Synergistic Effect of Simultaneous Doping of Ceria Nanorods with Cu and Cr on CO Oxidation and NO Reduction.

Shawn C Rood,Oriol Pastor‐Algaba,Salvador Eslava,Bruno Pinho,Laura Torrente‐Murciano,Albert Tosca‐Princep,Mark Isaacs

doi:10.1002/chem.202004623

Abstract

Ceria particles play a key role in catalytic applications such as automotive three‐way catalytic systems in which toxic CO and NO are oxidized and reduced to safe CO2 and N2, respectively. In this work, we explore the incorporation of Cu and Cr metals as dopants in the crystal structure of ceria nanorods prepared by a single‐step hydrothermal synthesis. XRD, Raman and XPS confirm the incorporation of Cu and Cr in the ceria crystal lattices, offering ceria nanorods with a higher concentration of oxygen vacancies. XPS also confirms the presence of Cr and Cu surface species. H2‐TPR and XPS analysis show that the simultaneous Cu and Cr co‐doping results in a catalyst with a higher surface Cu concentration and a much‐enhanced surface reducibility, in comparison with either undoped or singly doped (Cu or Cr) ceria nanorods. While single Cu doping enhances catalytic CO oxidation and Cr doping improves catalytic NO reduction, co‐doping with both Cu and Cr enhances the benefits of both dopants in a synergistic manner employing roughly a quarter of dopant weight.

Highlights

Ceria is widely used in catalytic applications across a broad range of fields, such as automotive three-way catalysis, due to its oxygen storage capability.[1,2,3,4,5,6,7,8] Doping ceria by replacing cerium atoms with other readily available metals has the potential to improve their low-temperature performance, otherwise typically achieved by the addition of expensive Pt-group metals.[9,10,11] In particular, the replacement of cerium atoms with other elements, those of lower valence, can lead to [a] Dr S
For NO reduction, our Cu/Cr-doped ceria nanorods performed slightly better at 150 8C but somewhat worse at 200 8C compared with a Cr-doped ceria catalyst (Ce20Cr1Ox) or a 0.07 % each Cu/Cr deposited on ceria (Table 2).[22]
Copper and chromium have been used as dopants for ceria nanorod catalysts produced via a hydrothermal synthesis method

Summary

Introduction

Ceria is widely used in catalytic applications across a broad range of fields, such as automotive three-way catalysis, due to its oxygen storage capability.[1,2,3,4,5,6,7,8] Doping ceria by replacing cerium atoms with other readily available metals has the potential to improve their low-temperature performance, otherwise typically achieved by the addition of expensive Pt-group metals.[9,10,11] In particular, the replacement of cerium atoms with other elements, those of lower valence, can lead to [a] Dr S. Chemistry - A European Journal published by WileyVCH GmbH. A template-free hydrothermal method is used to synthesize Cu and Cr-doped ceria nanorods with improved activities as low-temperature automotive catalysts. Doping ceria with Cr does not improve the CO oxidation conversions but does result in a catalyst with better lowtemperature performance for NO reduction. Co-doping ceria with both Cu and Cr provides a catalyst with enhanced performance for both CO oxidation and NO reduction. The use of doped ceria nanorods offers an attractive route to producing automotive catalysts with better low-temperature performance

Results and Discussion

Conclusions

Conflict of interest