Uncertainties in characterization of nanoporous carbons using density functional theory-based gas physisorption

Abstract

Nanoporous carbon materials have a wide range of applications in environmental and sustainable energy fields. Accurate quantification of micropores (<2nm) is essential to understanding and optimizing the performance of carbon materials in applications such as supercapacitors. To quantify micropores in carbon materials, the gas physisorption technique remains the most common. Despite its long history and popularity, the technique is still developing due to the recent progress in applying density functional theory (DFT) models to physisorption. Because of the complex nature of DFT, it remains a challenging task to accurately characterize porous structures of nanoporous carbons. In this work we use four distinct carbon samples and quantify the uncertainties associated with the DFT models. We demonstrate that more accurate interpretation of pore sizes in nanoporous carbons can be achieved by selecting the appropriate DFT kernels and adsorbates. We propose a procedure that joins two sets of pore size distribution (PSD) data provided by application of two DFT models (non-local DFT and quenched solid DFT) while using two adsorbates (N2 and CO2), respectively. It is hoped that this paper will serve as a practical guide for researchers who use the gas physisorption technique and consider adopting the DFT model.