H2S Molecules Research Articles

Record-Breaking H2S Capture and ppm-Level Sensing with a Chemically Stable Porous Organic Cage.

The first experimental investigation of a porous organic cage (POC) for the challenging task of H2S capture is reported. The N-containing cage molecular material, a tertiary amine POC (6FT-RCC3), demonstrates the highest H2S (hydrogen sulfide) capture (record capacity) for a porous material at room temperature and atmospheric pressure (20.6mmol H2S g-1; 25 H2S molecules per cage) combined with excellent reversibility for at least five adsorption-desorption cycles. In situ FTIR spectroscopy, solid-state 13C, and 15N CP MAS NMR spectroscopy experiments are applied to investigate the adsorption mechanism, identifying relatively weak interactions via hydrogen bonding. In addition, the fluorescence performances of this POC material are evaluated for the detection and sensing of H2S, where a clear H2S selectivity is observed over other gases. Remarkably, the limit of detection (LOD) is calculated to be 0.13mm (≈4.43ppm) in a tetrahydrofuran (THF) solution of H2S.

The gas-sensing mechanism of Nb2C monolayer for SF6 decomposition based on the DFT study

Abstract In addressing malfunctions in gas-insulated switchgear (GIS) systems, it is imperative to have a real-time tracking system for SF6 decomposition products to guarantee the safety and reliability of the equipment's operation. Although a variety of gas detection technologies are currently available on the market, low-power gas detection devices for SF6 decomposition products are still in the development stage, and technological advances in this area are of great significance for improving the reliability of GIS systems. Based on the density functional theory (DFT), the Nb2C crystal surface structure was established and six adsorption structures of SO2, H2S, SOF2, SO2F2, HF and CO gas molecules on Nb2C crystal surface were constructed by geometrical optimization in this paper. The gas-sensitive properties of each adsorption system were explored in terms of adsorption energy, charge transfer, electron density, density of states and recovery time. The results showed that the Nb2C crystal surface was unfit HF and CO gases detection, both of which showed weak physical adsorption; the adsorption energies of SO2, H2S, SOF2, and SO2F2 on the Nb2C crystal surface were -1.846 eV, -1.081 eV, -5.270 eV, and -10.582 eV, respectively, and all of them were strong chemical adsorption. It was further shown by theoretical recovery time calculations that the Nb2C crystal surface can act as SOF2 and SO2F2 gas scavengers, and are able to desorb H2S (4.69 s) and SO2 (2.26 s) gases by appropriately increasing the temperature, but the Nb2C crystal surface is more suitable for use as a low-power gas-sensitive material for H2S gas detection. Therefore, Nb2C is anticipated to be a promising material for high response, low-power consumption and fast recovery for H2S gas detection in SF6 decomposition gas.

High Performance H2S Sensor Based on Ordered Fe2O3/Ti3C2 Nanostructure at Room Temperature.

The utilization of a heterogeneous nanojunction design has shown significant enhancements in the gas sensing capabilities of traditional metal oxide gas sensors. In this study, a novel room temperature H2S gas sensor employing Fe2O3 functionalized Ti3C2 MXene as the sensing material has been developed. This sensor exhibits a broad detection range (0.01-500 ppm), low detection limit (10 ppb), and rapid response/recovery times (10 s/15 s), making it ideal for ppb-level H2S detection. The exceptional gas sensitivity of Fe2O3/Ti3C2 composite to H2S can be attributed to several key factors. First, the unique layered frame structure of Fe2O3/Ti3C2 significantly amplifies the surface area of the hybrid material, enhancing the absorption and diffusion capabilities of H2S molecules. Second, the abundance of functional groups (-O, -OH, and -F) on the surface of Ti3C2 MXene nanosheets provides additional active sites for H2S adsorption, The density functional theory calculation confirms that the adsorption energy of the Fe2O3/Ti3C2 composite for H2S (-2.93 eV) is significantly lower than that of pure Fe2O3 (-2.37 eV) and Ti3C2 (-0.2 eV). Lastly, the remarkable metal conductivity of Ti3C2 MXene ensures efficient electron transfer, thereby enhancing overall sensing performance.

