The emission of NO_X from heavy duty vehicles is the one of the biggest environmental problems affecting the globe. The legislative limit for NO_X emission in the exhaust gas from heavy duty diesel engines is becoming stricter worldwide. NO_X storage and reduction (NSR) is the promising technology which is able to reduce the NO_X emission from such vehicles. The NSR is a dual stage process on a bifunctional catalyst in the lean NO_X trap (LNT). NO_X is stored on alkali earth component (Ba, Ca) mediated by precious metals (Pt, Rh) under lean condition followed by injecting a rich pulse of shorter exposure to reduce the stored NO_X.             We employed Temporal Analysis of Products (TAP) experiments and micro-kinetic mechanistic modeling to further the understanding of NSR. TAP experiments are carried out isothermally in the Knudson diffusion regime thereby avoid thermal and mass limitations encountered in atmospheric pressure studies. Transient TAP studies performed on a series of Pt/BaO/Al₂O₃ catalyst having Pt loading between 0 and ca. 4 wt.% with the BaO loading fixed at 16 wt.%. NO storage and NO/H₂ pump probe experiments are performed on pre-oxidised, pre-reduced Pt/BaO/Al₂O₃ with different Pt dispersion and constant loading to elucidate the role of Pt/BaO interfacial chemistry and its affect on selectivity on NH₃ and N₂O production. Experiments are performed over a wide range of catalyst temperatures, NO/H₂ feed ratios, delay times, spacing etc. NO storage experiment at higher temperature (350 ⁰C) suggest that NO decomposes on surface to form N₂ as dominant product leaving oxygen adatoms on the Pt, which further inhibits the process. NO decomposition rate declines as temperature is decreased with negligible formation of N₂ at 150 ⁰C.  At higher temperature NO breakthrough occurs as Pt is saturated with oxygen adatoms and secondary product N₂O attains a maximum at NO breakthrough. At lower temperature NO adatoms inhibits reaction and breakthrough occurs as Pt is saturated with NO adatoms. During pump probe experiments, NO and H₂ are pulsed over a wide range of catalyst temperatures, NO/H₂ feed ratios, delay times for their affect on selectivity of N₂, NH₃ and N₂O. Pump probe experiments in excess of NO, N adatom react with NO adatom to form N₂O as major product. While in excess of H₂, at lower temperature NO adatom reacts with surrounding H adatoms to form NH₃ at lower temperature and N adatoms combine to form N₂ at higher temperature. NH₃ selectivity increase with decreasing temperature, NO/H₂ ratio and delay time (t_d). Micro-kinetic modeling attempt has been made to gain insight for the transport and reaction kinetics during NO storage and NO/H₂ pump probe experiments from bench scale to ultra high vacuum condition. The deviations, in transport mechanism from Knudson diffusion, produced by injecting a narrow pulse in vacuum are suitably characterized. Parameter estimation is accomplished by curve fitting between experimental exit flow rate and model exit flow rate. Kinetic parameters were initialized using kinetic theory of gases or taken from literature and modified using optimization technique. The modeling explains all essential trends for NO breakthrough, N₂O maxima, oxygen poisoning as well as determine state of catalyst with position and time.