Fast-response hydrogen sensors based on discrete Pt/Pd bimetallic ultra-thin films

This study presents the fast response-recovery characteristics of an ultra-thin discrete platinum/palladium (Pt/Pd) bimetallic film-based hydrogen (H2) sensor. Pt/Pd bimetallic nanoparticles (NPs) with a size of 2-11 nm were deposited on an alumina (Al2O3) substrate using a pulsed laser deposition (PLD) method. The metal loading and the composition of the Pt/Pd NPs were carefully controlled by varying the deposition conditions of the PLD system. The resultant discrete Pt/Pd bimetallic ultra-thin film was applied as a new H2 detection material, in which the fabricated Pt (3 nm)/Pd (3 nm) film showed noteworthy advantages, such as a large detection range of 10-40,000 ppm, high response magnitude, and fast response-recovery time. For a 10,000 ppm (1 vol.%) H2 concentration at 150 °C, a maximum sensor response of 13.56% and a response-recovery time of 4/5 s were observed. The observed fast response-recovery time characteristics can be attributed to the enhanced hydrogen-induced changes in the work function of the Pt/Pd ultra-thin film. The fabricated sensor also exhibits good reproducibility and a negligible humidity effect within the entire detection range.