Palladium‐polymer bilayer on a soft substrate for optical hydrogen sensing

Abstract

AbstractThe detection of hydrogen in air is essential because of the flammability of hydrogen gas (H2). Optical hydrogen sensor is safer than electrical hydrogen sensor because it can eliminate the potential risk of sparks by reading out remotely. Palladium‐based optical hydrogen sensors have attracted lots of attentions. However, impurity poisoning of the sensing materials is a severe problem for the utilization of hydrogen sensors. Here, we report that a palladium (Pd) ‐PMMA bilayer on a polydimethylsiloxane (PDMS) substrate can eliminate the adverse effect of the impurity (such as oxygen) in air. With a 16‐nm PMMA layer coating on the Pd surface, the hydrogenation time of a 25‐nm Pd film on PDMS can decrease to 5 seconds exposed to 4% H2 mixed with dry air. Meanwhile, the Pd‐PMMA bilayer on PDMS shows a high reflectance change over 22.7% at the whole visible band with the reflectance contrast more than 370% due to the light scattering on the wrinkling surface induced by the volume expansion of the Pd film on PDMS during hydrogenation. By setting the alarm threshold of the reflectance change of 4% at the 600‐nm wavelength, the response time of the sensor can be reduced to 1 second. This optical hydrogen sensor is low‐cost and easy‐operation with high optical contrast and fast response rate, showing great potential for practical applications.