Conductive metal-organic framework for ppb-concentration and highly selective SAW hydrogen sulfide sensing at room temperature

Hydrogen sulfide (H2S) sensing is utilized for monitoring the concentration in environment protection and industrial process control, of which high selectivity and ppb detection limit are required. Here, a ppb-concentration and highly selective surface acoustic wave (SAW) H2S sensing has been developed with the Cu3(HHTP)2 MOFs conductive metal-organic frameworks (MOFs), which have been synthesized by connecting Cu2+ with the organic ligands via hydrothermal process. Typically, as-prepared Cu3(HHTP)2 MOFs take on shapes including nanoparticles and nanorods. Beneficially, the SAW H2S sensing presents excellent selectivity to H2S and enables to detection of H2S as low as 6 ppb at room temperature (∼ 26 °C). Remarkably, the SAW sensor prototypes exhibit high sensitivity (0.02 mV/ppb) to 50–2000 ppb H2S, fast response (T90: 281 s) and 46 day-long stability at room temperature. Theoretically, such excellent H2S SAW sensing performance might be attributed to the interaction between Cu ions and H2S molecules and the strong acoustoelectric effect of SAW. Practically, our ppb-concentration and highly selective H2S SAW sensing have the potential in the real-time detection of H2S.

Exploring penta-ZnS2 monolayer as potential gas sensor for toxic gases based on first principles

To gain a deeper understanding of the application of ZnS2 monolayer in gas sensors, this paper predicts the electronic properties and gas sensing performance of CO, CH4, Cl2, H2S, NO and NH3 gas molecules adsorbed on ZnS2 monolayer based on first principles research. The results show that ZnS2 is sensitive to CO, Cl2, H2S, NO and NH3 by chemisorption and to CH4 by strong physisorption. The adsorption of gases effectively changes the electronic properties and gas sensing properties on ZnS2, and the bandgap of the adsorbed system changes significantly compared with the intrinsic ZnS2, and the characteristics of the work function can effectively distinguish various gases. Our calculations are of great significance for exploring the sensing applications of ZnS2 monolayer as a new member of the gas sensor family, and we expect that this work will provide new perspectives and theoretical foundations for the possible applications of ZnS2 monolayer in the sensing and processing of CO, CH4, Cl2, H2S, NO and NH3 gases.

Photo-induced loss of H2 from H2S, CH4, H2O and SiH4, when and why is it possible

We have explored the possibility of forming H⋅ and H2 from H2S, CH4, H2O and SiH4 in a series of ab initio calculations. The key finding is that H2S can give rise to direct photolytic ultrafast formation of H2 This finding is in agreement with the available experimental data and is a result of a directed pathway that leads toward H2 formation at easily accessible wavelengths. It arises at the (conical) intersection between the two lowest-lying electronic states. This intersection is a result of the valence orbital interaction of the two hydrogen atoms. This interaction is becoming more favorable as the S-H bonds simultaneously becomes longer. The H-S σ-σ∗ bonding interaction cannot compete with the bond formation that takes place between the hydrogens as two bonds stretch simultaneously. For oxygen this interaction it predominant. The reason is that sulfur has a higher principal quantum number and the interaction with the 1s of hydrogen therefore is less favorable. The excited states that are involved in the H2 formation from H2S could be populated by, for example, a two-photon 400 nm excitation. The other hydrides have a more entangled potential energy landscape close to the Franck-Condon region in the direction of the reaction coordinate that leads to H2 loss and as a result the direct loss of a hydrogen atom is favored. A two-photon excitation could be induced by femtosecond laser pulses that at the same time is proposed as a future platform for sensing the H2S molecules with the backward transient absorption scheme. The implication would be that both sensing and photoinduced H2 formation could be in place at the same time which justifies the use of expensive femtosecond light sources getting “two for the price of one”.

