Nanocrystalline CeO2-δ coated β-MnO2 nanorods with enhanced oxygen transfer property

作者:Huang, Xiubing; Zhao, Guixia; Chang, Yueqi; Wang, Ge*; Irvine, John T. S.*
来源:Applied Surface Science, 2018, 440: 20-28.
DOI:10.1016/j.apsusc.2017.12.197

摘要

In this research, beta-MnO2 nanorods were synthesized by a hydrothermal method, followed by a facile precipitation method to obtain nanocrystalline CeO2-delta coated beta-MnO2 nanorods. The as-prepared samples were characterized by XRD, HRTEM, FESEM, XPS and in-situ high-temperature XRD. The HRTEM results show that well dispersed CeO2-delta nanocrystals sized about 5 nm were coated on the surface of beta-MnO2 nanorods. The oxygen storage and transfer property of as-synthesized materials were evaluated using TGA under various atmospheres (air, pure N-2, and 5%H-2/95%Ar). The TGA results indicate that CeO2-delta modification could favour the reduction of Mn4+ to Mn3+ and/or Mn2+ at lower temperature as compared with pure beta-MnO2 nanorods and the physically mixed CeO2-delta-beta-MnO2 under low oxygen partial pressure conditions (i.e., pure N-2, 5%H-2/95%Ar). Specifically, CeO2-delta@beta-MnO2 sample can exhibit 7.5 wt% weight loss between 100 and 400 degrees C under flowing N-2 and 11.4 wt% weight loss between 100 and 350 degrees C under flowing 5%H-2/95%Ar. During the reduction process under pure N-2 or 5%H-2/95%Ar condition, the oxygen ions in beta-MnO2 nanorods are expected to be released to the surroundings in the form of O-2 or H2O with the coated CeO2-delta nanocrystals acting as mediator as inferred from the synergistic effect between the well-interacted CeO2-delta nanocrystals and beta-MnO2 nanorods.