Boosting H2-SCR of NO x via a Site-Separation Strategy over a Physically Mixed Pt-SAPO-18 and ZrTi Catalyst

Abstract The hydrogen-fueled internal combustion engine (H2-ICE) offers a promising route to carbon neutrality, with NOx being essentially the only unwanted emission. Selective catalytic reduction of NOx by hydrogen (H2-SCR) is highly suitable for NOx control. This study develops an efficient and economical H2-SCR catalyst system via a “site-separation” strategy. Even with a 50% reduction in Pt loading, the physically mixed Pt-SAPO-18 and ZrTi catalysts yield substantially higher H2-SCR performance than the single Pt-SAPO-18 catalyst. A cross-particle hydrogen spillover mechanism is demonstrated. Pt-SAPO-18 activates H2 to generate active hydrogen species, which migrate to adjacent ZrTi surfaces. ZrTi exhibits strong NOx adsorption, and the reduction of NOx on its surface is initiated by spillover hydrogen from Pt-SAPO-18. Concurrently, NH3 intermediates formed on ZrTi undergo reverse migration to Pt-SAPO-18, where they are captured by abundant Brønsted acid sites to form active NH4+ species, which can then reduce NOx. This bifunctional synergy enables targeted reaction between H2 and NOx on the NOx-rich surface, substantially improving hydrogen utilization and NOx removal efficiency. Since the activity of the ZrTi surface depends entirely on spillover hydrogen, this system provides an ideal model platform for understanding the hydrogen spillover mechanism in H2-SCR of NOx.