Hiroki A, Laverne Jay A
Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
J Phys Chem B. 2005 Mar 3;109(8):3364-70. doi: 10.1021/jp046405d.
The thermal decomposition of hydrogen peroxide, H(2)O(2), was determined in aqueous suspensions of SiO(2), Al(2)O(3), TiO(2), CeO(2), and ZrO(2) nanometer-sized particles. First-order kinetics were observed for the decomposition in all cases. Temperature dependence studies found that the activation energy was 42 +/- 5 kJ/mol for the overall decomposition of H(2)O(2) independent of the type of oxide. Oxide type had a strong effect on the pre-exponential rate term with increasing rate in the order of SiO(2) < Al(2)O(3) < TiO(2) < CeO(2) < ZrO(2). The rate coefficient for H(2)O(2) decomposition increases with increasing surface area of the oxide, but the number or efficiency of reactive sites rather than the total surface area may have the dominant role. Very efficient scavengers for OH radicals in the bulk liquid are not able to prevent formation of molecular oxygen, the main H(2)O(2) gaseous decay product, suggesting that decomposition occurs on the oxide surfaces. The decomposition of H(2)O(2) in the gamma-radiolysis of water is enhanced by the addition of ceramic oxides, possibly due to excess formation of hydrated electrons from energy deposited in the solid.
在二氧化硅（SiO₂）、氧化铝（Al₂O₃）、二氧化钛（TiO₂）、二氧化铈（CeO₂）和氧化锆（ZrO₂）纳米级颗粒的水悬浮液中测定了过氧化氢（H₂O₂）的热分解。在所有情况下，分解均符合一级动力学。温度依赖性研究发现，H₂O₂总体分解的活化能为42±5 kJ/mol，与氧化物类型无关。氧化物类型对指数前速率项有强烈影响，速率按SiO₂＜Al₂O₃＜TiO₂＜CeO₂＜ZrO₂的顺序增加。H₂O₂分解的速率系数随氧化物表面积的增加而增大，但反应位点的数量或效率而非总表面积可能起主导作用。本体液体中非常有效的羟基自由基清除剂无法阻止分子氧的形成，分子氧是H₂O₂的主要气态衰变产物，这表明分解发生在氧化物表面。在水的γ辐射分解中，添加陶瓷氧化物可增强H₂O₂的分解，这可能是由于固体中沉积的能量产生了过量的水合电子。
