Improvement of physico-chemical properties by addition of H₂O₂: an extensive case study on the RE-doped ceria system (RE = Gd, Sm)

Abstract

Effect of H₂O₂ on synthesis and powder properties such as surface area and agglomerate size of nanocrystalline Ce_0.8M_0.2O_1.90 (M: Sm, Gd) was explored by treating cerium nitrate and rare-earth nitrate with NaOH in the presence/absence of H₂O₂. The resultant products were characterized by x-ray diffraction, Raman spectroscopy, thermo-gravimetry–differential thermal analysis, dynamic light scattering, surface area analysis, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The presence of H₂O₂ was found to have a profound effect on powder properties such as surface area and particle size of these doped ceria samples and results in smaller crystallite size, softer agglomerates, and larger surface area. A mechanism is proposed to explain the observed better powder properties of the samples. It was also shown that the samples prepared in the presence of H₂O₂ can lower the conversion temperature of CO to CO₂, proving these to be better catalysts. Interestingly, temperature-programmed reduction studies on Sm³⁺-doped samples showed that the doping in conjunction with the use of H₂O₂ leads to enhanced reduction properties of the samples over multiple cycles.