Researchers led by the Institute of Science Tokyo have created an advanced nano-patterned sensor capable of detecting ultra-low concentrations of hydrogen gas quickly, marking a significant leap in industrial safety.
Hydrogen, often hailed as the clean fuel of the future, is rapidly gaining traction as a sustainable energy source. Despite its many benefits, hydrogen’s highly flammable nature poses significant risks. To mitigate these safety concerns, a team of researchers led by Yutaka Majima, a professor at the Institute of Science Tokyo, has developed a revolutionary sensor capable of detecting hydrogen gas at ultra-low concentrations almost instantaneously. This innovation was detailed in a study published in the journal Advanced Functional Materials.
The newly developed sensor is crafted from nano-patterned polycrystalline copper oxide nanowires (CuO NWs) and is mounted on a silicon substrate with platinum/titanium electrodes. This setup enables the sensor to detect hydrogen at concentrations as minuscule as 5 parts per billion (ppb), a substantial improvement over prior CuO-based sensors.
Remarkably, the sensor can identify hydrogen gas presence within just 7 seconds and reverts to normal conditions in only 10 seconds.
“We employed electron-beam lithography and two-step ex-situ oxidization to develop a reliable and reproducible process for preparing high-performance, nano-patterned 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,” Majima said in a news release.
The operation of the sensor hinges on detecting shifts in electrical resistance of the CuO NWs. In ambient air, oxygen molecules adhere to the CuO NWs’ surface, forming oxygen ions and triggering a layer of positive charge carriers, or holes, near the surface.
When hydrogen gas is present, it reacts with these surface oxygen ions to produce water, subsequently reducing the hole concentration. This results in a resistance increase within the NWs, signaling the presence of hydrogen.
The researchers introduced a pre-annealing step in a hydrogen-rich environment, followed by slow oxidation in dry air to enhance the sensor’s performance. This process transformed the freshly fabricated copper nanowires from rectangular shapes into semicircular arches, boosting their crystallinity. The oxidation subsequently converts the Cu NWs to CuO, enriching the surface with voids that heighten the active sites available for hydrogen and oxygen interaction.
In another significant enhancement, the team reduced the gap between the electrodes to 33 nm. This reduction bolstered the electric field, expediting the movement of charge carriers and hence, quickening the sensor’s response. Consequently, the sensor detected 1,000 ppm of hydrogen in a mere 5 seconds.
Emphasizing the broader potential of their technique, Majima added, “We will continue developing a wider range of gas sensors with this process to fabricate sensors for other hazardous gases as well.”
This breakthrough development holds the promise of transforming hydrogen safety protocols in industrial settings. By facilitating early leak detection and ensuring reliable monitoring of hydrogen levels, the sensor could play a pivotal role in advancing the safe and widespread adoption of hydrogen technologies. This advancement aligns with global efforts to transition to a hydrogen-based economy, potentially revolutionizing how industries manage and handle hydrogen gas.