Metal-organic framework derived cobalt and iron oxide nanosheets for ppb-concentration and highly selective hydrogen sulfide sensing

Hydrogen sulfide (H2S) sensing with ppb concentration detection limit and high selectivity is highly desired in future exhaled diagnoses of halitosis, asthma and down syndrome, however, needs further developing. Here, a ppb-concentration and highly selective H2S sensing has been developed with the two-dimensional cobalt and iron oxide nanosheets (CoFexOy NSTs), which is transformed from leaf-shaped zeolitic imidazolate frameworks {ZIF-L(Co)} by combined Fe2+ ion-etching and annealing. Typically, as-prepared CoFexOy NSTs are of ∼ 10 nm thick with rough surface. Beneficially, the CoFexOy NSTs present outstanding selectivity to H2S against other interfering gases and exhibit a detection limit as low as 50 ppb. Remarkably, the sensor prototypes exhibit high response to 10 ppm H2S (Ra/Rg = 23.8) and fast response speed (∼13 s to 10 ppm H2S). Theoretically, such excellent H2S sensing might be attributed to the high surface ratio of CoFexOy NSTs providing enriched adsorption sites for H2S molecules. Practically, a H2S sensing device built with the CoFexOy NSTs sensor prototype is simulated for detecting H2S with reliable response, which is potential in future intelligent healthcare.

Prediction of solubility of CO2, H2S, and their mixture in ionic liquids using the Cubic Two State equation of state

In this work, the capability of the Cubic Two State (CTS) equation of state (EoS) has been evaluated using the solubility of carbon dioxide (CO2), hydrogen sulfide (H2S), and their mixture in ionic liquids (ILs). The imidazolium-based ILs with [BF4], [PF6], and [Tf2N] anions have been studied. The self-association between IL molecules, CO2, and H2S molecules has been considered to optimize the pure model parameters. In addition to self-association between similar molecules, the cross-association between CO2-IL and H2S-IL in the binary mixtures has been considered. The results show that the CTS EoS can predict (kij=0.0) the solubility of H2S and CO2 in ILs ranging from 1 to 1000 bar satisfactory. The average ARD value for binary CO2-IL and H2S-IL systems has been obtained 20.3 % and 9.02, respectively. The CTS model has been used to predict the phase behavior of ternary systems containing CO2H2S-[C4mim][PF6], CO2H2S-[C8mim][PF6], and CO2H2S-[C8mim][Tf2N] at various temperatures. Finally, the CTS results have been compared to soft-SAFT and PC-SAFT EoSs. The results show that simple association contribution and the cubic term of the CTS EoS can model the molecular interactions between gases and ILs satisfactory. The CTS model can be considered as a robust and efficient thermodynamic model for the prediction of separation of CO2 and H2S using ILs.

Theoretical insight into the sulfurated poisoning process of rhenium-doped nickel catalyst

Three rhenium-doped nickel catalyst surfaces including Re-Ni(111), Re-Ni(200) and Re-Ni(220) were built via Re atom substituting one atom of upper layer Ni surfaces. The sulfurated poisoning process involving H2S adsorption and subsequent splitting steps (H2S→HS+H, HS→S+H) on the three surfaces was investigated and further compared using density functional theory (DFT) to understand the crystal-plane effect. For H2S adsorption, the H2S molecule is preferentially adsorbed on the Re top and bridge ReNi1 sites. Re-Ni(200) surface possessed lower H2S adsorption energy compared to Re-Ni(111) and Re-Ni(220) surfaces, due to its smaller coordination number and higher d-orbital intensity at Fermi level. For splitting steps, transition state search showed that the two processes on the three surfaces are all calculated as exothermic while the energy barrier is basically in the range of 0.23 eV∼0.44 eV, which signifies that the poisoning process is favorable both kinetically and thermodynamically. The splitting steps can be described as a dynamic procedure that contains intimate HS fragment activation, S–H bond stretching accompanied by H atom departure and final dissociation into HS+H or S+H co-intermediates. The valence bond changes during dissociation deduced from projected density of states (PDOS) analysis also proved the above procedure.

