Neighboring Pt Atom Sites in an Ultrathin FePt Nanosheet for the Efficient and Highly CO-Tolerant Oxygen Reduction Reaction.

Single atom catalyst and ultrathin two-dimensional (2D) nanostructures exhibit improved properties because of the improved exposure of more active atomic sites and optimized electronic structures. However, the oxygen reduction reaction (ORR) in fuel cells via a fast four-electron path usually uses at least two Pt atoms, which cannot be realized in highly isolated single Pt atoms. The synthesis of a densely dispersed single atom catalyst with adjacent atoms accessible at the same time on a matrix with a high surface area provides a feasible way and, however, is challenging. Here, we synthesize ultrathin FePt nanosheets (NSs) with 6.7 wt % neighboring dispersed Pt atoms. Different from the reported isolated Pt single atom catalysts, these ultrathin wrinkled FePt NSs with neighboring Pt sites adopt a four-electron reduction pathway, a high electrochemical active surface area (ECSA) of 545.54 m2 gPt-1, and an improved mass activity 7 times as high as Pt/C in the ORR. The improved performance results from the optimal use of neighboring Pt atoms dispersed in a more packed spacing and exposed on the surface of ultrathin sheets. The Pt atoms can interact synergistically to catalyze a fast ORR process. Furthermore, both the experiment and density functional theory (DFT) calculation indicated an outstanding CO-tolerance performance of this catalyst in the ORR.