First insight into fluorinated Pt/carbon aerogels as more corrosion-resistant electrocatalysts for Proton Exchange Membrane Fuel Cells Cathodes
Résumé
Proton exchange membrane fuel cells (PEMFC) are devices that convert chemical energy into electricity in a clean and efficient manner. They can be used in automotive, nomad, or stationary applications without emission of pollutants (neither gas nor particles).After several decades of scientific and technological improvements, the PEMFC technology is now mature and starts to be deployed on the field, but some drawbacks must be overcome; in particular, their durability in operation must be increased. The durability strongly depends on the technical choice of the PEMFC manufacturer (bipolar plates, membrane, and quality of the hydrogen) but also especially the resistance to degradation of the carbon support and the catalyst and the water management. This study evaluates the fluorination of a carbon aerogel and gives first insights into its durability when used as platinum electrocata-lyst substrate for proton exchange membrane fuel cell (PEMFC) cathodes. Fluorine has been introduced before or after platinum deposition (Figure 1). The different electrocatalysts are physico-chemically and electrochemically char-acterized, and the results discussed by compari-son with commercial Pt/XC72 from E-Tek. The results demonstrate that the level of fluori-nation of the carbon aerogel can be controlled. The fluorination modifies the texture of the carbons by increasing the pore size and decreasing the specific surface area, but the textures remain appropriate for PEMFC applications. Two fluorination sites are observed, leading to both high covalent C-F bonds and weakened ones, the quantity of which depends on whether the treatment is done before or after platinum deposition. The order of the different treatments is very important. Indeed, the presence of platinum contributes to the fluorination mechanism, but leads to amorphous platinum, which is demonstrated rather inactive towards the oxygen reduction reaction. On the contrary, a better durability was demonstrated for the fluorinated and then platinized catalyst compared both to the same but not fluorinated catalyst and to the reference commercial material (based on the loss of the electrochemical real surface area after accele-rated stress tests).