Abstract:  In the NO_x storage reduction (NSR) technology used to remove NO_x from lean burn engines, the NO_x storage material is crucial. For NiO/Al₂O₃ catalysts with different NiO loading prepared by coprecipitation, the maximum storage capacity for NO_x occurred at a Ni/Al molar ratio of 0.3 in the catalyst. The intensity of the NiAl₂O₄ diffraction peak decreased with increased nickel content. When the catalysts were pretreated by a non-thermal plasma (NTP) before calcination at high temperature, the adsorption capacities for NO_x increased, with an increase from 345 to 477 μmol/g on the NiO/Al₂O₃ catalyst with the Ni/Al molar ratio of 0.3. The metal dispersion was increased with the NTP treatment, which resulted in a high surface area. The NO_x storage mechanism was discussed on the basis of DRIFTS results, which indicated that NO was first adsorbed on the surface as bridged nitrites, and then the nitrites species was transformed into different kinds of NO₃^- adsorbed species.

Key words: nickel oxide, aluminum oxide, nitric oxides, non-thermal plasma, adsorption, storage capacity, lean burn engine