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Large Dimensional CeO 2 Nanoflakes by Microwave‐Assisted Synthesis: Lamellar Nano‐Channels and Surface Oxygen Vacancies Promote Catalytic Activity
Author(s) -
Ding Huihui,
Yang Jingxia,
Ma Shuyi,
Yigit Nevzat,
Xu Jingli,
Rupprechter Günther,
Wang JinJie
Publication year - 2018
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201800784
Subject(s) - high resolution transmission electron microscopy , materials science , x ray photoelectron spectroscopy , raman spectroscopy , catalysis , oxygen , nanoparticle , chemical engineering , lamellar structure , nanotechnology , solvothermal synthesis , analytical chemistry (journal) , transmission electron microscopy , chemistry , metallurgy , organic chemistry , physics , optics , engineering
Large nano‐structured flakes of CeO 2 (20–80 nm in thickness, up to 5.6 μm 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 −1 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.