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Oil-immersed power transformers generate characteristic gases after failure,Therefore, it is necessary to analyse and monitor the soluble gases in transformer oil samples. In this study, the DFT calculation method was used to study the adsorption properties of H2, CO, C2H2, and C2H4 gases in oil on both intrinsic MoTe2 and Rh-doped MoTe2 films. In order to analyse the adsorption characteristics, this paper first obtains the most stable Rh-doped MoTe2 monolayer model through the modelling and computational analysis of different doping sites, then, the adsorption of these gases on the material surface is studied by analysing adsorption energy, charge transfer, total state density, parting density, energy band structure, differential charge density map, molecular front orbital and desorption time, and finally concludes that Rh-MoTe2 monolayer film is the ideal material for hydrogen sensing elements, due to the extremely long desorption time of CO gas, indicating that CO gas is hard to desorption on the surface of adsorbent,which shows that this process has played a certain role in promoting CO removal. Highlights Study focused on gas adsorption using DFT: Rh-MoTe2 ideal for hydrogen sensing and effective for CO removal, intrinsic MoTe2 ineffective and required metal doping. Rh doping enhanced conductivity and gas adsorption capacity in MoTe2. Rh-MoTe2 was suitable for detecting H2, C2H2, and C2H4 gases. Desorption times vary with temperature, with CO removal particularly effective at higher temperatures. Findings suggest potential applications for Rh-MoTe2 in gas sensing and removal. [ABSTRACT FROM AUTHOR]

With the rapid development of global industrialization, industrial production leads to the emission of large quantities of toxic gases and long-term exposure of these gases to the air poses a serious threat to human health and the ecological environment. Therefore, online monitoring of toxic gases is a worthy task. In this work, the structures of pristine cerium oxide (CeO2) and nickel-doped cerium oxide (Ni-CeO2) surfaces are established based on the first-principles, and 12 adsorption structures of NH3, CH4, SO2, H2S, CO, C2H4 and gas molecules on the pristine CeO2 and Ni-CeO2 surfaces are constructed by geometrical optimization. We investigate the adsorption performance and gas-sensing mechanism of each adsorption system from various aspects, such as adsorption energy, band gap, electron density, density of states, frontier molecular orbital theory, conductivity, sensitivity, recovery time, and work function. The results showed that Ni-CeO2 significantly improved the adsorption properties of C2H4 (−1.784 eV), H2S (−1.036 eV), SO2 (−1.731 eV), and NH3 (−1.045 eV). The Ni-CeO2/C2H4 system exhibits high response (116.414), high work function (4.45 eV), and fast recovery (74.24 s) as well as strong resistivity changes. Hence, the theoretical simulation experiments in this paper provide theoretical guidance for the development of a highly sensitive, work function type (Ni-CeO2) gas sensor for the detection of the harmful gas C2H4 in the atmosphere. [ABSTRACT FROM AUTHOR]

The level of agricultural greenhouse intelligence is an important indicator of national agricultural modernization. Thus, it is important to achieve the detection of characteristic gases in the greenhouse to maintain the growth of crops. In this paper, NH3, NO2, and SO2 are the target detection gases in the greenhouse. The adsorption models of rhodium-doped indium selenide (Rh–InSe) and ruthenium-doped indium selenide (Ru–InSe) for the three characteristic gases were established based on density functional theory (DFT). By analyzing the adsorption energy, density of states, and deformation charge density of the two modified systems compared to the intrinsic InSe, it was found that the introduction of metal atoms effectively opened the energy gap of the intrinsic InSe and exhibited strong chemisorption. Finally, two gas-sensitive materials, Rh–InSe and Ru–InSe, are analyzed by comparing them in terms of frontier molecular orbital theory and desorption time. It can be seen that the adsorption energy of the Rh–InSe system is all higher than that of the Ru–InSe system, but Ru–InSe has higher conductivity and shorter desorption time than Rh–InSe and also exhibits stable chemisorption. By calculating the sensitivity of Rh and Ru–InSe, it can be found that Ru–InSe is more sensitive to the characteristic gas, which is favorable for gas adsorption. Therefore, Rh–InSe is more suitable as an adsorbent for three harmful gases, and the Ru-modified InSe monolayer has potential applications in the field of materials for realizing the detection of characteristic harmful gases in a greenhouse. [ABSTRACT FROM AUTHOR]

Dissolved gas analysis (DGA) is the most commonly used transformer fault diagnosis technology at present. In this paper, according to the method of first principles of density function theory (DFT), the gas-sensitive mechanisms of four oil-soluble characteristic gases (H 2 , CO, C 2 H 2 , C 2 H 4 ) on intrinsic SnS 2 and Cr 3 -SnS 2 were studied. The adsorption energy and electron transfer were calculated, and the density of states, energy bands, and recovery times were analyzed. It was concluded that H 2 and C 2 H 4 were physisorbed on the Cr 3 -SnS 2 monolayer, while CO and C 2 H 2 were chemisorbed. It is believed that the Cr 3 -SnS 2 material can be used in gas sensing for CO and C 2 H 2 . Cr 3 -SnS 2 is expected to serve as a gas detector for the detection of CO with both a good response and reusability. Therefore, Cr 3 -SnS 2 has very promising applications in the evaluation of the operation of oil-immersed transformers. This study will provide some help and inspiration for the development of the Cr 3 -SnS 2 monolayer in gas-sensitive materials.

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 HfS 2 (Pt-HfS 2 ) as gas-sensitive materials for the detection of dissolved H 2 , CO 2 , CH 4 , and C 2 H 2 in oil has been verified by analyzing the adsorption energy ( E ad ), 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 HfS 2 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 HfS 2 . The low adsorption energy implies that there is only weak physical adsorption between Pt-HfS 2 and CO 2 (-0.783 eV). In contrast, the highly hybridized atomic orbitals of Pt with H 2 , CH 4 , and C 2 H 2 indicate that strong chemical adsorption reactions occur. Two-dimensional Pt-HfS 2 as a gas sensor has a great monitoring performance for CH 4 at 298 K (room temperature). This research serves as theoretical guidelines for probing the application potential of Pt-HfS 2 in fault diagnosis and predictive maintenance of an oil-immersed transformer.