Influence of Pt–Ba Proximity on NOx Storage–Reduction Mechanisms: A Space- and Time-Resolved In Situ Infrared Spectroscopic Study
The influence of Pt–Ba proximity on the performance and mechanism of NOx storage–reduction (NSR) was investigated by a comparative study of Pt–Ba/CeO2, Pt/CeO2 and mechanically mixed Pt/CeO2–Ba/CeO2. NOx storage capacity, regeneration activity and selectivity to nitrogen and ammonia during periodic lean (NO + O2)–rich (H2) cycles were evaluated and the chemical gradients along the axial direction of the catalyst beds were monitored by space- and time-resolved in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The presence of Ba and its proximity to Pt greatly influenced the NSR process. In particular, the proximity was crucial to achieve better utilization of bulk Ba components as well as enhancing selectivity to N2. The space-resolved approach is shown to be a powerful tool to understand the impact of the proximity of Pt and Ba constituents on the final NSR performance.