## 3 Results and Discussion  
### Characterization of the Pd-Based Photocatalyst  
The FTIR, SEM, TEM and XPS analysis were used to prove the fact that the studied solid support, Florisil, was impregnated with the studied IL, Cyphos IL-101. This structural characterization was useful to understand what happened with the solid support during functionalization and which is the reason for its efficiency increasing, and how IL and Pd ions are bounded onto the Florisil surface in order to be sure of the photocatalyst stability.  
The FTIR spectra of the studied photocatalysts are presented in Figure 1. From the FTIR spectrum, the impregnation is confirmed by the appearance in the spectrum of the solid support of the vibrational bands characteristic for the ionic liquid, namely: the intense bands between 2950 and 2800 cm\({}^{-1}\) occur due to -CH\({}_{3}\) (methyl) and -CH\({}_{2}\)- (methylene) vibrations.  
The SEM images are presented in Figure 2. From the SEM images, it can be observed that the Florisil particles before impregnation are in various sizes and shapes, with many microcracks and network defects. After the impregnation, the surface of the Florisil particles is much more uniform. It can be observed the distribution of the ionic liquid particles on their surface by filling the microcracks.  
Figure 1: FTIR spectra of the studied materials.  
After Pd adsorption, the particle surface is very compact; Pd (II) adsorption is observed as a coating on the impregnated Florisil particles.  
In Figure 3 are presented the bright-field transmission electron microscopy (BFTEM) images of Florisil after impregnation with Cyphos IL-101 and the Florisil after impregnation and Pd(II) adsorption. It can be observed the Florisil particles with the uniform distribution of the IL in the pore structure (the black spots represent the IL particles which fill the pores of the Florisil) (Figure 3a). After Pd adsorption, the surface is very compact due to its coating with Pd ions (Figure 3b).  
Figure 3: Bright-field transmission electron microscopy (BFTEM) images of (**a**) Florisil after impregnation with Cyphos IL-101; (**b**) Florisil after impregnation and Pd(II) adsorption.  
Figure 2: SEM images of: (**a**) Florisil; (**b**) Florisil after impregnation with Cyphos IL-101; (**c**) Florisil after impregnation and Pd(II) adsorption.  
The impregnation of Florisil with trihexyl tetradecyl phosphonium chloride is proven by the EDX spectra (Figure 4), where besides the specific peaks of Florisil (Mg, O, Si), the specific peaks for the used ionic liquid (C, Cl and P) can be observed. For the sample obtained after Pd adsorption characteristic peak of this element is observed, evidencing its adsorption onto the studied material.  
In order to establish the elemental composition of the sample that will be used as a photocatalyst (Florisil impregnated with Cyphos IL-101 and loaded with Pd ions), the XPS wide scan was used (Figure 5a and Table 1).  
Figure 4: Energy-dispersive X-ray analysis (EDX) spectra of **(a)** Florisil after impregnation with Cyphos IL-101; **(b)** Florisil after impregnation and Pd(II) adsorption.  
Figure 5: \(Cont.\)  
The XPS wide scan spectrum proves that the Florisil (which is a magnesium silicate with trace concentration of sodium) was impregnated with the studied IL (Cyphos IL-101--trihexyl (tetradecyl) phosphonium chloride) and also it could be observed the presence of the Pd ions.  
By analyzing the high-resolution spectra of the elements, XPS allows the identification of the chemical structure. The high-resolution XPS spectra for C 1s and Pd 3d were analyzed in detail for the Pd-based photocatalyst (Figure 5b,c). The signal corresponding to C 1s was divided into two distinct components corresponding to the C\({}_{\text{aliphatic}}\) at 284.5 eV and C\({}_{\text{hetero}}\) at 286.6 eV. The signal corresponding to Pd 3d was decomposed into two distinct components corresponding to the Pd\({}^{2+}\) at 337.2 eV and to the Pd\({}^{4+}\) at 338.5 eV (Table 2).