Adsorption Behaviors Of Gas Molecules Research Articles

Adsorption behavior of gas molecules on B and Mo co-doped graphitic carbon nitride: A first-principles study

Adsorption mechanism studies of toxic gases (CH2O, SO2, NH3, CO, NO, and NO2) on pristine, one B-atom and Mo-atom (1B/Mo) and two B-atom and Mo-atom (2B/Mo) co-doped g-C3N4 were investigated based on the density functional theory. It is shown that gases adsorbed on the 1B(2B)/Mo-g-C3N4 surface exhibit a variety of bandgap types such as magnetic half-metal, magnetic metal, and magnetic semiconductor, and the magnetic properties change considerably. The partial density of states suggests strong hybridization between gas molecules with Mo-4d (B1-2p and B2-2p) and C-2p (N-2p). NH3 gas adsorbed on the 1B(2B)/Mo-g-C3N4 surface acts as a donor and the remaining five gas molecules act as acceptors. CH2O gas adsorbed on 1B/Mo-g-C3N4 has suitable adsorption energy, large charge transfer, short recovery time, and large conductivity change. Therefore 1B/Mo-g-C3N4 can be used as a good sensor to detect CH2O. Lower sensitivity, long recovery times, or insignificant conductivity changes make 1B/Mo-g-C3N4 unsuitable for the detection of CO, NO, NH3, and SO2 gases. However, 1B/Mo-g-C3N4 can be used as a one-time detection for NO2 gas. The recovery time of gases adsorbed on the surface of 2B/Mo-g-C3N4 ranges from 1.93 × 1020 h to 6.43 × 1068 h. However, the large adsorption energies (−2.12 eV to −4.99 eV), the high sensitivity, and the high electrical conductivity allow the use of 2B/Mo-g-C3N4 as a disposable assay for gas molecules.

Quantum mechanical analysis of adsorption for CH4 and CO2 onto graphene oxides

Graphene oxide (GO) surfaces with rich and diverse oxygen-containing functional groups might endow GOs with unique chemical adsorption activity. Exploring the adsorption behavior of gas molecules on GOs with different degrees of oxidation can help design highly efficient adsorbents and catalysts. Herein, the interaction energies between two kinds of gas molecules, CH4 and CO2, and the GO surfaces with varied oxidization degrees were simulated by density functional theory. It is numerically demonstrated that CO2 has a stronger interaction strength than CH4. More specifically, the interaction energies for the gases on GO surfaces do not show monotonous variation with the degree of oxidization. The results suggest that there exists an appropriate range of oxidized degrees on GOs, which can impose higher adsorption interaction. The AIM (atom in molecule) and NOCV (natural orbital for chemical valence) analyses were applied to reveal the interaction mechanisms between the gas molecules and GO surfaces. The adsorption free energy and adsorption coverage of CH4 and CO2 on GO surfaces were calculated. Generally, the gas adsorption on GO is thermodynamically unfavorable under standard conditions. The computational results provide an improved understanding of the adsorption mechanism, which might be valuable for the application of high-performance GO-based adsorbents and catalysts.

The Investigation of Adsorption Behavior of Gas Molecules on FeN3-Doped Graphene

Herein, we have investigated the adsorption behavior of gas molecules, including C2H2, H2S, SO2, SO3, and O2, on FeN3-doped graphene (FeN3-gra). The change of geometric stability, electric structure, and magnetic properties is discussed comprehensively. The results have demonstrated that the stability of the substrate is enhanced by the hybridization between Fe and N atoms in FeN3-gra. Besides, the Fe dopant can enhance the adsorption ability of gases on graphene. The gas molecules all exhibit high binding strength on FeN3-gra especially for SO3 with the adsorption energy of -3.30 eV. The mechanism of interaction between gases and substrate is investigated based on the charge density difference and density of states, which can clarify the distribution of electrons and magnetic moments. Moreover, the high stability and sensitivity of FeN3-gra are promising characters for gas detection. Our research has paved the way for the application of the graphene-based material in gas sensor and electronic instrument.

