Holey graphene frameworks for highly selective post-combustion carbon capture

Abstract

Atmospheric CO2 concentrations continue to rise rapidly in response to increased combustion of fossil fuels, contributing to global climate change. In order to mitigate the effects of global warming, development of new materials for cost-effective and energy-efficient CO2 capture is critically important. Graphene-based porous materials are an emerging class of solid adsorbents for selectively removing CO2 from flue gases. Herein, we report a simple and scalable approach to produce three-dimensional holey graphene frameworks with tunable porosity and pore geometry, and demonstrate their application as high-performance CO2 adsorbents. These holey graphene macrostructures exhibit a significantly improved specific surface area and pore volume compared to their pristine counterparts, and can be effectively used in post-combustion CO2 adsorption systems because of their intrinsic hydrophobicity together with good gravimetric storage capacities, rapid removal capabilities, superior cycling stabilities, and moderate initial isosteric heats. In addition, an exceptionally high CO2 over N2 selectivity can be achieved under conditions relevant to capture from the dry exhaust gas stream of a coal burning power plant, suggesting the possibility of recovering highly pure CO2 for long-term sequestration and/or utilization for downstream applications.

Figure 1. Illustration of the major steps involved in the preparation of HGFs.

The synthesis involves etching of in-plane nanopores into GO sheets and their self-assembly into a 3D interconnected network structure.

Figure 2. Structural characterization of HGFs.

(a) Wide angle XRD patterns, (b) XPS survey spectra, (c) Raman spectra and (d) N₂ adsorption/desorption isotherms of GO, NGF, and HGFs. The solid and open symbols represent adsorption and desorption, respectively.

Figure 3. Morphological characterization of HGFs.

FESEM images of (a) HGF-II and (b) NGF. (c,d) TEM images of HGF-II. The scale bars in (a–b), (c) and (d) represent 1 μm, 100 nm and 50 nm, respectively.

Figure 4. CO₂ adsorption performance of HGFs.

(a) Pure component CO₂ adsorption isotherms of NGF and HGFs at standard temperature and pressure (0 °C and 1 bar). (b) CO₂ adsorption kinetics of HGF-II at different temperatures. (c) Calculated isosteric heat of adsorption for HGF-II as function of CO₂ loading. (d) Cyclic CO₂ adsorption performance of HGF-II at 25 °C.