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

A hierarchically porous RuO2–CuO/(Al–ZrO2) nanocomposite, with RuO2 and CuO nanocrystals being homogeneously dispersed in the hierarchically porous structure of Al-doped ZrO2 (Al–ZrO2), has been developed by a hydrothermal and wet impregnation method for efficient ammonia-selective catalytic oxidation (SCO) applications. The microstructures of the RuO2–CuO/Al–ZrO2 nanocomposites were characterized by XRD, TEM, FESEM, EDX elemental mapping, and N2 sorption. XPS analysis and H2-TPR results indicate that the hierarchically porous RuO2–CuO/Al–ZrO2 composites possess a large number of oxygen vacancies and surface catalytic active sites, which endows the composite with high catalytic activity and N2 selectivity for NH3 oxidation. NH3 complete oxidization has been achieved at 195 °C with 100% N2 selectivity over an obtained RuO2–CuO/Al–ZrO2 composite at RuO/CuO = 1:1 (weight rate). The high efficiency of hierarchically porous RuO2–CuO/Al–ZrO2 nanocomposites for ammonia SCO reaction has been attributed to the synergetic catalytic effects among the metal oxides, in which the porous Al–ZrO2 support promotes oxygen activation by the generation of oxygen vacancies due to the Al doping, and the ultrahigh catalytic activity of RuO2 is responsible for the active NH3 oxidation. Successively, CuO plays a role of NO intermediate conversion for enhanced N2 selectivity.