Scalable gas diffusion electrodes doped with Sn²⁺ as a radical scavenger for durability enhancement of low-temperature PEMFCs

Presence of Sn²⁺ in the anode catalyst layer of a polymer electrolyte membrane fuel cell (PEMFC) was investigated in terms of its effects on the electrode performance and durability. Incorporation of Sn²⁺ in the anode catalyst layer was realized through a scalable route by direct addition of SnSO₄ in the catalyst inks to achieve various SnSO₄ loadings of 0, 2, 4 and 8 wt% of the solid content. Durability of the electrodes was accessed both through (i) an accelerated stress test (AST) in a liquid cell using a three-electrode configuration and (ii) a durability study of a single PEMFC consisting of the SnSO₄ containing anodes in the membrane electrode assembly (MEA). For the durability studies, SnSO₄ containing electrodes showed high durability, minor change in the catalyst crystallite size, and high retention of platinum (Pt) on the electrode during the AST. Interestingly, XPS analysis of the pre-AST and post-AST samples showed a low degradation of the perfluorosulfonic acid ionomer (-SO₃H group). Further, the interaction between Sn and Pt was observed, suggesting Sn sites act as the active nucleation centers for the redeposition of the Pt dissolved during AST. The simple precursor mixing method enables easy optimization and control of the dopant quantity in the catalyst layer. The approach may be adopted industrially as a scalable method to effectively enhance the low-temperature PEMFC durability.