Atomistic Insights Into V─O─W Active Sites in SCR Catalysts via Advanced EPR Spectroscopy

The development of more efficient selective catalytic reduction (SCR) systems remains crucial for mitigating NOx emissions during the transition toward sustainable energy technologies. VOx/WOx/TiO2 catalysts are widely used due to their high activity and robustness. Tungsten is believed to act as a promoter, enhancing surface acidity and regulating the dispersion of active VOx, yet its role in the reaction remains under debate. In this study, we employ a combination of advanced EPR techniques, to investigate reduced vanadium species under pseudo-in situ NH3-SCR conditions. Our results provide direct spectroscopic evidence for the coexistence of V⁴⁺─O─V⁵⁺ and V⁴⁺─O─W⁶⁺ surface dimers, their electronic structure, and distribution. Notably, the prevalence of V⁴⁺─O─W⁶⁺ moieties indicates that tungsten not only enhances vanadium dispersion but also actively promotes its reducibility through heteronuclear interactions. This study advances the molecular-level understanding of the NH3-SCR catalysis and showcases the power of advanced EPR methods in elucidating structure–reactivity relationships in complex oxide systems.