Chemo-resistive detection of hydrogen in argon using Pd nanoparticles on TiO2 nanotubes prepared via rapid breakdown anodization

The present work explores palladium sensitized Titania nanotubes (Pd/TiO2 NTs) as a potential sensor material for detecting hydrogen (H-2). TiO2 NTs powder was prepared as bundles via rapid breakdown anodization. Pd nanoparticles (NPs) were deposited over TiO2 NTs by sodium borohydride-based chemical reduction of palladium chloride (PdCl2) to form nanocomposite materials. Morphological analysis exposed the tubular architecture and provided the nanoscale dimensions of the synthesized materials. Structural analysis revealed the anatase phase and face-centered cubic crystal structure for TiO2 NTs and Pd nanoparticles (NPs), respectively. The presence of Pd over TiO2 NTs was established with compositional analysis. Thermal stability analysis confirmed that the deformation of phase takes place only after 550 degrees C, thereby indicating the suitability of the material to sense H-2 up to the required 350 degrees C temperature. A paste of Pd/TiO2 NTs was used to make a thick film sensor to sense H-2 in argon (Ar) as a function of Pd loading and temperature. A tremendous change in the sensor response of the sample was witnessed with different percentages of Pd. The sensor material was insensitive to H-2 up to a threshold temperature of 100 degrees Cowing to the formation of a surface oxide over Pd NPs. The sensors displayed an elevated response beyond the threshold temperature. The sensing behavior was selective only to H-2 gas, amid the presence of reducing gases like ammonia and methane and oxidizing gas like nitrogen oxide.