Insight into fuel injection aging effect on deactivation of PtPd bimetallic supported diesel oxidation catalyst: From engine performance evaluation of monolithic catalysts to microscopic characterization of active species

In this study, a comparative experimental study was carried out on DOC catalysts with different aging times (0 h, 40 h, 80 h) by using engine. Emission data were collected through engine testing, and the catalytic behavior of DOC catalysts was analyzed under different operating conditions. Extensive characterization was carried out using BET, XPS, HAADF-STEM and EDS. Research results show that the deterioration of NO oxidation performance of DOC catalyst was mainly reflected in the early stage of aging, and the impact on fuel oxidation ability in the later stage of aging was more significant. The relative contribution of Pt 0 mainly depends on the first 40 h of fuel injection aging, while the relative contribution of Pd 2+ is more easily affected by aging time. The platinum and palladium are mainly uniformly dispersed on the catalyst surface in the form of alloyed nanoparticles. The engine experiments showed the positive relationship between THC leakage and particle size of the catalyst during fuel oxidation, and a negative relationship with the relative contribution of surface Pd 2+ and Pt 0 , especially Pd 2+ . The maximum NO 2 /NO x ratio has a negative linear correlation with particle size and a positive linear correlation with the relative contribution of surface Pt 0 . The physical-chemical state evolution of the catalyst during its operational lifetime was studied. The structure-activity relationship between engine performance evaluation and microstructure of monolithic catalysts was established, which provides guidance for the design of DOC catalysts in practical application environments.