Palladium based sensing

Technology Approaches to Palladium-Based Hydrogen Detection and Sensing... 

Maier R, Jones B, Barton J, McCullocj S, Allsop T, Jones J, Bennion I (2007) Fibre optics in palladium-based hydrogen sensing. J Opt A Fhue Appl Opt 9 S45-S49... 

The design of the Pd-membrane reactor was based on the chip design of reactor [R 10]. The membrane is a composite of three layers, silicon nitride, silicon oxide and palladium. The first two layers are perforated and function as structural support for the latter. They serve also for electrical insulation of the Pd film from the integrated temperature-sensing and heater element. The latter is needed to set the temperature as one parameter that determines the hydrogen flow. 

R(200 ppm of alcohol vapor in air) are 50 and 140 for tin oxide (Sn0x) and palladium-gold/SnOx (PdAu/SnOx) sensors, respectively while the values of R(50 ppm of N0X in air)/R(air) are 60 and 5 for SnOx and PdAu/SnOx sensors, respectively. Possible sensing mechanisms based on XPS, Kelvin probe, Hall and electrical conductivity measurements are also discussed. 

Hydrogen detection. Detection of hydrogen (H2) is based on its high solubility in palladium. H2-induced lattice expansion of Pd causes the latter to swell, changes its conductivity and refractive index. The swelling effect can be sensed with FBGs in strain sensing mode. 

The selection of a noble metallic material as the sensing element of a microfabricated electrochemical sensor is based on the catalytic and electrochemical properties of the metal. As mentioned, platinum, gold, and silver are often the metallic materials of choice. Palladium, iridium, and rhodium have also been used as electrochemical sensing elements. 

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