Ni 3d Orbitals Research Articles

Research on the electronic properties of TiB2/γ-Fe(1 1 1) and TiB2/Ni(1 1 1) interfaces

In order to explore the interfacial bonding mechanisms of TiB2/γ-Fe and TiB2/Ni in the composites, the adhesion work, electronic properties and fracture toughness of the TiB2(001)/ γ-Fe(111) and TiB2(001)/Ni(111) interfaces were investigated using first-principles calculations. The results reveal that the surface energy of the TiB2 surface at the B-terminated is the smallest and the constructed TiB2(001)/ γ-Fe(111) interface has the largest adhesive energy. The electronic structures of the TiB2(001)/γ-Fe(111) and TiB2(001)/Ni(111) interfaces reveal that bonding at the interfaces is provided by the B-2p orbitals with the Fe-3d and Ni-3d orbitals, respectively, and that the formation of Fe-B and Ni-B covalent/ionic bonds is the main source of bonding and interaction. The bonding and strength of Fe-B in the TiB2(001)/γ-Fe(111) interface is stronger than that in the TiB2(001)/Ni(111) interface, which is due to the higher charge density accumulation of Fe atoms at the TiB2(001)/γ-Fe(111) interface. Using Griffith’s theory, the TiB2(001)/γ-Fe(111) interface is inferred to have the strongest fracture toughness. This study suggests that the chemical bonding stronger Fe-B bonds result in a high bond strength and a more stable interfacial structure at the TiB2(001)/ γ-Fe(111) interface, leading to better resistance to cracking in practice.

Effect of Rare-Earth Element Substitution in Superconducting R3Ni2O7 under Pressure

Abstract Recently, high temperature (T c ≈ 80 K) superconductivity (SC) has been discovered in La3Ni2O7 (LNO) under pressure. This raises the question of whether the superconducting transition temperature T c could be further enhanced under suitable conditions. One possible route for achieving higher T c is element substitution. Similar SC could appear in the Fmmm phase of rare-earth (RE) R3Ni2O7 (RNO, R = RE element) material series under suitable pressure. The electronic properties in the RNO materials are dominated by the Ni 3d orbitals in the bilayer NiO2 plane. In the strong coupling limit, the SC could be fully characterized by a bilayer single 3d x 2–y 2 -orbital t–J ∥–J ⊥ model. With RE element substitution from La to other RE element, the lattice constant of the Fmmm RNO material decreases, and the resultant electronic hopping integral increases, leading to stronger superexchanges between the 3d x 2–y 2 orbitals. Based on the slave-boson mean-field theory, we explore the pairing nature and the evolution of T c in RNO materials under pressure. Consequently, it is found that the element substitution does not alter the pairing nature, i.e., the inter-layer s-wave pairing is always favored in the superconducting RNO under pressure. However, the T c increases from La to Sm, and a nearly doubled T c could be realized in SmNO under pressure. This work provides evidence for possible higher T c R3Ni2O7 materials, which may be realized in further experiments.

Exciton Dissociation into Charge Carriers in Porphyrinic Metal-Organic Frameworks for Light-Assisted Li-O2 Batteries.

Light-assisted Li-O2 batteries exhibit a high round-trip efficiency attributable to the assistance of light-generated electrons and holes in oxygen reduction and evolution reactions. Nonetheless, the excitonic effect arising from Coulomb interaction between electrons and holes impedes carrier separation, thus hindering efficient utilization of photo-energy. Herein, porphyrinic metal-organic frameworks with (Fe2Ni)O(COO)6 clusters are used as photocathodes to accelerate exciton dissociation into charge carriers for light-assisted Li-O2 batteries. The coupling of Ni 3d and Fe 3d orbitals boosts ligand-to-metal cluster charge transfer, and hence drives exciton dissociation and activates O2 for superoxide (•O2 -) radicals, rather than singlet oxygen (1O2) under photoexcitation. These enable the light-assisted Li-O2 batteries with a low total overvoltage of 0.28V and round-trip efficiency of 92% under light irradiation of 100mW cm-2. This work highlights the excitonic effect in photoelectrochemical processes and provides insights into photocathode design for light-assisted Li-O2 batteries.

