Abstract
Palladium (Pd) nanogap hydrogen gas (H-2) sensors based on the large volume expansion of beta phase palladium hydride (beta-PdH) are highly promising, owing to their fast and accurate sensing capability at room temperature in air. However, such sensors do not work well at H-2 concentrations below 1%. At such low H-2 concentrations, Pd exists as alpha-PdH, which has a slow and insufficient volume expansion and cannot completely close nanogaps. Furthermore, the lattice strains induced from the phase transition (alpha-PdH -> beta-PdH) behavior degrade the stable and repeatable long-term sensing capability. Here, these issues are resolved by fabricating an array of periodically aligned alloyed palladium-gold nanoribbons (PdAu NRB) with uniform 15 nm nanogaps. The PdAu NRB sensor enables highly stable and ultrafast H-2 sensing at the full detection range of H-2 concentrations from 0.005% to 10% along with the excellent limit of detection (approximate to 0.0027%), which is sufficiently maintained even after seven months of storage in ambient atmosphere. These breakthrough results will pave the way for developing a practical high-performance H-2 sensor chip in the future hydrogen era.