Homogeneously dispersed CeO₂ nanoparticles on exfoliated hexaniobate nanosheets

Hexaniobate nanosheets derived from the parent compound K₄Nb₆O₁₇ have been decorated with CeO₂ nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO₂ nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO₂ nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO₂ nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO₂ nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA⁺ and K⁺ by Ce⁴⁺. Cerium ion exchange on the acid exchanged parent compound, H_2.9K_1.1Nb₆O₁₇, revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce⁴⁺/Ce³⁺ is around 4.4, in agreement with the formation of fluorite structure (CeO₂). Thus, these CeO₂ nanoparticle/nanosheet composites may be useful for catalytic processes.