Adsorption Of H2S Molecules Research Articles

Room temperature hydrogen sulfide gas detection using copper oxide nanotube/indium tin oxide nanoparticle heterojunctions

Various copper oxide nanotube/indium tin oxide (CuO/ITO) nanocomposite-based chemiresistive gas sensors were fabricated and tested toward hydrogen sulfide (H2S) in the presence and absence of ultra-violet (UV) light excitation at room temperature. Among these different combinations, 60:40 wt.% of CuO:ITO showed the highest sensing performance toward H2S gas (i.e., sensor response (S) = 5.7 toward 40 ppmm (parts per million by mass) H2S gas), which is ̴5.7 times higher than pristine CuO and ITO counterparts. The enhancement in the gas sensing performance by mixing ITO and CuO nanostructures might be due to the formation of p/n heterojunction between ITO nanoparticles and CuO nanotubes. The low limit of detection (LLOD) of 500 ppbm (part per billion by mass) of S = 1.2 was experimentally achieved by photo exciting sensing materials using 400 nm UV light. This might be attributed to the faster adsorption of H2S molecules and higher carrier concentration under light illumination. These sensors also maintained good H2S sensing performance in the presence of water vapors which makes these sensors suitable for practical application. This work paves a way to fabricate low-power H2S gas sensors by eliminating heaters.

Adsorption and purification of biogas inside graphitic nanopores: molecular dynamics simulation approach

Biogas is one of the most common sources of biomass energy. Due to the associated environmental pollution and costs, desulfurization, and purification are the most important challenges of biogas power generation. Using all-atom molecular dynamics (MD), we systematically simulated the isothermal adsorption behavior of biogas (comprising CH4, CO2, H2O, H2S, and H2) in graphite (Gr) slit nanopores. The impact of slit width, system temperature, and moisture content on the adsorption energy, adsorption ratio, and diffusion coefficient of biogas molecules was investigated. Simulation results revealed that due to strong interactions between graphite and H2S, graphite slits of width d = 48 ~ 80 Å displayed significant selective adsorption of H2S molecules. At temperatures between 300 and 500K, Gr slits can effectively separate H2S in biogas. Moreover, as the moisture content of biogas (vol%) increases from 0 to 20%, the formation and interactions of hydrogen bonds between water molecules create H2O films accumulating on the Gr surface and taking up the adsorption sites, which reduces the amount of hydrogen sulfide that can be adsorbed. Our findings provide important insights into the material design for biogas purification. A schematic representation of molecular interactions between adsorbates and the wall for biogas mixtures (comprising CH4, CO2, H2O, H2S, and H2) inside graphitic nanopores.

Theoretical and Experimental Research on the Adsorption Performance of Hydrogen Sulfide on the Surface of Stainless Steel

In this paper, the macro-surface and SEM micro-surface of stainless steel were studied, and the absorption curve of stainless steel to H2S was tested at first. Then, the geometric structure based on the first-principles calculation method of DFT was optimized and the adsorption of H2S molecules on the surface of stainless steel was calculated. H2S molecules could be spontaneously adsorbed to the surface of different types γ-Fe(111). H2S molecules could dissociate and adsorb owing to the vacancy defects, because the S–H bond in H2S would break at the vacancy site. The absolute value of the adsorption energy was high, so the adsorption amount of H2S was larger. H2S would preferentially adsorb to vacancy defect positions. However, due to the limited number of vacancies, H2S would gradually adsorb to other positions. While H2S molecules were adsorbed in a molecular state, dissociative adsorption was also proceeding. The absolute value of the adsorption energy was higher and the adsorption with the substrate was stronger. Moreover, the existence of vacancy defects would facilitate the dissociative adsorption of H2S molecules.

Computational study of H2S adsorption on the pristine and transitional metal-doped phosphorene.

This study aimed to investigate the H2S molecule adsorption on the pristine and X-doped phosphorene (X = first-row transition metal) using DFT+U method. The doping of X atoms on the phosphorene has been evaluated from energetic and electronics aspects. The binding energy values and the results of projected density of states (PDOS) analysis revealed that Ti-, V-, Fe-, and Sc-doped phosphorene have more capability to adsorb H2S molecule in comparison with other systems. Moreover, the cohesive energy values showed that these (Ti, V, Fe, and Sc) doped surfaces are also energetically feasible.

