Metal oxide-modified Janus HfSSe monolayers for SF6 decomposition gas detection: A DFT investigation

Abstract

Accurate detection of gases in gas-insulated switchgear (GIS) is essential for maintaining the safe and stable operation of power systems. Density functional theory (DFT) was employed to investigate the adsorption behavior of typical SF₆ decomposition gases (H₂S, SO₂, SOF₂, and SO₂F₂) on NiO-, ZnO-, and Ag₂O-modified Janus HfSSe monolayers. All three metal oxides preferentially bind to sulfur sites on the HfSSe surface, forming energetically stable configurations. These modifications significantly enhance the monolayer's conductivity, yielding reduced band gaps of 0.45 eV (NiO), 0.42 eV (ZnO), and 0.37 eV (Ag₂O), while simultaneously improving sensitivity and selectivity toward the target gases. At room temperature (298 K), NiO-HfSSe exhibits favorable desorption times for H₂S (6.38 s), SO₂ (2.95 s), and SOF₂ (0.03 s), whereas ZnO- and Ag₂O-HfSSe show optimal desorption for SO₂ at 0.58 s and 15.67 s, respectively. Combined with short recovery times and significant band gap modulation, NiO-, ZnO-, and Ag₂O-modified HfSSe monolayers demonstrate strong potential as reusable, room-temperature gas sensors. This study provides theoretical insight into the application of these modified monolayers for evaluating the insulation status of GIS equipment, laying the groundwork for future experimental validation and optimization of monolayer-based sensors in practical GIS monitoring applications.