Solvothermal synthesis of InNbO₄ cubes for efficient degradation of pefloxacin

A novel solvothermal process for synthesizing InNbO₄ nanomaterials was developed. In this manner, a series of InNbO₄ samples was synthesized. It was shown that reaction temperature and precursor pH had strong influence on the attributes of InNbO₄ samples. The X-ray diffraction patterns revealed that all the samples possessed monoclinic structure and the optimal reaction condition was found at 250 °C with a pH of 5. Scanning electron microscopy images of different InNbO₄ samples showed various morphologies. Transmission electron microscopy verified the synthesized InNbO₄-pH 5 was single-crystal cubes. X-ray photoelectron spectra verified the existence of In, Nb, and O in InNbO₄-pH 5 sample. The band gap of InNbO₄-pH 5 was calculated to be 2.51 eV. The photocurrent intensity of InNbO₄-pH 5 was the highest among the prepared samples. The photocatalytic degradation of pefloxacin was investigated using these samples. The InNbO₄-pH 5 exhibited best degradation efficiency among these samples. The removal efficiency of pefloxacin with InNbO₄-pH 5 could reach 80.2% in 60 min. Based on free radical capture results, superoxide radicals and holes showed to be the dominant active species. In addition, UHPLC/MS/MS was used to identify the degradation intermediates. Five new pefloxacin degradation products were found and possible degradation pathways were suggested.