DFT insights into the TM(Cu, Ni, Ag) and TMO(CuO, NiO, Ag2O) modified HfSe2 for detecting PD fault gases

[Display omitted] •The differences in the modification of HfSe2 monolayer by transition metal single atoms (Cu, Ni and Ag) and their oxides (CuO, NiO and Ag2O) were compared, and the influence of the addition of oxygen atoms on the electrical properties of the substrate was explored.•Modified with oxides (CuO, NiO and Ag2O), the conductivity of the HfSe2 monolayer is significantly improved.•CO and C2H2 are chemically adsorbed on all adsorption systems, and the selective detection effect of C2H2 on NiO-HfSe2 and Ag2O-HfSe2 is obvious. Partial Discharge (PD) in oil-immersed transformers threatens the safe and stable operation of the transformer. PD causes the transformer oil to decompose and produce fault gas. Therefore, the operating status of the transformer can be evaluated through the detection of characteristic fault gas. Through simulation research, this paper proposes to use HfSe2 substrate modified with metal single atoms (Cu, Ni and Ag) and their oxides (CuO, NiO and Ag2O) to detect decomposed fault gases (CO, C2H2, CH4) in transformer oil. DFT was used to systematically study the adsorption of the target gas on the surface of the original substrate and the modified substrate. The research results show that the conductivity of the doped HfSe2 substrate increases to a certain extent, and the band gap also drops from the undoped 0.563 eV to 0.108–0.554 eV. By analyzing the adsorption parameters, it was found that the adsorption capacity of metal single atoms (Cu, Ni and Ag) is lower than metal oxides (CuO, NiO and Ag2O). Among the six substrates, the adsorption capacity of the target gases is ranked as CO > C2H2 > CH4, in which CO and C2H2 are chemically adsorbed, while CH4 is physically adsorbed. In terms of sensing performance, it was found through recovery time and sensitivity analysis that NiO-HfSe2 and Ag2O-HfSe2 can be used to selectively detect C2H2. The research results can provide a theoretical basis for the application of HfSe2 in oil-immersed transformer operating status detection and gas-sensitive sensor detection.