Hydrogen is an important component in the pursuit of clean and renewable energy. However, one significant challenge to this transition is that the gas is explosive when mixed with air. As a result, it is critical to be able to detect hydrogen leaks as soon as possible. Researchers from Chalmers University of Technology, Vrije Universiteit Amsterdam, and Eindhoven University of Technology have developed an optical sensor capable of detecting extremely low levels of hydrogen.
Hydrogen is seen as an important part of the heavy transport sector’s decarbonization, and hydrogen-powered trains, trucks, and airplanes are being developed and deployed around the world. Even in heavy industry, hydrogen is regarded as critical, such as in the production of fossil-free steel.
The risks of storing or using hydrogen are well known. Only four percent hydrogen is required in air for the formation of an explosive mixture (knallgas) that can ignite at the slightest spark. Therefore, it is important that ultra-sensitive sensors are in place to monitor leaks and alarm at critical levels.
Safety is paramount in all aspects of hydrogen use and storage. If leaks are detected early, they can be repaired so that the plant or vehicle is not taken out of service at all.
Professor Christoph Langhammer
Safety of utmost importance in hydrogen use
Together with Dutch colleagues, researchers at the Department of Physics at Chalmers University of Technology, Sweden, have now developed an optical hydrogen sensor that detects record-low levels of hydrogen. As a result, it has joined the ranks of the world’s most sensitive sensors. The new findings are published in Nature Communications.
“Safety is paramount in all aspects of hydrogen use and storage. If leaks are detected early, they can be repaired so that the plant or vehicle is not taken out of service at all” According to Chalmers Professor Christoph Langhammer, one of the scientific article’s main authors.
AI technology led the way
The optical hydrogen sensor consists of many metal nanoparticles that work together to detect hydrogen in their surroundings. The approach to how the new sensor was designed differs from what has been done previously. Instead of producing a large number of samples and testing them individually to see which one works best, the researchers have used advanced AI technology to create the optimal interaction between the particles based on their distance to each other, diameter and thickness. The result is a sensor that detects changes in hydrogen concentration that are as small as a few hundred thousandths of a percent.
The secret behind the new sensor’s low detection limit is the combination of the arrangement of the particles in a regular pattern on a surface and their fine-tuned dimensions. This turned out to be more favourable for the sensitivity of the sensor than the random particle arrangement used in previous sensors of the same type.
Christoph Langhammer’s research group has previously demonstrated the world’s fastest hydrogen sensor. For him, it is obvious that many different types of sensors are required, and that they must be optimized for specific applications.
“Because hydrogen technology has advanced so much, today’s sensors must be more accurate and tailored to specific applications. Sometimes a very fast sensor is required, while other times one that works in a harsh chemical environment or at low temperatures is required. A single sensor design cannot meet all requirements “says Christoph Langhammer, one of the founders of a new competence center called TechForH2.
Industry and academia in new collaboration on hydrogen
The new Chalmers-led center brings together academia and industry to develop new hydrogen technology with a focus on decarbonizing heavy transport systems. TechForH2 is led by Chalmers Professor Tomas Grönstedt at the Department of Mechanics and Maritime Sciences.
“When the research community and industry collaborate, we can advance to the next level, where what we produce can be applied and meet the industry’s needs and challenges. This includes sensor development as well as research into hydrogen gas propulsion for heavy vehicles or airplanes “According to Tomas Grönstedt, an electric aircraft with a 500-kilometer range could increase its range to 3000 kilometers if powered by hydrogen.
How the optical hydrogen sensor works
The sensor that the researchers have developed is based on an optical phenomenon, plasmons, which occur when metal nanoparticles capture light and give the particles a distinct colour. If the nanoparticles are made of palladium or a palladium alloy, their colour changes when the amount of hydrogen in the surroundings varies, and the sensor can trigger an alarm if the levels become critical.
To achieve the highest possible sensitivity to hydrogen exposure, the researchers used an artificial intelligence algorithm called particle swarm optimisation to find the optimal combination of surface arrangement and particle geometry in the sensor. The solution was to arrange the particles in a very precisely defined regular pattern.
The optimized optical hydrogen sensor was built and tested based on the AI-design to be the first of its kind to optically detect hydrogen in the “parts per billion” range (250 ppb). The new sensor is based on an optical phenomenon known as plasmons, which occur when metal nanoparticles capture light and impart a distinct color to the particles.
