Fast Hydrogen Sensors

 


Hydrogen is becoming more important in the clean energy sector. It can be burned, only producing water as a by product. Hydrogen is highly flammable, even at concentrations as low as 4%. Hydrogen is both odorless and colorless, making leak detection a high priority.

Professor Yutaka Majima is from the Institute of Science Tokyo. His team have been working on a sensor that detects hydrogen in very low concentrations within a short response time. Advanced Functional Materials published the research on November 5, 2024. 

The sensor is created from nanopatterned polycrystalline CuONWs. These are very sensitive to hydrogen gas. They are placed on a silicon substrate and platinum or titanium electrodes are added. 

Professor Majima explains, "We employed electron-beam lithography and two step ex-situ oxidation to develop a reliable and reproducible process fr preparing high-performance, nanopatterned CuO nanowire-nanogap hydrogen gas sensors with voids, which is considerably different from conventional free-standing single-crystal CuO nanowires directly grown from copper sources."

The sensor is exposed to hydrogen gas. It detects changes in the electrical resistance of CuONWs. In open air, oxygen molecules attach to CuONWs at the surface. This forms oxygen ions that create a positive charge carrier (hole) near the surface.

Hydrogen is introduced and it reacts with the oxygen ions on the surface of the CuONWs to form water. This lowers the hole concentration, and the nanowires become less conductive. When the increase in resistance is measured, the sensor can analyze the concentration of hydrogen gas. The latest sensors can recognize hydrogen concentrations as low as 5 parts per billion (ppb). The sensor reacts fast, working just in 7 seconds.

Professor Majima summarizes, "We will continue developing a wider range of gas sensors with this process to fabricate sensors for other hazardous gases as well."

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