Defect-driven electron reservoir in MOF-derived Pd@CeO₂ for efficient ethane combustion

The complete catalytic oxidation of ethane (C₂H₆) represents a critical challenge in volatile organic compound (VOC) abatement due to the high kinetic barrier for C-H bond scission and the sluggish oxygen cycling characteristic of conventional Pd-based catalysts. In this study, a metal-organic framework (MOF)-templated pyrolysis strategy was employed to construct a robust Pd@CeO₂-P catalyst featuring a high density of Ce³⁺/V_O defect pairs. The catalyst achieved a T₉₀ of 314 °C for C₂H₆ oxidation, successfully lowering the reaction temperature by 36 °C compared to the hydrothermally synthesized Pd/CeO₂-H. Concurrently, it delivered a remarkable TOF of 0.432 s⁻¹ and a specific reaction rate (r_s) of 24.69 nmol·m⁻²·s⁻¹ at 310 °C, substantially outperforming the reference catalyst by 9.63- and 2.21-fold, respectively. Systematic characterizations and in situ spectroscopic analyses demonstrated that Ce³⁺/V_O defect pairs function as dynamic electron reservoirs, inducing a strong electronic metal-support interaction (EMSI) that effectively stabilizes the highly active Pd²⁺ state through continuous interfacial charge transfer at Pd²⁺–O–Ce³⁺ interfacial sites. Simultaneously, this synergistic electronic modulation significantly lowered the formation energy of V_O, increasing the mobility and reactivity of surface lattice oxygen (O_sur) to participate in the reaction. C₂H₆-TPR/TPSR and in situ DRIFTS analyses demonstrate that Pd²⁺–O–Ce³⁺ interfacial sites facilitate the initial C-H bond cleavage, while the Ce³⁺/V_O electron reservoir promotes rapid gas-phase O₂ activation and lattice oxygen replenishment, thereby effectively promoting the formation of acetate intermediates. Moreover, the catalyst demonstrated remarkable stability over 50 h of continuous operation, maintaining C₂H₆ conversion above 89%. This performance suggests significant potential for industrial applications in deep VOC mineralization.