Chemical Transformations of Vanadium-Containing Silica Gel in Contact with Water Vapor According to AFM and ESDR Data

The adsorption of water by highly porous silica gels under dynamic conditions was studied by atomic force microscopy (AFM) and electronic spectroscopy of diffuse reflection (ESDR). It was found that a liquid sorbate meniscus is formed in the throats of the pores, which prevents the access of H2O molecules to the intrapore space of silica gel. It was shown that on the surface of IVS-1 silica gel, H2O molecules are coordinated on vanadium oxide centers, increasing the coordination number of vanadium atoms to 5 and 6 in a ratio of 1 : 1. The range of the vanadium oxide monolayer resistance to hydrolytic degradation was revealed, and it was proposed to regenerate IVS-1 when the silica gel reaches a dark red color, which corresponds to the adsorption of similar to 2.5 mmol H2O/g.

Automated summary

The adsorption of water by highly porous silica gels under dynamic conditions was studied using AFM and ESDR. It was found that a liquid sorbate meniscus forms in the pores, preventing the access of water molecules to the intrapore space. The coordination of water molecules on the surface of IVS-1 silica gel was also investigated, showing an increased coordination number of vanadium atoms. The resistance of the vanadium oxide monolayer to hydrolytic degradation was revealed, and a method for regenerating the gel was proposed.