Three-Dimensional-Order Macroporous AB2O4 Spinels (A, B =Co and Mn) as Electrodes in Zn-Air Batteries.

In this work, atomically substituted three-dimensionally ordered macroporous (3DOM) spinels based on Co and Mn (MnCo2O4 and CoMn2O4) were synthetized and used as cathodic electrocatalysts in a primary Zn-air battery. Scanning/transmission electron microscopy images show a 3DOM structure for both materials. Skeleton sizes of 114.4 and 140.8 nm and surface areas of 65.3 and 74.6 m2 g-1 were found for MnCo2O4 and CoMn2O4, respectively. The increase in surface area and higher presence of Mn3+ and Mn4+ species in the CoMn2O4 3DOM material improved battery performance with a maximum power density of 101.6 mW cm-2 and a specific capacity of 1440 mA h g-1, which shows the highest battery performance reported to date using similar spinel materials. The stability performance of the electrocatalyst was evaluated in half-cell and battery cell systems, showing the higher durability of CoMn2O4, which was related to its better capability to perform the electrocatalytic process as adsorption, electron transfer, and desorption. It was found through density functional theory calculations that the CoMn2O4 spinel has a higher density of states in the Fermi level vicinity and better conductivity. Finally, the unique shape of 3DOM spinels promoted a high interaction between electroactive species and catalytic sites, making them suitable for oxygen reduction reaction applications.