Enhanced Sensing of SF₆ Decomposition Products on Co-, Ni-, and Rh-Doped F-Diamane: Insight from a DFT Study

During the operation of insulation equipment, arc discharge can induce the thermal decomposition of SF₆, resulting in the formation of various sulfur-containing byproducts. Monitoring of these SF₆ decomposition products (SDPs (SO₂, H₂S, SOF₂, and SO₂F₂)) using gas sensors offers an effective approach for diagnosing the operational state of insulation systems. In this study, density functional theory (DFT) calculations were performed to systematically investigate the adsorption mechanisms and sensing properties of transition metal-doped F-diamane (TM/F-diamane, where TM = Rh, Ni, or Co) with respect to the four SDPs. The results indicate that TM doping markedly enhances the adsorption capability of F-diamane for SDPs. Specifically, Rh/F-diamane exhibits strong adsorption toward SO₂ and H₂S, while Ni/F-diamane further strengthens the interaction with SOF₂. In contrast, Co/F-diamane displays robust chemisorption in all four SDPs. These findings are further validated by analyses of the electron density difference, density of states, and charge transfer. Furthermore, evaluations of the work function, band gap, and sensing response reveal that Rh/F-diamane is exclusively highly sensitive to SO₂, whereas Ni- and Co-doped F-diamane show superior sensitivity to all SDPs. Finally, the relative energy and theoretical recovery times of each adsorption system at different temperatures and pressures are also discussed. The results suggest that Ni/F-diamane can serve as a reusable SO₂F₂ gas-sensing material at room temperature, while Co/F-diamane is suitable for high-temperature detection of H₂S and SO₂F₂. Overall, this study provides a solid theoretical basis for the design and development of high-performance F-diamane-based gas sensors or scavengers for the SDPs.