Adsorption of Thiophene on M(111) (M=Pd, Pt, Au) Surfaces

The adsorption of thiophene on Pd(111), Pt(111), and Au(111) surfaces was investigated by periodic density functional theory (DFT) calculations at the GGA/PW91 level. The results showed that the adsorption energies of thiophene on the different surfaces following the order Pd(111)>Pt(111)>Au(111). The adsorption structure on the Au(111) surface showed almost no change, and the most stable adsorption structure was tilted adsorption on the top site through the S atom of thiophene. For the Pd(111) and Pt(111) surfaces, the most stable adsorption structure was parallel adsorption to the hollow site through the ring plane of thiophene. After adsorption, the H atom of thiophene moved upward and the structure of thiophene was distorted and folded. The aromaticity of thiophene was disrupted and the C atoms were characteristic of sp(3) hybridization. Furthermore, the electrons of the M(111) surfaces and thiophene were redistributed after adsorption. The electron transfer from thiophene to the M(111) surfaces was in the order Pd(111)>Pt(111)>Au(111). The electrons of the M(111) surfaces were also back-denoted to the empty orbitals of the thiophene molecule. These processes eventually lead to the adsorption of thiophene on the M(111) surfaces.