A Ppb-level hydrogen sensor based on activated Pd nanoparticles loaded on oxidized nickel foam

•Novel H2 sensor based on Pd nanoparticles loaded on oxidized Ni foam is fabricated.•Ppb-level H2 can be stably detected by the sensor activated by 4 % H2 treatment.•The activated mechanism of the sensor is proposed firstly and analyzed innovatively.•H2 with a large concentration range (7 ppb-2 %) can be detected by the sensor at 30 °C.•It has high cycling stability, humidity stability and selectivity, and is suitable for RT. A novel hydrogen sensor with ppb-level detection limit was fabricated in this work. The oxidized Ni foam was chosen as the substrate, whose 3D porous structure contributed to gas circulation, and insulating NiO nanowrinkles provided a large specific surface area. Pd nanoparticles as hydrogen sensing material were loaded on it by magnetron sputtering. Unprecedentedly, the incompletely reversible lattice distortion caused by the generation of Pd-H β-phase was applied to activate the hydrogen sensor, which significantly improved the response to low concentration H2. The activation mechanism was proposed firstly and analyzed innovatively. Therefore, hydrogen with a large concentration range (7 ppb ∼ 2 %) can be detected by the prepared sensor, and the response changes regularly as H2 concentration changes. The optimum temperature of the sensor is 30 °C, and it exhibits high cycling stability, humidity stability and gas selectivity. This work provides a brand new strategy for the development of low detection limit hydrogen sensors.