Large Dimensional CeO₂ Nanoflakes by Microwave‐Assisted Synthesis: Lamellar Nano‐Channels and Surface Oxygen Vacancies Promote Catalytic Activity

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.

Shape‐Dependent CeO2@BiOI for Degradation of Aqueous Cr(VI)

“…Figure 4a shows the Ce 3d high‐resolution spectrum in NP@BiOI, NR@BiOI, NO@BiOI, and NC@BiOI. The proportion of Ce 3+ were calculated by the previously published method in literature [ 30–32 ] because the ratio of Ce 3+ is important for the surface defects and photocatalytic activity of ceria‐based systems. [ 33–35 ] The calculated ratios of Ce 3+ were 23.9 (NP@BiOI), 18.7 (NR@BiOI), 12.0 (NO@BiOI), and 10.1% (NC@BiOI), respectively.…”

Ce3+-enriched spherical porous ceria with an enhanced oxygen storage capacity

“…† 33 In this reaction, the oxidation of benzyl alcohol is promoted by redox sites on the ceria, while the subsequent condensation reaction between benzaldehyde and aniline is facilitated by the Lewis acid sites on the material. [34][35][36][37] The associated reaction proles are presented in Fig. 4c.…”

Highly Enhanced Visible‐light Photocatalytic Activity via a Novel Surface Structure of CeO2/g−C3N4 toward Removal of 2,4‐dichlorophenol and Cr(VI)

“…[3] With the development of solar technology, a pile of photocatalytic nanomaterials, which has boosted band structures and highefficiency photoelectric separation effect, are expected to solve the above problems more effectively. [4] Ceria (CeO 2 ), a wildly abundant rare metal in the earth, is widely used in industrial catalysis, [5][6][7] fuel cells and other fields. [8] Particularly, CeO 2 shows preponderance in contamination degradation, on account of its brilliant redox ability due to variable valence in Ce 3 + /Ce 4 + .…”

“…[9] However, CeO 2 has a wide bandgap, and photogenerated electrons and holes are easily recombined. In order to eliminate the disadvantages, researchers tuned the CeO 2 exposing crystal planes by changing its morphology and the exposed facets, which related to the redox ability, electron structures, adsorption property and so forth, [6][7][8][9][10] to optimize its catalytic effect. Besides the morphology control, the combination of CeO 2 with another material is an efficient way to improve the forthputting of visible light and charge separation.…”