Tailoring Ni 3d orbitals in Ni-Fe/Ni foam heterostructures for enhanced H* adsorption and boosted electrocatalytic nitrate reduction performance

The electrochemical nitrate (NO3−) reduction (ENR) in wastewater, a promising remediation strategy, is often impeded by the essential use of costly noble metals. This study introduces an innovative non-noble Ni-Fe/Ni foam cathode fabricated via one-step electrodeposition technique. Efficient nitrate removal (99.4 %) was achieved with the selectivity of 83.6 % to NH3. The exceptional performance can be ascribed to the augmented active sites and the synergistic interaction between Ni and Fe. The leftward shift of the 3d orbitals density of Ni and the elevation of density at the Fermi level on Ni foam heterostructures, consequent to Fe doping, enhance the adsorption of H*. The addition of reactive chlorine species, generated through anodizing in Cl− mediated system, further improves N2 selectivity by oxidizing intermediate NH4+ product. The coupled anodic oxidation method employed herein achieves nearly 100 % removal efficiency of total nitrogen (TN) for initial concentration of 100 mg/L within 180 min, under the conditions of 1.5 g/L Cl− concentration and a current density of 25 mA cm−2. The findings underscore the potential of the Ni-Fe/Ni foam cathode within a Cl− mediated electrocatalytic framework for nitrate wastewater treatment, providing novel insights into the design of cathode catalysts and anodic coupling strategies for efficient TN removal.

Expediting sulfur redox kinetics by redistributing d-orbital states in Ni2P via cation doping for high-performance lithium–sulfur battery

Doping engineering is considered as a key approach to develop catalysts for Li-S batteries that can mediate redox reaction and chemisorption immobilization of polysulfides. However, the rationalization of doping elements selection and the intrinsic regulatory essences remain elusive. Herein, we propose a sensible strategy of modulating the electron-filled state of d-orbital of the Ni elements to accelerate redox dynamics of polysulfides. Concretely, we introduce dopants (V3+ or Mn2+) that feature empty or half-filled vacant 3d orbitals to substitute partial cations of Ni2P. The analysis confirms that the electrons of Ni 3d orbitals can be transferred to the doped atoms with unoccupied orbitals, resulting in a reduced electron-filling number of the Ni 3d orbitals. Notably, the electrons are more inclined to transfer to V with empty orbitals compared to Mn with partially occupied orbitals. More importantly, we delineate the relationship between electron-filled state of the Ni 3d orbitals and polysulfides adsorption-catalytic activity as well as corresponding intrinsic mechanism. Benefiting from the above advantages, the cell with V-Ni2P separator can achieve a discharge capacity of 1052 mAh g–1 at high sulfur loading (5.4 mg cm–2) and lean electrolyte (E/S = 6 μLE mg–1S) condition. This work illustrates essential link between d-electron filling state of metal atoms and adsorption-catalytic activity of polysulfides, which provides a pointer for rational selection of doping elements.

Tuning d–p Orbital Hybridization of NiMoO4@Mo15Se19/NiSe2 Core‐Shell Nanomaterials via Asymmetric Coordination Interaction Enables the Water Oxidation Process

AbstractThe electrocatalytic performance of MoNi‐based nanomaterials undergo selenization has garnered significant interest due to their modified electronic structure, while still posses certain challenges for obtained bimetallic selenides. Here, a novel MoNi‐based electrocatalyst of NiMoO4@Mo15Se19/NiSe2 core‐shell nanomaterials is constructed to promote the desorption of OOH* which can facilitate the water oxidation process. NiMoO4@Mo15Se19/NiSe2 core‐shell nanoarrays show that the “cores” are mainly NiMoO4 nanorods while the “shells” are the bimetallic selenides nanoflakes, which are super architectures that can expand more active sites and accelerate the electron transfer. Moreover, the hybridization interaction between Ni 3d, Mo 4d, and Se 4p orbitals leads to an asymmetric distribution of electric clouds, which decreases the adsorption energy and transformation of oxygen‐containing species. Electrochemical data displays that the overpotentials of NiMoO4@Mo15Se19/NiSe2 core‐shell nanomaterials are only 195 mV, 220 mV, and 224 mV for oxygen evolution reaction (OER) in alkaline freshwater, alkaline simulated seawater, and alkaline natural seawater. The current density decay is negligible after 100 h stability at about 1.46 V with a three‐electrode system in alkaline natural seawater. The low cost and the unique MoNi‐based bimetallic selenides in this work provide a more constructive solution for designing efficient and stable OER catalysts in the future.

Impact of Polarity Mismatch in Infinite-Layer Nickelates.

