Hierarchical Porous Carbonized Co₃O₄ Inverse Opals via Combined Block Copolymer and Colloid Templating as Bifunctional Electrocatalysts in Li–O₂ Battery

Hierarchically organized porous carbonized-Co₃O₄ inverse opal nanostructures (C-Co₃O₄ IO) are synthesized via complementary colloid and block copolymer self-assembly, where the triblock copolymer Pluronic P123 acts as the template and the carbon source. These highly ordered porous inverse opal nanostructures with high surface area display synergistic properties of high energy density and promising bifunctional electrocatalytic activity toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). It is found that the as-made C-Co₃O₄ IO/Ketjen Black (KB) composite exhibits remarkably enhanced electrochemical performance, such as increased specific capacity (increase from 3591 to 6959 mA h g⁻¹), lower charge overpotential (by 284.4 mV), lower discharge overpotential (by 19.0 mV), and enhanced cyclability (about nine times higher than KB in charge cyclability) in Li–O₂ battery. An overall agreement is found with both C-Co₃O₄ IO/KB and Co₃O₄ IO/KB in ORR and OER half-cell tests using a rotating disk electrode. This enhanced catalytic performance is attributed to the porous structure with highly dispersed carbon moiety intact with the host Co₃O₄ catalyst.