Enhancing the performance of Mn/CeZrOx passive NOx adsorbers through triethanolamine-modulated Mn-support interactions

Passive NO x adsorbers (PNAs) are promising materials for mitigating cold-start NO x emissions, yet their performance is often limited by poor adsorption kinetics and insufficient hydrothermal durability. Herein, we report a triethanolamine (TEOA)-assisted synthesis strategy for Mn/CeZrO x PNAs that enables highly dispersed MnO x species with strengthened Mn-support interactions. Compared with conventionally prepared Mn/CeZrO x , the TEOA-modified materials exhibit (i) faster NO x adsorption rates during the initial cold-start relevant stage, (ii) a higher nitrate formation rate and a more suitable nitrate decomposition window (200–400 °C) in which the downstream selective catalytic reduction unit utilizing Cu-SSZ-13 SCR catalysts typically displays optimized NO x reduction efficiency, and (iii) enhanced hydrothermal stability with reduced MnO x agglomeration after aging. A combination of spectroscopic and microscopic techniques (XPS, UV–vis, DRIFTS, TEM/EDS) reveal that TEOA modulation promotes uniform MnO x dispersion, increases surface O ads species, and shifts MnO x speciation toward more active states. These structural and chemical modifications collectively account for the improved PNA performance. This work demonstrates a simple yet effective synthesis approach to optimize Mn-based PNAs, providing new insights into the design of thermally robust, precious-metal-free cold-start NO x control materials.