Adsorption behavior of H2S on P‒doped, V/P, Nb/P, and Ta/P‒codoped graphitic carbon nitride: A first-principles investigation

The adsorption behavior of H2S gas on the P‒doped, V/P, Nb/P, and Ta/P‒codoped g-C3N4 were theoretically investigated using density functional theory. The computed adsorption energy of H2S molecules over the P‒doped, V‒embedded, Nb‒embedded, Ta‒embedded, V/P‒codoped, Nb/P‒codoped, and Ta/P‒codoped g-C3N4 systems are −0.188, −3.141, −2.850, −3.388, −3.263, −2.970, and −3.523 eV, respectively. These results revealed that with embedding and codoping of g-C3N4, the interaction energy between H2S and V/P, Nb/P, Ta/P‒modified g-C3N4 systems significantly enhances. Furthermore, the band structure results exhibited that with adsorption of H2S on g-C3N4 and also embedded and codoped systems, the electrical conductivity of the g-C3N4 systems remarkably decreases owing to the induced new impurity energy states near the Fermi energy level. Also, the results of the relaxed structures displayed that with adsorption of H2S molecules on g-C3N4 and also the modified g-C3N4 with V, Nb, and Ta and also P elements, the initial planar structure of the pristine g-C3N4 automatically become buckle because the stability of wrinkles structure of g-C3N4 is more than that of the flat structure. Additionally, the results of the Lowdin charge analysis revealed that electron transfer occurs from orbitals of transition metals to the orbitals of H2S molecules for all of the g-C3N4 systems. Finally, current research introduces Ta/P‒codoped g-C3N4 system with adsorption energy of −3.523 eV as the highest sensitive, and low-cost gas sensor candidate for sensing and removing H2S gas from the atmosphere.

Impedance Spectroscopy-Based Reduced Graphene Oxide-Incorporated ZnO Composite Sensor for H2S Investigations.

Electrochemical impedance spectroscopy (EIS) has been applied to measure the H2S gas response of the sensor fabricated on reduced graphene oxide (rGO)-incorporated nano-zinc oxide (n-ZnO) composites. These nanocomposites were prepared by a facile one-step solution route at room temperature. The structural, surface morphological, and elemental analyses of the composite material have been investigated. EIS was carried out to study the H2S gas-sensing properties of fabricated sensors. The developed sensor showed an optimal H2S gas response to various concentrations ranging from 2 to 100 ppm at 90 °C. The H2S gas-sensing performances of pure n-ZnO and various concentrations of rGO-incorporated n-ZnO were evaluated. The H2S gas-sensing results showed that n-ZnO/rGO composites exhibited high response when compared to pure n-ZnO. The enhanced H2S response was speculated to be ascribed due to two factors. First, rGO creates reactive sites for H2S molecule adsorption. Second, rGO has great electrical conductivity compared to n-ZnO that enables the active transport of electrons from H2S gas on interaction with the sensing layer, resulting in enhanced gas response at 90 °C temperatures.

Hydrogen sulfide interaction with pristine, defected and M-decorated black phosphorous (M= B, Co, V, Ti, Ni & Cu): A DFT study

Two-dimensional materials due to their unusual properties originating from quantum size effect have attracted much research attentions. These properties have led to many promising applications in nano-electronics, catalysis, gas separation and energy storage. In this study, the details of H2S adsorption on the pristine, decorated and defected single layer black phosphorous (SBP) were investigated using density function theory (DFT). Electronic structure calculations were performed using B97D exchange together with 6-31 + G* basis set. The results showed that structural modification could significantly change the total electron density of the systems. Structural modifications on SBP decrease the amount of Eg in all studied systems compared to pristine one. We found that the adsorption of H2S molecule on SBP nano-structures highly depends on the type of decorated metals and the orientation of the H2S molecule. The highest adsorption energies were obtained for Co -, V- and Ti-decorated SBP systems with the values of −25.63, −23.33 and −21.95 kcal/mol, respectively. It was found that adsorption energies for systems wherein H2S adsorbed on SBP from the H side are not significant. The results suggested that decorating SBP with Co, V, and Ni changes the gap width of the system. The details of DOS changes before and after H2S adsorption for all systems were discussed. Finally it was suggested that while decorated SBP systems with transition metals (TMs) could be used in H2S storage applications, pristine, defected and B-SBP may be utilized in designing new gas sensor materials.

