Quantitative Characterization of Thermodynamic/Kinetic Parameters to Reveal the Nanosize Effect on Surface Adsorption

The size effect of nanomaterials plays a crucial role in practical applications such as surface adsorption. However, quantitative extraction of the thermodynamic and kinetic parameters that intrinsically control the size-dependent adsorption behavior remains a significant challenge. Herein, a facile and broadly applicable measurement method was proposed to establish quantitative correlations between nanosize and thermodynamic/kinetic parameters. The nanosize effect on the adsorption of molecules can be traced back to the thermodynamic enthalpy and kinetic activation energy. With mesoporous silica SBA-15 as an example, a continual decrease in the nanopore wall thickness brings a dramatic rise in enthalpy −ΔH°, which indicates a significant change in molecular interactions from reversible adsorption to a strong chemical reaction, and the decrease in the activation energy Ea demonstrates an increased adsorption speed. Such size effects on the thermodynamic and kinetic properties are found in various nanomaterials. Our results show that size-dependent rules widely exist in the interior of nanomaterials, which can lead to stronger and faster surface interactions.