Adsorption and Dissociation of Ammonia on Graphene Oxides: A First-Principles Study

Abstract

The interactions of ammonia with graphene oxides (GO) were studied by density functional theory calculations. Our results indicate that the adsorption of NH3 on GO is generally stronger than that on graphene because of the presence of diverse active defect sites, such as the hydroxyl and epoxy functional groups and their neighboring carbon atoms. These surface oxygen sites can form OH center dot center dot center dot N and O center dot center dot center dot HN hydrogen bonds with NH3 and enhance charge transfers from NH3 to the graphene oxide. The dissociation of the adsorbed NH3 into the chemisorbed NH2 or NH species through the H atom abstractions leads to hydroxyl group hydrogenation and ring-opening of epoxy group. The reactions of NH3 with the hydroxyl and epoxy groups are predicted to be exothermic with different energy barriers, depending on the oxidation species and the atomic arrangement of these groups. The hydroxyl group exhibits relatively higher reactivity toward hydrogen abstraction from the adsorbed NH3 than the epoxy group in GO with a single oxygen group. The presence of a neighboring OH group may activate the oxygen groups to facilitate the surface reaction of NH3. Followed by the ring-opening of the epoxy group, the newly formed hydroxyl group can be removed by the second H atom abstraction from NH2. The calculated density of states of the adsorbed systems also reveals strong interactions between GO and NH3. The calculated results show good agreement with available experimental observations.National Science Foundation of China [21103026, 21133007]; Ministry of Science and Technology [2011CB808504, 2012CB214900

Cu2O nanorods modified by reduced graphene oxide for NH3 sensing at room temperature

“…39 Other research also proves that rGO can be used as excellent adsorbents for NH 3 , and its surface and structure play an important role in the adsorption of NH 3 molecules. 40 The chemically derived rGO consists of defect sites and functional groups, which act as highly reactive centres for NH 3 . When in contact with the reducing NH 3 gas, NH 3 molecules diffuse to the surface of rGO and then interact with rGO through hydrogen bonding at the defect sites and with the functional groups (carboxyl, carbonyl, epoxy, and hydroxyl).…”

Graphene oxide: A promising nanomaterial for energy and environmental applications

“…Further incorporation of additional active materials such as polyoxometalate [234], Al 13 [235] and MnO 2 [236] into graphite oxides can dramatically enhance the ammonia accommodation. Moreover, first-principles calculations showed that the diverse active sites on GO (hydroxyl and epoxy functional groups and their neighboring carbon atoms) are effective for facilitating the charge transfer between NH 3 and GO [237]. Later, the co-contribution of epoxide groups and carbon vacancies to NH 3 dissociation has been confirmed by in situ IR microspectroscopy experiments combined with DFT calculations [238].…”

“…In addition to the greenhouse gases, GO/RGO-based composites have excellent adsorption capability of ammonia [230][231][232][233][234][235][236][237][238]. Bandosz's group found that the oxygenated groups, remained sulfonic groups, and water molecules play important role in the ammonia adsorption of graphite oxides [230][231][232][233].…”

Tunable Hybridization Between Electronic States of Graphene and Physisorbed Hexacene

“…18,19 Recent studies have suggested that in graphene physisorbed with small molecules such as NO 2 and NH 3 , the application of a transverse external electric field can further enhance the tunability of the electronic structure of graphene by affecting the charge redistribution. [20][21][22][23][24][25] Among the organic compounds that are amenable to physisorption on graphene, aromatic molecules are of particular interest. 9,26 The face-centered parallel stacking of aromatic molecules on graphene surface can lead to a stable hybrid system via van der Waals (vdW) interactions, 19 while the enhanced π-π electron interaction is expected to influence the electronic structure of graphene.…”