First principles study for Ag-based core-shell nanoclusters with 3d-5d transition metal cores for the oxygen reduction reaction

The depletion of traditional fossil fuels, as well as the increase in global energy demand, is currently driving the need for sustainable energy solutions. The primary challenge in the practical application of hydrogen fuel cells is to reduce or replace the use of platinum material in the electrode catalysts. In this work, by using density functional theory (DFT) we investigate the oxygen reduction reaction of Ag-based core-shell nanoclusters with 12 different 3d-5d transition metal (TM) cores (groups 8-11). The stability is assessed by calculating the binding, excess and segregation energies, indicating that the most stable mixing is found in the noble metal-encapsulated structures, such as Pd@Ag, Pt@Ag, Rh@Ag and Ir@Ag particles. The reaction barrier for OH formation is found to be the limiting step with values ranging from 0.59 to 1.36 eV among the core-shell Ag-based nanoclusters, which are comparable with the energy barrier of the Pt(111) surface (0.97 eV). However, the correlation of the d-band center and activation barriers indicate that Ru@Ag, Rh@Ag, and Os@Ag mixings are the most suitable for the oxygen reduction reaction. These results indicate that small Ag-based core-shell nanoclusters with transition metal cores are active for the ORR application in alkaline media.