Preparation, testing and modeling of three-dimensionally ordered catalytic layers for electrocatalysis of fuel cell reactions

The arrays of vertically aligned carbon nano-filaments (VACNF) were synthesized by catalytic chemical vapor deposition on TiOx substrates, obtained via oxidative treatment of polycrystalline Ti and Ti thin films on Si(1 0 0). VACNF were studied using scanning and transmission electron microscopies. The Pt deposition on VACNF was utilized to prepare a set of model catalysts, which were investigated in two fuel cell related reactions: the oxygen reduction (ORR) and the hydrogen oxidation (HOR) reactions. The experimental data were compared with the results of mathematical modeling performed for a fast (quasi)reversible and a slow irreversible electrochemical reaction. The approach made it possible to study electrochemical reactions (HOR, ORR) on nano-materials under well defined mass transport conditions. The influence of the catalytic layer thickness and the Pt coverage on the penetration depth of the reactive species inside the layer and consequently on the performance and on the Pt effectiveness factor were analyzed.