Charge Shielding Effect of Sodium Ions in Improving The Hydrophobicity and Performance of Co/Na‐SSZ‐13 Zeolite for Passive NO_x Adsorber

Abstract With increasingly stringent regulations, the reduction of NO_x emissions during vehicle cold start is a major challenge. Pd‐modified zeolites are considered as the most promising passive NO_x adsorber (PNA) for cold start NO_x control. Nevertheless, the scarcity and the high cost of Pd limit its practical application. Herein, a non‐precious metal modified Co/Na‐SSZ‐13 zeolite for low‐temperature NO_x adsorption is reported. This one‐pot synthesized Co/Na‐SSZ‐13 exhibits an extraordinary NO_x storage capacity (212 µmol g_cat⁻¹) under humid conditions (3% H₂O v/v), which is more than double that of conventional Co or Pd‐modified SSZ‐13. This is attributed to the absence of the inert cobalt phyllosilicate commonly found in conventional Co‐SSZ‐13, as well as the highly dispersed Co and Na ions as the effective NO_x adsorption sites in Co/Na‐SSZ‐13. Moreover, the presence of Na ions shields the negative charge generated by the Al center and weakens the local electric field strength of the Al and Co centers. This lowers the H₂O adsorption energy and improves the zeolite hydrophobicity, which enhances the NO storage capacity of the Co/Na‐SSZ‐13 under humid conditions. This work highlights the Co/Na‐SSZ‐13, synthesize via a simple and high‐efficiency method, as a promising substitute for noble metal PNA materials.