Comprehensive steady-state experiments of the selective catalytic reduction of NO on a series of Pt, Pt/BaO, and BaO monolithic catalysts were carried out. The reaction between NO and H₂ produces a mixture containing N₂O, NH₃, and N₂, the composition of which is a function of the catalyst temperature and NO/H₂ ratio in the feed. NO inhibits the reaction at low temperatures as revealed by light-off temperature and supporting kinetic data. NH₃ is a major product under O₂ deficient conditions typical of the rich pulse in NSR. NH₃ oxidation ignites on Pt catalysts at 170-180°C; in the ignited state a mixture of N₂, NO, NO₂ and N₂O is produced, the composition of which is sensitive to the NH₃/O ₂ feed ratio and temperature. Experiments involving a feed containing H₂, NH₃, and NO reveal that H₂ is a much more effective reductant than NH₃.

NSR experiments were replicated for a series of monoliths of progressively decreasing length, enabling the construction of spatio-temporal profiles of reactant and product concentrations. The results show that there are two primary competing routes to the desired N2 product; specifically a direct route from the reduction of stored NOx by H₂ (H₂ + NOx → N₂) or by a sequential route through NH₃ (H₂ + NOx → NH ₃; NH₃ + NOx → N ₂). A comparison between H₂ and NH₃ as reductants during NSR revealed H₂ is a more effective reductant in terms of NOx conversion for temperatures below approximately 230°C.

The impact of Pt dispersion on NH₃ formation and NOx storage and reduction was evaluated. As the dispersion increased, the amount of NOx stored and regenerated increased. For both anaerobic and aerobic regeneration feeds, the most (net) NH₃ was generated by the 50% dispersion catalyst at the lowest temperature, by the 3% dispersion catalyst at the highest temperature, and by the 10% dispersion catalyst at the intermediate temperatures.

The performance of a Pt/BaO/Al₂O₃ monolith catalyst was studied using H₂ as the reductant. The dependence of product selectivities on operating parameters is reported; including the durations of regeneration and storage times, feed composition and temperature, and monolith temperature. NOx reduction efficiency and product distribution are also compared with and without water in the feed.