Synthesis and characterization of iron(III) oxides as supports for Au(0)-based catalysts

A series of iron(III) hydrated oxide/oxyhydroxide/oxide was prepared by precipitation from Fe(III) aqueous solutions, to obtain supports suitable as Au(0)-based catalysts. During synthesis, all parameters – pH, temperature and adding rate – were strictly controlled in order to achieve highly reproducible synthesis. The method of purification was also planned in order to remove nitrate ions that can influence the catalytic activity and/or the support properties, without modifying the structure or particle dimension of the support. Dialysis was identified as the best method for purifying the hydrated oxide/hydroxide, i.e., ferrihydrite and goethite; while ammonium carbonate washing proved to be the most successful for the other hydroxide/oxides. Mössbauer spectroscopy and X-ray powder diffraction pointed out the complexity of all these systems, proving the extreme importance of synthesis temperature for crystallinity, particle dimension, and amount of hydroxide/oxide.