Molecular insight on unusually high specific hydrogen adsorption over silicon carbide

Hydrogen adsorption over silicon carbide of different nature was investigated. High specific hydrogen adsorption (up to 15 μmol/m²), nontypical for silicon carbide was obtained for the materials prepared by the template method. A more perfect truly "carbide" structure (with a higher content of Si–C bonds in the form of carbide) in this type of materials contributes to an increase of the specific hydrogen adsorption. However, some non-stoichiometricity manifested in the presence of carbon in other (non-carbide) bonds (graphite or terminal and sp³ hybridized C) is required for exceptionally high specific hydrogen adsorption. The influence of the adsorbate nature for several gases (Н₂, N₂, CO) was found to be less prominent for SiC compared to carbon and silica materials. This feature inherent only to silicon carbide exhibiting an increased level of specific hydrogen adsorption, is due to cooperative adsorption, accompanied by an abnormally high loading of the adsorbent surface in the supercritical region.