The Uncertainty Evaluation of Determining the Trace H2S in SF6/N2 Insulating Gas Mixture by Cavity Ring-Down Spectroscopy

Abstract H2S is one of the most important characteristic components of sulfur hexafluoride gas insulated electrical equipment. The detection of trace H2S is of great significance for early fault diagnosis of such equipment. Based on the 1578 nm wavelength distributed feedback diode laser (DFB-DL), cavity ring-down spectroscopy (CRDS) can effectively measure the concentration of trace H2S in SF6/N2 gas mixtures. Starting from the principle of methodology, this article establishes a mathematical model for evaluating the measurement uncertainty of CRDS and analyzes its sources of uncertainty: gas constant R1 , temperature T, Avogadro constant NA , gas pressure p in the optical cavity, volume V of the optical cavity, speed c of light, the absorption cross-section parameter σ(ν) of H2S molecules in the laser frequency ν, the ring-down time τ with absorption sample H2S and the ring-down time τ0 without absorption sample. After evaluating the uncertainty components, it was found that the main component was σ(ν) and the secondary components were τ and τ0. The H2S content in the 80% SF6-20% N2 mixed gas measured is (7.64 ± 0.12) × 10−6 mol/mol.

Li-decorated B12C6N6 hybrid nanocage for sensing Cl2, COCl2, H2S and NH3 gas molecules

We examined the gas sensing abilities of Li-decorated B12C6N6 (B12C6N6Li) hybrid nanocage, introducing B12C6N6 for the first time in sensing applications. The toxic gas molecules like Cl2, COCl2, H2S, and NH3 were considered. The B12C6N6 nanocage with C2V symmetry displayed the lowest energy among its isomers. Li exhibited stronger anchoring above B3C2N ring compared to B2C2, B2N2, and B3CN2 rings of B12C6N6 nanocage, displaying a binding energy of −3.30 eV. Li decoration resulted in asymmetric spin-up and spin-down states near Fermi level, indicating magnetic nature of complexes. B12C6N6, an electron-deficient nanocage, displayed charge transfer from Li atom to the nanocage. Substantial changes in electronic states occurred following the adsorption of Cl2 and COCl2 molecules. COCl2, H2S, and NH3 adsorption is thermodynamically favourable over a wide temperature and pressure range, while Cl2 adsorption is favourable only within a confined range. Earlier findings indicate dissociative adsorption of Cl2 on nanocages rendering the substrate to be non-reusable. B12C6N6Li considered here is superior over other nanocages as Cl2 adsorbs in molecular form while B12C6N6Li also demonstrates significant sensitivity. B12C6N6Li nanocage is unsuitable for sensing H2S and NH3 gas molecules but holds promise as a potential candidate for sensing Cl2 and COCl2 gas molecules.

First-principles study of hydrogen sulfide decomposition on Sc-Ti3C2O2 single-atom catalyst.

Hydrogen sulfide gas poses significant risks to both human health and the environment, with the potential to induce respiratory and neurological effects, and a heightened fatality risk at elevated concentrations. This article investigates the catalytic decomposition of H2S on a Sc-Ti3C2O2 single-atom catalyst(SAC) using the density functional theory-based first-principles calculation approach. Initially, the adsorption behavior of H2S on Ti3C2O2-MXene was examined, revealing weak physical adsorption between them. Subsequently, the transition metal atom Sc was introduced to the Ti3C2O2 surface, and its stability was studied, demonstrating high stability. Further exploration of H2S adsorption on Sc-Ti3C2O2 revealed direct dissociation of H2S gas molecules into HS* and H*, with HS* binding to Sc and H* binding to O on the Ti3C2O2 surface, resulting in OH groups. Using the transition state search method, the dissociation of H2S molecules on the SAC's surface was investigated, revealing a potential barrier of 2.45eV for HS* dissociation. This indicates that the H2S molecule can be dissociated into H2 and S with the action of the Sc-Ti3C2O2 SAC. Moreover, the S atom left on the catalyst surface can aggregate to produce elemental S8, desorbing on the catalyst surface, completing the catalytic cycle. Consequently, the Sc-Ti3C2O2 SAC is poised to be an efficient catalyst for the catalytic decomposition of H2S. The Dmol3 module in Materials Studio software based on density functional theory is used in this study. The generalized gradient approximation method GGA-PBE is used for the exchange-correlation function. The complete LST/QST and the NEB methods in the Dmol3 module were used to study the minimum energy path of the dissociation of hydrogen sulfide molecules on the catalyst surface.

