Improving the nitrogen oxide sensing capabilities of MXene

What is it about?

MXene is a metal carbide that is used in gas sensors for detecting harmful pollutants like nitrogen dioxide (NO₂). It has a two-dimensional layered structure which provides abundant surface area for gas adsorption and, therefore, excellent gas sensing abilities. However, when exposed to air, MXene can get oxidized. This can hurt its lifespan, response time, and recovery to its initial state or baseline after gas detection. The authors of this study propose a new way of dealing with this problem. They used a technique called atomic layer deposition (ALD) to passivate the MXene surface with tin oxide (SnO₂). Simply put, they deposited a layer of SnO₂ on MXene i2C3Tx to make the oxygen-containing groups present on its surface less reactive. The authors found that extra hydroxyl groups on MXene surface, that would otherwise lead to oxidation, enabled proper deposition of SnO₂ via ALD. Furthermore, the gas detection tests revealed that the passivated MXene@SnO₂ was three times better at sensing NO₂ than pure MXene sensors. The new sensors also showed a quick response time of 18 seconds and did a complete recovery to baseline within 27 seconds.

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Photo by Matt Boitor on Unsplash

Photo by Matt Boitor on Unsplash

Why is it important?

NO₂ gas emitted by vehicles and industrial exhausts is bad for both the environment and human health. Hence, we need chemical sensors that can detect NO₂ even at lower concentrations. So, we need sensitive yet stable materials like MXene@SnO₂. It has great NO₂ detecting abilities and can be used to design compact and low-power gas sensors. The new MXene@SnO₂ sensor showed excellent response to NO₂ at different concentrations, ranging from 35.2% to 20 parts per million. KEY TAKEAWAY: The new universal synthesis strategy presented in this study successfully overcomes the challenges faced by MXene. This can pave the way for designing versatile gas sensors that are reliable, fast, and have a long life.