Charge-regulated, electric-field and combined effect controlled switchable CO2 capture and separation on penta-C2N nanosheet: A computational study

Abstract

The discovery of a new 2D material for CO2 capture and separation is a noteworthy aspect of this work. Recently, a novel approach of charge-regulated/electric-field gas capture and storage has been proposed using density functional theory (DFT) computations, which provides important advantages such as controllable kinetics and reversibility. Here, we investigate the adsorption of CO2, H2, CH4 and N2 on the penta-C2N sheet with different charge densities and electric-field. The CO2 adsorption energy can be significantly enhanced through the strategies of electrochemical methods such as addition of negatively charged states or applying an external electric field, while the adsorption of H2, CH4 and N2 on penta-C2N is slightly influenced with the above strategies. In addition, we explored a new promising approach for combining a charged state with an external electric field to study the combined effect. The effect of an electric field was found to further strengthen and induce a stronger bending of the CO2 molecule and C-O bond length elongation at the presence of charged states with an electric field on the penta-C2N sheet. For instance, the adsorption energy of CO2 molecule at the electric field of 0.030 a.u. with a charged state (combined effect) is −64.22 kcal/mol which is 23.85 kcal/mol more stable than that (−40.37 kcal/mol) of the electric field. Interestingly, CO2 molecules can spontaneously adsorb and desorb from the surface by injecting or removing additional charge densities and/or electric fields. Notably, the charge density (0.91 × 1014 e−/cm2), electric field (0.020 a.u.) and combined effect (0.005 a.u.) beyond this range is applicable for highly selective adsorption of CO2 from gas mixtures (H2, CH4 and N2). The results could provide new insights in searching for advanced materials with exceptionally high CO2 capture capacity.