Adsorption and Sensing Performances of MoTe2 Monolayers Doped with Pd, Ni, and Pt for SO2 and NH3: A DFT Investigation

First-Principles Predictions of MoS2-WS2 In-Plane Heterostructures for Sensing Dissolved Gas Species in Oil-Immersed Transformers

This work from first-principles insight uses a MoS2-WS2 in-plane heterostructure as a potential sensing material for detection of CO and C2H2, two typical dissolved gases in oil-immersed transformers, in order to evaluate the operation status. The adsorption performance of the MoS2-WS2 heterostructure upon two gas species is assessed via three adsorption sites and compared with isolated MoS2 and WS2. Results indicate that MoS2-WS2 performs with a much stronger binding force and charge-transfer for adsorptions of CO and C2H2 in comparison to the isolated counterpart, which gives rise to more obvious deformation in the electronic property of MoS2-WS2 as well as a much larger resistance-based sensing response. The recovery time of MoS2-WS2 for desorption of CO and C2H2 molecules is also appropriate to allow the reusability of such a sensor. The findings in this work uncover the admirable sensing potential of transition metal dichalcogenides (TMDs)-based heterostructures upon oil dissolved gases, which opens up a new way to explore novel 2D nanomaterials as resistive gas sensors for dissolved gas analysis in electrical oil-immersed transformers.

Metal (Ni, Pd, and Pt)-Doped BS Monolayers as a Gas Sensor upon Vented Gases in Lithium-Ion Batteries: A First-Principles Study

Real-time monitoring of the vented gases emitted by the thermal runaway of lithium-ion batteries (LIBs) is of great significance to the normal use of LIBs. We study systematically the adsorption and sensing performances of pristine and metal-doped BS monolayers to five typical gases (CO, CO2, CH4, C2H2, and C2H4) emitted from LIBs employing the first-principles method. The adsorption structure and energetics, charge transfer, band structure, density of states, sensitivity, and recovery time are simulated and analyzed. Outstanding sensing properties are predicted for the Ni-, Pd-, and Pt-doped BS monolayers, although their recently synthesized pristine counterpart shows little sensing potential for those gases. The magnitude of the adsorption energy increases from 0.249 eV to 2.32 eV (Ni-BS), 1.954 eV(Pd-BS), and 2.994 eV (Pt-BS) for the CO gas after doping. Besides, significant variation of band gap is observed after gas adsorption in doped BS nanosheets, which leads to huge theoretical values of the sensitivity. The sensitivity for CO, CO2, CH4, C2H2, and C2H4 on Pt-BS may reach up to 5.87 × 105, 1.57 × 106, 1.81 × 105, 8.33 × 104, and 8.18 × 103, respectively. In addition, the calculated recovery times indicate that the doped BS monolayers have strong selectivity for the adsorption and detection of these five gases. The three metal-doped BS monolayers should have great potential for application in sensors monitoring the gases emitted from LIBs.

Adsorption of NO2, SO2, H2S, and NH3 on Os-Doped WSe2 Monolayers: A First-Principles Study

In this study, DFT calculations are used to analyze the adsorption of industrial waste gases (NO2, SO2, H2S, and NH3) on WSe2 monolayers. The adsorption energy, energy band, density of states, charge transfer, and recovery time of the adsorption structures between the target gas molecules and the Os-doped WSe2 are studied. Compared with pure WSe2 monolayer, Os surface bonding doping WSe2 (Os-modified WSe2) and Os doping with Se vacancy of WSe2 (Os-embedded WSe2) exhibit improved gas molecule adsorption ability. Among them, the adsorption energy of the Os-modified WSe2 monolayer on NO2, SO2, H2S, and NH3 is greater than that of the WSe2 monolayer. At the same time, it is proved that the Os-embedded WSe2 can be used as a gas sensor for H2S and NH3 gas molecules at a high temperature.

Pt-Doped HfS2 Monolayer as a Novel Sensor and Scavenger for Dissolved Gases (H2, CO2, CH4, and C2H2) in Transformer Oil: A Density Functional Theory Study

Detecting the types and concentrations of dissolved gases in insulating oil by resistivity-type sensors is an extremely effective means for diagnosing faults in an oil-immersed transformer. However, further breakthroughs and innovations are needed in gas-sensitive materials for preparing high-performance resistivity-type sensors. In this investigation, the application possibility of using Pt-doped HfS2 (Pt-HfS2) as gas-sensitive materials for the detection of dissolved H2, CO2, CH4, and C2H2 in oil has been verified by analyzing the adsorption energy (Ead), differential charge density (DCD), density of states (DOS), frontier molecular orbital, and desorption time based on density functional theory (DFT). The outcomes suggest that the band gap of HfS2 is obviously narrowed after doping Pt at the position of the bridge between the S and Hf atoms, resulting in a significant increase in the conductivity of HfS2. The low adsorption energy implies that there is only weak physical adsorption between Pt-HfS2 and CO2 (-0.783 eV). In contrast, the highly hybridized atomic orbitals of Pt with H2, CH4, and C2H2 indicate that strong chemical adsorption reactions occur. Two-dimensional Pt-HfS2 as a gas sensor has a great monitoring performance for CH4 at 298 K (room temperature). This research serves as theoretical guidelines for probing the application potential of Pt-HfS2 in fault diagnosis and predictive maintenance of an oil-immersed transformer.

Adsorption Properties of Ptn (n = 1-3) Cluster-Doped SnS2 and MoTe2 toward Vehicle Emissions: CO, CO2, and NO

The interaction mechanism between CO, CO2, and NO gas molecules and Ptn-SnS2 (n = 1-3) and Ptn-MoTe2 (n = 1-3) is analyzed based on density functional theory calculations. For Pt2-SnS2, the structure of Pt2-SnS2 is deformed during CO2 adsorption. For Pt3-SnS2, its structure is also significantly deformed when the gas is adsorbed. Pt2-SnS2 is not suitable for the detection and adsorption of CO2 gas, while Pt3-SnS2 is not suitable for the detection and adsorption of these three gases. According to the density of states and molecular orbital analysis, the conductivity of the adsorption system of Pt-SnS2 remains almost unchanged after the adsorption of CO, so Pt-SnS2 is not suitable for the detection of CO gases. The adsorption of gases on intrinsic MoTe2 is a weakly interacting physical adsorption. Doping with one to three Pt atoms all resulted in different degrees of enhancement of the adsorption capacity of the substrates for these three target gases. However, for Pt2-MoTe2 and Pt3-MoTe2, the structure of these two materials undergoes significant deformation upon NO adsorption. In addition, the interaction between Pt3-MoTe2 and CO2 is weak, and the conductivity of this system is almost unaffected by CO2 adsorption. In addition, all other constructions are suitable for the detection of the corresponding gases. This paper provides a theoretical basis for the development of gas sensors for the detection of automotive and industrial emission gases.