Manganese-doped cobalt spinel oxide as bifunctional oxygen electrocatalyst toward high-stable rechargeable Zn-air battery

High-performance and low-cost bifunctional electrocatalysts for ORR and OER are urgently required for rechargeable Zn-air batteries. Herein, a series of Mn-doped Co3O4 nanoparticles grown on carbon nanotubes (Mn-Co3O4@CNTs) bifunctional electrocatalysts are designed. Owing to the moderate doped Mn atoms, the Mn-Co3O4 heightens ORR activity via the synergistic effect between Co and Mn atoms, and more Co3+ active sites are exposed on the surface of Mn-Co3O4 to enhance the OER rate. As a result, the 40% Mn-doped Mn-Co3O4@CNTs electrocatalyst exhibits higher ORR (E1/2 = 0.84 V) and OER (eta 10 = 356 mV at 10 mA cm-2) performance. More significantly, the Mn-Co3O4@CNTs equipped with rechargeable ZAB displays a high power density of 116 mW cm-2, a low charge-discharge voltage gap of 0.94 V at 10 mA cm-2, and superior cycling stability of over 425 h and 1200 cycles, being much more outperforming than Pt-and Ru-based ZABs.

Automated summary

A series of Mn-doped Co3O4 nanoparticles grown on carbon nanotubes (Mn-Co3O4@CNTs) bifunctional electrocatalysts are designed for rechargeable Zn-air batteries, aiming for high-performance and low-cost catalysts. The Mn-Co3O4 with moderate doping of Mn atoms exhibits enhanced ORR activity due to the synergistic effect between Co and Mn atoms, and more Co3+ active sites are exposed on the surface to enhance the OER rate. The Mn-Co3O4@CNTs catalyst with 40% Mn doping shows higher ORR and OER performance, and when applied in rechargeable ZAB, it demonstrates excellent power density, low charge-discharge voltage gap, and superior cycling stability compared to Pt-and Ru-based ZABs.