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes was investigated. The diameter of Pd particle increases with increasing sputtering power. With this change, the membrane shows a signification reduction in hydrogen permeability/or flux, but its durability and stability increases significantly, which can be mainly attributed to a decrease in hydrogen solubility coefficient. In addition, H2S impurity in mixed gases can greatly degrade membrane performance, especially the hydrogen permeability, whereas the Ar impurity content has less effect in the temperature range of 523–673 K. Lowering of permeability caused by the change of gas purity can be attributed to a decrease in hydrogen solubility, which is closely related to the stronger adsorption of H2S molecules to the Pd overlayer of the membrane. Thus, it is concluded that aside from the optimum design for composition of Nb-based hydrogen permeable alloy to improve their permeability, the control of Pd overlayer film on membrane surface and gas purity in the feed gas is important.

Characterization of three-dimensional reduced graphene oxide/copper oxide heterostructures for hydrogen sulfide gas sensing application

Three-dimensional reduced graphene oxide (3D-rGO) structures decorated with CuO particles (GCu) are synthesized through a simple and scalable method for detection of hydrogen sulfide (H2S) gas. For characterization and investigation of porous structure various techniques were employed. Decorated 3D structures demonstrated higher sensitivity and selectivity in comparison to pure structure. Optimized structure for sensing was obtained through introducing different amounts of CuO. The GCu heterostructures containing 35 μmol of CuO powder demonstrated reproducible response of about 30% to the concentration of 10 ppm at room temperature, while complete recovery was obtained through heating to 150 °C. Sensing behaviour of the samples to H2S gas was investigated at temperatures in the range of 25–150 °C and in different relative humidity levels from 3 to 80%. We discussed the sensing model based on the adsorption of H2S molecules on the additives, and electron injection to the sample, resulting in the electrical resistance enhancement.

Density functional study of hydrogen sulfide adsorption mechanism on activated carbon

A systematic theoretical study using the density functional theory was performed to provide molecular-level understanding on the adsorption of hydrogen sulfide (H2S) on activated carbon. Both zigzag and armchair edge sites of benzene ring models were considered as the possible active sites. The results indicate that the adsorption of H2S molecule on activated carbon is highly thermally favorable. The adsorption energies of H2S on zigzag and armchair edges are −664.9 and −349.6kJ/mol, respectively. Activated carbon plays double role, not only facilitates the dissociation of H2S molecule but also offers active sites for H2S adsorption. The dissociative adsorption and evolution of H2S lead to the formations of CS, CSC and CSH, which is in agreement with experimental data. The shape of the local active site has a strong effect on H2S adsorption. The atomic charge of zigzag edge sites is more negative than that of armchair edge sites. Thus, the zigzag edge sites provide stronger force to attract H2S than the armchair edge sites. Direct adsorption of H2S leads to the formations of CS or CSH on activated carbon surface, followed by their evolution into CSC. These sulfur species including CS, CSC and CSH are stable on activated carbon.

H2S adsorption and dissociation on NH-decorated graphene: A first principles study

The removal of H2S gas poses an emerging environmental concern because of the lack of knowledge of an efficient adsorbent. A detailed theoretical study of H2S adsorption and dissociation on NH-doped graphene (GNH) has been carried out by means of density theory calculations. Our results reveal that the adsorption of H2S molecule on GNH composite is enhanced by the presence of active site such as the NH radicals. These NH radical sites formed NHH bonds and increase the charge transfer from H2S to GNH. The dissociation of the adsorbed H2S molecule leads the chemisorption of SH radical via H-transfer to GNH, while the formation of GNH2 at a weight percent of 3.76 wt% of NH radical is an endothermic process with an energy of 0.299 eV and 0.358 eV for ortho and para-position respectively. However, at 7.25 wt% NH radical, we observed a complete dissociation of H2S molecule with an energy released of 0.711 eV for the chemisorbed S atom on GN2H4. Moreover, the H-transfer of the second H atom of H2S molecule at 3.76 wt% was energetic unfavorable. The trend of predicted results within this study reveals that NH-doped graphene (GNH) successfully adsorbed and eliminated of H2S molecule; this work unveils definitive theoretical procedures which can be tested and validated experimentally.

Synthesis of biomorphic tube-like CuO using pomelo white flesh as biotemplate and its sensing properties over H2S at room temperature

Biomorphic tube-like CuO was synthesized using pomelo white flesh as biotemplate for the first time. The sample showed a good selectivity to H2S in gasoline 92#, formaldehyde, CH4, H2, CO, toluene, acetone, and ethanol. Although there was an obvious change in response/recovery time with H2S concentration from 10 ppb to 10 ppm, all the response/recovery times were <60 s. Moreover, the sample exhibited stable detection performance for 5 ppm H2S at room temperature over a testing period of 3 months. The detection levels were uniform during cycling. This outstanding sensing performance is attributed to the unique structure, which was convenient for H2S molecule adsorption and facilitated the transformation of semiconducting p-type CuO to metallic CuS during H2S detection.

