Highly sensitive hydrogen sensing properties of Pt-Pd alloy thin films on a flexible substrate

In the present study, the thin films of platinum-palladium (Pt-Pd) alloy with various compositions are prepared on a flexible polyamide substrate by using the magnetron co-sputtering technique. The atomic Pd content in the alloy was varied from 25% to 63% and the Pt-Pd alloy film thickness was approximately 2 nm. The Pt-Pd alloy thin films were tested in a wide range of hydrogen concentrations from 10 ppm to 4% hydrogen at various temperatures between room temperature to 200 degrees C. The hydrogen sensing mechanism of Pt-Pd alloy thin films is dominated by Pt atoms in the alloy and could be explained by surface scattering. The highest sensor response ( triangle R/RH ) is received as about 8.1% for Pt50Pd50 alloy thin films during exposure to 1000 ppm hydrogen at 50 degrees C. The sensor response and the response time of all Pt-Pd alloy thin films decreased with rising temperature in the measurement temperature range. Another result of this study is that Pt-Pd alloy thin film sensors require oxygen in the working environment to achieve both high sensor response and full recovery. As a summary, Pt-Pd alloy thin film sensors show high sensitivity, hysteresis free, low temperature operation and selective to hydrogen.