Porous Co3O4 nanoplates as the active material for rechargeable Zn-air batteries with high energy efficiency and cycling stability

Efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for rechargeable Zn-air batteries. We report porous Co3O4 nanoplates with the average size and thickness of ∼100 and ∼20 nm, respectively, and a surface area of 98.65 m2 g−1. The mesoporous nanostructure shortens the lengths for ion/electron transport and provides abundant reaction sites. In the alkaline solution, the Co3O4 nanoplates exhibit a comparable limiting current density to that of Pt/C in the ORR and a superior activity in the OER. Redox reactions corresponding to the oxidation/reduction of cobalt species with a high pseudocapacitance and stability are observed, indicating the multifunctional properties. Using Co3O4 nanoplates in the air electrode, the Zn-air battery delivers a maximum power density of 59.7 mW cm−2. At a current density of 1 mA cm−2, a gravimetric energy density of 901.6 Wh kgZn−1 and an energy efficiency of 67.3% are achieved. Moreover, the voltage gaps between discharge and charge as well as the energy efficiency of 58% at 10 mA cm−2 are maintained for 100 cycles. The porous Co3O4 nanoplate is a promising active material for efficient Zn-air batteries with excellent cycling stability and high energy density.