On the role of Fe3+ions in FexOy/C catalysts for hydrogen productionfrom the photodehydrogenation of ethanol

Abstract

FexOy/C photocatalysts at different iron content were prepared by the incipient wet impregnation methodand calcined at 773 K. The photocatalysts were characterized by means of nitrogen adsorption–desorptionisotherms, surface fractal dimension, non-local density functional theory, X-ray diffraction, Rietveldrefinement and UV–vis spectroscopy. The photocatalytic activity was evaluated using the photodehy-drogenation of ethanol as a model reaction for the production of hydrogen. The specific surface areasof FexOy/C substrates, with 15, 20 and 30 wt% iron content, diminished from 638 to 490 m2/g, as theiron content increased. X-ray diffraction analysis showed that iron oxides coexist as wustite and mag-netite in samples with Fe contents of 15 and 20 wt%; for sample with 30 wt% Fe, wustite, magnetite andhematite phases were observed. The photophysical, textural and structural properties were modified bythe hematite phase formed by thermal treatment. The Rietveld refinements denoted changes in occu-pancy of Fe3+and Fe2+in FexOycrystallites. A relationship between the Fe3+ions content and the reactivityfor the hydrogen production from the photodehydrogenation of ethanol (from 1360 to 2125 mol h−1),was evidenced.