Crack-Engineered Palladium Nanocrack Networks for Trace-to-Leak Hydrogen Monitoring under Ambient Conditions

Conventional palladium (Pd) nanogap hydrogen sensors generally operate through abrupt electrical switching induced by hydrogen-driven gap closure, which limits stable low-concentration sensing performance. Here, we report a crack-engineered Pd thin-film sensor that enables concentration-dependent resistive hydrogen sensing through electrically connected Pd nanocrack networks. Dense Pd nanocracks with average widths below 10 nm were generated by combining sonication-assisted crack formation with controlled hydrogen activation in Pd thin films deposited on PDMS substrates. Unlike fully opened Pd nanogaps, the proposed nanocrack structure enables continuous modulation of electrical transport pathways during hydrogen absorption and desorption, allowing stable concentration-dependent sensing behavior under ambient air and room-temperature conditions. The optimized sensor exhibited reliable hydrogen detection from 100 ppb to 1% H₂ together with excellent selectivity, humidity tolerance, cyclic stability, and long-term operational reliability. These results demonstrate that crack-engineered Pd thin films provide an effective platform for room-temperature trace-level hydrogen sensing and offer strong potential for hydrogen safety monitoring, early leak detection, and lithium-ion battery thermal runaway monitoring.