HC-SCR system combining Ag/Al2O3 and Pd/Al2O3 catalysts with resistance to hydrothermal aging for simultaneous removal of NO, HC, and CO

•Coexistent H2 lowered the operating temperature window of NOx abatement over Ag/Al2O3.•Combination of upstream Ag/Al2O3 and downstream Pd/Al2O3 could simultaneously reduce NOx, C3H6, CO, and H2.•Sequential arrangement of Ag/Al2O3 and Pd/Al2O3 affected the HC-SCR performance.•Combined HC-SCR system could suppress the reductant slip.•Combined HC-SCR system exhibited the superior resistance to hydrothermal aging.