27 December 2018A team of physicists from the Immanuel Kant Baltic Federal University together with their colleagues from the National Research Nuclear University MEPhI (NRNU MEPhI) have developed a tungsten oxide-based detector of hydrogen in gas mixes. They manufactured thin tungsten oxide films with various additives and compared their characteristics. One of the film detectors demonstrated a 100 times increase in sensitivity when compared to the control sample. The article was published in the Thin Solid Films journal.
Hydrogen is one of the most widely used gases in the world. Its molecules have the smallest possible mass and size. Due to this, hydrogen is extremely difficult to keep in any vessel, as it leaks from almost any opening. Hydrogen leakages are very dangerous for the industry, as hydrogen mixed with oxygen forms an explosive cocktail known as the detonating gas.
With the development of hydrogen energy sector the prevention of leakages became a burning issue. Moreover, hydrogen is actively used in chemical industry and in controlled nuclear fusion experiments.
To prevent hydrogen leakages, its concentration in an industrial facility should be constantly monitored. Usually it is done with gas detectors of various types, the most popular of which are amperometric analyzers. They are based on the ability of gases to change the electrical conductivity of metals upon contact with them. In the course of measurements fixed voltage is applied to the ends of a metal plate, and a device measures the strength of current going through it. As the strength of current directly depends on the conductivity of a material, when the concentration of hydrogen increases, it changes as well. The sensitivity of measurements is determined by the properties of the sensor, i.e. the plate under voltage.
IKBFU scientists together with their colleagues from NRNU MEPhI studied new materials based on tungsten oxide (WOx). One of them was obtained by means of depositing WOx on a silicone carbide (SiC) substrate. Another material was developed in the same manner, but the tungsten oxide layer was covered with additional platinum coating. Then the scientists determined the sensitivity of the two films by applying voltage to them and putting them into an oxygen environment. After that 2% of hydrogen were added to it. The material without the platinum coating demonstrated a 15 times increase in the current strength compared to pure tungsten oxide. When the same property was measured in the second material, it showed a 100 times increase.
Dr Alexander Goikhman, a co-author of the article and the head of the Research and Educational Centre “Functional Nanomaterials” (IKBFU):
We’ve studied nanomaterials that may be used as a basis for hydrogen leakage sensors. In the course of our work we identified the requirements for the structural properties of these materials that should secure high gas detecting efficiency.
Fig. 1. Morphology of the Pt/WOx /SiC structure. Source: V.V. Zuyev et al./a letter to the Journal of Technical Physics, 2015.