Absorption-desorption of carbon dioxide in carbon honeycombs at elevated temperatures

Abstract

The recently synthesized honeycomb carbon allotrope has numerous potential applications, in particular for storage of gases inside carbon matrices. In this work this carbon form was experimentally studied in its denser form in order to estimate the upper temperature limit for keeping a gas inside the cellular structure. Along with the previously reported random honeycombs of a zigzag type we have also revealed the densest armchair structure. The mechanism of absorption-desorption of carbon dioxide studied by means of high energy electron diffraction at low temperatures showed the two-stage character of the observed desorption at elevated temperatures. This effect is associated to the weaker or stronger bonding of molecules with pore walls depending on the specific configuration of channels with different sizes. We have found that complete desorption of CO 2 does not occur even at the temperatures about three times higher as compared with the sublimation point of carbon dioxide in our vacuum conditions.

Absorption of atomic and molecular species in carbon cellular structures (Review article)

“…In the later experiments with CO 2 [6] the deposition temperature ~ 80 K was close to the sublimation point and the absorption effect was very strong already during deposition ( Fig. 9).…”

“…2. But in the more recent study [6] it had been revealed the contribution of the structures not only of the zigzag type (hcZn0) but also armchair (hcA1) with the highest possible density predicted and considered in [9] (Fig. 3).…”

“…The procedure of production of CHs used in experiments on absorption [1,[4][5][6] most exhaustively described in [1,4] (Fig. 1).…”

“…The experimental studies of the CH structures produced by the method described above as well as composites based on carbon structures filled with absorbed gases were performed in [1,[4][5][6] by means of Transmission High-Energy Electron Diffraction (THEED). The analysis method typically applied to the sets of the diffraction data obtained in the low-temperature experiment can be briefly described as follows [4,6].…”

“…In the procedure of the comparison of experimental and calculated intensities we apply the reliability factor [6]: a fragment of a regular densest honeycomb structure of a zigzag type (hcZn0), the densest honeycomb structure of an armchair type [9] (hcA1) (here a is a parameter of the hexagonal honeycomb lattice) and a small graphitic fragment (Gr), whose contribution to the total diffraction intensity, as a rule, does not exceed ~ 5%. In the hcA1 structure, the distance d 100 corresponds to the diffraction peak (100) hcA1 shown in Fig.…”