Pt monatomic wire supported on graphene nanoribbon for oxygen reduction reaction

Abstract

Among the issues inherent to fuel cells, the high cost of the Pt electrocatalyst restricts its widespread application. Controlling nano- or subnano-material structures could improve the utilization of Pt. Here, the catalytic activity of the oxygen reduction reaction (ORR) on Pt monatomic wire that is supported on the zigzag edges of graphene nanoribbon (Pt–GNR) is studied using density functional theory. It is found that Pt–GNR is inert for ORR, due to the strong binding of OH and H₂O. However, when Pt–GNR is covered by the chain of OH and H₂O (cPt–GNR), it becomes catalytically active for ORR. Through the free energy diagrams on cPt–GNR, we demonstrate that the highest potential U for ORR as an exothermic process is 0.82 eV. When U is larger than 0.82 V, the rate-determined step (RDS) of ORR is located at the reduction of O₂* to OOH* (* denotes adsorbed species) where the energy barrier ΔG is less than 0.41 eV. These results support cPt–GNR as a candidate for ORR.