Institut de Chimie Séparative de Marcoule, UMR5257, CEA-CNRS-UM2-ENSCM, Centre de Marcoule, Bat. 426, BP 17171, 30207 Bagnols-sur-Cèze, France.
CEA/DEN/MAR/DRCP, Nuclear Energy Division, Radiochemistry and Process Department, BP17171, 30207 Bagnols sur Cèze, France.
Ultrason Sonochem. 2016 Mar;29:512-6. doi: 10.1016/j.ultsonch.2015.11.006. Epub 2015 Nov 4.
Kinetics of hydrogen formation was explored as a new chemical dosimeter allowing probing the sonochemical activity of argon-saturated water in the presence of micro- and nano-sized metal oxide particles exhibiting catalytic properties (ThO2, ZrO2, and TiO2). It was shown that the conventional sonochemical dosimeter based on H2O2 formation is hardly applicable in such systems due to catalytic degradation of H2O2 at oxide surface. The study of H2 generation revealed that at low-frequency ultrasound (20 kHz) the sonochemical water splitting is greatly improved for all studied metal oxides. The highest efficiency is observed for relatively large micrometric particles of ThO2 which is assigned to ultrasonically-driven particle fragmentation accompanied by mechanochemical water molecule splitting. The nanosized metal oxides do not exhibit particle size reduction under ultrasonic treatment but nevertheless yield higher quantities of H2. The enhancement of sonochemical water splitting in this case is most probably resulting from better bubble nucleation in heterogeneous systems. At high-frequency ultrasound (362 kHz), the effect of metal oxide particles results in a combination of nucleation and ultrasound attenuation. In contrast to 20 kHz, micrometric particles slowdown the sonolysis of water at 362 kHz due to stronger attenuation of ultrasonic waves while smaller particles show a relatively weak and various directional effects.
氢形成动力学被探索为一种新的化学剂量计，允许探测在表现出催化性能的微纳米尺寸金属氧化物颗粒存在下的氩饱和水中的声化学活性（ThO2、ZrO2 和 TiO2）。结果表明，由于氧化物表面上 H2O2 的催化降解，基于 H2O2 形成的传统声化学剂量计在这种系统中几乎不适用。H2 生成的研究表明，在低频超声（20 kHz）下，所有研究的金属氧化物的声化学水分解都得到了极大的改善。对于相对较大的微米级 ThO2 颗粒，观察到最高的效率，这归因于超声驱动的颗粒破碎伴随着机械化学水分子分裂。纳米尺寸的金属氧化物在超声处理下不会表现出颗粒尺寸减小，但仍然产生更多的 H2。在这种情况下，声化学水分解的增强很可能是由于异质体系中更好的空化核形成。在高频超声（362 kHz）下，金属氧化物颗粒的作用导致成核和超声衰减的结合。与 20 kHz 相反，由于超声波的衰减更强，微米级颗粒在 362 kHz 下减慢了水的超声分解，而较小的颗粒则表现出相对较弱和各种方向的影响。
