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-.
Scopus Subject Areas
- Process Chemistry and Technology
- Physical and Theoretical Chemistry
- NO decomposition
- NdBa CuO
- Redox action