How Reproducible are Surface Areas Calculated from the BET Equation?

Abstract

Porosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer–Emmett–Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro‐ and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already‐measured raw adsorption isotherms were provided to sixty‐one labs, who were asked to calculate the corresponding BET areas. This round‐robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called “BET surface identification” (BETSI), expands on the well‐known Rouquerol criteria and makes an unambiguous BET area assignment possible.

High-surface-area activated carbon from pine cones for semi-industrial spray deposition of supercapacitor electrodes

“…The procedure takes into account Rouquerol parameters and is provided as a part of standard Quantachrome ASiQWin software package. 42 The value of the BET SSA was also verified using the BETSI software 44 which provided nearly identical values (see Table 1 in the ESI† file). The slit-pore QSDFT equilibrium model was applied to evaluate the cumulative surface area, pore volume and pore size distribution.…”

Densified HKUST-1 Monoliths as a Route to High Volumetric and Gravimetric Hydrogen Storage Capacity

“…We then evaluated the porosity using N 2 adsorption at 77 K (Figures 3b, S2, and S3). Table S19 compares the densities, gravimetric and volumetric Brunauer, Emmett, and Teller (BET) areas calculated using Rouquerol ́s updated criteria implemented in BETSI (Figures S4 and S5), 30 and pore volumes of mono-HKUST-1 with those of powder and densified benchmark MOF materials. While mono HKUST-1 displays one of the lowest observed gravimetric BET areas (1552 m 2 g −1 ) and total pore volume (0.634 cm 3 g −1 ) of the materials presented, the critical advantage of the monolithic MOF is the high bulk density, which enables benchmark volumetric performance (BET area = 1,651 m 2 cm −3 ; pore volume = 0.675 cm 3 cm −3 ) which far exceeds that of powdered and mechanically pressed MOF counterparts (Table S19 and Figure S46).…”

Mechanistic Principles for Engineering Hierarchical Porous Metal–Organic Frameworks

“…At the nanoscale level, the morphology and particle size of HP-MOFs are analyzed by SEM and/or TEM. It is worth noting that the measured porosity of HP-MOFs can vary when employing different kinds of instruments, and even the same type of instrument produced by different companies, which has been frequently observed in testing the surface area and pore volume of MOFs based on gas sorption isotherms …”