The recent discovery of superconductivity in infinite-layer Sr-doped NdNiO2 grown on SrTiO3(001) provides a new platform to explore the conducting mechanism of unconventional superconductors. However, the electronic structure of infinite-layer nickelates remains controversial. In this paper, we systematically compare the structural and electronic properties of NdNiO2 films grown on SrTiO3 and LaAlO3 substrates using first-principles calculations. Our results show that the lattice reconstruction accompanied by electronic reconstruction occurs in nickelate films on both substrates. Although both heterostructures (HSs) are conducting at the interface, the SrTiO3-based HS shows distinct atomic displacement in the interfacial TiO2 layer and significant electron accumulation deep into three SrTiO3 layers below the interface, while the LaAlO3-based HS shows negligible atomic displacement and electron localization in the interfacial AlO2 layer, reflecting the impact of polarity mismatch on the electronic structure. Further, Wannier function calculations reveal that the interface stress has no obvious effect on the splitting energy and hopping integral between Ni 3d and Nd-layer orbitals. Although the hybridization between Ni 3dx2-y2 and Nd 5d orbitals is tiny, the hybridization between the Ni 3dx2-y2 orbital and an itinerant interstitial s (IIS) orbital is significantly strong in both cases, suggesting that the IIS orbital may play a critical role in the superconductivity of nickelates.

Ni Nanoclusters Anchored on Ni-N-C Sites for CO2 Electroreduction at High Current Densities.

Transition metal catalyst-based electrocatalytic CO2 reduction is a highly attractive approach to fulfill the renewable energy storage and a negative carbon cycle. However, it remains a great challenge for the earth-abundant VIII transition metal catalysts to achieve highly selective, active, and stable CO2 electroreduction. Herein, bamboo-like carbon nanotubes that anchor both Ni nanoclusters and atomically dispersed Ni-N-C sites (NiNCNT) are developed for exclusive CO2 conversion to CO at stable industry-relevant current densities. Through optimization of gas-liquid-catalyst interphases via hydrophobic modulation, NiNCNT exhibits as high as Faradaic efficiency (FE) of 99.3% for CO formation at a current density of -300 mA·cm-2 (-0.35 V vs reversible hydrogen electrode (RHE)), and even an extremely high CO partial current density (jCO) of -457 mA·cm-2 corresponding to a CO FE of 91.4% at -0.48 V vs RHE. Such superior CO2 electroreduction performance is ascribed to the enhanced electron transfer and local electron density of Ni 3d orbitals upon incorporation of Ni nanoclusters, which facilitates the formation of the COOH* intermediate.

First principles study on electronic, magnetic and optical properties of Gd2NiMnO6

The double perovskite oxide materials have various applications in light absorber, solid oxide fuel cells, electrode materials for electrochemical energy devices, solid state thermoelectric devices, etc. The calculations of electronic, optical and magnetic properties of Gd2NiMnO6 (GNMO) double perovskite are aimed in the present work. GNMO crystallizes in monoclinic structure with P21/n (14) space group. Implementing first principles density functional theory, we have reported the spin-polarised electronic band structure, density of states (DOS), optical absorption property and magnetic moment of GNMO double perovskite. Furthermore, the effect of on-site d-d Coulomb interaction energy (Ueff) on the electronic and optical properties were investigated by applying a range of Hubbard parameters from 0 to 6 eV on Ni-3d and Mn-3d orbitals within the local spin density approximation (LSDA) and generalised gradient approximation (GGA). Interestingly, on applying Ueff in this range, band gap of GNMO enhanced progressively in both majority and minority spins and also for Ueff = 4 and 6 eV implemented on Ni-3d and Mn-3d orbits, respectively, we observe the band gap value 1.16 and 2.12 eV for the spin-up and spin-down states which is in good agreement with the previously reported experimental band gap value (1.5 eV). In this regard, the electronic structure and light absorption of GNMO have been analysed for Ueff = 4 and 6 eV implemented on Ni-3d and Mn-3d orbits, respectively. The calculations revealed suitable narrow band gap and large visible light absorption coefficient in GNMO, which are extremely desired for the high photovoltaic performance.

Theoretical Study on the Vapochromic Ni(II)-Quinonoid Complex: One-Dimensional Stacking Structure-Based Color Switching.

