Reliability of hydrogen sensing based on bimetallic Ni–Pd/graphene composites

Graphene-supported nickel–palladium (Ni–Pd) bimetallic nanoparticles (Ni–Pd/Gr) were synthesized using a simple chemical method, followed by a post-thermal annealing process. The characteristics of resistivity-type hydrogen (H2) sensors composed of Pd–Gr composites (with small amounts of Ni added to the Pd nanoparticles (Pd NPs)) were investigated in detail. Pd NPs with various amounts of Ni embedded into the Pd lattice were synthesized by varying the molar ratios of the Ni/Pd precursors. The results from this work indicate that the addition of Ni not only enhances performance, but also reduces the hysteresis behavior of the Pd–Gr composite based H2 sensors. H2 was detectable from 1 to 1000 ppm based on a rapid recovery response with suitable Ni/Pd percentages. At the optimal Ni/Pd percentage of 7% (Ni/Pd ∼7%), sensors showed a small enhancement of sensitivity, fast recovery, and minimum hysteresis effect. From our experiment, the addition of Ni to Pd NPs results in a reduction of the hysteresis effect and reliability on H2 sensors based on Pd–Gr composites.