Based on their high NOx storage capacities (NSCs), a series of M/Ba/Al (M = Mn, Fe, Co, Ni, Cu) catalysts were evaluated in NOx storage-reduction catalysis. Although the M/Ba/Al catalysts exhibited high NSC values, they exhibited much lower activity during lean-rich cycling compared with a traditional Pt/Ba/Al catalyst, indicating that regeneration of stored NOx is the rate limiting step for the M/Ba/Al samples. By employing an H-2-plasma in the rich phase to assist reduction of the stored NOx, the NOx conversion was greatly improved, especially at low temperature. (C) 2015 Elsevier B.V. All rights reserved.