Optimizing the Properties of Hybrids Based on Graphene Oxide for Carbon Dioxide Capture

Abstract

The reduction of CO 2 emissions and its elimination from the atmosphere has become one of the major problems worldwide, since CO 2 is the main cause of the greenhouse effect and climate change. In recent years, a great number of carbonaceous materials that can be used as CO 2 adsorbents have been synthesized. The strategy is usually to synthesize the materials and determine their adsorption capacity without studying previously the factors that influence this capacity. In this work, different properties of the adsorbents are analyzed to study their influence on the CO 2 adsorption capacity. For this purpose, 10 adsorbents have been synthesized using different strategies and characterized with X-ray photoelectron spectroscopy, X-ray diffraction, and micro-Raman spectroscopy. The percentage of sp 2 carbons, the position of the D + D′ peak of the second-order Raman spectrum, the micropore volume, and the grain size of the C sp 2 domains have been related to the amount of CO 2 adsorbed by the adsorbents. The results confirm a linear relationship between the volume of the micropores and the CO 2 uptake and it proves that CO 2 retention is favored in those materials that, in addition to having a high volume of micropores, also have low grain size of C.

Decoding Carbon-Based Materials’ Properties for High CO2 Capture and Selectivity

“…A glimpse of this correlation was provided by Merchán and co-workers in their recent report, wherein they suggested that this structural property can improve the micropore volume and thus CO 2 uptake. 23 Carbon in sp 2 hybridization states is considered to adsorb CO 2 through π–π interactions since sp 2 bonds (C=C) are polarizable. 38 Therefore, it can be concluded that the BUGC’s short- and long-range graphitic ordering, which is a polarizable π-electron system, has the potential to interact with CO 2 molecules effectively through dispersion forces.…”

“… 27 , 29 Moreover, D* (∼1110 cm –1 ), D″ (1500–1540 cm –1 ), and D′ (1680–1695 cm –1 ) bands were also present, corresponding to the disordered graphitic lattice due to C sp3 carbon centers, amorphous phases, and defects of the basal plane, respectively ( Figure S5 , SI). 23 The defect ratio ( I D / I G ) was also determined for all samples and summarized in Table S3 , SI. Importantly, the I D / I G ratio was lowest in BUGC, implying that the sp 2 carbon character was the highest in BUGC, which validates the results obtained from XPS spectroscopy ( vide supra ).…”

“…The Raman spectra of all materials were fitted and analyzed (Figure S5, SI). Two major peaks at 1330 and 1590 cm –1 were observed due to defects (D-band) and stretching of sp 2 carbons (G-band) in carbon lattice, respectively (Figure S5, SI). , Moreover, D* (∼1110 cm –1 ), D″ (1500–1540 cm –1 ), and D′ (1680–1695 cm –1 ) bands were also present, corresponding to the disordered graphitic lattice due to C sp3 carbon centers, amorphous phases, and defects of the basal plane, respectively (Figure S5, SI) . The defect ratio ( I D / I G ) was also determined for all samples and summarized in Table S3, SI.…”

“…In this context, Merchán and co-workers prepared hybrid hydrogels from graphene oxide and activated carbon fibers and focused on correlating various textural properties with CO 2 uptake. 23 However, these materials had distinct domains of activated carbon fiber and GO, which resulted in difficulties correlating adsorption characteristics with graphene-like structures. The novel idea of investigating the relation between the properties of materials and CO 2 adsorption can help researchers to synthesize new materials that can achieve extraordinary CO 2 adsorption capacity and selectivity.…”

“…These materials have shown great potential for CO 2 adsorption application, which suggests that a detailed study to understand the impact of various structural features of these nanomaterials on CO 2 uptake is of great importance. In this context, Merchán and co-workers prepared hybrid hydrogels from graphene oxide and activated carbon fibers and focused on correlating various textural properties with CO 2 uptake . However, these materials had distinct domains of activated carbon fiber and GO, which resulted in difficulties correlating adsorption characteristics with graphene-like structures.…”