Sb-Doped SnO2 Hollow Spheres Offering Micro- and Nanoporosity in Fuel Cell Electrode Structures

Sb‐doped SnO2 (ATO) is used as an alternative support material to replace carbon in the highly corrosive environment of a fuel cell cathode. Two ATO powders with different morphologies are decorated with Pt nanoparticles and afterwards used as the cathode catalyst. The commercial ATO powder exhibits crystallites in the nanometer range, while the home‐made ATO powder, which was synthesized by ultrasonic spray pyrolysis, consists of polycrystalline hollow spheres. The spheres have diameters in the micrometer range and are composed of individual nanocrystallites. The unusual morphology of the home‐made ATO offers nano‐ and microporosity at the same time and opens up new possibilities for the controlled design of electrode structures in low‐temperature polymer electrolyte fuel cells. Both materials are characterized by XRD, SEM, and TEM and tested in a single cell set‐up. While almost no current is gained from the membrane electrode assembly with the commercial ATO support, the cell with the home‐made ATO achieves a mediocre performance. This higher activity, however, is obtained with approximately half the Pt content compared to the catalyst with the commercial support. The different behaviours of both ATO powders can therefore mainly be attributed to differences in the specific support morphology. Sb‐doped SnO2 (ATO) with a novel hollow sphere morphology can be synthesized by ultrasonic spray pyrolysis and used as an alternative support material in fuel cell cathodes. The unique morphology leads to a porous electrode structure with a controlled nanoscale and microscale porosity. This structure offers efficient mass transport and is believed to prevent the collapse of the electrode structure during operation.