Multi-scale correlation model: Theoretical analysis of the high-performance sensing mechanism of FeNx@TP-GDY for SF6 decomposition products

Abstract

Sulfur hexafluoride (SF${}_6$) is widely used in electrical insulating switches. However, the aging of equipment causes SF${}_6$ decomposition and produces harmful gases such as H${}_2$S and SO${}_2$. This study investigates the adsorption behavior and sensing mechanism of SF${}_6$ decomposition products (SO${}_2$ and H${}_2$S) on FeN${}_x$@TP-GDY (x = 0, 1, 2) surfaces using density functional theory. We employ an innovative dual-site modification strategy to modify TP-GDY. Specifically, transition metal atoms are embedded into the substrate, and neighboring atoms are substituted with N. The results indicate that the coordination number of N atoms significantly affects the position of the d band center of Fe. By analyzing the frontier Wannier orbitals of Fe in the three materials, FeN₂@TP-GDY shows stronger interaction due to greater overlap between the d${}_{x^2-y^2}$ orbital of Fe and the O p${}_z$ orbital. However, the response value of FeN${}_x$@TP-GDY decreases with increasing N doping. Fe@TP-GDY exhibits excellent sensing response to SO${}_2$ (8467.5%) and H${}_2$S (15209.6%) at room temperature, with a recovery time of only 22.4 s for H${}_2$S. A multiscale “coordination–electronic–response” model is proposed to guide the design of TP-GDY sensors. Fe@TP-GDY shows great potential for early and real-time dual-gas fault monitoring in SF${}_6$-insulated equipment.