Fabrication of Hierarchically Porous RuO2–CuO/Al–ZrO2 Composite as Highly Efficient Catalyst for Ammonia-Selective Catalytic Oxidation

A hierarchically porous RuO 2 –CuO/(Al–ZrO 2 ) nanocomposite, with RuO 2 and CuO nanocrystals being homogeneously dispersed in the hierarchically porous structure of Al-doped ZrO 2 (Al–ZrO 2 ), has been developed by a hydrothermal and wet impregnation method for efficient ammonia-selective catalytic oxidation (SCO) applications. The microstructures of the RuO 2 –CuO/Al–ZrO 2 nanocomposites were characterized by XRD, TEM, FESEM, EDX elemental mapping, and N 2 sorption. XPS analysis and H 2 -TPR results indicate that the hierarchically porous RuO 2 –CuO/Al–ZrO 2 composites possess a large number of oxygen vacancies and surface catalytic active sites, which endows the composite with high catalytic activity and N 2 selectivity for NH 3 oxidation. NH 3 complete oxidization has been achieved at 195 °C with 100% N 2 selectivity over an obtained RuO 2 –CuO/Al–ZrO 2 composite at RuO/CuO = 1:1 (weight rate). The high efficiency of hierarchically porous RuO 2 –CuO/Al–ZrO 2 nanocomposites for ammonia SCO reaction has been attributed to the synergetic catalytic effects among the metal oxides, in which the porous Al–ZrO 2 support promotes oxygen activation by the generation of oxygen vacancies due to the Al doping, and the ultrahigh catalytic activity of RuO 2 is responsible for the active NH 3 oxidation. Successively, CuO plays a role of NO intermediate conversion for enhanced N 2 selectivity.