Highly sensitive hydrogen detection at low ppm levels using Pd70Ag30 alloy thin films: Role of structural evolution probed by in situ synchrotron XRD

In the present study, Pd70Ag30 alloy thin film, containing 70 at. % Pd, synthesized by cosputtering using two direct current magnetrons was investigated for precise hydrogen sensing. The hydrogen sensing measurements were undertaken to evaluate the sensor response of the alloy thin films for hydrogen by assessing the change in electrical resistivity upon exposure to hydrogen. The performance of the sensor was evaluated by measuring its response to hydrogen concentration ranging from 25 to 125 ppm at atmospheric pressure. In situ synchrotron x-ray diffraction (XRD) measurements were conducted to investigate the minute structural changes that occur during hydrogen absorption and desorption cycles. The current study demonstrates the remarkable potential of PdAg alloy thin films for sensing at 25 ppm of hydrogen concentration with sensor response of 10.3%, at room temperature along with long-term durability upto 5 months with the stable response of 10.1%, good cycle life, and low detection limit. Additionally, the sensing measurements were also performed at 125 ppm of hydrogen concentration at relative humidity from 20% to 90%, and the present work highlights the feasibility of using Pd70Ag30 alloy thin film as a sensor to detect H2 in humid environments. For a fundamental insight, an in situ synchrotron XRD measurements were conducted to investigate the minute structural changes that occur during hydrogenation and dehydrogenation cycles.