Core-Shell Nanostructured Au@NimPt2 Electrocatalysts with Enhanced Activity and Durability for Oxygen Reduction Reaction

Fabricating Pt-alloy and core-shell nanostructures with Au NPs in the cores are considered as two general approaches to improving the performance of Pt-based catalysts for the cathodic oxygen reduction reaction (ORR) in acidic electrolyte. These two approaches are combined herein to develop a heteroseed-mediated solvothermal method for synthesizing nearly monodisperse core-shell structured Au@NimPt2 nanoparticles (NPs) of 5.0-6.5 nm (with the atomic ratio of Ni/Pt/Au = m/2/1) as ORR catalysts. With respect to controlling the amount and relative concentrations of the metal precursors in the starting solution, this method enables not only facile manipulation of the shell composition and thickness but also fine-tuning of the core-shell interaction and surface electronic structures of the resultant Au@NimPt2 NPs, endowing the Au@NimPt2 NPs with improved Pt activity and durability for ORR. Subjecting the Au@NimPt2 NPs to an ex situ pretreatment in flowing 2%CO/Ar at 300 degrees C is shown to result in further improved Pt activity. Data are also presented to correlate the intrinsic Pt activity with experimentally determined CO adsorption property (CO-stripping peak potential) of Pt for the Au@Ni(m)Pt2 samples, and to show the excellent electrochemical durability of the Au@NimPt2 NPs during 20 000 potential cycles between 0.6 and 1.1 V (vs RI-IE) in O-2-saturated 0.1 M HClO4. Compared with the commercial E-TEK Pt/C catalyst, the most-active Au@Ni2Pt2 NPs exhibit 3-4- and 4-6-fold higher Pt activity at 0.9 V before and after the 20 000 potential cycles, respectively. Factors relevant to the activity and durability control of the Au@NimPt2 catalysts for ORR are discussed.