Methanol Adsorption on PtCo(111). A DFT Study

V. ORAZI; P. BECHTHOLD; E. GONZÁLEZ; P. JASEN; A. JUAN

Dailan

Conferencia; 2nd International Conference on Applied Surface Science; 2017

The use of methanol as fuel has several advantages in comparison to hydrogen: it is a cheap liquid fuel, easily handled, transported, and stored, and with a high theoretical energy density. Pt is the most activemetal for methanol electrooxidation. However, its low abundance, high cost limit commercial applications and its performance are far from acceptable for their use as electrode in fuel cells. The alloying of Pt with Co have comparable and even better catalytic activity.First-principles calculations were performed using DFT, using the VASP code with Van der Waals corrections. Electronic structure was analyzed by the total density of states (TDOS) and partial density of states (PDOS). Bond Order (BO) and Overlap Population (OP) as implemented in the DDEC6 method and vibrational frequencies was also calculated.The molecule is adsorbed at 2.24 Å over the surface. The C-O-Co angle decrease to 142° and the H-C-O angle is about 109° (see Figure 1b). The molecule presents a small distortion after adsorption. The C-H bonds are strengthened whereas the C-O and O-H bonds are weakened. The C-O BO decrease about 12% while the O-H between 16% and 24%.The TDOS curves (see Figure 2a) present small peaks at -22.3, -13.0 and -8.7 eV related to methanol. The shift of the black curve to lower energies indicates that methanol is stabilized after adsorption and that the interaction is mainly through the Co atom.The vibrational frequencies for methanol present a red shift compared to gas-phase.The main result is the favourable interaction of methanol with the surface. The starting point for methanol reaction would be the O-H bond weakening followed by intermediary?s methoxy species.