Structural Properties of PtCuO/Al2O3 surface catalyst for selective NH3 oxidation using operando spectroscopy

Selective catalytic oxidation (SCO) of NH3 to N2 is one of the most effective methods to eliminate NH3 emissions. However, achieving high conversion over a wide operating temperature range while avoiding over-oxidation to NOx is a significant challenge. Commercial Pt catalysts have full NH3 conversion at low temperatures but suffer from low N2 selectivity. To mitigate this challenge, it is crucial to limit the over-oxidation of NH3. In this study, we developed a bi-metal surface catalyst with improved Pt atom efficiency. The PtSCuO/Al2O3 catalyst consists of Pt atoms on the surface of CuO nanoparticles. It achieves full NH3 conversion at 250 °C with WHSV of 600 mlNH3h-1g-1 which is 50 °C lower than the commercial Pt/Al2O3, and maintains high N2 selectivity through all temperature window (150-450 °C). At 200 °C, PtSCuO/Al2O3, exhibited a staggering 30-fold increase in activity compared to the commercial Pt/Al2O3. Operando XAFS studies reveal that the surface Pt atoms in PtSCuO/Al2O3 not only enhance the redox ability of Cu species but also alter the redox rate of Cu species, which improves the while reaction rate of the NH3-SCO reaction. Moreover, the synergistic effect of Pt sites and Cu sites in PtSCuO/Al2O3 contributes to improved selectivity via the internal selective catalytic reduction (i-SCR) route.