Anchoring High-Concentration Oxygen Vacancies at Interfaces of CeO_2–x/Cu toward Enhanced Activity for Preferential CO Oxidation

Abstract

Catalysts are urgently needed to remove the residual CO in hydrogen feeds through selective oxidation for large-scale applications of hydrogen proton exchange membrane fuel cells. We herein propose a new methodology that anchors high concentration oxygen vacancies at interface by designing a CeO2-x/Cu hybrid catalyst with enhanced preferential CO oxidation activity. This hybrid catalyst, with more than 6.1% oxygen vacancies fixed at the favorable interfacial sites, displays nearly 100% CO conversion efficiency in H2-rich streams over a broad temperature window from 120 to 210 °C, strikingly 5-fold wider than that of conventional CeO2/Cu (i.e., CeO2 supported on Cu) catalyst. Moreover, the catalyst exhibits a highest cycling stability ever reported, showing no deterioration after five cycling tests, and a super long-time stability beyond 100 h in the simulated operation environment that involves CO2 and H2O. On the basis of an arsenal of characterization techniques, we clearly show that the anchored oxygen vacancies are generated as a consequence of electron donation from metal copper atoms to CeO2 acceptor and the subsequent reverse spillover of oxygen induced by electron transfer in well controlled nanoheterojunction. The anchored oxygen vacancies play a bridging role in electron capture or transfer and drive molecule oxygen into active oxygen species to interact with the CO molecules adsorbed at interfaces, thus leading to an excellent preferential CO oxidation performance. This study opens a window to design a vast number of high-performance metal-oxide hybrid catalysts via the concept of anchoring oxygen vacancies at interfaces.

Facile Synthesis and Electrochemical Properties of Perovskite‐type CeMnO3 Nanofibers

“…As shown in Figure (a), in the survey spectrum peaks corresponding to Ce 3d, Mn 2p, and O 1s are clearly observed. Generally, Ce 3d exhibits relatively complicated features owing to the fractional occupancy of the valence 4 f orbitals . As depicted in Figure (b), six different XPS peaks of Ce 3d can be clearly seen.…”

A Novel Post‐Synthesis Modification of CuO‐CeO2 Catalysts: Effect on Their Activity for Selective CO Oxidation

“…The couple v′‐u′ is considered as the fingerprint of Ce 3+ species. Therefore by calculating the ratio of the relative area of the Ce 3+ peaks to the whole Ce 3d region, we can make an estimation of the reduction degree (amount of Ce 3+ on the surface of the catalysts) …”

Structure of the catalytically active copper–ceria interfacial perimeter

“…Theoretical investigations on the growth of copper atoms/clusters on reduced ceria surfaces have verified that the Cu-O-Ce interfacial interaction is energetically comparable to the Cu-Cu intracluster interaction; the competition between them determines the morphology of Cu clusters19,20 . The strong binding between copper and the reduced ceria surface, especially on the defect sites, was addressed both experimentally and theoretically with regards to the reduction degree of the ceria surface and the copper coverage21,22,43 . Onone hand, the Cu-Cu intracluster interaction, i.e.…”