Increasing the Efficiency of Gold-Ceria Catalyst for the Massive Production of Hydrogen

摘要

We have studied the adsorption of molecular water at the (111) surface of cerium dioxide (CeO2) singe crystals by means of atomic force microscopy (AFM) working with atomic resolution. Our AFM data reveal that single molecular water does not dissociate upon adsorption at the bare CeO2(111) surface, but it remains stably adsorbed at the surface over the temperature rage in which we have performed this study (300K to 10K). We have been able to manipulate individual water molecules with the tip of the AFM and positioning them at will on the CeO2(111) surface. By using this technique, we have studied the interaction between individual water molecules and surface oxygen vacancies, finding a considerable energy barrier for individual water molecules to enter into oxygen vacancies. We have also deposited atomic gold on the CeO2(111) surface and studied this system with AFM. Deposition of atomic Au over the CeO2(111) surface at a 77K temperature yielded to the formation of small clusters of Au atoms sparsely distributed on the surface and nucleated over intrinsic defect of the surface as well as at kink positions at the step edges. By using atom manipulation techniques, we produced and investigated the selective dissociation of water molecules over Au clusters deposited over the CeO2(111) surface. The elucidation of the atomistic mechanism for the selective dissociation of molecular water is pending of corroboration of our experimental observations by first principle simulations that are currently carrying out our collaborators.