Improved hydrothermal durability of Cu-SSZ-13 NH3-SCR catalyst by surface Al modification: Affinity and passivation

•Nano Al2O3 layer is coated on Cu-SSZ-13 by chemical liquid deposition (CLD).•High-Temperature SCR activity of aged Cu-SSZ-13 is preserved by Al modification.•Aggregated Cu is passivated as CuAlO2 that are inert for NH3 oxidation.•CuAl2O4 and Al2O3, comparing with CuO, have higher affinity for Cu(OH)2.•CuAl2O4 forms with Al modification and captures detached Cu as CuAlO2 upon aging.