Vapochromic crystals of Ni(II)-quinonoid complexes were theoretically investigated using density functional theory (DFT) calculations. Kato et al. previously reported that the purple crystals of a four-coordinate Ni(II)-quinonoid complex (1P) exhibited vapochromic characteristics upon exposure to methanol gas, resulting in orange crystals of the six-coordinate methanol-bound complex (1O) [Angew. Chem., Int. Ed.2017, 56, 2345-2349]. However, the authors did not characterize the crystal structure of 1P. In the present study, we computationally predicted the crystal structure of 1P by performing a crystal structure search with classical force-field computations followed by optimization using DFT calculations. The simulated powder X-ray diffraction pattern of the DFT-optimized structure agreed with experimental observations, indicating that our predicted crystal structure is reliable. Investigation of the optimized crystal structure of 1P revealed that its color change arose from changes in its 1D-band structure, which consists of Ni 3d orbitals and quinonoid π-orbitals. Intermolecular interactions were weakened upon the binding of methanol to the Ni(II) center in 1O. Consequently, the intermolecular 3d-π interaction in 1P lowered the band gap and induced the red-shifting of the monomeric four-coordinate Ni(II)-quinonoid complex. Meanwhile, the obtained absorption spectrum of 1O closely corresponded to that of the monomeric six-coordinate Ni(II)-quinonoid complex. Our study provides a new strategy for accurately predicting molecular crystal structures and reveals a new insight into vapochromism based on band structure color switching.

Ultrafast modification of the electronic structure of a correlated insulator

A non-trivial balance between Coulomb repulsion and kinematic effects determines the electronic structure of correlated electron materials. The use electromagnetic fields strong enough to rival these native microscopic interactions allows us to study the electronic response as well as the timescales and energies involved in using quantum effects for possible applications. We use element-specific transient x-ray absorption spectroscopy and high-harmonic generation to measure the response to ultrashort off-resonant optical fields in the prototypical correlated electron insulator NiO. Surprisingly, fields of up to 0.22 V/{\AA} leads to no detectable changes on the correlated Ni 3d-orbitals contrary to previous predictions. A transient directional charge transfer is uncovered, a behavior that is captured by first-principles theory. Our results highlight the importance of retardation effects in electronic screening, and pinpoints a key challenge in functionalizing correlated materials for ultrafast device operation.

Optimizing thermoelectric performance of CoSbS0.85Se0.15 by doping 3d transition metal ions M (M = Cr, Mn, Fe and Ni)

Transitional metal compound CoSbS attracted much attention as a thermoelectric material in the past decades. The configuration of the transition metal octahedra has a close relationship with the thermoelectric performance. This study reports the optimized thermoelectric performance of CoSbS through tuning Co octahedra distortion. The substitution of M (M ​= ​Cr, Mn, Fe and Ni) on Co sites could remarkably reduce the lattice thermal conductivity, and typically, Cr substitution endows the lowest lattice thermal conductivity owing to its strongest effect on the octahedra distortion, whereas Ni substitution induces to a relatively weak octahedra distortion at the same substitution level. Additionally, band structure calculations demonstrate that Ni-3d orbitals contribute shallow impurity levels near the conduction band minimum, strikingly increasing the carrier concentration and power factor. As a result, CoSbS0.85Se0.15 with Ni substitution on Co sites exhibits a much higher thermoelectric performance compared with the other counterparts. Furthermore, by optimizing Ni content, a maximum zT value of 0.52 ​at 876 ​K was achieved in Ni0.10Co0.90SbS0.85Se0.15. This study provides an exemplary approach to optimize the thermoelectric performance via polyhedral distortion.

Surface stability and electronic structure of CuNi alloy (111) as a potential catalyst for graphene growth-a density-functional theory study

Controlling the number of graphene layers during its growth is essential in realizing its practical application as a transparent conductive electrode. Growth with CuNi alloy catalysts can effectively control the number of graphene layers. However, research at the experimental level has not been supported by research at the theoretical level. Therefore, we will study the growth of graphene on a CuNi catalyst using the density functional theory (DFT). However, in this paper, we only focus on studying the stability of the surface of CuNi as a preliminary study. Based on geometry optimization, CuNi (111) has a wrinkled surface in the slab model due to the anisotropy shift of the atoms. Furthermore, CuNi (111) has a surface energy of 1.511 J/m2, which is between the surface energies of its components. This condition indicates that CuNi (111) has excellent stability. When forming CuNi alloy, electrons in the Cu 4s and Ni 3d orbitals have an enormous contribution in forming the metallic bonds indicated by a significant shift of the band center energy and change of the number of states at the Fermi level. Our results show that the CuNi system can become a potential catalyst for graphene growth.

