Compressively Strained Fe₃O₄ in Core—Shell Oxygen Reduction Electrocatalyst Boosts Zinc—Air Battery Performance

Abstract Fe₃O₄ is barely taken into account as an electrocatalyst for oxygen reduction reaction (ORR), an important reaction for metal—air batteries and fuel cells, due to its sluggish catalytic kinetics and poor electron conductivity. Herein, how strain engineering can be employed to regulate the local electronic structure of Fe₃O₄ for high ORR activity is reported. Compressively strained Fe₃O₄ shells with 2.0% shortened Fe─O bond are gained on the Fe/Fe₄N cores as a result of lattice mismatch at the interface. A downshift of the d‐band center occurs for compressed Fe₃O₄, leading to weakened chemisorption energy of oxygenated intermediates, and lower reaction overpotential. The compressed Fe₃O₄ exhibits greatly enhanced electrocatalytic ORR activity with a kinetic current density of 27 times higher than that of pristine one at 0.80 V (vs reversible hydrogen electrode), as well as potential application in zinc‐air batteries. The findings provide a new strategy for tuning electronic structures and improving the catalytic activity of other metal catalysts.