Mo-doped h-BN Monolayer as a Novel Sensor for Online Monitoring of Insulation Degradation

The insulating materials in transformers may generate $\text{NO}_{2}, \mathrm{H}_{2}\mathrm{S},$ and $\text{CO}_{2}$ decomposition gases due to their physicochemical and electrical properties due to various fault characteristics. Therefore, real-time, accurate, and long-term monitoring of decomposed gases is critical. This study proposed a new type of gas sensor Mo-doped h-BN Monolayer (Mo-BN, one Mo atom instead of one $\mathrm{N}$ atom) for monitoring the decomposition components of insulating materials. The gas sensing mechanism and sensitivity of Mo-BN to the above three kinds gases were analyzed by analyzing and comparing the adsorption structure, adsorption energy, charge distribution, TDOS, and other adsorption parameters of each system. The results showed that Mo-BN had a strong adsorption effect on NO2 and $\mathrm{H}_{2}\mathrm{S}$ , which was between physical adsorption and chemical adsorption. The absolute value was $\text{NO}_{2} > \mathrm{H}_{2}\mathrm{S}$ . Mo-BN has relatively low sensitivity to $\text{CO}_{2}$ , and its interaction force is dominated by the van der Waals force. Therefore, Mo-BN has high selective detection for the above three decomposed gases and has great potential as a new type of resistive gas sensor in the field of insulation material monitoring.