One-Pot Template-Free Synthesis of Mesoporous ZnCo₂O₄ Microbubbles for Oxygen Evolution Reaction

Spinel ZnCo₂O₄ is an important multi-functional material with wide applications, such as electrocatalytic oxygen evolution reaction. However, it still remains a challenge to synthesize ZnCo₂O₄ with complex morphologies by a simple synthetic method. Here, mesoporous ZnCo₂O₄ microbubbles with hollow structures have been successfully synthesized by a facile one-pot calcination at 400°C in air. The achieved ZnCo₂O₄ shows a hollow bubble-like microstructure constructed by mesoporous walls, which consist of small primary nanoparticles 9.8 nm in diameter. Although the synthesis route is template/surfactant-free, the pore-size distribution curve shows a sharp peak at 7.6 nm with a very narrow distribution. The specific surface area and pore volume were 68 m²/g and 0.21 cm³/g, respectively. Due to the greatly enhanced mass transfer, the mesoporous ZnCo₂O₄ microbubbles show attractive electrochemical activity for oxygen evolution reaction.