Interfacial Energy Transfer during Gamma Radiolysis of Water on the Surface of ZrO₂ and Some Other Oxides

Abstract

The effect of an oxide interface on 60 Co gamma radiolysis of water molecules was studied. On the basis of the molecular hydrogen yield when compared with the radiolysis of the control ampules without oxides, all the tested materials can be generally classified into three groups: I. Oxides that lower the H 2 yield (MnO 2 , Co 3 O 4 , CuO, and Fe 2 O 3 ); II. Oxides with H 2 yields that are close to G values obtained in control experiments

Water Radiolysis: Influence of Oxide Surfaces on H2 Production under Ionizing Radiation

“…This is illustrated in the work of Petrik et al, who studied the H 2 yield as a function of the band gap of different oxides (Figure 1) submitted to  radiation with adsorbed water molecules at their surface [60]. We point out that the yields are determined with respect to the energy deposited directly by -rays to the water molecules adsorbed on oxides.…”

“…Low-LET radiation (gamma radiation, accelerated electrons, high-energy X-rays) deposits energy discretely along the path of the particles whereas high-LET radiation (heavy ions, alpha particles and neutrons) deposits it densely. Gamma radiation of 60 Co has thus a LET value of 0.2-0.3 keV µm −1 whereas the value is 140 keV µm −1 in the case of 5.3 MeV alpha particles ( 210 Po) [8]. The LET is one of the important parameters to account for the yields of products obtained in radiolysis.…”

“…Among them, 137 Cs and 60 Co sources made it possible to get clean sources of radiation (-radiation, and not a mixture of different types of radiation leading to complex chemistry) with high dose rates and high penetrating power enabling the rapid development of radiation chemistry studies. Moreover, starting from 1960, much experimental work was carried out to develop pulse radiolysis equipment to directly measure the time dependence of some of the reactive species formed and the corresponding rate constants.…”

“…It was found that the type of oxide greatly impacts the H 2 production [58][59][60][61][62]. This is illustrated in the work of Petrik et al, who studied the H 2 yield as a function of the band gap of different oxides (Figure 1) submitted to  radiation with adsorbed water molecules at their surface [60].…”

“…If the H 2 yield thus calculated is greater than the value obtained in bulk water, then an energy transfer from the oxide to water is to be expected. This study enabled the authors to sort oxides into three groups [60] Figure 1 exhibits a resonant maximum for a band gap of the oxide of 5 eV corresponding to the energy of the H-OH bond in a water molecule (5.1 eV). The resonant character of the H 2 yield as a function of the band gap of the oxide is consistent with an exciton transfer mechanism [60].…”