Ni-Decorated PtS2 Monolayer as a Strain-Modulated and Outstanding Sensor upon Dissolved Gases in Transformer Oil: A First-Principles Study

The first-principles theory is conducted in this paper to investigate the adsorption and electronic properties of a Ni-decorated PtS2 (Ni-PtS2) monolayer upon two dissolved gas species (CO and C2H2) in the transformer oil, thus illustrating its sensing performance and related potential to evaluate the working condition of the oil-immersed transformers. We then highlight the effect of the biaxial strain on the configuration, charge transfer, and bandgap of the adsorbed systems to expound its potential as a strain-modulated gas sensor. Results indicate that the Ni-PtS2 monolayer undergoes chemisorption upon two species, with an Ead value of -1.78 eV for the CO system and -1.53 eV for the C2H2 system. The reduced bandgap by 0.164 eV (20.05%) in the CO system and 0.047 eV (5.74%) in the C2H2 system imply the large feasibility of the Ni-PtS2 monolayer to be a resistance-type sensor for CO and C2H2 detection, which is also verified by the I-V analysis of these systems. Besides, the applied biaxial strain can exert geometric activations on the Ni-PtS2 monolayer, and specifically, the compressive force can further reduce the bandgap in two systems, thus promoting its sensing response upon two gases. Our work is meaningful to broaden the exploration of noble transition metal dichalcogenides for gas sensing.