Fast and reversible hydrogen sensing properties of Pd-capped Mg ultra-thin films modified by hydrophobic alumina substrates

•Quantum size Pd-capped Mg bimetallic nanoparticles were deposited on alumina substrate as an ultra-thin film manner by RF magnetron sputtering system.•Computational analysis of bimetallic nanoparticles/ultra-thin films for hydrogen sensing.•Feasibility of H2 sensing properties is investigated.•The mechanism for H2 response was described by diffusion pathway.

This work reports on the hydrogen sensing abilities of palladium (Pd)-capped magnesium (Mg) bimetallic ultra-thin films, which were prepared by RF magnetron sputtering. The metal loading and the composition of the quantum-sized Pd-capped Mg nanoparticles (NPs) were carefully controlled by varying the deposition conditions of the RF magnetron sputtering system. The as-fabricated structure shows hydrogenation at room temperature and dehydrogenation at increased temperatures. The change in electrical resistance during the hydrogenation/dehydrogenation process is found to be reversible. Along with this, the as-fabricated sensor also showed remarkable advantages, such as a large detection range (1-40,000 ppm) and fast response time. For a 10,000 ppm (1 vol.%) H2 concentration at room temperature, a response time of 6 s was observed. The fabricated sensor also exhibited good selectivity and a negligible humidity effect over the entire detection range. These Pd-capped Mg bimetallic ultra-thin films deposited on alumina (Al2O3) substrates can be used as a fast response, affordable, and low-temperature hydrogen sensing material.