Bandgap Engineering and Oxygen Vacancies of NixV2O5+x (x = 1, 2, 3) for Efficient Visible Light‐Driven CO2 to CO with Nearly 100% Selectivity

It is difficult to design a new single‐component photocatalyst to simultaneously possess a bandgap small enough to absorb most of sunlight and strong redox ability to reduce CO2 into value‐added chemical fuels. Herein, bandgap engineering of nickel vanadate compounds (NixV2O5+x, x = 1, 2, 3) is rationally designed to overcome the above challenge. Through changing the Ni:V ratio, the bandgap and band edge positions of nickel vanadates can be regulated, enabling Ni2V2O7 and Ni3V2O8 to reduce CO2 in the presence of water under visible light irradiation that do not exist in NiV2O6. Ni 3d orbitals of Ni2V2O7 and Ni3V2O8 replace V 3d orbitals of NiV2O6 and hybridize with O 2p orbitals to form the valence band maximums, resulting in their negative shifts. Meanwhile, the relatively weaker effect of the crystal field in VO4 tetrahedron over Ni2V2O7 and Ni3V2O8 results in less V 3d split, thus making the conduction band edges to shift upward. In addition, higher concentration of oxygen vacancies over Ni2V2O7 can further enhance its photocatalytic activity for CO2 conversion into CO with nearly 100% selectivity by prolonging the lifetime of photogenerated carriers and improving the chemisorption of CO2.

Inside Back Cover: Gadolinium Changes the Local Electron Densities of Nickel 3d Orbitals for Efficient Electrocatalytic CO2 Reduction (Angew. Chem. Int. Ed. 18/2022)

A Ni-Gd-N ternary doped porous carbon black catalyst was developed for electrocatalytic CO2 reduction, as reported by Lang Xu and co-workers in their Research Article (e202201166). NiI active sites with high product selectivity and Ni nanoparticles with high conductivity are integrated within one catalyst. The Gd atoms not only tailor the sizes of the Ni nanoparticles but also change the local densities of the Ni 3d orbitals, thus enabling the catalyst to achieve high faradaic efficiency, large current density, and excellent stability.

Gadolinium Changes the Local Electron Densities of Nickel 3d Orbitals for Efficient Electrocatalytic CO2 Reduction

AbstractGenerally, in terms of electrocatalytic CO2 reduction, single‐atom catalysts show high selectivities yet low current densities whereas conventional nanoparticle catalysts exhibit relatively high current densities but low selectivities. This work combines the advantages of the two classes of catalysts by constructing a Ni‐Gd‐N‐doped carbon black electrocatalyst within which NiI active sites are exposed outside the carbon layers and Ni nanoparticles are encapsulated inside the carbon layers. The Gd atoms can not only influence the local electron densities of Ni 3d orbitals, thus strengthening the electronic activity, but also tailor the sizes of the Ni nanoparticles, thereby minimizing the activity toward hydrogen evolution. Accordingly, this electrocatalyst yields both a high CO faradaic efficiency (97 %) and a large current density (308 mA cm−2), alongside an outstanding stability (100 h).

Gadolinium Changes the Local Electron Densities of Nickel 3d Orbitals for Efficient Electrocatalytic CO2 Reduction.

Generally, in terms of electrocatalytic CO2 reduction, single-atom catalysts show high selectivities yet low current densities whereas conventional nanoparticle catalysts exhibit relatively high current densities but low selectivities. This work combines the advantages of the two classes of catalysts by constructing a Ni-Gd-N-doped carbon black electrocatalyst within which NiI active sites are exposed outside the carbon layers and Ni nanoparticles are encapsulated inside the carbon layers. The Gd atoms can not only influence the local electron densities of Ni 3d orbitals, thus strengthening the electronic activity, but also tailor the sizes of the Ni nanoparticles, thereby minimizing the activity toward hydrogen evolution. Accordingly, this electrocatalyst yields both a high CO faradaic efficiency (97 %) and a large current density (308 mA cm-2 ), alongside an outstanding stability (100 h).

