Pt–Pd bimetallic effect in PtxPd1−x/(Ce,Zr,La)O2 catalysts for NOx, HC and CO elimination

Abstract

(Ce,Zr,La)O₂-Supported Pt, Pd and Pt–Pd bimetallic catalysts for NO_x, HC and CO elimination were synthesized. It is found that the Pt–Pd bimetallic catalysts all exhibit an atomic-level alloy structure, and the surplus precious metals are present as isolated PMO_x (precious metal oxides) species on the Pt–Pd alloy or the surface of the CZL supports. The closer interaction between the support and separate PMO_x particles highly dispersed on the surface could stabilize the precious metals and promote the dynamic oxygen storage/release capacity (DOSC) and oxygen mobility, which increases the concentration of surface-active oxygen species, thereby resulting in superior catalytic performance for HC and NO_x elimination and the broadening of the dynamic operation window. The formation of the Pt–Pd alloy also obviously improves the thermodynamics of the samples. The Pt_0.8Pd_0.2/CZL catalyst exhibits the best catalytic activity for NO and HC conversions among all the catalysts, which could be attributed to the larger DOSC values and the enhanced activation of surface oxygen. Moreover, the presence of H₂O and CO₂ has little influence on the catalytic performance of Pt_0.8Pd_0.2/CZL.