Highly stable and reversible hydrogen sensors using Pd-coated SnO₂ nanorods and an electrode–substrate interface as a parallel conduction channel

We demonstrated highly stable and reversible H₂ sensors using a dual electron-conduction channel comprising Pd-coated SnO₂ nanorods (NRs) and a parallel conduction channel containing Cr/native oxide/p-type Si interface. The dual-channel sensor exhibited highly reversible resistance changes during H₂ in-and-out cycles at operating temperatures of 25 °C− 100 °C, while typical single-channel sensors with SnO₂ NRs fabricated on SiO₂ (300 nm)/Si substrates showed irreversible response because of insufficient recovery from Pd-H_x to Pd-O_x. In particular, the sensor showed significantly high repeatability, long-term stability, and selectivity for H₂ sensing at 80 °C. Additionally, the time taken to detect H₂ above 1% was less than 2 s and the response to H₂ above 500 ppm was unaffected by high humidity. These results indicate that the dual-channel Pd-coated SnO₂ NR sensor is suitable for applications such as hydrogen leak detectors that require high speed and precision. Moreover, it was found that the sensor could detect H₂ below 0.5 ppm even at low temperatures. This work provides a pathway for improving gas-sensing performance by interface engineering, enabling various practical hydrogen sensor applications.