Turning seawater chloride ion from corrosion agent to OER accelerator and stabilizer via oxygen vacancy engineering and application in zinc-air seawater batteries

Zinc-air seawater batteries (ZASBs) are a promising seawater battery technology owing to their high energy density, eco-friendly nature, and low cost. However, their performance is limited by slow oxygen evolution reaction (OER) and rapid OER electrocatalyst deactivation due to Cl − corrosion. Here, we propose an innovative oxygen vacancy strategy that not only avoids the Cl − corrosion but also exploits Cl − as the OER accelerator and catalyst protector. Specifically, oxygen vacancies are introduced into NiFe 2 O 4 via in-situ grown on self-supported carbon substrates. Oxygen vacancies enhance Cl − adsorption to form Cl − -O V -NiFe 2 O 4 , as evidenced by density functional theory (DFT) calculations. This synergistic interaction enables superior OER activity with a low overpotential of 285 ​mV at 100 ​mA ​cm −2 in alkaline seawater, while pristine NiFe 2 O 4 cannot reach this current density threshold. Moreover, oxygen vacancies (O V ) with Cl − adsorption stabilize spinel structure and prevent the leaching of Fe active sites, ensuring long-lasting high catalytic performance for over 300 ​h. Consequently, owing to the Cl − -O V -NiFe 2 O 4 catalyst, the ZASB achieves a long lifespan exceeding 400 cycles, which is 45 times that of pristine NiFe 2 O 4 (9 cycles). The proposed oxygen vacancy strategy not only promotes the practical application of ZASBs but also provides insights for advancing seawater battery technologies.