H atom production and reaction in the gamma radiolysis of thermally modified boehmite

The correlation between the formation of H atoms and H2 was observed in the radiolysis of thermally modified boehmite (γ-AlOOH). Boehmite was pretreated by heating to 300, 400, and 550 °C, loaded with adsorbed water, and irradiated with γ-rays. Long-lived H atoms trapped in the interstitial matrix were observed by electron paramagnetic resonance techniques, and the amount of gaseous H2 was detected by gas chromatography. Heating the boehmite to 400 °C before radiolysis results in the collapse of the matrix with loss of trapped H atoms and a substantial increase in the production of H2. Samples without added water postheating showed no production of H2, suggesting that it is formed by the diffusion of H atoms to the surface followed by an abstraction reaction with water. Boehmite heated to 550 °C has completely converted to alumina, and the radiolytic responses of each are similar. Post-irradiation heating of boehmite to 300 °C results in a doubling of the H2 yield at pretreated temperatures below 300 °C due to the release of trapped H atoms.