Unraveling the Rich Fragmentation Dynamics Associated with S-H Bond Fission Following Photoexcitation of H2S at Wavelengths ∼129.1 nm.

H2S is being detected in the atmospheres of ever more interstellar bodies, and photolysis is an important mechanism by which it is processed. Here, we report H Rydberg atom time-of-flight measurements following the excitation of H2S molecules to selected rotational (JKaKc') levels of the 1B1 Rydberg state associated with the strong absorption feature at wavelengths of λ ∼ 129.1 nm. Analysis of the total kinetic energy release spectra derived from these data reveals that all levels predissociate to yield H atoms in conjunction with both SH(A) and SH(X) partners and that the primary SH(A)/SH(X) product branching ratio increases steeply with ⟨Jb2⟩, the square of the rotational angular momentum about the b-inertial axis in the excited state. These products arise via competing homogeneous (vibronic) and heterogeneous (Coriolis-induced) predissociation pathways that involve coupling to dissociative potential energy surfaces (PES(s)) of, respectively, 1A″ and 1A' symmetries. The present data also show H + SH(A) product formation when exciting the JKaKc' = 000 and 111 levels, for which ⟨Jb2⟩ = 0 and Coriolis coupling to the 1A' PES(s) is symmetry forbidden, implying the operation of another, hitherto unrecognized, route to forming H + SH(A) products following excitation of H2S at energies above ∼9 eV. These data can be expected to stimulate future ab initio molecular dynamic studies that test, refine, and define the currently inferred predissociation pathways available to photoexcited H2S molecules.

Influence of Be vacancy on 2D BeN4 single-layer for enhanced H2S sensing: prediction from first-principles simulations

Abstract A notable surge in research interest directed towards the exploration and development of two-dimensional materials, specifically in the realm of advancing nano-devices, with a special focus on applications in gas detection, has been observed. Among these materials, the spotlight has fallen on a newly synthesized single-layered Dirac Semimetal, known as BeN4, which holds great promise as a potential candidate for an efficient gas sensor. The current investigation uses first-principles calculations to examine the H2S detection capability of pristine and point-defect-tempted BeN4 single-layers. The H2S molecule has been observed to be weakly adsorbed on pure BeN4 through weak van der Waals interaction exhibiting very low adsorption energy of −0.0726 eV and insignificant charge transport. The impact of the Be vacancy point defect in BeN4 was the surge in H2S adsorption energy to −0.582 eV, manifested by enhanced charge transmission (0.02 e) from the H2S molecule to the BeN4 with Be defects. The reasonable physical steadiness and modest recovery time (6 ms) at ambient conditions indicate the possibility of Be point-defected BeN4 being a contender as a sensor material for designing and developing a robust H2S gas sensor. In addition, the sensor exhibited a selective response towards the H2S gas molecules. Our findings will provide a reference line for the fabrication of innovative H2S detectors, showcasing the practical implications of the observed enhancements in H2S adsorption energy and charge transmission in Be point-defected BeN4 structures.

Cooperativity between Intermolecular Hydrogen and Carbon Bonds in ZY···CH3CN/CH3NC···HX Trimers (ZY = H2O, H2S, HF, HCl, HBr, NH3, and H2CO; HX = HF, HCl, and HBr).

