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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.


Top and side views of the lowest-energy configurations of a single CO2 molecule absorbed on the (a) neutral and (b) 2 e− negatively charged g-C4N3. The blue, grey and red balls represent N, C and O atoms, respectively, and the adsorption energies of the CO2 molecule on neutral and 2 e− negatively charged g-C4N3 are listed.
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f2: Top and side views of the lowest-energy configurations of a single CO2 molecule absorbed on the (a) neutral and (b) 2 e− negatively charged g-C4N3. The blue, grey and red balls represent N, C and O atoms, respectively, and the adsorption energies of the CO2 molecule on neutral and 2 e− negatively charged g-C4N3 are listed.

Mentions: We next shift our attention to a single CO2 adsorption on neutral and negatively charged g-C4N3. Since g-C4N3 is a (2 × 2) reconstructed structure, there are many different adsorption sites for a CO2 molecule. Here, we considered all the adsorption sites: directly on top of a C or N atom, above the midpoint of a bond linking the C and N atoms, and above the center of a honeycomb-like hexagon. Figure 2 shows the lowest-energy configurations of a CO2 absorbed on neutral and 2 e− negatively charged g-C4N3. On neutral g-C4N3 (Fig. 2(a)), the linear CO2 molecule is parallel to g-C4N3 and locates on top of three nitrogen atoms. The distance between the C atom of CO2 and closest N atom is 2.966 Å, and the linear CO2 molecule shows little structural change compared to a free CO2 molecule with the O-C-O angle and two double C=O bonds being 178.2° and 1.176 Å, respectively. Mulliken population analysis suggests that the amount of transferred electron from the absorbed CO2 molecule to g-C4N3 is negligible (about 0.004 e−). For the neutral case, the CO2 molecule is weakly adsorbed (i.e. physisorbed) onto neutral g-C4N3 with small adsorption energy of 0.24 eV.


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

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

Top and side views of the lowest-energy configurations of a single CO2 molecule absorbed on the (a) neutral and (b) 2 e− negatively charged g-C4N3. The blue, grey and red balls represent N, C and O atoms, respectively, and the adsorption energies of the CO2 molecule on neutral and 2 e− negatively charged g-C4N3 are listed.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Top and side views of the lowest-energy configurations of a single CO2 molecule absorbed on the (a) neutral and (b) 2 e− negatively charged g-C4N3. The blue, grey and red balls represent N, C and O atoms, respectively, and the adsorption energies of the CO2 molecule on neutral and 2 e− negatively charged g-C4N3 are listed.
Mentions: We next shift our attention to a single CO2 adsorption on neutral and negatively charged g-C4N3. Since g-C4N3 is a (2 × 2) reconstructed structure, there are many different adsorption sites for a CO2 molecule. Here, we considered all the adsorption sites: directly on top of a C or N atom, above the midpoint of a bond linking the C and N atoms, and above the center of a honeycomb-like hexagon. Figure 2 shows the lowest-energy configurations of a CO2 absorbed on neutral and 2 e− negatively charged g-C4N3. On neutral g-C4N3 (Fig. 2(a)), the linear CO2 molecule is parallel to g-C4N3 and locates on top of three nitrogen atoms. The distance between the C atom of CO2 and closest N atom is 2.966 Å, and the linear CO2 molecule shows little structural change compared to a free CO2 molecule with the O-C-O angle and two double C=O bonds being 178.2° and 1.176 Å, respectively. Mulliken population analysis suggests that the amount of transferred electron from the absorbed CO2 molecule to g-C4N3 is negligible (about 0.004 e−). For the neutral case, the CO2 molecule is weakly adsorbed (i.e. physisorbed) onto neutral g-C4N3 with small adsorption energy of 0.24 eV.

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.