Enhanced sensitivity towards hydrogen by a TiN interlayer in Pd-decorated SnO₂ nanowires

In this study, we designed a new structure based on Pd-decorated TiN-coated SnO₂ nanowires (NWs) for the selective detection of H₂ gas. Initially, SnO₂ NWs were prepared by a simple vapor-liquid-solid growth method. Then, atomic layer deposition (ALD) was used to grow a continuous TiN layer and, subsequently, Pd nanoparticles on the NW networks. The TiN thickness was precisely set to 0.5, 1, 2, and 5 nm, while the Pd loading was adjusted by varying the number of ALD cycles (25 to 200 cycles). Various characterization techniques revealed the amorphous nature of TiN, a homogeneous dispersion of Pd NPs and the uniform morphology and single crystallinity of the SnO₂ NWs. H₂ gas sensing studies revealed that the sensor with a TiN thickness of 1 nm exhibited the highest response. Pd decoration further improved the response to H₂ gas. Hence, the Pd-decorated gas sensor with a 1 nm-thick TiN layer showed the highest H₂ sensing performance at 250 °C among all gas sensors. Due to the unique chemical reaction between Pd and hydrogen, the fabricated sensor shows excellent performance in detecting hydrogen gas. The underlying sensing mechanism is discussed in detail. The optimized sensor has a sensitivity of 8.18 for hydrogen gas, which is four times higher than that of other gas species, showing that it is suitable for detecting hydrogen gas. We believe that this new design is a highly valuable gas sensor for the real application of H₂ monitoring with high selectivity.