Hierarchical NiO Cube/Nitrogen-Doped Reduced Graphene Oxide Composite with Enhanced H2S Sensing Properties at Low Temperature.

A novel hierarchical NiO cube (hc-NiO)/nitrogen-doped reduced graphene oxide (N-rGO) composite is synthesized via a facile hydrothermal method and a postcalcination treatment without any templates and surfactants added. The NiO cubes assembled by abundant nanoparticles in situ grow on the surface of N-rGO layers. The combination of hc-NiO and N-rGO results in enhanced sensing properties with the contributions of the N-rGO providing high specific surface area and more efficient active sites for the adsorption of H2S molecules and the hierarchically structured NiO cubes providing high sensitivity and distinctive selectivity to H2S gas. At the optimal operating temperature of 92 °C, the hc-NiO/N-rGO composite based sensor shows not only high response to H2S in a range of 0.1-100 ppm but also excellent selectivity for H2S against the other seven gases. The gaseous product, produced from the contact of H2S with the hc-NiO/N-rGO composite at 92 °C, is measured by GC-MS technique. The change of the surface composition and the chemical state of the hc-NiO/N-rGO composite before and after exposure to H2S are investigated by XPS. The possible sensing mechanism of the hc-NiO/N-rGO composite is similar to that of semiconductor oxides. The H2S molecules that absorbed on the sensor surface transform to SO2 by reacting with the adsorbed oxygen anions. Meanwhile, the electrons restricted by the surface-adsorbed oxygen return to the bulk and neutralize the holes, producing a change in resistance.

Physisorption to chemisorption transition of H2S on carbon nanocone induced by decoration of Be2O2 cluster

We investigated geometric and electronic properties of pristine and Be2O2-decorated carbon nanocones (CNCs) in the presence and absence of an H2S molecule using density functional calculations. It was found that the H2S molecule is physisorbed on the pristine nanocone, but it presents much higher reactivity toward the decorated CNC by Be2O2 cluster. The addition of more H2S molecules has also been considered on the Be2O2/CNC surface. With the increase of H2S coverage, the interaction between H2S molecules and Be2O2/CNC becomes weaker, and up to four H2S molecules can be chemisorbed on the cone, in which adsorption energies ranged from −27.21 to −10.28 kcal/mol at the B3LYP/6-31G(d) level of theory. The results also indicate that decoration of the Be2O2 cluster on the surface of the cone induces some changes in electronic properties of the cone and its Eg is changed after the adsorption of H2S molecule.

Adsorbing H2S onto a single graphene sheet: A possible gas sensor

The electronic structure of pristine graphene sheet and the resulting structure of adsorbing a single molecule of H2S on pristine graphene in three different sites (bridge, top, and hollow) are studied using the full potential linearized augmented plane wave method. Our calculations show that the adsorption of H2S molecule on the bridge site opens up a small direct energy gap of about 0.1 eV at symmetry point M, while adsorption of H2S on top site opens a gap of 0.3 eV around the symmetry point K. We find that adsorbed H2S onto the hollow site of pristine graphene sheet causes to push the conduction band minimum and the valence band maximum towards Fermi level resulting in a metallic behavior. Comparing the angular momentum decomposition of the atoms projected electronic density of states of pristine graphene sheet with that of H2S–graphene for three different cases, we find a significant influence of the location of the H2S molecule on the electronic properties especially the strong hybridization between H2S molecule and graphene sheet.

Adsorption of H2S molecules on non-carbonic and decorated carbonic graphenes: A van der Waals density functional study

The adsorption of hydrogen sulfide (H2S) molecules on non-carbonic (B, Al, and Ga nitride) graphene was studied using a first-principles van der Waals density functional (vdW-DF) method. For the adsorption of a single molecule, we determined the most stable configurations, equilibrium geometries, adsorption energies, and electronic properties by approaching the molecule on the surface of non-carbonic graphenes at different possible sites. The Ga nitride (GaN) graphene was more capable of H2S molecule adsorption than the other graphenes due to the higher binding energy value and shorter bonding distance between the H2S molecule and the graphene surface. Electron transfer calculations confirmed that the electronic properties of GaN graphene changes significantly compared to other graphenes after H2S molecule adsorption. The density of states results indicated a stronger physical hybridization between H2S and GaN graphene. Furthermore, co-adsorption of two H2S molecules on the GaN graphene as a single-layer/bi-layer of adsorbed molecules was examined. Finally, Al and Ga metal atoms decorated on carbonic graphene (Al- and Ga-cargraph) to investigate H2S adsorption. The adsorption of H2S on Al- and Ga-cargraph was weaker than that on the non-carbonic graphenes. Therefore, based on the obtained results, GaN graphene is promising for uses in gas sensor devices for detect H2S.

