Adsorption of HF and HS on α-AlO (0001) Surfaces: A DFT Study.

Ex-service SF adsorbents in SF gas-insulated electric equipment contain many toxic substances. Inside, HF and HS are two typical toxic gases. Based on the first principle, the interaction process between HF/HS and α-AlO (0001) surfaces was calculated using the density functional theory (DFT). The results showed that the adsorption of HF on α-AlO (0001) is stronger than that of HS. Under the five adsorption sites, the adsorption effect of HF-H and HF-F was similar. At O-2 site, the adsorption energy of HS-H adsorption configuration is significantly higher than that of the other four sites. The density of states (DOS) indicated that new peaks appeared after adsorption. The DOS and partial density of states (PDOS) indicated that the adsorption of HF and HS occurs via chemical adsorption. The DOS and PDOS shifted to the right when the S atom was approaching, proving that the system shifts to instability. Compared with the energy gap of α-AlO (0001), HF and HS adsorption systems decreased significantly. The energy gap of the HF adsorption system was 1.173 eV larger than that of the HS system and the geometry was relatively stable, which is consistent with the DOS and PDOS adsorption calculation results. Thus, the adsorption of HF and HS on α-AlO (0001) surfaces was clearly different. The findings of this study may provide theoretical guidance for the adsorption of other gases or developing a new adsorbent.