3D-nanoarchitectured Pd/Ni catalysts Prepared by atomic layer deposition for formic acid electrooxidation
Résumé
Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition
(ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an
acidic medium (0.5 M H2 SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously
monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy
and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni
and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orienta-
tion along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide
contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of
HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activi-
ties are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the
cluster size effect, electronic interactions between Pd and Ni, or diffusion effects.