Ammonia induced formation of N-doped (BiO)2CO3 hierarchical microspheres: the effect of hydrothermal temperature on the morphology and photocatalytic activity

Abstract

Three types of N-doped (BiO)₂CO₃ hierarchical microspheres composed of 2D nanosheets were fabricated by a one-pot template-free hydrothermal method from bismuth citrate and an ammonia solution under different hydrothermal temperatures. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV-visible diffuse reflectance spectroscopy. Here, the ammonia worked as a nitrogen resource, doping (BiO)₂CO₃, and a solvent hydrolyzing the bismuth citrate. The temperature was found to influence the thickness of the nanosheets and the morphology of the N-doped (BiO)₂CO₃ microspheres. The fascinating morphology of N-doped (BiO)₂CO₃, including rose-like, hydrangea flower-like and peony flower-like microspheres, can be controllably fabricated by adjusting the hydrothermal temperature. The photocatalytic activities of the as-prepared samples were evaluated towards the removal of NO under visible-light irradiation. Compared to pure (BiO)₂CO₃, the N-doped (BiO)₂CO₃ hierarchical microspheres showed enhanced photocatalytic activity. In addition, the hydrangea flower-like and the peony flower-like N-doped (BiO)₂CO₃ microspheres displayed admirable photocatalytic activity. Finally, a possible formation mechanism of the various morphologies of N-doped (BiO)₂CO₃ mediated by the reaction temperature was proposed. This work could provide new insights into the controlled synthesis of photocatalytic nano/microstructures for potential environmental applications.