A transition metal (Ti, V, and Mn)-decorated CrS₂ monolayer as a propitious gas scavenger for SF₆ decomposition remnants: acumen from density functional theory simulations

Developing a sensitive and selective gas sensor for the detection of SF₆ gas decomposition products in a gas-insulated switchgear is crucial for environmental protection and human health. This study delves into the adsorption of H₂S, SO₂, SO₂F₂, and SOF₂ gases over the pristine and transition metal (TM = Ti, V, and Mn)-decorated monolayer CrS₂ using the first principles method. The TM decoration strategy is adopted to improve the adsorption capacity of the pristine CrS₂ monolayer. The optimal doping positions for the TMs on the CrS₂ monolayer were identified, with the most stable configuration occurring directly above the Cr atom. The results show that the TM-CrS₂ monolayers are energetically stable, with negative binding energies, and the highest <i>E</i>_b (-5.546 eV) and Δ<i>Q</i> (-0.231e) values were observed for Mn decoration. Thermal stability of the TM-decorated CrS₂ monolayers at ambient temperature (300 K) was confirmed by <i>ab initio</i> molecular dynamics (AIMD) simulations. The assessment of the mechanical properties reveals that the decorated monolayers are mechanically stable with high values of bulk moduli. It is observed that the TMs not only alter the magnetic state but also induce a significant reduction in the electronic band gap of the CrS₂, which is highly beneficial for gas sensing applications. After introducing TMs, the adsorption process shifted from physisorption to chemisorption with the formation of strong chemical bonds between the adsorbate and adsorbent. The <i>E</i>_ads values for Ti increase from -0.200 eV to -3.258 eV, for V from -0.200 eV to -3.21 eV, and for Mn from -0.200 eV to -2.645 eV. The adsorption mechanism of the gas-adsorbent interactions was revealed by analyzing metrics such as energy band structures, charge transfer, charge density difference, and partial density of states plots. Upon adsorption of gases, the band gap of TM-decorated CrS₂ monolayers undergoes considerable changes, suggesting high sensitivity for these gases. For the investigated SF₆ decomposition components, the Mn-CrS₂ sensor exhibits ideal recovery times and excellent sensitivity values; at room temperature, the sensing response of the monolayer Mn-CrS₂ to SOF₂ reaches a high value of 256.318. Taking into account the balance of adsorption strength, sensitivity, and recovery time, monolayer Mn-CrS₂ emerges as a sustainable and recyclable gas sensor for detecting SF₆ decomposition gases in electrical equipment.