Magnetic resonance study of co-modified (Fe,N)-TiO2

Iron and nitrogen co-modified TiO2, nFe,N-TiO2 (n = 1, 5 and 10 wt.%), nanocomposites were prepared by impregnation of amorphous titanium dioxide with Fe(NO3)3 followed by high temperature calcination (800 °C) in ammonia atmosphere. The nanocomposites exhibited high photocatalytic activity towards the degradation of acetic acid under visible light, with optimum performance for the n = 5% sample. To obtain insight in the electronic properties of the co-modified photocatalysts underlying their visible light photocatalytic activity, the magnetic properties of the (Fe,N)-TiO2 nanocomposites have been investigated by FMR/EPR spectroscopy in 4-290 K range. The FMR spectra of iron nanoparticle agglomerates were dominant in the whole temperature range for all samples, with the lowest intensity for 5Fe,N-TiO2 sample at RT. In addition, the EPR spectra of free radicals and trivalent titanium ions were recorded at low temperatures. The highest concentration of trivalent titanium ions was observed for n = 5Fe,N-TiO2 and the lowest for n = 10Fe,N-TiO2 sample. It is proposed that in the case of the former sample, the largest amount of iron is involved in the modification of titania, resulting in the appearance of the highest concentrations of trivalent titanium ions that correlates favorably with the optimum visible light photocatalytic reactivity.