Formation and characterisation of nanosize α-Rh2O3 particles

Amorphous rhodium (hydrous)oxide precursor was prepared from Rh(NO3)3 aqueous solution using NH4OH solution as a precipitating agent. The precipitate was subsequently washed, dried at 60 °C, then heated in air atmosphere up to 650 °C. Samples were characterised by XRPD, FT-IR, RAMAN, FE-SEM and EDS. The XRPD of sample prepared at 400 °C showed a broad and intensive peak, which can be assigned to the amorphous nature of this sample. The peak was positioned at Bragg angles corresponding to the prominent peaks of α-Rh2O3. For the same sample the FT-IR spectrum showed one very broad band centred at 544 cm−1. On the other hand, the Raman spectrum of the same sample showed broad peaks at 268, 411, and 556 cm−1, which can be assigned to poorly crystallized α-Rh2O3. The Raman spectrum of the sample prepared at 650 °C showed bands at 276, 422, 568 and 610 cm−1, which can be assigned to α-Rh2O3 particles. The sample prepared at 500 °C also contained RhO2 as an intermediate phase. FE-SEM images showed a gradual increase in size of α-Rh2O3 particles (in the nanometer range), prepared from 400 to 650 °C.