Estudio por XPS y TGA de nanocatalizadores de hierro soportados sobre silicio bajo tratamientos térmicos, en oxígeno e hidrógeno

Resumen

Ultra-fine particle sized and well dispersed catalysts, pH=5 and pH=11, were prepared using Barbier et Al´s modified method. The catalysts were studied using TGA and XPS techniques. The TGA curves, under hydrogen flow show a weight loss at 300oC, which could correspond to the transformation of a small fraction of Fe2O3 to metallic iron. However, XPS results show that the iron oxidation state (+3) in these catalysts do not change during the sample thermal treatments in O2, H2 and in vacuum, but its chemical environment is definetely modified. The last behavior can be clearly observed in the evolution experienced by the Fe2p3/2 shake-up which is related to the valence energy levels. The apparent contradiction between XPS and TGA results could be related to the iron coordination state in this particular sample.