Morphological engineering of 3D hollow urchin-like MnO2 spheres as bifunctional oxygen electrocatalyst for zinc-air batteries

Favorable stability and cost-efficient bifunctional catalysts are highly desirable for rechargeable zinc-air batteries. alpha-MnO2 has been considered a promising candidate with moderate electrochemical performance. Morphological engineering offers a feasible approach to further optimize the intrinsic and specific activities of alpha-MnO2. Herein, three-dimensional hollow Urchin-like alpha-MnO2 microspheres (denoted as the hollow alpha-MnO2) were successfully prepared by a facile hydrothermal reaction. The unique structure endows alpha-MnO2 with abundant accessible active sites and enhanced intrinsic activity. Profited from surface reconstruction, abundant oxygen vacancies were created and maintained high activity during electrocatalytic processes. As a result, the hollow alpha-MnO2 displays excellent oxygen reduction reaction activity with the half-wave potential at 0.80 V versus reversible hydrogen electrode (vs RHE), oxygen evolution reaction with an overpotential of 465 mV to reach the current density of 10 mA.cm(-2), and remarkable rechargeable zinc-air battery performance with an open-circuit voltage of 1.48 V and a higher power density of 110.9 mW cm(-2) at 0.64 V (vs zinc).

Automated summary

In this study, hollow alpha-MnO2 catalysts with abundant accessible active sites and enhanced intrinsic activity were successfully prepared and showed excellent electrocatalytic performance in rechargeable zinc-air batteries.