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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 deformation electronic density of (a) neutral and (b) 2 e− negatively charged g-C4N3. Green and yellow refer to electron-rich and -deficient area, respectively. The isosurface value is 0.02 e/au. (c) The total charge density distribution of a single CO2 molecule on (c) neutral and (d) 2 e− negatively charged g-C4N3. The isosurface value is 0.8 e/au. The overlap of the electron densities of the C atom of CO2 and surface N atom of g-C4N3 in (d) indicates the formation of a new bond.
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f3: The deformation electronic density of (a) neutral and (b) 2 e− negatively charged g-C4N3. Green and yellow refer to electron-rich and -deficient area, respectively. The isosurface value is 0.02 e/au. (c) The total charge density distribution of a single CO2 molecule on (c) neutral and (d) 2 e− negatively charged g-C4N3. The isosurface value is 0.8 e/au. The overlap of the electron densities of the C atom of CO2 and surface N atom of g-C4N3 in (d) indicates the formation of a new bond.

Mentions: To understand the underlying mechanism of CO2 capture on negatively charged g-C4N3, we plotted the deformation electronic density of neutral and 2 e− negatively charged g-C4N3 by subtracting the electronic density of isolated N and C atoms from the sheet in Fig. 3. Obviously, for the neutral case (Fig. 3(a)), some electrons are extracted from the C atoms and delocalized over the N atoms, as implied by the green regions. Mulliken population analysis indicated that the electrons distribute at N, C1 and C2 are −0.302, 0.294 and −0.036 /e/, respectively. When two extra electrons are introduced (Fig. 3(b)), the extra electrons are almost evenly distributed on N and C atoms. Mulliken population analysis suggest that each atom gains −0.07 ~ −0.09 /e/, and the electrons distribute at N, C1 and C2 are −0.383, 0.222 and −0.122 /e/, respectively. Compared with the neutral case, more electrons are distributed and delocalized at N atoms, as implied by the green regions in Fig. 3(b). As CO2 is a Lewis acid and it prefers to accept, rather than donate, electrons during reaction, the N atom of negatively charged g-C4N3 can donate electrons to CO2, and form a new bond between the C atom of CO2 and surface N atom of g-C4N3 (Fig. 3(d)), which is significantly different from the case that CO2 on neutral g-C4N3 (Fig. 3(c). This is the reason why the CO2 molecule has a strong interaction with negatively charged g-C4N3.


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 deformation electronic density of (a) neutral and (b) 2 e− negatively charged g-C4N3. Green and yellow refer to electron-rich and -deficient area, respectively. The isosurface value is 0.02 e/au. (c) The total charge density distribution of a single CO2 molecule on (c) neutral and (d) 2 e− negatively charged g-C4N3. The isosurface value is 0.8 e/au. The overlap of the electron densities of the C atom of CO2 and surface N atom of g-C4N3 in (d) indicates the formation of a new bond.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: The deformation electronic density of (a) neutral and (b) 2 e− negatively charged g-C4N3. Green and yellow refer to electron-rich and -deficient area, respectively. The isosurface value is 0.02 e/au. (c) The total charge density distribution of a single CO2 molecule on (c) neutral and (d) 2 e− negatively charged g-C4N3. The isosurface value is 0.8 e/au. The overlap of the electron densities of the C atom of CO2 and surface N atom of g-C4N3 in (d) indicates the formation of a new bond.
Mentions: To understand the underlying mechanism of CO2 capture on negatively charged g-C4N3, we plotted the deformation electronic density of neutral and 2 e− negatively charged g-C4N3 by subtracting the electronic density of isolated N and C atoms from the sheet in Fig. 3. Obviously, for the neutral case (Fig. 3(a)), some electrons are extracted from the C atoms and delocalized over the N atoms, as implied by the green regions. Mulliken population analysis indicated that the electrons distribute at N, C1 and C2 are −0.302, 0.294 and −0.036 /e/, respectively. When two extra electrons are introduced (Fig. 3(b)), the extra electrons are almost evenly distributed on N and C atoms. Mulliken population analysis suggest that each atom gains −0.07 ~ −0.09 /e/, and the electrons distribute at N, C1 and C2 are −0.383, 0.222 and −0.122 /e/, respectively. Compared with the neutral case, more electrons are distributed and delocalized at N atoms, as implied by the green regions in Fig. 3(b). As CO2 is a Lewis acid and it prefers to accept, rather than donate, electrons during reaction, the N atom of negatively charged g-C4N3 can donate electrons to CO2, and form a new bond between the C atom of CO2 and surface N atom of g-C4N3 (Fig. 3(d)), which is significantly different from the case that CO2 on neutral g-C4N3 (Fig. 3(c). This is the reason why the CO2 molecule has a strong interaction with negatively charged g-C4N3.

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.