Researchers propose hydrogen alarm for remote hydrogen leak detection
22 January 2020
Researchers have suggested new sensors could act as the basis for a “hydrogen alarm” that can detect leaks of explosive hydrogen from hundreds of metres away. Tomsk Polytechnic University and University of Chemistry and Technology of Prague researchers have proposed the new sensors which are based on widely available optical fibre and ensure accurate detection of hydrogen molecules in the air.
Hydrogen filling station - Image: Jóhann Heiðar Árnason/Wikimedia
According to the research published in the journal ACS Sensors, the sensors are reusable and resistant to oxidizer gases which are harmful to traditional sensors with electronic components. Hydrogen is seen as a promising alternative energy source with many advantages such as its pollutant-free emissions, the abundance of hydrogen from several different sources including garbage, and its rapid refuelling capabilities compared to electric vehicles.
However, its application as an energy carrier is complicated due to its highly explosive nature when mixed with oxygen. These dangerous situations may arise, for example, in case of hydrogen leaks from the tank where it is stored.
"Therefore, it is necessary to detect hydrogen molecules in a gas mixture. Currently, there are various methods, including electronic sensors, although they are a potential source of spark. In this respect, we turned our attention to optical fibre. This is a simple and commercially available material. In addition, a sensor can be operated remotely, since optical fibre provides rapid and easy information transfer over long distances. The sensor can be installed in the engine of a hydrogen-powered machine or refuelling station,” said Pavel Postnikov, one of the authors and Associate Professor of the TPU Research School of Chemistry & Applied Biomedical Sciences.
Optical fibre is a thin filament of optically transparent material, e.g. glass or plastic, capable of transmitting digital information in the form of a light pulse. The researchers modified them by removing a fragment of the fibre sheath and applying a fine layer of gold onto this place through magnetron sputtering. On the surface of this golden area, the effect of surface plasmon resonance arises. It is the source of the analytical signal. The researchers used this golden area from a matrix solution as a basis for a metal-organic framework consisting of zinc molecules and particular organic compounds.
Image: Tomsk Polytechnic University
"This frame is extremely sensitive to hydrogen, since it captures its molecules from the air. Moreover, it is inert to other gases. Such sensors are comparable to a stationary chromatograph that is ten times more expensive and requires qualified personnel. For now, we have managed to achieve sensitivity and detection limit below 2%. In other words, our sensor can detect hydrogen in the air at a concentration below 2%, while the lower explosive threshold of a mixture of hydrogen and oxygen is about 4%,” Pavel Postnikov said.
The main advantages of the sensor embrace simplicity, sensitivity, and an option for quick remote diagnostics. "Another important feature is the sensor resistance to oxidising gases, for instance, carbon dioxide, and various oxides. It is a problem for the modern sensors since these gases interfere with the sorption of hydrogen. Our sensor can easily work in the open air full of such gases," Pavel Postnikov added.
The sensors could help in the development and increased use of hydrogen fuel cell vehicles (FCVs). However, although seen as a viable alternative to fossil fuels for vehicles, the majority of hydrogen for use in FCVs is currently produced by steam methane reforming, a process which emits carbon dioxide.
In addition, the building of refuelling infrastructure for FCVs is expensive with each hydrogen filling facility costing many times more than an electricity charging point. Opposition to hydrogen stations has also grown since a fatal FCV filling station incident in May 2019 when a hydrogen tank explosion killed two people and injured six at an industrial park in the city of Gangneung, 240 kilometres east of Seoul, South Korea. A preliminary investigation found the blast was caused by a spark after oxygen found its way into the tank. One month later, there was also an explosion at a hydrogen refuelling station in Norway.