In Situ Spectroscopic Control of Gas Adsorption Selectivity Under an Electric Field

Abstract Microscopic carbon/SiO ₂ composites are composed of a huge number of interfacial contacts. When those are exposed to moderate ohmic fields gas adsorptivity of the composite is modulated. Herein it shows that it is possible to manipulate, modify, and follow gas adsorption selectivity by in situ spectroscopy under electrical charging. In a model gas mixture of CO ₂ and N ₂ , for the first time it can be shown that a change in gas composition is observed and can be controlled locally above an electrically charged carbon/SiO ₂ surface using in situ Raman spectroscopy. The technique is implemented in an ongoing non‐stationary adsorption process using the advantage of the fast on‐off switchability of the electric field as compared to the typically slow equilibration kinetics of adsorption on activated carbon. An increase in gas phase concentration of 3.5% and 5.5% of CO _2, which is equivalent to a change in selectivity of 11% and 24% of CO ₂ over N _2, just by applying an electrical input power of 0.53 and 1.12 W is achieved and quantified by Raman spectroscopy, respectively. The method bears general potential for mixtures of gases with different responses to the electric field, as well as for processes where a local manipulation of gas concentrations is necessary.