Hydrogen-bonding and carbon-bonding interactions are widespread in nature. We studied the cooperativity between these interactions in 42 trimeric complexes ZY···CH3CN/CH3NC···HX, where ZY molecules are H2O, H2S, HF, HCl, HBr, NH3, and H2CO, and HX molecules are HF, HCl, and HBr. Acetonitrile (CH3CN) and isoacetonitrile (CH3NC) act as hydrogen bond acceptors as well as carbon bond donors in these trimers. Various theoretical methods, such as electronic structure calculations, quantum theory of atoms in molecule (QTAIM), natural bond orbital (NBO), and reduced density gradient analysis, are employed to study these trimers, and the results are compared with the corresponding ZY···CH3CN/CH3NC and CH3CN/CH3NC···HX dimers. Electronic structure calculations are performed at the second-order Mo̷ller-Plesset perturbation theory using the 6-311++G(2d,2p) basis set. We show that both the interactions act synergistically in these trimers leading to an increase in their bond strength as compared to the strength in the individual dimers. The cooperative energies for these trimers are in the range of 0.69 to 3.22 kJ/mol. It is seen that the carbon bonds benefit more from the cooperativity than the hydrogen bonds. The trends of cooperativity and correlations of interaction energies and cooperative energies with relevant QTAIM and NBO parameters are reported.

Adsorption behavior of hydrogen sulfide in the channels of Li-ABW zeolite: A study using density functional theory

H2S is a highly toxic, flammable gas that poses risks to health, the environment, and industrial infrastructure. Zeolites, with their high porosity, offer a promising solution for its removal. This study employs density functional theory (DFT) to investigate the adsorption behavior of H2S within the Li-ABW zeolite framework, focusing on the synergistic effect of co-adsorbed water molecules. Six distinct systems were modeled: empty Li-ABW zeolite, half and full filled Li-ABW with H2O or H2S molecules, and equally filled zeolite with H2S and H2O molecules. Detailed analysis of geometric, energetic, and electronic properties reveals that the presence of water significantly enhances H2S adsorption in Li-ABW. Increased bond lengths between H2S and the zeolite framework suggest possible dissociative adsorption, while weakened H2S-zeolite interaction compared to H2O-zeolite interaction indicates facile H2S desorption. Furthermore, charge transfer analysis and HOMO/LUMO plots highlight stronger interactions and a more balanced electron distribution in the co-adsorbed system. Interestingly, the presence of water minimizes structural deformations of the zeolite framework while facilitating the formation of additional hydrogen bonds, potentially further promoting H2S desorption through water extraction. These findings demonstrate that Li-ABW zeolite, particularly in conjunction with water molecules, exhibits remarkable potential for efficient and selective H2S adsorption, offering promising avenues for practical applications in gas sweetening and industrial gas purification. In order to realize this potential, further investigation into the effects of solvents and cation exchange is necessary, which are outlined for future research.

The sensing properties of asphyxiating gas molecules (CH4, CO and H2S) adsorption on GaP3 monolayer: A first principle study

In this work, we theoretically investigate the adsorption properties of three asphyxiating gas molecules (CO, CH4, and H2S) adsorption on monolayer GaP3 and explore its feasibility of being used as a potential material in the asphyxiating gas sensor through first-principles calculations. The absorption energy (Eads), transfer charge (Q), band structure, and recovery time (τ) of absorption systems are calculated and analyzed. Our results indicate that monolayer GaP3 is sensitive to CO and H2S molecules adsorption, with reasonable absorption energies of −0.580 eV and −0.955 eV, respectively. It is found that all studied gas molecules are acceptors to gain electrons from the monolayer GaP3. The potential of monolayer GaP3 as a sensor for asphyxiating gases is analyzing combined with the gas recovery time at different working temperature. As the temperature increases from 298 K to 348 K, and then to 418 K, the recovery time of H2S molecules adsorption decreases from 1.4 × 104 s to 67 s and 3.2 s, respectively. It implies that the monolayer GaP3 holds promise as a detection material for H2S gas molecules. In addition, we applied extra biaxial strains to monolayer GaP3 and found that all absorption systems exhibit a more obvious response to the compressive strain than the tensile strain. The applied tensile strain can remarkably facilitate the desorption of the H2S molecules. Therefore, we suggest that applying extra strain can tune the adsorption properties of considered gas molecules. Moreover, our study implies that monolayer GaP3 can be used as a promising material for asphyxiating gas (CH4, CO, and H2S) molecule sensing applications.

