Lowering the Operating Temperature of Perovskite Catalysts for N₂O Decomposition through Control of Preparation Methods

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.