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Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture.

Tan X, Kou L, Tahini HA, Smith SC - Sci Rep (2015)

Bottom Line: At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%.In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2.These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

View Article: PubMed Central - PubMed

Affiliation: Integrated Materials Design Centre (IMDC), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia.

ABSTRACT
Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

No MeSH data available.


The energy change of (a) the relaxation (capture) of a CO2 molecule on g-C4N3 after two extra electrons are introduced, and (b) the reverse relaxation (release) process of a captured CO2 molecule from g-C4N3 after two extra electrons are removed from the adsorbent.
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f4: The energy change of (a) the relaxation (capture) of a CO2 molecule on g-C4N3 after two extra electrons are introduced, and (b) the reverse relaxation (release) process of a captured CO2 molecule from g-C4N3 after two extra electrons are removed from the adsorbent.

Mentions: In order to investigate the kinetic process of CO2 capture/release on 2 e− negatively charged g-C4N3, we next studied the energy change of a CO2 molecule adsorbed on g-C4N3 after the introduction or removal of the two extra electrons. In Fig. 4(a), we started with the lowest-energy configuration of neutral g-C4N3 with a physisorbed CO2 molecule. Two electrons are then added to the neutral g-C4N3, and we examined the energy changes as the system relaxes to the 2 e− negatively charged optimized state. In Fig. 4(b), we started with the lowest-energy configuration of the 2 e− negatively charged g-C4N3 with a chemisorbed CO2 molecule. Two electrons are removed, and then the system is allowed to relax, forming a physisorbed CO2 molecule. When two extra electrons are introduced into g-C4N3, the interactions between the CO2 molecule and the 2 e− negatively charged g-C4N3 are significantly larger than that with neutral g-C4N3, and the CO2 molecule spontaneously relaxes to chemisorption configuration. This process is exothermic by 1.08 eV without any energy barrier. On the other hand, when two extra electrons are removed from the 2 e− negatively charged g-C4N3, the CO2 molecule spontaneously returns to the weakly bound state and desorbs from g-C4N3. This process is also exothermic by 1.39 eV without any energy barrier. Therefore, the CO2 storage/release processes on negatively charged g-C4N3 are reversible with fast kinetics, and can be easily controlled via adding/removing the extra electrons.


Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture.

Tan X, Kou L, Tahini HA, Smith SC - Sci Rep (2015)

The energy change of (a) the relaxation (capture) of a CO2 molecule on g-C4N3 after two extra electrons are introduced, and (b) the reverse relaxation (release) process of a captured CO2 molecule from g-C4N3 after two extra electrons are removed from the adsorbent.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664948&req=5

f4: The energy change of (a) the relaxation (capture) of a CO2 molecule on g-C4N3 after two extra electrons are introduced, and (b) the reverse relaxation (release) process of a captured CO2 molecule from g-C4N3 after two extra electrons are removed from the adsorbent.
Mentions: In order to investigate the kinetic process of CO2 capture/release on 2 e− negatively charged g-C4N3, we next studied the energy change of a CO2 molecule adsorbed on g-C4N3 after the introduction or removal of the two extra electrons. In Fig. 4(a), we started with the lowest-energy configuration of neutral g-C4N3 with a physisorbed CO2 molecule. Two electrons are then added to the neutral g-C4N3, and we examined the energy changes as the system relaxes to the 2 e− negatively charged optimized state. In Fig. 4(b), we started with the lowest-energy configuration of the 2 e− negatively charged g-C4N3 with a chemisorbed CO2 molecule. Two electrons are removed, and then the system is allowed to relax, forming a physisorbed CO2 molecule. When two extra electrons are introduced into g-C4N3, the interactions between the CO2 molecule and the 2 e− negatively charged g-C4N3 are significantly larger than that with neutral g-C4N3, and the CO2 molecule spontaneously relaxes to chemisorption configuration. This process is exothermic by 1.08 eV without any energy barrier. On the other hand, when two extra electrons are removed from the 2 e− negatively charged g-C4N3, the CO2 molecule spontaneously returns to the weakly bound state and desorbs from g-C4N3. This process is also exothermic by 1.39 eV without any energy barrier. Therefore, the CO2 storage/release processes on negatively charged g-C4N3 are reversible with fast kinetics, and can be easily controlled via adding/removing the extra electrons.

Bottom Line: At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%.In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2.These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

View Article: PubMed Central - PubMed

Affiliation: Integrated Materials Design Centre (IMDC), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia.

ABSTRACT
Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

No MeSH data available.