Ultra-durable two-electrode Zn–air secondary batteries based on bifunctional titania nanocatalysts: a Co2+ dopant boosts the electrochemical activity

Abstract

High energy density, low cost and ultra-stable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are important for commercializing the rechargeable Zn–air batteries. Co-doped TiO₂ nanoparticles as an ultra-stable and cheap electrocatalyst exhibited excellent activity for both ORR and OER in alkaline media. A real air cathode made of the Co-doped TiO₂ electrocatalyst further offered superior high energy density (778 mA h g_Zn⁻¹ and 938.5 W h kg_Zn⁻¹ at 5 mA cm⁻², and 785.9 mA h g_Zn⁻¹ and 911.3 W h kg_Zn⁻¹ at 20 mA cm⁻²) and ultra-high stability (37 cycles for 750 h of operation at 20 mA cm⁻² and 3150 cycles for 1050 h of operation at 5 mA cm⁻²) in two-electrode Zn–air batteries.