CoMn-K was mechanically mixed with a Pd/Ba/Al2O3 catalyst to enhance its NOx storage and reduction properties. The Pd/Ba/Al2O3 and CoMn-K mixture showed a synergetic effect with respect to NOx storage capacity and improved NOx reduction ability. The addition of K+ ions promoted the catalytic performance by increasing NOx oxidation activity and therefore NOx storage via the creation of active surface oxygen species on the catalysts. The stored NOx reduction by H-2 was also improved, being ascribed to the fact that Pd was mainly present as Pd-0 due to the electronic interactions between Pd and K+ ions. NOx conversions and N-2 selectivity at low temperatures (80-200 degrees C) could be further enhanced by assistance of non-thermal plasma in rich phase.