Nanohole Arrays Coated with Poly(methyl methacrylate) for High-Speed Electrical Hydrogen Sensing with a Part-per-Billion Detection Limit*

As hydrogen gas increasingly becomes critical as a carbon-free energy carrier, the demand for robust hydrogen sensors for leak detection and concentration monitor will continue to rise. However, to date, there are no lightweight sensors capable of meeting the required performance metrics for the safe handling of hydrogen. Here, we report an electrical hydrogen gas sensor platform based on a resistance nanonetwork derived from Pd-Co composite hole arrays (CHAs) on a glass substrate, which meets or exceeds these metrics. In optimal nanofabrication conditions, a single poly(methyl methacrylate)(PMMA)-coated CHA nanosensor exhibits a response time (t₈₀) of 1.0 s at the lower flammability limit of H₂ (40 mbar), incredible sensor accuracy (<1% across 5 decades of H₂ pressure), and an extremely low limit of detection (LOD) of <10 ppb at room temperature. Remarkably, these nanosensors are extremely inert against CO and O₂ gas interference, display robust long-term stability in air over 2 months with diminutive power requirement (∼2 nW) and applied magnetic field (up to 3 kOe), a crucial metric for leak detection and concentration control. Further, a 50-nm thin film of fullerene C₆₀ is sandwiched between the glass substrate and Pd-Co layer for the purpose of maximizing the interacting surface area of the sensor. Remarkably, C₆₀/PdCo/PMMA sensor exhibits a superior response time t₉₀ of <0.5 s at 40 mbar while the accuracy, LOD, inertness and stability are conserved.