Design of SnPt/C cathode electrocatalysts with optimized Sn/Pt surface composition for potential use in Polymer Electrolyte Membrane Fuel Cells

Model Sn-Pt catalytic surfaces were prepared using electroless deposition of adsorbed tin atoms (via catalytic disproportion of Sn2+) onto smooth polycrystalline Pt disc to clarify the relationship between the Sn/Pt surface composition and the oxygen reduction reaction (ORR) activity. According to the optimization results the most promising surface Sn/Pt atomic ratio was ca. 1:3. Based on the ORR results obtained on model Sn-Pt catalytic surfaces alloy-type Sn-Pt/C catalysts with Sn/Pt 1:3, 1:2.5 and 1:2 ratios were prepared by Controlled Surface Reactions (CSRs). The selective incorporation of Sn onto Pt sites was achieved resulting in exclusive formation of Pt-Sn alloy phases without decoration of the support with tin species. According to the results the most promising surface Sn/Pt atomic ratio was observed on the SnPt(1:2.5)/C catalyst pre-treated in H-2 at 350 degrees C with the highest content of the fcc Pt3Sn alloy phase. The increased activity of the SnPt(1:2.5)/C catalyst in the ORR compared to the catalysts with Sn/Pt 1:3 and 1:2 ratios can be attributed to the optimal ratio between the interfacial surface sites with oxophilic and metallic chemical nature.

Automated summary

By preparing Sn-Pt catalytic surfaces using electroless deposition, it was found that a Sn/Pt atomic ratio of approximately 1:3 showed the most promising ORR activity. Alloy-type Sn-Pt/C catalysts prepared by CSR exhibited higher activity in the ORR, potentially due to the optimal ratio between oxygen-affine and metallic chemical sites.