Studies on the decomposition of N2O over Nd2CuO4, Nd1.6Ba0.4CuO4 and Nd1.8Ce0.2CuO4

L. Z. Gao, Chak Tong AU*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

Nd2CuO4, Nd1.6Ba0.4CuO4 and Nd1.8Ce0.2CuO4 were prepared by means of the citric acid complexing method. The catalytic performances of N2O decomposition to N2 over this series of K2NF4-type cuprates have been evaluated. Techniques such as XRD, XPS, EPR, TPD, pulsing, in situ DRIFT, and FT-Raman as well as chemical analysis were employed to investigate the nature of the active sites and to identify the possible reaction intermediates. A catalytic reaction mechanism has been proposed. The N2O decomposition activities declined in the order of Nd1.8Ce0.2CuO4 > Nd1.6Ba0.4CuO4 > Nd2CuO4 when the reaction temperatures were below 400°C. Above 400°C. Nd1.8Ce0.2CuO4 was inferior to Nd1.6Ba0.4CuO4. The results of chemical analysis and XPS studies revealed that there are (i) Cu2+, Cu3+, and extra oxygen in Nd2CuO4; (ii) Cu2+, Cu+, and extra oxygen in Nd1.8Ce0.2CuO4; and (iii) Cu3+, Cu2+, and oxygen vacancies in Nd1.6Ba0.4CuO4. There are Cu+, Cu2+, Cu3+ and active oxygen species such as O- (O22-) or O2- in the used catalysts. The results of EPR, in situ DRIFT and Raman studies suggested that during N2O decomposition NO3-, NO2-, N2O22-, NO-, and oxygen species (O-, O22-, and O2-) were generated. The productions of NO and N2 are competitive. The reaction mechanism includes the redox actions amidst Cu+ ⇔ Cu2+ ⇔ Cu3+ and O2- ⇔ O-(O22-) ⇔ O2 - ⇔ O2. Oxygen vacancies are important sites for N2O adsorption and oxygen species O- are required for the formation of the crucial intermediate N2O22-.

Original languageEnglish
Pages (from-to)173-186
Number of pages14
JournalJournal of Molecular Catalysis A: Chemical
Volume168
Issue number1-2
DOIs
Publication statusPublished - 1 Mar 2001

Scopus Subject Areas

  • Catalysis
  • Process Chemistry and Technology
  • Physical and Theoretical Chemistry

User-Defined Keywords

  • Intermediates
  • NO decomposition
  • NdBa CuO
  • NdCeCuO
  • NdCuO
  • Redox action

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