Detectors
One way to improve the performance of resistor-based hydrogen sensors is to use a thin film made of a semiconductor material with a high specific surface area. Wang and co-workers developed an on-chip self-assembled sensor using SnO2 nanowires (NWs) extending from one side to the other of comb-shaped interdigital electrodes. As the gap between the electrodes decreases, the NWs spatial density increases, thereby increasing the sensor response.
Another method for improving the performance of SMOs hydrogen sensors is to use palladium as a sensing element. Pd is a noble metal with a unique interaction with hydrogen: it lowers the Schottky barrier, which allows hydrogen to pass through. Researchers have used Pd-based sensors of the MOS capacitor, MOS field effect transistor (MOSFET) and Schottky diode types to detect hydrogen. Several studies have shown that the sensitivity of these devices is affected by the adsorption of carbon monoxide (CO).