Carbon aerogels coated with tin dioxide as catalyst supports for proton exchange membrane fuel cells
Résumé
Proton exchange membrane fuel cells (PEMFC) are energy converters that can be used for nomad, automotive or stationary applications without emission of pollutants. This technology is already used but some drawbacks, such as durability, must be overcome to enable large-scale deployment. The insufficient durability is strongly linked to the corrosion of the carbon support in the cathode [1] so studies have been done on alternative materials. Metal oxides are known to be stable in fuel cell working conditions but they are semiconductors. In this work, we synthesized a composite material associating the conductivity and the texture of carbon aerogel to the stability of metal oxide by coating the surface of aerogel with tin dioxide. Thanks to their high specific areas and their controlled pore size distributions, carbon aerogels as catalyst support favor dispersion of catalyst nanoparticles and decrease the gas diffusion losses (better water management). Carbon aerogel was prepared by mixing resorcinol and formaldehyde with Na2CO3 in water [2]. The gel was supercritically dried (CO2) and pyrolysis (1050°C, N2). Grinded carbon aerogel was mixed with SnCl2.2H2O and HCl in ultrapure water to obtain SnO2 deposit. A study of the reaction parameters (mixing time, pH, and quantity of precursor) was performed in order to optimize the coating. The raw material and the SnO2/carbon aerogel samples were physically and chemically characterized (XRD, SEM, EDX, nitrogen sorption, TGA and electric conductivity). Nanoparticles of platinum were deposited on the bare and the coated samples. The results are discussed and compared to the PEMFC electrocatalyst specifications. [1] J. Wu et al., J. Power Sources, vol. 184, no 1, p. 104‑119, (2008). [2] Ouattara-Brigaudet et al, Int. J. Hydrogen Energy 37, 9742-9757 (2012)