The Absorption Mechanisms of CO2, H2S and CH4 Molecules in [EMIM][SCN] and [EMIM][DCA] Ionic Liquids: A Computational Insight

This study investigates the absorption mechanisms of carbon dioxide (CO2), hydrogen sulfide (H2S), and methane (CH4) molecules in two imidazolium-based ionic liquids, namely 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) and 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]). We employed molecular dynamics (MD) simulations applying umbrella sampling technique to calculate free energy profiles (FEPs) for gas molecules in the ILs. The results reveal CO2's pronounced affinity for the interface over the bulk in both ionic liquids (IL), whereas H2S exhibits facile penetration into both regions. CH4 shows limited penetration into the IL bulk, remaining predominantly near the interface. We further explore the influence of ILs' anionic structures on gas accumulation sites by performing normal MD simulations. For instance, density profiles also confirm CO2's higher density in [EMIM][DCA] compared to [EMIM][SCN], reflecting the influence of anionic composition on CO2 solubility. These insights offer valuable knowledge for designing efficient ILs for gas capture and separation applications.

Investigating the adsorption performance of CO, NO, NO2, NH3, and H2S molecules on C9N4 through DFT for potential gas sensor applications

In this work, the feasibility of using transition metal doped C9N4 as an efficient gas sensor is comprehensively investigated by density functional theory methods. Firstly, the calculated Ef and Udiss values show that most of M-C9N4 and M2-C9N4 have good thermodynamic and electrochemical stability. Secondly, for CO, NO, NO2, NH3, and H2S on Cr-C9N4, the Eads values are −2.07, −3.05, −2.53, −1.76, and −2.14 eV, respectively. For these gases on Fe2-C9N4, the Eads values are −2.60, −3.07, −2.45, −2.39, and −2.21 eV, respectively. The results show that Cr-C9N4 and Fe2-C9N4 have good adsorption strengths for all gases, which can provide good theoretical guidance for the design of excellent sensing materials. Finally, by calculating band structures of all catalysts, they all have small band gap values, such as, Fe2-C9N4 with the 0.10 eV, which all shows stable catalysts possess good conductive properties. The DOS results show that there is an obvious orbital hybridization between metal, N, C, and O atoms, indicating that there is a certain interaction between them, which is an important factor leading to the good adsorption of the catalyst to the molecular gas. This work can provide theoretical guidance for searching efficient sensor materials.

Adsorption behavior of CO2/H2S mixtures in calcite slit nanopores for CO2 storage: An insight from molecular perspective

It is acknowledged that injecting CO2 into oil reservoirs and saline aquifers for storage is a practical and affordable method for CO2 sequestration. Most CO2 produced from industrial exhaust contains impurity gases such as H2S that might impact CO2 sequestration due to competitive adsorption. This study makes a commendable effort to explore the adsorption behavior of CO2/H2S mixtures in calcite slit nanopores. Grand Canonical Monte Carlo (GCMC) simulation is employed to reveal the adsorption of CO2, H2S as well as their binary mixtures in calcite nanopores. Results show that the increase in pressure and temperature can promote and inhibit the adsorption capacity of CO2 and H2S in calcite nanopores, respectively. CO2 exhibits stronger adsorption on calcite surface than H2S. Electrostatic energy plays the dominating role in the adsorption behavior. Electrostatic energy accounts for 97.11% of the CO2-calcite interaction energy and 56.33% of the H2S-calcite interaction energy at 10 MPa and 323.15 K. The presence of H2S inhibits the CO2 adsorption in calcite nanopores due to competitive adsorption, and a higher mole fraction of H2S leads to less CO2 adsorption. The quantity of CO2 adsorbed is lessened by approximately 33% when the mole fraction of H2S reaches 0.25. CO2 molecules preferentially occupy the regions near the pore wall and H2S molecules tend to reside at the center of nanopore even when the molar ratio of CO2 is low, indicating that CO2 has an adsorption priority on the calcite surface over H2S. In addition, moisture can weaken the adsorption of both CO2 and H2S, while CO2 is more affected. More interestingly, we find that pure CO2 is more suitable to be sequestrated in the shallower formations, i.e., 500–1500 m, whereas CO2 with H2S impurity should be settled in the deeper reservoirs.