A First-principles Study on Strain-induced Change of Adsorption Behaviour of Gas Molecules on Graphene for Multi-gas Detecting Sensor

In order to improve the selectivity, the interaction between graphene and various gas molecules (CO, H2O, and NH3) with and without applied tensile strain were calculated by using first-principles calculation. The changes in adsorption energy and charge transfer (including Bader charge analysis and charge density difference) were further investigated by applying 0%-10% uniaxial tensile strain on the graphene surface. It was found that the adsorption behavior of distinct gas molecules on the graphene surface varied linearly and has different trends under the application of tensile strain. Some gas molecules such as CO and NH3 gradually desorbed, while other gas molecule such as H2O, on the contrary, adsorb more stably with increasing tensile strain. These findings provide feasibility and guidance for further experiments that strain engineering can be used to improve the selectivity of graphene-based gas sensors for further applications in health monitoring.

The Adsorption Behavior of Gas Molecules on Co/N Co-Doped Graphene.

Herein, we have used density functional theory (DFT) to investigate the adsorption behavior of gas molecules on Co/N3 co–doped graphene (Co/N3–gra). We have investigated the geometric stability, electric properties, and magnetic properties comprehensively upon the interaction between Co/N3–gra and gas molecules. The binding energy of Co is −5.13 eV, which is big enough for application in gas adsorption. For the adsorption of C2H4, CO, NO2, and SO2 on Co/N–gra, the molecules may act as donors or acceptors of electrons, which can lead to charge transfer (range from 0.38 to 0.7 e) and eventually change the conductivity of Co/N–gra. The CO adsorbed Co/N3–gra complex exhibits a semiconductor property and the NO2/SO2 adsorption can regulate the magnetic properties of Co/N3–gra. Moreover, the Co/N3–gra system can be applied as a gas sensor of CO and SO2 with high stability. Thus, we assume that our results can pave the way for the further study of gas sensor and spintronic devices.

First-principles calculation on the uniaxial-strain-induced change of the adsorption behavior of gas molecules on graphene

First-principles calculation on the uniaxial-strain-induced change of the adsorption behavior of gas molecules on graphene

A new bifunctional C3N nanosheet of NO2, SO2 gas sensor and CO2 separation: A first-principles study

A new-style two-dimensional C 3 N monolayer, unlike the honeycomb C 3 N monolayer, is proposed as a gas sensor, capture and separation. By using the first-principles method, the adsorption behaviors of gas molecules (NH 3 , H 2 S, SO 2 , CO, CO 2 , NO, NO 2 , CH 4 , HCN, N 2 , H 2 and O 2 ) on the C 3 N monolayer were investigated, and the charge density difference, density of state and Hirshfeld charge of those adsorption systems were also discussed. The results show that the SO 2 and NO 2 are chemisorbed on the C 3 N nanosheet with large adsorption strength, while the other gases are adsorbed by weak physisorption. The analysis of charge density difference and density of state suggests that SO 2 and NO 2 gain much charge from C 3 N sheet, and the hybridizations between C 3 N sheet and SO 2 /NO 2 -p orbitals lead to strong gas-adsorbent interactions. The recovery time of SO 2 and NO 2 is predicted to be 7.47 × 10 −4 s and 15.91 s at room temperature. Additionally, the CO 2 can be captured and separated from the mixtures of CO 2 , NH 3 , H 2 S, CO, CH 4 , H 2 through injecting two electrons into C 3 N sheet. Therefore, the new C 3 N nanosheet can be a promising bifunctional material as SO 2 , NO 2 sensor and CO 2 separation.

Adsorption of CO, NH3, NO, and NO2 on pristine and defective g-GaN: Improved gas sensing and functionalization

The adsorption behaviors of gas molecules, including CO, NH3, NO, and NO2 on pristine and defective g-GaN, and their adsorption energy, charge transfer, and magnetic moment are investigated using first-principles calculations. The small adsorption energy of all the gas molecules on pristine g-GaN suggests the physisorption characteristics. Among these gas molecules, the binding between NH3 and pristine g-GaN is stronger than the other molecules owing to the hybridization of its frontier orbitals with the 2p orbital of N atoms in pristine g-GaN. To improve the sensing ability of g-GaN, the adsorption behaviours of these gas molecules on g-GaN with Ga and N single vacancies are also examined. All these gas molecules exhibit much larger adsorptions energy on the defective g-GaN than that on the pristine form. For most of the gas molecule adsorption on defective g-GaN, the charge transfer is more significant that in the corresponding gas molecule adsorption on pristine g-GaN. Besides, the magnetisms are found in many gas molecules adsorbed defective g-GaN. Our work not only provides an effective approach to improve the sensing ability of g-GaN but also offers an effective approach for functionalization of g-GaN.

