Engineering the microenvironment of Pd nanoparticles on porous MnOx matrix to improve catalytic toluene combustion

Abstract

Tuning the microenvironment of noble-based catalyst is a key issue for improved catalytic performance. Here, the porous MnOx enclosed Pd nanoparticles were successfully fabricated by template-free method, that was based on an acid-etching strategy using Pd-doped manganite perovskite (e.g., LaPd0.1Mn0.9O3) as precursor. The performance of prepared Pd/MnOx catalyst is beyond the performance of acid-treated MnO2 and traditional Pd/MnO2 catalyst, showing a T90 of 200 °C under a space velocity of 60,000 mL/(g.h). The superior performance should be attributed to the exposure of Pd active sites, the large surface area, abundant oxygen vacancies and the synergistic effect between Pd and MnOx support. XPS spectra demonstrated that the change of Pd oxidation state was well associated with catalytic activity, and the mixed Pd0/Pdn+ species were benefit for improved activity. On the basis of in-situ XRD and TG results, it was revealed that the thermal deactivation was caused mainly by the structural change of MnOx other than the Pd oxidation state. And the structural stability could be strengthened by the thermal treatment at high temperature (e.g., 500 °C), and remained a robust performance over the long-term stability test.