Co-existence of atomically dispersed Ru and Ce3+ sites is responsible for excellent low temperature N2O reduction activity of Ru/CeO2

Abstract

Nitrous oxide N2O reduction is a big challenge due to high global warming potential of N2O. (∼300 times higher compared with CO2). The best known catalysts, such as Rh/ceria, require relatively high temperatures for N2O decomposition. Herein, we report that Ru/ceria catalysts with low Ru loading of ∼0.25 wt% efficiently catalyze low temperature N2O reduction by CO starting at 100 ℃ (full N2O conversion below 200 ℃) under industrially relevant flow rates and gas concentrations. This remarkable performance stems from maintaining isolated Ru cations even on reduced ceria surface and, simultaneously, the propensity of Ru to affect ceria surface to form labile surface oxygen thereby creating large number of oxygen vacancies (Ce3+ cations) in the presence of CO. In contrast, for Rh/CeO2 catalysts with equivalent metal loading, the activity is much lower because atomically dispersed Rh sinters into metallic clusters at the onset reaction temperature (∼200 °C): these clusters are much less effective than isolated single Ru ions, with lower Ce3+ concentration maintained on reduced Rh/CeO2 catalyst. Our study highlights the benefits of gaining molecular-level insight into the dynamic nature of catalytically active sites under reaction conditions for preparing catalysts containing low loading of precious metals with unsurpassed low temperature activity.