For wide application of metal-air batteries, the key factor is the development of catalysts for air cathodes. In the present study, PdCo/C bimetallic nanocatalysts are prepared by a facile borohydride reduction method. To improve the activity and stability, the catalysts are heat-treated at 200 degrees C in H-2/Ar atmosphere from 4 h to 24 h. The optimal heat treatment time is found to be 8 h, at which the highest activity for both oxygen reduction reaction and oxygen evolution reaction is obtained. With the 8 h heat-treated PdCo/C catalyst, the rechargeable zinc-air battery exhibits a high power density of 180 mW cm(-2) and retains stability for more than 50 h at a discharge-charge current density of 10 mA cm(-2), while the magnesium-air battery obtains a power density of more than 200 mW cm(-2) and remains stable within 8 h at a discharge current density of 65 mA cm(-2). (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.