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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.


(a) The maximum number and the average adsorption energies of captured CO2 molecules on negatively charged g-C4N3 with different charge densities. (b) Top and (c) side views of the lowest-energy configuration of six CO2 molecules adsorbed on negatively charged g-C4N3 with charge density 61.7 × 1013 cm−2.
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f6: (a) The maximum number and the average adsorption energies of captured CO2 molecules on negatively charged g-C4N3 with different charge densities. (b) Top and (c) side views of the lowest-energy configuration of six CO2 molecules adsorbed on negatively charged g-C4N3 with charge density 61.7 × 1013 cm−2.

Mentions: To estimate CO2 capture capacity on negatively charged g-C4N3, we studied the maximum number and the average adsorption energy of captured CO2 molecules on negatively charged g-C4N3 with different charge densities (Fig. 6(a)). Here, we determinate the maximum number of captured CO2 for each negatively charged g-C4N3 with different charge density by gradually increasing the number of CO2 molecules on negatively charged g-C4N3 until no more CO2 can be absorbed. The average adsorption energy of captured CO2 is calculated as the total adsorption energy divided by the maximum number of captured CO2. The results show that no CO2 molecules can be captured by negatively charged g-C4N3 with small charge density (≤12.3 × 1013 cm−2). As the charge density increase from 18.5 × 1013 to 61.6 × 1013 cm−2, the negatively charged g-C4N3 can capture two, four and six CO2 molecules with the average adsorption energy of captured CO2 molecules ranging from 0.72 to 3.58 eV. We note that a further increase in the number of CO2 molecules leads to some CO2 molecules moving far away from the adsorbent during the geometry optimization even if we further increase the charge density of g-C4N3. Therefore, we define six CO2 molecules in each 2 × 2 supercell (i.e. CO2 capture capacity 73.9 × 1013 cm−2 or 42.3 wt%) as the likely saturation CO2 capture coverage (Fig. 6(b,c)). It should be noted that surface defective sites such as N vacancies or un-condensed amino group could lower CO2 capture capacity. However, considering the high CO2 capture capacity of negatively charged g-C4N3, we believe this may nevertheless represent a feasible high-capacity CO2 capture material.


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

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

(a) The maximum number and the average adsorption energies of captured CO2 molecules on negatively charged g-C4N3 with different charge densities. (b) Top and (c) side views of the lowest-energy configuration of six CO2 molecules adsorbed on negatively charged g-C4N3 with charge density 61.7 × 1013 cm−2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: (a) The maximum number and the average adsorption energies of captured CO2 molecules on negatively charged g-C4N3 with different charge densities. (b) Top and (c) side views of the lowest-energy configuration of six CO2 molecules adsorbed on negatively charged g-C4N3 with charge density 61.7 × 1013 cm−2.
Mentions: To estimate CO2 capture capacity on negatively charged g-C4N3, we studied the maximum number and the average adsorption energy of captured CO2 molecules on negatively charged g-C4N3 with different charge densities (Fig. 6(a)). Here, we determinate the maximum number of captured CO2 for each negatively charged g-C4N3 with different charge density by gradually increasing the number of CO2 molecules on negatively charged g-C4N3 until no more CO2 can be absorbed. The average adsorption energy of captured CO2 is calculated as the total adsorption energy divided by the maximum number of captured CO2. The results show that no CO2 molecules can be captured by negatively charged g-C4N3 with small charge density (≤12.3 × 1013 cm−2). As the charge density increase from 18.5 × 1013 to 61.6 × 1013 cm−2, the negatively charged g-C4N3 can capture two, four and six CO2 molecules with the average adsorption energy of captured CO2 molecules ranging from 0.72 to 3.58 eV. We note that a further increase in the number of CO2 molecules leads to some CO2 molecules moving far away from the adsorbent during the geometry optimization even if we further increase the charge density of g-C4N3. Therefore, we define six CO2 molecules in each 2 × 2 supercell (i.e. CO2 capture capacity 73.9 × 1013 cm−2 or 42.3 wt%) as the likely saturation CO2 capture coverage (Fig. 6(b,c)). It should be noted that surface defective sites such as N vacancies or un-condensed amino group could lower CO2 capture capacity. However, considering the high CO2 capture capacity of negatively charged g-C4N3, we believe this may nevertheless represent a feasible high-capacity CO2 capture material.

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.