No abstract

Large nano-structured flakes of CeO 2 (20-80 nm in thickness, up to 5.6 mm in diameter) were synthesized by a combination of microwave (MW), ultraviolet (UV) and ultrasound (US), with or without pressure (P). The CeO 2 structures were systematically examined by XRD, SEM, N 2 sorption, HRTEM, XPS, Raman and H 2 -TPR. The synthesized CeO 2 nanoflakes were composed by 3.0-7.5 nm nanoparticles with the (111) surface exposed, and laminated to nanoflakes with 3.42-3.85 nm nano-channels in between. MW-assisting was beneficial to form a higher surface Ce 3 + /(Ce 3 + + Ce 4 + ) ratio and surface oxygen vacancies during short synthesis procedure. A Raman peak at 480 cm À1 correlating with bulk Ce 3 + was detected. H 2 -TPR found MW and MW + P had more surface Ce 3 + (surface oxygen vacancies). CO oxidation and imine conversion proved that MW + P was the optimum condition to produce highly active CeO 2 nanoflakes. The much better catalytic performance than CeO 2 from solvothermal preparation, due to the larger channel gap (3.85 nm),a higher Ce 3 + /(Ce 3 + + Ce 4 + ) ratio (32 %) and more surface oxygen vacancies on the particles of the organized flake structures.

No abstract

No abstract

No abstract