Photopyroelectric Pd-PVDF hydrogen sensor

A novel hydrogen sensor made of thin, commercially available polyvinylidene difluoride (PVDF) pyroelectric film sputter-coated with palladium (Pd) is described. An infrared laser beam, produced by an infrared (ca. 800-nm) semiconductor laser, created alternating temperature gradients on the Pd-PVDF and on reference Ni-Al-PVDF films which, in turn, generated AC voltages due to the photopyroelectric effect. Exposure to hydrogen gas produces an increased differential signal between the Pd and reference electrodes; this is tentatively attributed to the adsorption and dissociation of hydrogen molecules on the Pd surface, which caused a shift on the Pd-PVDF pyroelectric coefficient, due to interactions at the Pd-PVDF interface. The differential signal has been found to follow a Langmuir isotherm in the range of 4 to 200 Pa. Other characteristics such as the response time, the reversibility, and the durability of the photopyroelectric sensor also are studied