Oxygen Spillover Effect at Cu/Fe₂O₃ Heterointerfaces to Enhance Oxygen Electrocatalytic Reactions for Rechargeable Zn–Air Batteries

Rational design and synthesis of high-performance electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are critical for practical application of Zn–air batteries (ZABs). In this work, the bifunctional composite Cu–Fe2O3/PNC was prepared by a simple and effective wet-hydrothermal coupled dry-annealing synthesis strategy. The Cu–Fe2O3/PNC displayed excellent catalytic activity in ORR and OER with a potential difference of 0.63 V. More importantly, the ZAB assembled with Cu–Fe2O3/PNC exhibited a high-power density of 138.00 mW cm–2 and an excellent long-term cyclability. X-ray photoelectron spectroscopy (XPS) demonstrated that the excellent performance is due to the strong electronic interaction between Cu and Fe2O3 that arises as a result of the fast electron transfer through the Cu–O–Fe bond and the higher concentration of surface oxygen vacancies. Meanwhile, the spillover factor Bsp/2zF of Cu/PNC and Cu–Fe2O3/PNC obtained by the rotating disk experiment was 1.00 × 10–7 and 1.10 × 10–7 cm2·s–1, respectively, indicating that the oxygen spillover effect between Cu and Fe2O3 lowers the energy barrier, increases the number of active sites, and alters the rate-determining reaction step. This work demonstrated the significant potential of Cu–Fe2O3/PNC in energy conversion and storage applications, providing a new perspective for the rational design of bifunctional electrocatalysts.