Mechanistic study on the enhanced N2 selectivity for NH3 selective oxidation over Pt-encapsulated cu-ZSM-5 catalysts

Ammonia (NH 3 ) has emerged as a promising zero‑carbon energy source for energy and transportation. However, its utilization leads to the emission of NH 3 , which contributes to PM 2.5 formation and disrupts the global nitrogen cycle. Selective catalytic oxidation (SCO) represents a mainstream technology for NH 3 treatment, yet achieving both sufficient activity and high N 2 selectivity across a broad temperature window remains challenging. Here, a core-shell Pt@Cu-ZSM-5 catalyst was employed for NH 3 catalytic abatement by encapsulating metallic Pt clusters (Pt 0 ) inside the channels of Cu ion-exchanged ZSM-5. The optimal sample achieved a complete NH 3 conversion below 250 °C and maintained over 92% N 2 selectivity from 250 to 500 °C due to the synergism between the Pt Cu dual sites. Mechanistic studies revealed that NH 3 oxidation preferentially occurred on Pt 0 sites with excellent redox capacity to produce N 2 O and NO x at relatively low and high temperatures, respectively. And the presence of Cu ions (Cu δ+ ) could efficiently both inhibit the formation of N 2 O on Pt 0 sites and reduce NO x emission, thereby improving the N 2 selectivity. At relatively low temperatures, NH 3 -solvated Cu + (NH 3 ) 2 could migrate to the adjacent Pt sites and reduce the adsorbed NO* species from NH 3 oxidation, damping the formation of N 2 O. At high temperatures, the NO and NO 2 emitted from Pt 0 sites could be reduced on Cu δ+ sites via a typical selective catalytic reduction. This study provides new insights into the rational design of bifunctional SCO catalysts and offers a comprehensive understanding of the synergistic effects in Pt Cu dual-site systems.