Samsung Advanced Institute of Technology

Direct nitrogen oxide decomposition (DND) is a promising alternative to the selective catalytic reduction (SCR) of nitrogen oxides for emissions control, as it eliminates the need to inject reductants such as urea/ammonia. The present study investigates the implementation of Rh-supported metal oxides for the DND reaction. Rh supported on each of PrO_X, TiO₂, Al₂O₃, and CeO₂ were characterized, and we found that initially the catalytic activity on Rh/PrO_X and Rh/TiO₂ was very high, though it deactivated over time due to strong poisoning by adsorbed oxygen. This deactivation by oxygen poisoning was verified through in-situ DRIFTS, XPS, NEXAFS, O₂-TPD measurements and density functional theory (DFT) calculations, respectively. This catalytic deactivation was positively regenerated by reductive treatments with CO or H₂. This study discovers the mechanism of DND deactivation and regeneration over Rh-supported metal oxides, which will provide significant insight into further development of DND.