Humidity-resistant hydrogen sensor could boost safety in clean energy systems

Researchers at Sweden’s Chalmers University of Technology have developed a compact hydrogen gas sensor that performs better in humid conditions, a breakthrough that could significantly improve safety as hydrogen use expands in the global clean energy transition.

Hydrogen is widely seen as a key energy carrier for decarbonising transport, heavy industry and steel production. But the gas is highly flammable when mixed with air, making reliable leak detection essential in storage sites, pipelines, fuel cells and industrial facilities. A long-standing challenge has been that most existing hydrogen sensors lose sensitivity or respond more slowly in humid environments, precisely the conditions where hydrogen is often present.

The Chalmers team, however, has designed a “catalytic plasmonic hydrogen gas sensor” that turns humidity into an advantage. “Many sensors become slower or perform less effectively in humid environments. When we tested our new sensor concept, we discovered that the more we increased the humidity, the stronger the response to hydrogen became,” said lead researcher Athanasios Theodoridis, a doctoral student at Chalmers, describing the findings published in ACS Sensors.

The fingertip-sized device uses platinum nanoparticles that act both as catalysts and sensing elements. When hydrogen reacts with oxygen in the air on the particle surface, heat is generated, causing a thin film of moisture on the sensor to evaporate. The amount of hydrogen present determines how much of this water layer “boils away”. By optically measuring changes in the thickness of this moisture film, observed through colour shifts caused by plasmonic light interactions, the sensor can determine hydrogen concentration and trigger alarms at critical levels.

Because higher humidity creates a thicker water film, the sensor’s sensitivity actually improves in moist air. This makes it particularly suited for real-world hydrogen environments, where water vapour is common from ambient air, industrial processes and fuel cells, which themselves require moisture to function.

The team tested the sensor under continuous exposure to humid air for more than 140 hours, demonstrating stable and reliable performance. It can detect hydrogen concentrations as low as 30 parts per million, placing it among the most sensitive hydrogen sensors designed for humid conditions.

Professor Christoph Langhammer, who leads hydrogen sensor research at Chalmers, said the energy transition is raising expectations for sensing technologies. “There is currently strong demand for sensors that perform well in humid environments. As hydrogen plays an increasingly important role in society, there are growing demands for sensors that are smaller, more flexible, scalable and lower cost. Our new sensor concept satisfies these requirements well,” he said.

Researchers believe future hydrogen safety systems may combine multiple materials to balance speed, sensitivity and environmental robustness. But the platinum-based design marks a major step toward safer large-scale hydrogen deployment, particularly in industrial and transport applications where moisture has long been a technical obstacle.