Adsorption behaviors and vibrational spectra of hydrogen peroxide molecules at quartz/water interfaces

Abstract

The effect of H₂O₂ concentration on the change of H-bonds at a water/quartz interface was systematically examined by surface-specific sum-frequency generation (SFG) spectroscopy. Molecular dynamics (MD) simulation was further utilized to interpret the specific molecular dynamics as well as the configuration and evolution of water and H₂O₂ molecules at the interface. The results from this study demonstrated the important role of surface H-bonds on determination of the stability of adsorbed H₂O₂ at solvated, silica, xerogel surfaces. It was revealed that prior to reaching the surface saturation with H₂O₂ molecules (less than 20% in bulk solution), multiple H-bonds were formed with silanols at relatively short interactive distances. These H-bonds proved to be strong enough to enable the overall stability of adsorbed H₂O₂. However, once saturated, the H₂O₂ molecules would be adsorbed at longer distances away from the surface, and could easily migrate to the bulk solution; therefore, in this case, the bonds failed to support stable H₂O₂ adsorption. These new findings explained the detailed molecular mechanism of the relationship between H₂O₂ concentration and H₂O₂ stability in H₂O₂–silica xerogels. This solves the current challenge of effective H₂O₂ storage, and provides fundamental insight for predicting the adsorption behavior of H₂O₂ at the silica surface.