Ultra-fast and sensitive Magneto-Optical Hydrogen Sensors Using a Magnetic Nano-cap Array

Magnetism in curved nano-geometries has opened a new path to designing novel characteristics and phenomena that could dramatically impact the future fundamental and applied studies of materials. In this presentation, a hexagonally packed array of magnetic nano-caps (or nano-patches, NP) exhibiting unique magnetic property and optimal nanostructure for fast hydrogen kinetics is explored as a sensing element for the spark-free magnetic-circular-dichroism (MCD) H₂ sensor. The MCD H₂ sensor outperforms the state-of-the-art optical sensors reported to date and satisfies the most challenging performance targets imposed by the US Department of Energy. In particular, a stacked Pd₆₇Co₃₃/TAF (Teflon-AF 2400) MCD sensor exhibits a response time of <0.4 s and a recovery time of <2.8 s over the entire 1-100 mbar H₂ partial pressure range. When the Pd₆₇Co₃₃/TAF is coated with poly(methyl methacrylate) (PMMA), the sensor preserves excellent accuracy (<2.5% full scale), achieves a <1 ppm limit of detection (LOD), exhibits strong selectivity against interference gases and moisture, and shows a slow aging effect, while the sorption times essentially remain the same. The MCD nano-cap sensor platform may have a great impact on the future deployment of H₂ fuel, the development of other high performance optical gas sensors, and fast proton-based magneto-ionic devices.