# Theoretical Study of SOF\({}_{2}\) Adsorption on Pd/Pt-Ni(111) Bimetallic Surfaces
## 3 Results and Discussion
### Adsorption of SOF\({}_{2}\) on Pt-Ni(111) and Ni-Pt-Ni(111) Surface  
Similarly, Pt atoms were used to replace the supernatant and subsurface Ni atoms to obtain stable Pt-Ni(111) and Ni-Pt-Ni(111) surfaces. After that, the SOF\({}_{2}\) molecule was placed in different initial positions and directions to get different adsorption structures. The results are shown in Figure 5, and the adsorption energy and relevant structural parameters are listed in Table 2.  
As shown in Figure 5, M5 and M6 are structures of SOF\({}_{2}\) adsorption on the Pt-Ni(111) surface, while M7 and M8 are adsorption structures on the Ni-Pt-Ni(111) surface. In the M5 structure, the SOF\({}_{2}\) molecule adsorbs on the top site, and forms a chemical bond between the S atom and Pt atom. After SOF\({}_{2}\) adsorption, the position of the supernatant Pt atoms changed a lot, demonstrating a strong interaction between them. In the M6 structure, one S atom and two F atoms interacted with the Pt-Ni(111) surface, but the adsorption distance was relatively far. Therefore, it can be roughly judged that the adsorption is weaker than M1. As for the Ni-Pt-Ni(111) surface, its adsorption capacity seems to be weaker. In the M7 structure, the S-O bond occupies the bridge site, and the adsorption distance is \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Surface** & **Structure** & **\(E_{\text{ads}}\) (eV)** & **Q\({}_{\text{T}}\) (e)** & **Distance (Å)** & **Comparison** \\ \hline Ni(111) & 3 thf & \(-1.550\) & \(-0.182\) & \(1.820\) & [PERSON] et al. [21] \\ \hline Pt-Ni(111) & M5 & \(-2.123\) & \(0.14\) & \(2.168\) & \\  & M6 & \(-0.745\) & \(0.018\) & \(3.282\) & \\ \hline Ni-Pt-Ni(111) & M7 & \(-0.344\) & \(-0.015\) & \(3.173\) & \\  & M8 & \(-0.361\) & \(-0.033\) & \(3.434\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The adsorption parameters of SOF\({}_{2}\) adsorbed by Ni(111), Pt-Ni(111), and Ni-Pt-Ni(111) surfaces. Figure 5: The top and side views of adsorption structures. **(a,b)** SOF\({}_{2}\) adsorption on Pt-Ni(111) surface for M5 and M6 structures, **(c,d)** SOF\({}_{2}\) adsorption on Ni-Pt-Ni(111) surface for M7 and M8 structures. 3.173 A. Similarly, the M8 structure also has a long adsorption distance, indicating a weak interaction between SOF\({}_{2}\) and Ni-Pt-Ni(111) surface. Table 2 shows some adsorption parameters of the structures in Figure 5. The \(E_{\text{ads}}\) of M5 and M6 are \(-\)2.123 eV and \(-\)0.745 eV respectively, which are larger than M7 (\(-\)0.344 eV) and M8 (\(-\)0.361 eV), indicating that the ability of Pt-Ni(111) to adsorb SOF\({}_{2}\) is stronger than the Ni-Pt-Ni(111) surface. In addition, the \(E_{\text{ads}}\) of M5 is larger than 3 th (\(-\)1.550 eV), but the adsorption distance of 3 thf is shorter than M5. This is because the 3 thf structure is a dissociative adsorption structure, which needs more energy to cross the energy barrier during the reaction process. As for charge transfer, M5 and M6 have a positive \(Q_{\text{T}}\), which means electrons transfer from the SOF\({}_{2}\) molecule to the Pt-Ni(111) surface during the adsorption process. But the circumstances on the Ni-Pt-Ni(111) surface is the opposite. The most stable adsorption structures on the Pt-Ni(111) and Ni-Pt-Ni(111) surfaces were selected to analyze the density of states. Figure 6 shows the TDOS and PDOS of M5 and M8. In Figure 6, it is obvious that there was an increase from \(-\)5.5 eV to \(-\)1 eV after SOF\({}_{2}\) adsorption. According to the PDOS in Figure 6, we found that the increase mainly consisted of F 2p, Ni 3d, and Pt 5d orbitals. The large overlapping area between Ni 3d and Pt 5d means there is a strong interaction between them. In Figure 6, the TDOS rose in the range of \(-\)10 eV to \(-\)7 eV and \(-\)6 eV to \(-\)4 eV after SOF\({}_{2}\) adsorption. The increased area of TDOS mainly consists of 2p orbital of F atoms and a 5d orbital of Pt atoms. Moreover, the hybridization between F 2p and Pt 5d signifies a strong interaction between the F atoms and Pt atoms.