Unraveling the Mechanism of High N2 Selectivity in Ammonia Selective Catalytic Oxidation on Pt-V Tandem Catalyst

V_0.5/Pt/TiO₂ tandem catalysts exhibit both an outstanding low-temperature NH₃ conversion rate and high N₂ selectivity in NH₃-SCO reactions, but the mechanism of high N₂ selectivity remains unclear. In this work, V<i>_x</i>/Pt/TiO₂ tandem catalysts were synthesized through a two-step impregnation-deposition method. The modulating effect of the V loading mount on NH₃-SCO performance was evaluated, and the relevant reaction mechanism was explored systematically. The results demonstrated that the synergistic effect of tandem NH₃ oxidation and NH₃-SCR reactions could be regulated by changing the V loading amount, thereby modulating N₂ selectivity. Compared with other V<i>_x</i>/Pt/TiO₂ catalysts and previously reported SCO catalysts, the V_0.5/Pt/TiO₂ catalyst with a V loading amount of 0.5 wt.% exhibited outstanding NH₃-SCO performance, which achieved complete NH₃ conversion and >90% of N₂ selectivity within a range of 250-450 °C. XPS, NH₃-TPD, and O₂-TPD results suggested that the increase in the V loading amount from 0.1 wt.% to 0.5 wt.% was conducive to increasing the relative contents of Pt⁰ and V⁵⁺ species, as well as the amount of acid sites, oxygen species, and oxygen vacancies. Consequently, the synergistic effect of tandem NH₃ oxidation and NH₃-SCR reactions was significantly enhanced, enabling the catalyst to exhibit excellent N₂ selectivity. A further increase in the V loading amount from 0.5 wt.% to 0.9 wt.% would bring about the opposite effect to the above, resulting in a decline in catalytic performance. In situ DRIFTS results showed that a V loading amount of 0.5 wt.% was beneficial for -NH₂ species to participate in NH₃-SCO reactions, thereby boosting N₂ selectivity.