Sensing hydrogen in the gas phase using ferromagnetic Pd–Co films

•The applicability of ferromagnetic Pd–Co film as hydrogen sensing device is demonstrated.•The magnetic susceptibility of Pd–Co film depends on the H2 concentration in gas phase.•The measurable H2 concentration is confirmed as the range from 9.1 vol% to 0.2 vol%.•The oxygen in air affects the hydrogen sensing properties.

It is demonstrated that Pd–Co films can be used to sense the hydrogen concentration in the gas phase using the changes in the magnetic susceptibility, caused by the hydrogen uptake at ambient temperature. The induced voltage, which is proportional to the magnetic susceptibility of the Pd–Co films, was changed by the hydrogen concentration under the flow of the hydrogen/nitrogen mixture, and saturated under a constant flow. The saturated value of the induced voltage decreased with the hydrogen concentration in the gas phase and the change in the induced voltage was detected at a hydrogen concentration of 0.2 vol%. Under the flow of dry air, the induced voltage also reacted to hydrogen. However, the induced voltage did not have a clear change under a hydrogen concentration of 0.2 vol% in dry air. Moreover, the response time it took to reach saturation, from the injection of hydrogen, was slower than that under a hydrogen/nitrogen mixture. This behavior was likely caused by the water-forming reactions, hindering the absorption of hydrogen in the Pd–Co films in the presence of oxygen.