Rich-Defect Ru–Tb ₂ Ce ₂ O _{7+ <i>x</i>} Catalysts for Highly Efficient Soot Particulate Elimination: Insights into the key roles of Ru–O–Ce/Tb Interfacial Bonds, Ru ⁰ Sites, and Surface Vacancies

Catalytic combustion with a DPF honeycomb is currently a feasible way to abate soot particulate pollution, but it is still of great necessity to develop more efficient and cost-effective catalysts. To accomplish this, Ru was adopted to decorate a Tb₂Ce₂O_7+<i>x</i> solid solution in its lattice (Ru-TC) or on its surface (Ru/TC-DP). The addition of Ru promotes the formation of catalytically critical Ru-O-Ce/Tb interfacial bonds and abundant oxygen vacancies, both of which are more numerous in Ru/TC-DP. DFT calculations confirm that Ru lowers the oxygen vacancy formation energy and the O₂ adsorption energy, especially on Ru/TC-DP, enhancing the generation of reactive oxygen anions (O₂^-, O₂^2-). Isotopic ¹⁸O₂-TPSR-MS shows that Ru/TC-DP has a better capability to activate O₂ than Ru-TC. Furthermore, Ru/TC-DP owns more surface Ru⁰ sites conducive to activating gaseous O₂. Quasi <i>in situ</i> XPS revealed that Ru decoration promotes the dual Tb⁴⁺/Tb³⁺ and Ce⁴⁺/Ce³⁺ redox cycles, particularly with Ru/TC-DP. The excellent performance arises from synergy among three components: metallic Ru⁰ sites adsorb and weaken O₂, Ru-O-Ce/Tb interfacial bonds act as electron transfer channels that drive --O cleavage and stabilize oxygen vacancies, and the abundant vacancies serve as acceptors for activated oxygen species. This cooperative mechanism establishes an efficient cycle for continuous oxygen activation and lattice oxygen replenishment. Consequently, Ru/TC-DP exhibits remarkable soot combustion activity (<i>T</i>₅₀ = 333 °C, TOF = 2.90 × 10^-3 s^-1). This work demonstrates that loading Ru onto the surface of Tb₂Ce₂O_7+<i>x</i> provides a cost-effective strategy for designing high-performance soot combustion catalysts through multisite synergy.