Supercritical preparation of hexagonal gamma-alumina nanosheets and its electrocatalytic properties.

Alumina precursors were prepared via a sol-gel process by refluxing aqueous solutions containing urea and 0.4 M Al3+ (the [urea]/[Al3+] ratio was 3.0). The obtained precursor precipitates were dried in supercritical ethanol. The resultant gamma-alumina nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrometry (FTIR). Hexagonal sheet gamma-alumina (gamma-Al2O3) nanoparticles with a diameter of 8.48 nm were successfully prepared. The electrocatalytic properties of the nano-gamma-alumina/carbon paste electrode for oxidation of alizarin in 1.0 M H2SO4 solution have been investigated by cyclic voltammetry (CV), and excellent electrocatalytic activity was observed.