A standardization for BET fitting of adsorption isotherms

Brunauer–Emmett–Teller (BET) theory is a popular method to interpret nitrogen adsorption isotherms for determining the specific surface area. Besides the monolayer capacity nmnm, the BET equation depends on one single additional parameter C that is adjusted to fit the experimental adsorption curves. BET analysis is key in surface characterization and is widely applied even when the underlying assumptions are not strictly justified. For example, disregarding its weaker physical interpretation, the BET surface area is generally accepted as an important characterization of microporous materials. However, whereas the accuracy of the adsorption techniques has tremendously increased in recent years, experimentally derived BET values do not yet meet the same standards. The reason for this is due to some intrinsic ambiguities in its fitting procedure. In this letter, we propose a procedure that is uniquely defined, given a certain pressure range, and is independent of arbitrary experimental details such as the distribution of data points. It puts an equal weight on both monolayer and multilayer formation and gives an additional reproducible measure that is related to the inherent deviation from the BET behavior.

We propose a new BET fitting method that considerably improves the reproducibility and rationally balances the accuracy of description of monolayer and multilayer adsorption regardless the density of data points they contain.Figure optionsDownload as PowerPoint slideHighlights
► Brunauer–Emmett–Teller (BET) is a popular method in surface characterization.
► Present BET fitting procedures have poor reproducibility.
► We propose a new procedure that is independent of arbitrary experimental details.