Structural, electronic and optical studies of Sr2NiTeO6 double perovskite by first-principle DFT–LDA + U calculation

The structural, electronic and optical properties of monoclinic Sr2NiTeO6 double perovskite have been studied using corrected density functional theory–local density approximation with applying of Hubbard U corrected energy (DFT–LDA + U) method in plane-wave pseudopotential basis. The influence of on-site Coulomb interaction on structural, electronic and optical properties of Sr2NiTeO6 double perovskite compound, which consists of strongly localized Ni 3d electrons, were investigated. The highly Coulomb repulsion between electrons was corrected using Hubbard U parameter, varying from 0 to 8 eV for Ni 3d orbitals. The calculated results demonstrated that Sr2NiTeO6 double perovskite was sensitive to the change in U values. The optimized structural properties give a good agreement with experiment and other calculation data with lattice parameters a = 5.673 Å, b = 5.565 Å, c = 7.847 Å, α = 89.999°, β = 90.257° and γ = 90.000°. The DFT–LDA + U predicted the calculated electronic band structure of Sr2NiTeO6 was showed metallic behaviour (0 and 2 eV) and insulator behaviour (4, 6 and 8 eV). The density of state (DOS) shows that there was a significant effect on hybridization of Ni 3d and O 2p states at the conduction and valence band, respectively. Moreover, the results of optical studies such as dielectric function, absorption and reflectivity were found significant to the variation of U values applied indicates that the U values give a better description on the electronic localization of Ni 3d states.

Phase Diagram of Nickelate Superconductors Calculated by Dynamical Vertex Approximation

We review the electronic structure of nickelate superconductors with and without effects of electronic correlations. As a minimal model, we identify the one-band Hubbard model for the Ni 3dx2−y2 orbital plus a pocket around the A-momentum. The latter, however, merely acts as a decoupled electron reservoir. This reservoir makes a careful translation from nominal Sr-doping to the doping of the one-band Hubbard model mandatory. Our dynamical mean-field theory calculations, in part already supported by the experiment, indicate that the Γ pocket, Nd 4f orbitals, oxygen 2p, and the other Ni 3d orbitals are not relevant in the superconducting doping regime. The physics is completely different if topotactic hydrogen is present or the oxygen reduction is incomplete. Then, a two-band physics hosted by the Ni 3dx2−y2 and 3d3z2−r2orbitals emerges. Based on our minimal modeling, we calculated the superconducting Tc vs. Sr-doping x phase diagram prior to the experiment using the dynamical vertex approximation. For such a notoriously difficult to determine quantity as Tc, the agreement with the experiment is astonishingly good. The prediction that Tc is enhanced with pressure or compressive strain has been confirmed experimentally as well. This supports that the one-band Hubbard model plus an electron reservoir is the appropriate minimal model.

Single Ni atom doped WS2 monolayer as sensing substrate for dissolved gases in transformer oil: A first-principles study

Insulation defects and equipment failure often exist in power transformer, and insulating oil in transformer will experience decomposition with a series reaction. By detecting the dissolved gases in insulating oil, the operation status of transformer can be evaluated. In this study, the adsorption and gas sensing of several kinds of typical dissolved gas molecule (H2, C2H2, and CO) on pristine and single Ni atom doped WS2 monolayer (Ni-WS2) was theoretically investigated based on first-principles density functional theory. To discuss the adsorption behavior, the structures, adsorption energies, and electron transfers were calculated and compared. As to the electronic properties and chemical interactions between gas molecule and Ni-WS2, the band structures, density of states (DOS), and work functions were studied. The results show that, after the doping of Ni, the adsorption energies of H2, C2H2 and CO on WS2 monolayer increase dramatically, from −0.06 eV to −0.52 eV, −0.23 eV to −1.44 eV, and −0.15 eV to −1.68 eV, respectively. On Ni-WS2, H2 and C2H2 lose electrons while CO shows little electron transfer. Only the adsorption of C2H2 obviously reduces the band gap of Ni-WS2. For all three kinds of gas adsorption, hybridization of states between Ni 3d and atomic orbitals in molecule can be observed in DOS, indicating considerable chemical interactions. In addition, the adsorption of CO increases the work function of Ni-WS2 from 5.56 eV to 5.80 eV. Based on the change of different physical and chemical properties, the Ni-WS2 as sensing material in different gas sensors was evaluated and the desorption time was compared in order to shed light on the experimental realization to detect dissolved gas molecule in insulating oil with high sensitivity and selectivity.