Facile synthesis of hierarchical porous Co3O4 nanoboxes as efficient cathode catalysts for Li–O2 batteries

Abstract

Rechargeable Li–O₂ batteries with remarkably high theoretical energy densities have attracted extensive attention. However, to enable Li–O₂ batteries for practical applications, numerous challenges need to be overcome, e.g. high overpotential, low rate capability, and poor cycling stability. The key factor to tackle these issues is to develop highly-efficient cathode catalysts. Moreover, cathode catalysts with a porous structure and large surface area are favorable in Li–O₂ batteries. In this paper, hierarchical porous Co₃O₄ nanoboxes with well-defined interior voids, functional shells and a large surface area have been facilely synthesized via an ion exchange reaction between Prussian blue analogue nanocubic precursors and OH⁻ at a low temperature (60 °C). The obtained products possess hierarchical pore sizes and an extremely large surface area (272.5 m² g⁻¹), which provide more catalytically active sites to promote the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as a Li–O₂ battery cathode, as well as facilitating the diffusion of oxygen and the electrolyte. The hierarchical porous Co₃O₄ nanobox cathode shows enhanced discharge capacity, reduced overpotential, improved rate performance and cycle stability, in comparison with the EC-300J carbon cathode. The superb performance of the hierarchical porous Co₃O₄ nanoboxes, together with the facile fabrication approach, presents an alternative method to develop advanced cathode catalysts for Li–O₂ batteries.