Molecular Iron Oxide Clusters Boost the Oxygen Reduction Reaction of Platinum Electrocatalysts at Near-Neutral pH

The oxygen reduction reaction (ORR) is a key energy conversion process, which is critical for the efficient operation of fuel cells and metal-air batteries. Here, we report the significant enhancement of the ORR-performance of commercial platinum-on-carbon electrocatalysts when operated in aqueous electrolyte solutions (pH 5.6), containing the polyoxoanion [Fe₂₈ (μ₃ -O)₈ (L-(-)-tart)₁₆ (CH₃ COO)₂₄ ]^20- . Mechanistic studies provide initial insights into the performance-improving role of the iron oxide cluster during ORR. Technological deployment of the system is demonstrated by incorporation into a direct formate microfluidic fuel cell (DFMFC), where major performance increases are observed when compared with reference electrolytes. The study provides the first examples of iron oxide clusters in electrochemical energy conversion and storage.