Synthesis of Cu₂PO₄OH hierarchical superstructures with photocatalytic activity in visible light

Using a wet-chemical method and without any surfactants or templates, various 3D hierarchical superstructures of Cu₂PO₄OH were synthesized by simply adjusting the pH. The resulting hierarchical superstructures were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high resolution-TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman, and UV-Vis spectroscopy. With an increase in pH from 2.5 to 7.0, the morphology of Cu₂PO₄OH varied from microrods to walnut-shaped microspheres of self-assembled nanoparticles. A possible mechanism for the formation of the Cu ₂PO₄OH hierarchical superstructures was also proposed. The optical properties of the Cu₂PO₄OH hierarchical superstructures were strongly related to their morphologies and the size of the assembled crystallites. We further demonstrated the useful photocatalytic activity of these complex structures in the degradation of methylene blue (MB) dye under visible light irradiation (λ > 410 nm). The best photocatalytic performance was achieved by Cu₂PO₄OH with a walnut-shaped morphology due to the excellent absorption of visible light as well as a high BET surface area.