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 similar to 100 and similar to 20 nm, respectively, and a surface area of 98.65 m(2) g(-1). The mesoporous nano structure 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 kg(Zn)(-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. (C) 2018 Elsevier Ltd. All rights reserved.