Yinlin Chang,Tao Liu,Jingyuan Rao,Min Fu,Yijun Guo,Shuliang Zou,Dewen Tang,Zetian Tao
The safe immobilization of radiotoxic strontium (Sr) in high-level radioactive waste (HLW) remains a major challenge due to its tendency to segregate and leach under aqueous conditions. In this study, a surface vanadium (V) engineering strategy is proposed to enhance the chemical stability of Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) ceramics. V-doped samples (SFMV), synthesized via a sol-gel method with 0.05 mol V partially substituting Mo, show improved resistance to Sr migration. DFT calculations reveal that V modification increases the Sr migration barrier from 0.14 eV (in SFM) to 0.34 eV (in SFMV) and induces the formation of strong Fe-O-V, and Mo–O–V effectively suppressing Sr surface segregation. Additionally, the formation of SrMoO 4 phases may act as Sr sinks, further enhancing stability. Leaching tests show that the Sr release from SFMV drops from 7.43 × 10 −4 to 2.89 × 10 −6 g·cm −2 ·d −1 over 42 days, representing a 64 % reduction compared to pristine SFM. This work provides a promising strategy for designing durable ceramic hosts for Sr-containing HLW.
An depth understanding of the fundamental interactions between surface termination and catalytic activity is crucial to prompt the properties of functional perovskite materials. The elastic energy due to size mismatch and electrostatic attraction of the charged Sr dopant by positively charged oxygen vacancies induced inert A-site surface enrichment rearrangement for perovskites. Lower temperatures could reduce A-site enrichment, but it is difficult to form perovskite crystals. La 0.8 Sr 0.2 CoO 3-δ (LSCO) as a model perovskite oxide was modified with additive urea to reduce the crystallization temperature , and suppress Sr segregation. The LSCO catalysts with 600 °C annealing temperature (LSCO-600) exhibited a 19.4-fold reaction reactivity of toluene oxidation than that with 800 °C annealing temperature (LSCO-800). Combined surface-sensitive and depth-resolved techniques for surface and sub-surface analysis, surface Sr enrichment was effectively suppressed due to decreased oxygen vacancy concentration and smaller electrostatic driving force. DFT calculations and in-situ DRIFTs spectra well revealed that tuning the surface composition/termination affected the intrinsic reactivity. The catalyst surface with lower Sr enrichment could easily adsorb toluene, cleave, and decompose benzene rings , thus contributing to toluene degradation to CO 2 . This work demonstrates a green and efficient way to control surface composition and termination at the atomic scale for higher catalytic activity.
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