Pd–Ni hydrogen sponge for highly sensitive nanogap-based hydrogen sensors

We have successfully fabricated sub-100 nm nanogaps in Pd–Ni alloy thin films on an elastomeric substrate by simple stretching. The nanogaps-containing Pd–Ni films were utilized as hydrogen-sensing sponges and their performance was demonstrated to dominate over the performance of similar mobile thin films comprised of pure Pd in major aspects such as the response time, sensitivity in high H2 concentrations, and H2 detection limit. Notably, Pd87.5Ni12.5 hydrogen sensing sponges showed ultra-high sensitive and reversible On-Off behaviors and low detection limit of ∼100 ppm, which were attributed to the reduced nanogap width and the enhanced volume expandability of Pd–Ni lattice. The effects of Ni added to Pd and a search for an optimum Ni concentration were also systematically studied.

► Alloying Pd with Ni causes both the reduction of nanogap width and the increase of film expandability. ► The gaps can be closed even at low H2 concentrations. ► PdNi nanogap-based sensor enhances the H2 detection discernibility. ► The sensors enable a linear response behavior over broad H2 concentrations. ► An optimum Ni concentration in Pd–Ni alloys was determined.