Insights into the role of surface functional species in Cu-Mn-O thin film catalysts for N2O decomposition

Abstract

Efficient N2O decomposition using catalytic materials has been gaining attention for long time. Catalytic materials based on noble metals have proved good feasibility; however, their applications are restricted because of the high cost and limited resources. Herein, low-cost catalysts based on copper manganese oxides were synthesized by chemical vapor deposition technique for N2O decomposition. The obtained catalysts were characterized to identify the structure, morphology, composition and arrangement of formed species. The results showed that the particles are getting agglomerated when increasing Mn content, which could be due to the difference in growth and crystallization rates of Cu and Mn. XPS analysis exhibited the existence of several active species such as, Cu and Mn cations, hydroxides and metal carbonates. The ratio of Cu/Mn in bulk is found to be in correlation with the catalytic activity. The catalytic tests of N2O decomposition revealed good activity of all catalysts, and the quality and quantity of the formed surface species have dramatic effect on the activity of the catalysts. When doping by Mn to promote the catalytic activity, formed Cu(OH)2 species at catalysts’ surface appeared to be good promoters in the studied reaction of N2O decomposition by C3H6. However, the existence of Cu metal, as more reduced Cu state, at the surface of catalysts is appeared to decrease the catalytic activity, which may play an inhibitor role in this studied reaction. In addition, Cu auger peak identification revealed the existence of Cu cations with varied oxidation states, leading to establish a correlated sequence of Cu1+>Cu2+>Cu0 with the catalytic activity. This approach of fine-tuning the surface formed species could lead to enhance the performance of other catalysts in different applications.