Lowering the Operating Temperature of Perovskite Catalysts for N<sub>2</sub>O Decomposition through Control of Preparation Methods
Nia Richards, James Carter, Luke A. Parker, Samuel Pattisson, Daniel G. Hewes, David Morgan, Thomas E. Davies, Nicholas F. Dummer, Stanislaw E. Golunski, Graham J. Hutchings
Abstract
Discovering catalysts that can decompose N2O at low temperatures represents a major challenge in modern catalysis. The effect of a preparative route on N2O decomposition activity has been examined for a PrBaCoO3 perovskite catalyst. Initially, citric acid preparation was utilized, where the A site ratio was altered in order to increase phase purity. Comparable compositions were then prepared by an oxalic acid precipitation method and by a supercritical antisolvent (SAS) technique to produce perovskites with a higher surface area (>30 m2 g–1). By altering the A site ratio, it was possible to reduce the temperature required to produce a pure phase perovskite while maintaining a higher surface area. The use of the different preparation methods resulted in perovskites with varying properties, as determined by N2 adsorption, X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption, and hydrogen temperature-programmed reduction (H2-TPR). This work confirms the importance of lattice oxygen species that have high oxygen mobility for enhanced decomposition of N2O, as oxygen recombination is considered the rate-limiting step. Here, the formation of molecular oxygen is limited by surface-adsorbed O species being within a distance at which oxygen recombination is possible. The most active PrBaCo-based catalyst did not have the highest percentage of lattice oxygen as shown by XPS; however, the catalytic activity could be correlated to the mobile oxygen species and high surface area. The PrBaCo-based catalyst prepared by SAS converted 50% of the N2O present in the feed (T50) at 410 °C, which represents a significant improvement over reported catalytic performance measured under similar conditions.