Edgar Valenzuela

ABSTRACT Nowadays, one of the major issues of the PEMFC concerns the durability. Historically, carbon has been used as a catalyst support in PEMFC; nevertheless, under the environmental conditions of the cell, the carbon is oxidized, leaving the catalyst unsupported. In order to increase the stability and durability of the catalyst in the PEMFC, a novel nanostructured metallic oxide support is proposed. In this work, TiO2 was doped with Nb to obtain a material that combines chemical stability, high surface area, and an adequate electronic conductivity in order to be a successful catalyst support candidate for long-term PEMFC applications. The TiO2-Nb nanostructured catalyst support was physically and electrochemically characterized. According to the results, the TiO2-Nb offers high surface area and good particle dispersion; also, the electrochemical activity and stability of the support were evaluated under high potential conditions, where the TiO2-Nb proved to be much more stable than carbon.

The photocurrent response of TiO2 nanoparticles synthesized via the sol-gel process was studied in the presence of methanol, ethanol, and isopropanol. The nanocrystalline nature of photoelectrodes showed an important photocurrent in the presence of alcohol following the order: methanol ≈ ethanol > isopropanol > H2O. This process mimics the photoelectrochemical response and therefore a correlation of the photo-deposition process of platinum nanoclusters on TiO2 particles in the presence of alcohol molecules was devised. The photodeposition mechanism of platinum nano-islands at the surface of a nanocrystalline TiO2 powder is discussed in the light of the photoelectrochemical results.