Theoretical study of the adsorption behaviors of gas molecules on the Au-functionalized MoS2 nanosheets: A search for highly efficient gas sensors

Using the density functional theory calculations, we explored the electronic, and magnetic properties of Au and Pt adsorbed MoS2 systems. We examined the binding of some gas molecules (CO, CO2, NH3, NO, NO2, and O3) on these noble metal adsorbed structures. Stability analysis based on binding energy calculations indicate that both Au-adsorbed and Pt-adsorbed MoS2 monolayers are energetically stable and can be considered as a promising nanostructure media for gas sensing and capturing. The binding strength of gas molecules over the Au-adsorbed structures was found to be higher than that over the non-adsorbed systems, being attributed to their higher adsorption energies. Band structure calculations reveal a metallic characteristics for Au-adsorbed MoS2 systems, while Pt-adsorbed ones show semiconductor nature. The substantial overlaps of the local density of states of the Au atom and substrate’s interacting atoms are an indication of a covalent interaction and consequently chemisorption process at the interface.

Effects of Mn, Fe, and Ce doping on the adsorption property of gas molecules and oxidation of SO2 on the NiO (1 0 0) surface

The effects of transition metal doping on the adsorption behavior of gas molecules related the denitration reaction and SO2 oxidation on the NiO (1 0 0) surface were studied by a density functional theory. NH3, O2, and H2O molecules are easy to absorb on the Ni-top site of NiO (1 0 0) surface, while NO and SO2 molecules are difficult to attach to the surface. After doping the transition metal, the adsorption property of gas molecules on the NiO (1 0 0) surface changes. Among them, the influence of Ce doping is greater than that of other two transition metals. The dopings of Mn, Fe, and Ce also influence the SO2 oxidation on the NiO (1 0 0) surface. Mn doping contributes to the oxidation of SO2 to SO3 on the NiO (1 0 0) surface. Fe doping on the Fe-NiO (1 0 0) can make SO2 easy to generate SO4 cluster. Ce doping on the NiO (1 0 0) surface can increase the energy barrier of the reaction of SO2 to SO3.

Adsorption behaviors of gas molecules on the surface of ZnO nanocrystals under UV irradiation

A UV-activated room temperature chemiresistive gas sensor based on ZnO nanocrystals film was fabricated. Its gas sensing properties under various conditions were also investigated in detail. The results shed new insight into the adsorption behaviors of gas molecules on the surface of ZnO nanocrystals under UV irradiation. The chemisorbed oxygen species (O2(ads)−(hv)) induced by UV light govern the adsorption and desorption ways of other gas molecules on the surface of ZnO nanocrystals, which is dependent on the electron affinity of gas molecules. Gas molecules with higher electron affinity than oxygen molecules can be adsorbed on the surface by the competitive adsorption way, extracting electrons from the surface. Gas molecules with lower electron affinity than oxygen molecules are attracted by the adsorbed O2(ads)−(hv) layer, releasing electrons to the surface. These processes can influence the gas sensing properties of the sensor. Our findings will pave the way for the fundamental understanding and design of UV-activated gas sensor in the future.

Gas sensing properties of two-dimensional penta-BP5: A first-principle study

Motivated by the huge potential for two-dimensional materials in gas sensors, the adsorption behavior of gas molecules on the surface of penta-BP5 is investigated by first principles calculations. Results show that CO and CO2 have slight influence on the electronic property of penta-BP5 and the charge transfers are small, revealing that penta-BP5 is not suitable for detecting these two gases. However, penta-BP5 is sensitive to CH2O, SO2, O2 and NO because that considerable adsorption energies and charge transfers can be found in the adsorption systems, indicating that penta-BP5 could be a potential sensing material for detecting these gases.

