钯催化H2O2分解的机制探讨

高放废物（HLW）处置库近场地下水的辐解能够产生H₂O₂，其被裂变产物合金颗粒（ε-颗粒）的催化分解属于多相表界面反应。本工作选用钯粉模拟ε-颗粒，采用高压反应釜研究体系总压和H₂分压对反应的影响，并按一级动力学模型拟合实验数据。添加HO·的捕获剂和淬灭剂的实验证明无H₂反应过程中存在HO·的生成步骤。钯的催化活性及形态变化与反应时间的关系表明，产物氧吸附在钯的表面对反应具有毒化作用。通过持续监测滤液中H₂O₂浓度的变化，发现溶液中存在类似于Haber-Weiss的反应持续消耗H₂O₂。推导出钯对H₂O₂分解的机制过程和影响因素，为处置库的安全评估提供基础数据。

Mechanism of H2O2 Decomposition Catalyzed by Palladium

The radiolysis of near-field groundwater in high-level radioactive waste(HLW) repository will produce H₂O₂ which is catalytically decomposed by fission product alloy particles(ε-particle) belongs to the surface interface process. In this work, palladium powder was used to simulate ε-particles. The effects of total pressure and partial pressure of hydrogen on H₂O₂ decomposition reaction were studied by autoclave experiments. The reaction rate constant is derived by the first-order kinetic model fitting. The formation of detectable HO· in the reaction process without hydrogen was proved by experiments with adding capture agent and quencher of HO·.The catalytic activity and morphological changes of palladium particles as a function of time were investigated. It is inferred that the product oxygen adsorbed on the surface of palladium has toxic effect. By continuously monitoring the change of H2O2 concentration in the filtrate, it was detected that the decomposition of H₂O₂ in the filtrate is similar to Haber-Weiss reaction in reaction process. The influence mechanism of palladium particles on the decomposition of H₂O₂ is deduced, and the results of this work can provide significant reference data for the safety assessment of the repository.