TEM–XRD analysis of PdO particles on TiO2 support for chemochromic detection of hydrogen

Safety is always a concern in all applications that utilize hydrogen (H2) in one form or another. Hydrogen leaks are invisible and odorless. In addition, blending odorants or additives into hydrogen in a manner similar to natural gas is generally undesirable for certain applications, including proton exchange membrane fuel cells. To facilitate detection of the location of hydrogen leaks, a special nonreversible chemochromic H2 sensing material that employs titania (TiO2) supported palladium oxide (PdO) pigments encapsulated within a special silicone matrix has been developed at the Florida Solar Energy Center (FSEC) and field tested at National Aeronautics and Space Administration, Kennedy Space Center. Several batches of PdO hydrogen gas sensing pigments were synthesized using various TiO2 supports, and their hydrogen detection activity was determined. TEM and particle size distribution analysis showed that smaller particles with a hemispherical, crystalline structure produced faster coloration kinetics when exposed to H2 gas. However, agglomerated PdO particles on the TiO2 surface displayed greater color contrast. XRD analysis indicated that the crystalline phase of TiO2 had no effect on the chemochromic performance of the pigments in a laboratory environment.