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-ZrO ₂ 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 N ₂ selectivity.