While various types of hydrogen sensors exist, they often require high temperatures to function.

A team from the Delft University of Technology have developed a highly sensitive and versatile hydrogen sensor made of a thin layer of tungsten trioxide that works at room temperature.

“It is also much more sensitive than commercially available products and it can be reused in a matter of minutes,” Giordano Mattoni, the lead author, said in a statement. “Also, by increasing or decreasing the temperature of the sensor, the sensitivity range can be tuned for different applications.”

Hydrogen has been targeted as a potential replacement for fossil fuels because it has the highest energy per mass of any fuel and can be produced sustainably. However, hydrogen is flammable, making sensors that can detect it necessary to transition to a hydrogen economy.

The new sensor is able to operate at room temperature due to the tungsten trioxide that features a crystal lattice structure that contains a lot of open space. This structure enables the material to be easily doped.

“By itself, tungsten trioxide is an insulator,” Mattoni said. “But when  you dope it, you add electronic charges which turn the material into a different color and also gradually change it into a metal. We wanted to try to dope thin films of tungsten trioxide with hydrogen gas to see if it could function as a sensor.”

In the study, the researchers first developed thin sheets of tungsten trioxide using a method called pulsed laser deposition that enabled the team to deposit single layers of the material onto a substrate one by one.

“Using this method, we created sheets of tungsten trioxide with a thickness of only nine nanometers,” Mattoni said.

Next, the researchers put platinum droplets, which is known to function as a catalyst, on top of the thin layers of tungsten trioxide to separate the hydrogen molecules into single hydrogen atoms. The atoms could then enter the lattice structure of the tungsten trioxide and slowly turn it from an insulator into a metal.

“This means that, by measuring the resistance of the material, we can determine the amount of hydrogen present in the environment,” Mattoni said.

The sensor also can be scaled up towards mass production due to the thin films nature and compatibility with current semiconductor technologies.

Mattoni and TU Delft have filed a patent application for this novel sensing technology.