Pt- and Pd-Modified Two-Dimensional GeSe for Ethylene and Acetylene Sensing during Poly(vinyl chloride) Cable Overheating

Poly(vinyl chloride) (PVC) outer sheaths undergo pyrolysis during thermal faults or partial discharges in high-voltage cables, releasing marker gases such as ethylene (C2H4) and acetylene (C2H2). Developing sensing materials capable of sensitively identifying these gases is important for early safety monitoring of high-voltage cable outer sheaths. To address the limited interaction of weakly polar C2H2 and C2H4 with GeSe surfaces and the difficulty of regulating gas adsorption and charge transfer, Pd-GeSe and Pt-GeSe sensing materials were prepared by combining density functional theory (DFT) screening with hydrothermal synthesis, and the effects of the two noble-metal modification routes on structural changes and sensing performance were compared. Gas-sensing measurements showed that the response/recovery times of Pd-GeSe toward 100 ppm of acetylene and ethylene were 104/84 and 92/72 s, respectively; the corresponding values for Pt-GeSe were 73/76 and 63/91 s, with higher overall response magnitudes. Structural characterization showed that both materials retained the principal GeSe structure. Pd-GeSe exhibited Pd-related diffraction features and more evident surface roughening, whereas Pt-GeSe showed slight changes in the GeSe diffraction peaks, indicating that Pd and Pt affect the GeSe structure and interface differently. Under the same idealized models and computational conditions, DFT calculations showed that Pd and Pt incorporation altered the adsorption energies, Mulliken charge transfer, and electronic structures of GeSe interacting with C2H2/C2H4. These theoretical results are broadly consistent with the experimentally observed sensing differences between the two modified materials and provide a possible explanation for their performance variations. This study provides theoretical and experimental guidance for interfacial regulation of GeSe-based sensing materials and detection of marker gases from PVC thermal degradation.