AFM studies of the catalytic reaction of hydrogen with oxygen on thin Pd and Pt films under pressure ∼101 kPa

Surface phenomena arising on thin Pt and Pd films in the course of the catalytic reaction of hydrogen with oxygen in the flow reactor at 298 K, under pressure similar to101 kPa were studied by atomic force microscopy (AFM). It is known that H, interaction with Pd leads to palladium hydride formation (equilibrium pressure similar to1 kPa at 298 K) while Pt does not form hydrides. H-2 interaction with Pd films of average thickness 50-100 nm resulted in the drastic change of the surface corrugation. Local characteristic structures arose, several hundred nanometer high. Replacing H-2 with Ar restored the original Pd surface. We suggest that this phenomenon is evidence for PdHx formation around specific defects. This is associated with the creation of stresses and followed by the uphill diffusion of hydrogen into the reverse side of the film. Hydrogen interaction with oxygen on Pd and Pt films led to multilayer deposit of water detected by AFM as the apparent rectangular shape of the film grains. (C) 2002 Elsevier Science B.V. All rights reserved.