Co, Rh decorated GaNNTs for online monitoring of characteristic decomposition products in oil-immersed transformer

[Display omitted] •The decoration mechanism of Co and Rh on GaNNTs.•The electrical conductivity and theoretical recovery time analysis.•Adsorption mechanism of Co and Rh decorated GaNNTs. Oil-immersed transformer is one of the most widely used electrical equipment in modern power systems due to its high utilization, safe reliability, and high space utilization. Real-time operation status and insulation fault monitoring of oil-immersed transformer have attracted widespread attention in recent years. In this study, Co, Rh decorated GaN nanotubes is proposed as a novel gas-sensing material for diagnosing the discharge faults in oil-immersed transformer by on-line detecting the characteristic decomposition products. The gas-sensing properties and adsorption mechanism of H2, C2H2 and CH4 on Co, Rh decorated GaNNTs are deeply analyzed from the atomic size. Pristine GaNNTs has circumscribed response to the characteristic decomposition products. While Co, Rh modification can significantly enhance the adsorption capacity of GaNNTs surface, which acts as active sites for gas adsorption due to its virtue of eminent electropositive and catalytic oxidation. Both Co and Rh decorated GaNNTs has strong selectivity to C2H2 and H2 molecules, except CH4 molecule, as only a weak physical adsorption acts on CH4. All calculation data in this work can be employed for practical production of Co, Rh decorated GaNNTs gas sensors, ultimately realizing online monitoring of oil-immersed transformer.