Adsorption behavior of gas molecules on hydrogenated Fe(1 1 1)

The adsorption properties of gas molecules are studied on γ-Fe(1 1 1) surface with pre-adsorbed hydrogen, using density functional theory methods. Our results indicate that γ-Fe(1 1 1) is active for the adsorption of typical gas molecules, although it is the most stable facet of γ-Fe. The effect of hydrogen impurity on binding strength between gas molecules and γ-Fe(1 1 1) depends on the adsorption sites and the coverage of hydrogen. In general, when hydrogen atoms migrate from surface to inside of the iron, the effect of hydrogen on the adsorption of gas molecules on the iron surface becomes weaker. At the low hydrogen adsorption coverage of 1/16 ML, the main role of hydrogen atoms is to enhance the adsorption strength. As the adsorption coverage of hydrogen atoms increases to 1/4 ML, the binding energy of gas molecules will be weakened. These findings offer important clues for tuning the reactivity of γ-Fe(1 1 1) surface.

Modulating the gas sensing properties of nitrogen coordinated dopants in graphene sheets: A first-principles study

Abstract The stable geometry, electronic property and chemical reactivity of dopants (Co, Mo and B) incorporated N4 centers in graphene sheets (D-GN4) are investigated using the first-principles calculations. It is found that the GN4 sheet can strongly stabilizes the dopant and makes it more positively charged, which would regulate the adsorption behaviors of gas molecules. Compared with the adsorbed CO molecule, the D-GN4 substrates exhibit high sensitivity toward the O 2 molecule. The individual CO (or O 2 ) on the Mo-GN4 have the largest energy difference, while they have moderate adsorption energies on B-GN4 sheet. Besides, the dopants (or adsorbed gases) can effectively regulate the electronic structure and magnetic properties of GN4 (or D-GN4) systems, such as the adsorption of O 2 (or CO) can decrease (or increase) the magnetic moment of Mo-GN4 system and the magnetic property of Co-GN4 is enlarged by the adsorbed O 2 . As a result, we may distinguish the kinds of adsorbed gases by testing the change in magnetic property of the system, which can provide important reference for exploring the surface reactivity of graphene-based materials and designing the novel gas sensors or spintronic devices.

Markedly different adsorption behaviors of gas molecules on defective monolayer MoS2: a first-principles study.

Sulfur vacancy (SV) is one of the most typical defects in two-dimensional monolayer MoS2, leading to reactive sites. We presented a systematic study of the adsorption behaviors of gas molecules, CO2, N2, H2O, CO, NH3, NO, O2, H2 and NO2, on monolayer MoS2 with single SV by first-principles calculations. It was found that CO2, N2 and H2O molecules physisorbed at the proximity of single SV. Our adsorption energy calculations and charge transfer analysis showed that the interactions between CO2, N2 and H2O molecules and defective MoS2 are stronger than the cases of CO2, N2 and H2O molecules adsorbed on pristine MoS2, respectively. The defective MoS2 based gas sensors may be more sensitive to CO2, N2 and H2O molecules than pristine MoS2 based ones. CO, NO, O2 and NH3 molecules were found to chemisorb at the S vacancy site and thus modify the electronic properties of defective monolayer MoS2. Magnetism was induced upon adsorption of NO molecules and the defective states induced by S vacancy can be completely removed upon adsorption of O2 molecules, which may provide some helpful information for designing new MoS2 based nanoelectronic devices in future. The H2 and NO2 molecules were found to dissociate at S vacancy. The dissociation of NO2 molecules resulted in O atoms located at the S vacancy site and NO molecules physisorbed on O-doped MoS2. The calculated results showed that NO2 molecules can help heal the S vacancy of the MoS2 monolayer.

Effect of Pore Geometry on Gas Adsorption: Grand Canonical Monte Carlo Simulation Studies

In this study, we investigated the pure geometrical effect of porous materials in gas adsorption using the grand canonical Monte Carlo simulations of primitive gas-pore models with various pore geometries such as planar, cylindrical, and random pore geometries. Although the model does not possess atomistic level details of porous materials, our simulation results provided many insightful information in the effect of pore geometry on the adsorption behavior of gas molecules. First, the surface curvature of porous materials plays a significant role in the amount of adsorbed gas molecules: the concave surface such as in cylindrical pores induces more attraction between gas molecules and pore, which results in the enhanced gas adsorption. On the contrary, the convex surface of random pores gives the opposite effect. Second, this geometrical effect shows a nonmonotonic dependence on the gas-pore interaction strength and length. Third, as the external gas pressure is increased, the change in the gas adsorption due to pore geometry is reduced. Finally, the pore geometry also affects the collision dynamics of gas molecules. Since our model is based on primitive description of fluid molecules, our conclusion can be applied to any fluidic systems including reactant-electrode systems.