Fe–Sn–N–C Catalysts: Advancing Oxygen Reduction Reaction Performance
Julia Buschermöhle, Julia Müller‐Hülstede, Henrike Schmies, Dana Schonvogel, Tanja Zierdt, Rene Lucka, Franz Renz, Peter Wagner, Michael Wark
Abstract
High Resolution Image Download MS PowerPoint Slide High-temperature proton exchange membrane fuel cells (HT-PEMFCs) typically rely on platinum-based catalysts, which require high loadings due to Pt deactivation by phosphates from the phosphoric acid-doped membrane. As alternative catalysts for the oxygen reduction reaction, metal–nitrogen-carbons (M–N–Cs) are promising due to their high intrinsic activity and tolerance to phosphates. However, low volumetric activity compared to Pt nanoparticles on carbon blacks (Pt/C) and insufficient stability limit their applicability. In order to enhance the stability and activity of Fe–N–Cs, this study investigates the incorporation of tin as a second metal, resulting in Fe–Sn–N–Cs, prepared by a metal–organic framework (MOF)-based approach. Stable and highly active catalysts with total mass activities of 8.2 A g –1 (Fe–Sn–N–C (1:1)) and 19.3 A g –1 (Fe–Sn–N–C (1:0.3)) in 0.5 mol L –1 H 3 PO 4, drastically exceeding those of the commercial Fe–N–C catalyst PMF-014401 (Pajarito-Powder, 4.8 A g –1 ), are obtained by a synthesis without the need for subsequent purification steps. A stress test under harsh conditions (0.6–1.0 V RHE, 10,000 cycles, O 2 -saturated electrolyte) ascertains stability-enhancing effects of tin, highlighting an increase in stability in conjunction with the tin content. These results provide a valuable contribution to the development of cost-effective HT-PEMFCs by significantly enhancing the catalytic activity of platinum group metal-free catalysts.