Pt/Fe₂O₃ with Pt–Fe pair sites as a catalyst for oxygen reduction with ultralow Pt loading

Platinum is the archetypal electrocatalyst for oxygen reduction—a key reaction in fuel cells and zinc–air batteries. Although dispersing platinum as single atoms on a support is a promising way to minimize the amount required, catalytic activity and selectivity are often low due to unfavourable O₂ adsorption. Here we load platinum onto α-Fe₂O₃ to construct a highly active and stable catalyst with dispersed Pt–Fe pair sites. We propose that the Pt–Fe pair sites have partially occupied orbitals driven by strong electronic coupling, and can cooperatively adsorb O₂ and dissociate the O=O bond, whereas OH* can desorb from the platinum site. In alkaline conditions, the catalyst exhibits onset and half-wave potentials of 1.15 V and 1.05 V (versus the reversible hydrogen electrode), respectively, mass activity of 14.9 A mg⁻¹_Pt (at 0.95 V) and negligible activity decay after 50,000 cycles. It also shows better performance than 20% Pt/C in a zinc–air battery and H₂–O₂ fuel cell in terms of specific energy density and platinum utilization efficiency.