Adsorption of Sulfur‐Containing Species on LaCrO3 (001) Surface: A First‐Principles Study

AbstractDensity functional theory calculations are employed to investigate the adsorption of sulfur‐containing species on the (001) surface of LaCrO3 (LCrO). Molecular adsorption is found to be stable with H2S binding preferentially at O site on the LaO‐terminated surface. The adsorption of H2S molecule leads to the electrons transferring from the substrate to the molecule and the charges rearrangement within the molecule. In addition, the adsorption of the corresponding S‐containing dissociated species (SH and S) is investigated. SH and S are found to be preferentially bind at the Cr site. We further predict the adsorption energies of sulfur‐containing species increase following the sequence H2S&lt;SH&lt;S for all the adsorption sites on LCrO (001) surface. Based on the adsorption energy comparison, LCrO is more sulfur‐tolerant than traditional Ni‐based anode materials, which is qualitatively in line with available experimental results. This study provides a scientific basis for rational design of sulfur‐tolerant anode materials for SOFCs.

Density Functional Study of H&lt;sub&gt;2&lt;/sub&gt;S Adsorption on Small Ag&lt;sub&gt;n&lt;/sub&gt; (&lt;i&gt;n&lt;/i&gt; = 1–5)

The global-minimum geometries and electronic states of AgnH2S (n=1-5) clusters have been calculated using density-functional theory. Our calculations predicate that the stable geometries of AgnH2S clusters can be got by directly adding the H2S molecule on different site of Agn clusters, Agn (n=1-5) clusters would like to bond with sulfur atom and the H2S molecule is partial to hold the top location and single fold coordination site in the clusters. After adsorption, the structures of Agn clusters and H2S molecule keep the original structures and are only distorted slightly. The averaged binding energy reveals that adsorption of H2S molecule can strengthen the stabilities of AgnH2S clusters. The second difference in energy and the energy gaps between the HOMO and LUMO of Agn and AgnH2S have been studied.

Ag Supported Si-Doped Graphene for Hydrogen Sulphide Detection: A First-Principles Investigation

The adsorption of H2S molecule on Si-doped and Ag supported Si-doped graphene is studied by first-principles calculations. We find that the H2S floats on the Si-doped graphene sheet, indicating a weak physisorption. The calculated net charge transfer, charge density difference and density of states give evidence that the adsorption of H2S on Ag supported Si-doped graphene is by chemisorption. Moreover, the desorption and dissociation of H2S adsorbed on Ag supported Si-doped graphene occur at the external electric field of 1.4 and -0.8 V/Å, respectively. Therefore, the Ag supported Si-doped graphene can be expected to be a novel sensor for the detection of H2S gas.

Hydrogen sulfide adsorption on a defective graphene

AbstractWe have used density functional theory (DFT) to study adsorption of H2S molecules onto defective graphene as a function of vacancy concentration. The calculations are performed with the Quantum Espresso code, a plane‐wave realization of the DFT with norm‐conserving pseudopotentials. The Perdew et al. generalized gradient approximation to the density functional for exchange correlation energy of a many‐electron system is used. The computations show that a hydrogen sulfide molecule interacts stronger with the carbon atoms surrounding the vacancy than with the carbon atoms in a perfect arrangement. The most favorable energetically configuration is the one with the sulfur atom heading the center of the vacancy. Such a configuration facilitates covalent binding of the sulfur atom with three carbon atoms with unsaturated bonds. The density of states of perfect, defective graphene and defective graphene with chemisorbed sulfur demonstrate that the systems change their conductivity. The chemisorption is followed by a release of the hydrogen atoms, which form a H2 molecule. In the presence of more isolated vacancies per unit cell, more H2S molecules are chemisorbed. This process opens very interesting applications in the environmental and energy research. © 2012 Wiley Periodicals, Inc.