Departamento de Química y Física

Platinum was electrodeposited onto Y-zeolite and Y-zeolite(Y)/Vulcan XC-72R(V) to produce Pt/Y/V and Pt/Y catalysts using a rotating disk slurry electrode technique. The activities of the two catalysts were measured towards methanol electro-oxidation in alkaline media by cyclic voltammetry and chronoamperometry. The materials were examined using electron microscopy. The results were compared to those obtained on commercial catalysts. Pt/Y/V (with 14 wt.% Pt) catalyst was the most active, even so more than a commercial Pt/V catalyst with 20 wt. % Pt. The Pt/Y/V catalysts contained Pt nanoparticles and tetrahedron, likely a consequence of the nucleation and growth within the zeolite framework.

The catalytic performance of nanoparticles can be tuned either by their composition, which mediates electronic structure, or by shape. The shape of a particle is determined by the surface atomic arrangement and coordination. This is affected by the chosen route to synthesize the particle. The route we employed for treating Pt nanoparticles through the application of a square-wave potential is presented. This treatment enhanced the ammonia oxidation stability at platinum modified boron-doped diamond electrodes. Starting from Pt nanoparticles electrodeposited on diamond substrate instead of bulk Pt, we obtained tetrahexahedral Pt nanoparticles. SEM images showed platinum particles with an irregular shape, close to it several regular sharp shaped platinum particles with a size regime of tenths (100-10 nm) of nanometers. Skeleton type particles appear to be the remains of the precursor platinum particles after the square wave treatment breaks down the platinum particles. Platinum featur...

The ammonia oxidation reaction has been a topic of interest due to its possible use as a fuel in alkaline fuel cell systems. This may play a role on wastewater treatment for a stand-alone purification device. Nevertheless, the oxidation of ammonia is a complex surface process that needs catalyst development and synthesis. The Pt (100) facet has shown to be the most active catalyst surface and tailored synthesis of Pt nanocubes has been presented. An effort has been developed to transform Pt nanoparticles to nanocubes by square wave voltammetry at boron doped diamond electrodes. It is an electrochemical route for the synthesis of shape control platinum particles. During square wave voltammetry, a periodic oxidation and reduction of platinum occurs at the surface of the boron doped diamond electrode. The parameters and electrolytes used during this treatment determine the final platinum nanoparticle structure. In this work, platinum structure previously electrodeposited on boron doped diamond electrodes were modified using square wave voltammetry in ascorbic acid and acetone in a sulfuric acid solution, respectively, as electrolyte during the treatment. Three duration time of square wave voltammetry were used. The Pt nanoparticle modified boron doped diamond electrodes were characterized by cyclic voltammetry, scanning electron microscopy and were tested for the ammonia oxidation reaction. Nanoparticles were restructured to nanocubes by 10 min of square wave voltammetry treatment in ascorbic acid solution. The peak current densities for the ammonia oxidation reaction increased ca. 80%, 15% and 20% for 30, 15, and 10 min treatments, respectively. On the other hand, different platinum nanostructures were generated using acetone during square wave voltammetry treatment.

This paper evaluates whether public support from innovation from the central government or the European Union spurs innovation in Austrian firms. The effect is estimated separately on R&D expenditures and the output side of innovation, measured by the share of total sales due to new or substantially modified products. A distinction is also made between products new to the firm and products new to the market. The analysis is based on the micro data from the third wave of Community Innovation Survey, CIS 3, covering the years 1998-2000. The effectiveness is estimated using a structural model explaining the determinants of various sources of government support and their effects on R&D and innovation output. Receiving central government support increases the intensity of R&D by 2.3 percentage points. EU support is never significant once national support is taken into account. Central government support yields a 2.5 percentage point increase in the share of new to firm innovative sales. When new to market product innovations are considered, central government support leads to a total effect on the share of new to market innovative sales of 3.4 percentage points.