Electrocatalytically Switchable CO₂ Capture: First Principle Computational Exploration of Carbon Nanotubes with Pyridinic Nitrogen

Abstract

Carbon nanotubes with specific nitrogen doping are proposed for controllable, highly selective, and reversible CO2 capture. Using density functional theory incorporating long-range dispersion corrections, we investigated the adsorption behavior of CO2 on (7,7) single-walled carbon nanotubes (CNTs) with several nitrogen doping configurations and varying charge states. Pyridinic-nitrogen incorporation in CNTs is found to induce an increasing CO2 adsorption strength with electron injecting, leading to a highly selective CO2 adsorption in comparison with N2 . This functionality could induce intrinsically reversible CO2 adsorption as capture/release can be controlled by switching the charge carrying state of the system on/off. This phenomenon is verified for a number of different models and theoretical methods, with clear ramifications for the possibility of implementation with a broader class of graphene-based materials. A scheme for the implementation of this remarkable reversible electrocatalytic CO2 -capture phenomenon is considered.

Materials design for electrocatalytic carbon capture

“…25,26 For example, while CO 2 molecules are predicted to be weakly adsorbed (i.e., physisorbed) on neutral h-BN, when negative charge is simulated in the supercell, density functional theory (DFT) calculations reveal that CO 2 adsorption can be dramatically enhanced via a charge-induced chemisorption interaction. 25 The same chargeresponsive chemisorption of CO 2 is seen to occur at pyridinic nitrogen sites, in elementary azabenzene molecules 27 as well as in doped carbon nanotube and graphene materials.…”

“…25 The same chargeresponsive chemisorption of CO 2 is seen to occur at pyridinic nitrogen sites, in elementary azabenzene molecules 27 as well as in doped carbon nanotube and graphene materials. 26 CO 2 is not transformed chemically in this process (although this eventuality should not be excluded and could be highly desirable). However, we believe that the phrase electrocatalytic gas capture is appropriate, since the presence of charge is both quantitatively and qualitatively changing the chemical interactions (i.e., the potential energy surface) in the system and thereby enabling formation of a new chemical bond between the material and the CO 2 .…”

“…Doped carbon nanotubes or graphenes with pyridinic-nitrogen defects 26 have the advantage of relatively good electrical conductivity, so that charge can be readily added or removed by manipulating voltage. However, pyridinic nitrogen is a minority defect structure in comparison with substitutional N doping; hence, it is not clear how to impart a sufficient density of pyridinic N defects into carbon nanotubes or graphene so as to enable efficient CO 2 capture.…”

“…Some progress has been made in each of these directions and the new results we report below relate to direction (iii). Interestingly, however, this leads us back around to a new perspective on materials that we already worked on from the start of this adventure, namely, N-doped graphenes and/or carbon nanotubes, 26 but this time with the majority substitutional N defect rather than the minority pyridinic N defect!…”

Growth and Electrochemical Characterization of Carbon Nanospike Thin Film Electrodes

“…44,45 While not explored here in depth, this indicates that the CNS electrocatalytic functionality is tunable through the nitrogen functionality. A recent report by Jiao et al 27 detailed simulations on pyridinic nitrogen-doped carbon nanotubes for electrochemical capture of CO 2 . The CNS reported here, with high nitrogen content and conformal coating of 3D structures as described below, present an interesting route to possible strategies for CO 2 mitigation.…”