Density Functional Theory and Experimental Study of Detection of Dissolved Gas in Transformer Oil on Ru-doped 2D MoO3−x Monolayer

Dissolved gas analysis (DGA) has emerged as a noninvasive diagnostic method for assessing transformer health, enabling the timely detection of incipient faults through the quantitative monitoring of evolving gas concentrations in dielectric fluids.On the basis of first-principles calculations integrated with experimental investigations, in this study, we systematically examine the adsorption characteristics and gas sensing mechanisms of different molybdenum oxide structures, particularly with respect to ruthenium doping, in response to dissolved gases such as carbon monoxide (CO), acetylene (C 2 H 2 ), and hydrogen (H 2 ) present in oil-immersed transformers.The sensitivities of molybdenum trioxide (MoO 3 ), MoO 3-x , Ru-doped MoO 3 (MoO 3 @Ru), and Ru-doped high-defect-concentration MoO 3-x (H-MoO 3-x @Ru) to these gases were evaluated through adsorption energy, charge distribution, and band structure changes.Results showed that oxygen vacancies in molybdenum oxide enhance CO absorption and significantly affect electrical conductivity.Although H-MoO 3-x has a high carrier concentration, CH adsorption has a minimal impact on its electronic properties, limiting its sensor application potential.Ru atoms are most stable at terminal or oxygen-deficient sites in MoO 3 and MoO 3-x .The H-MoO 3-x @Ru structure exhibits strong CO adsorption performance, making it a promising candidate for CO gas sensing.Overall, Ru-modified molybdenum oxide materials show great potential for detecting dissolved gases in transformer oil.Fig. 7. (Color online) (a) Low-magnification TEM images of H-MoO 3-x @Ru.(b) HRTEM images of H-MoO 3-x @ Ru. (c) Corresponding magnified areas and FFT plots of H-MoO 3-x @Ru.(d) EDS mapping of H-MoO 3-x @Ru.(e) Dynamic response to CO concentrations (60-180 ppm).The response (%) is defined as (Ra -Rg)/Rg, where Rg and Ra are the resistance values of the gas sensor when exposed to the target gas and air, respectively (f) Calibration curve of sensor response versus CO concentration.