Nature of Oxygen Adsorption on Defective Carbonaceous Materials

Abstract

Plane-wave density functional theory has been used to study oxygen adsorption on graphene, graphite, and (12,0) zigzag single-walled carbon nanotubes with and without Stone–Wales (SW) and single-vacancy (SV) defects to understand the role of defects on carbonaceous material reactivity. Atomic oxygen adsorption leads to the formation of an epoxide on defect-free graphene and graphite and an ether on the exterior wall of carbon nanotubes and SW-defected materials. O2 chemisorption is endothermic on defect-free graphene and graphite and slightly exothermic on defect-free nanotubes. O2 chemisorption energies are predicted to be −1.1 to −1.4 eV on an SW defect and −6.0 to −8.0 eV on an SV defect. An SW defect lowers the energy barriers by 0.90 and 0.50 eV for O2 chemisorption on graphene and nanotubes, respectively. The formation of a C–O–O–C group is important for O2 dissociation on defect-free and SW-defected materials. The energy barrier is less than 0.30 eV on an SV defect. The more reactive SW defect toward O adsorption on graphene is mostly due to the strained defective carbon atoms being able to donate more electrons to an O to form an ether. The larger 2s character in the hybrid orbitals in an ether than in an epoxide makes the ether C–O bond stronger. Stronger C–O binding on an SW-defective carbon nanotube than on a defect-free nanotube is in part due to more flexibility of the defect to release the epoxide ring strain to form an ether.

Flexible Full-Surface Conformal Encapsulation for Each Fiber in Graphene Glass Fiber Fabric against Thermal Oxidation

“…The adsorption energy of oxygen on the perfect graphene surface (Situation 1) (−0.22 eV) is significantly higher than that on G sw defect (Situation 2) (−3.45 eV), indicating that the defect centers are more preferential to absorb oxygen and to be oxidized. This is consistent with the previous reports that graphene oxidation generally started from the defects since the carbon atoms at the defective centers can donate more electrons to oxygen . In contrast, the adsorption energy of oxygen above the h -BN-encapsulated G sw defect (Situation 3) increases significantly, along with the reduced adsorption life, which implies that the encapsulation of h -BN can hinder oxygen adsorption and mitigate graphene oxidation.…”

“…This is consistent with the previous reports that graphene oxidation generally started from the defects since the carbon atoms at the defective centers can donate more electrons to oxygen. 53 In contrast, the adsorption energy of oxygen above the h-BN-encapsulated G sw defect (Situation 3) increases significantly, along with the reduced adsorption life, which implies that the encapsulation of h-BN can hinder oxygen adsorption and mitigate graphene oxidation.…”

In Situ Synthesis of Hierarchical Flower-like Sn/SnO2 Heterogeneous Structure for Ethanol GAS Detection

“…The redox reaction mechanism is commonly used to explain the sensitivity mechanism of metal oxide SnO 2 . SnO 2 materials are N-type semiconductor materials with a broad bandgap (3.6 eV), and, under normal conditions, the internal O 1s are usually composed of two types of oxygen; one is lattice oxygen (O lat ), and the other is adsorbed oxygen (O ads ) on the surface [ 37 , 38 ]. In the air, ion-adsorbed oxygen generates spatially induced charges on the semiconductor surface and creates surface potential barriers that bend the energy band upward, resulting in a decrease in the surface mobility of the SnO 2 material due to the decrease in the electron concentration after the adsorption of oxygen.…”

Immersion infrared reflection‐absorption spectroscopy studies on diamond‐like carbon surfaces. I. Formation of electrophilic groups on surfaces of amorphous carbon films aging in ambient air

“…[ 77 ] Mechanisms of O 2 chemisorption and the evolution of functional groups on graphene are part of an actively developing area of research. [ 78 ] In independent theoretical calculation it was consistently found that vacancy defects in graphite (0001) surfaces, [ 79 ] graphene sheets, [ 80,81 ] and CNTs [ 81 ] lower the energy barrier for dissociative chemisorption drastically, for example, from 270 kJ/mol for defect‐free graphene to less than 30 kJ/mol for a single‐vacancy defect. Low‐energy ion bombardment is known to induce defects in graphene sheets.…”