DFT investigations on the interaction of oxygen reduction reaction intermediates with Au (100) and bimetallic Au/M (100) (M = Pt, Cu, and Fe) surfaces

Background: Density functional theory was used to demonstrate how the presence of second metals can modify the adsorption energies of oxygen reduction intermediates on Au (100) surfaces. Taking the importance of the modification of oxygen reduction reaction in fuel cell activity into consideration, the adsorption energy and the stable adsorption sites for the intermediates of this reaction in Au (100) and bimetallic Au/M (100) (M= Pt, Cu, and Fe) systems were closely examined. After optimization of the structures, calculations of the density of states, d-band center, electron charge transfer, and adsorption energies of the intermediates of oxygen reduction reaction were accomplished. Results: The d-band center has been shown to be shifted because of strain and ligand effects in these bimetallic systems. The important role of hydroxyl species (OH) on catalytic surfaces was revealed while studying intermediates of oxygen reduction reaction. Hydroxyl species are strongly adsorbed on the catalytic surfaces and decrease the kinetic of oxygen reduction reaction by occupying the active adsorption sites. Conclusions: Au-Pt-Au (100) has the biggest OH adsorption energy. Therefore, it can be concluded that the presence of the submonolayer of Pt in this bimetallic system has helped hydroxyl species occupy the active sites, and consequently, it is not an appropriate catalyst for oxygen reduction reaction.