Spherical CuO superstructures originating from hierarchical malachite microspheres by different post-treatment routes: a comparison study of the morphology and the catalytic property

Abstract

In this paper, spherical CuO superstructures were obtained by employing freshly-produced hierarchical malachite (Cu₂(OH)₂CO₃) microspheres as the precursor in two different post-treatment approaches. Experiments showed that spherical CuO superstructures constructed by porous nanocuboids with a mean size of ∼50 nm were prepared after the hierarchical malachite microspheres had been calcined in air at 300 °C for 2 h, while spherical CuO ones built up of abundant nanosheets with a mean thickness of ∼10 nm were formed by post-treatment of the hierarchical malachite microspheres in NaOH solution at 60 °C for 15 min. The products were characterized by XRD, SEM, HRTEM/TEM, IR and TG-DTA. It was found that CuO superstructures with different shapes presented different catalytic activities for the reduction of 4-nitrophenol to 4-aminophenol in excess NaBH₄ solution and for the thermal decomposition of NH₄ClO₄.