Enhanced photocatalytic activity of nanocrystalline N-doped ZnSb2O6: role of N doping, cation ordering, particle size and crystallinity

Trirutile antimonate N-doped nanocrystalline ZnSb2O6 has been synthesised by a facile solution combustion method for the first time. The as synthesized products obtained with different oxidant to fuel ratios (O/F) are crystalline single phasic N-doped ZnSb2O6 as confirmed by powder X-ray diffraction (XRD). The products have been characterized well by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX), Transmission Electron Microscopy (TEM), Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). Raman spectral modes of all the products show characteristic features of the trirutile structure with shifting and broadening of spectral peaks in nanocrystalline products compared to that of microcrystalline products. UV-visible Diffused Reflectance Spectra (DRS) spectra confirm the decrease of band gap with increase in O/F and is in the range of 3.20-2.82 eV. Micro and nanocrystalline N-doped ZnSb2O6 show significant photocatalytic activity for degradation of Rhodamine (RhB). Furthermore, production of (OH)-O-center dot hydroxyl radicals was monitored through photoluminescence study by trapping cOH radicals generated in the reaction mixture with terephthalic acid. The activity is found to correlate with the concentration of (OH)-O-center dot radicals and is found to be maximum for nanocrystalline ordered N-doped ZnSb2O6 which exhibits the highest activity indicated by its degradation efficiency and rate constant. The enhanced photocatalytic activity of combustion synthesized nanocrystalline N-doped ZnSb2O6 is reported for the first time here and the activity is found to correlate with N-doping, cation ordering, particle size and crystallinity.