PROCESOS DE FORMACIÓN DE NANOESTRUCTURAS METÁLICAS CON APLICACIÓN TECNOLÓGICA

RUBÉN E. AMBRUSI

SAM

Asociación Argentina de Materiales

Año: 2017

1668-4788

Inthe present work the study of the electrochemical formation process andcharacterization of nanostructures composed by one and two metals, withpotential electrocatalytic properties for the reduction reaction of nitrateions, was performed. The studied systems were structures composed of Ag, Cd andCd/Ag supported on HOPG and VC carbon substrates. In this sense, conventionalelectrochemical methods together with surface characterization techniques, suchas ex-situ STM and AFM microscopy, SEM and XPS, were used. The nucleation andgrowth kinetics of Ag nanocrystals on HOPG and VC were analyzed. The metals electrochemicaldeposits on HOPG and VC electrodes from acidic aqueous solutions containingsalts of the metals were characterized by ex-situ AFM, analyzing theirmorphology, size and distribution. In the case of the HOPG substrate, suitableexperimental conditions were also obtained for the formation of one-dimensionalstructures (nano-wires) on the step edges of the HOPG, reducing the deposits onthe terraces, being characterized by SEM. Cd underpotential deposition (UPD) onAg nanoparticles was studied in order to adjust the polarization time andpotential conditions to obtain bimetallic Ag-Cd particles on both carbonaceoussubstrates. The alloying process between both metals was evaluatedelectrochemically, verifying the formation of alloyed phases during deposition ofCd on the Ag nanoparticles, further corroborated by measurements of XPS. Finally,the potential electrocatalytic properties of the obtained deposits wereexamined for the reduction reaction of nitrate ions showing a synergisticeffect of Ag and Cd on this reaction in the case of bimetallic particles. Onthe other hand, a theoretical study was carried out by computationalsimulation, using DFT (Functional Density Theory), determining the mostfavorable adsorption sites for Ag deposition on a stepped surface of HOPG,being inferred with high feasibility the formation of one-dimensional Agstructures on the stepped graphite surface. We also analyzed the interactionsbetween Ag and Cd, showing that energetically alloyed structures of thesemetals are more stable than other structures such as Cd adatoms or single-layerson the Ag surface.