Adsorption of phenol on Fe (110) and Pd (111) from first principles

The adsorption of phenol on the Fe (110) and Pd (111) surfaces was studied using density functional theory with the inclusion of van der Waals corrections. Model structures with the phenol adsorbing both via the aromatic ring (parallel) and via the oxygen functional group (perpendicular) were studied. The parallel adsorption sites were found to be significantly more favorable than the perpendicular sites on both surfaces, with the Pd (111) surface binding stronger with the adsorbate than the Fe (110) surface. The preference of the parallel sites over the perpendicular sites was found to be due to the increased amount of charge transfer between the surface and adsorbate in the parallel configuration through the aromatic ring. Comparing the differential charge density distributions for phenol's adsorption on the Fe (110) and Pd (111) surfaces shows that there is a small amount of electronic exchange that occurs between the oxygen atom and the Fe surface, while the Pd surface exchanges electrons with the hydroxyl group's hydrogen atom instead. Overall, our results show that the Fe (110) surface produces a greater degree of distortion of the CO bond while the Pd surface has a stronger surface-adsorbate interaction.