Constructing Pt skin on intermetallics has been confirmed as an efficient strategy to boost oxygen reduction reaction (ORR) kinetics. However, there still lacks a systematic study on revealing the influence of low-Pt-content intermetallic substrates (L12-PtM3). In this paper, Pt skin-encapsulated low-Pt-mole-fraction L12 Cu3Pt has been constructed (denoted as Pt-o-Cu3Pt/C) and compared with its disordered analogue (denoted as Pt-d-Cu3Pt/C). The L12 substrate shows a contracted lattice structure and provides Pt-o-Cu3Pt/C with an excellent specific activity of 1.73 mA cm–2, which is 1.4- and 8.4-fold higher than that of Pt-d-Cu3Pt/C and commercial Pt/C, respectively. Density functional theory calculations reveal that this superior performance is attributed to the more favorable oxygen adsorption energy of surface Pt atoms. Furthermore, the lower formation energy of L12 Cu3Pt combined with the enhanced antioxygenation of Pt provide Pt-o-Cu3Pt/C with a superior durability, showing only a 12.5% loss in mass activity after 5000 potential cycles. Therefore, it is suggested that L12 atomic ordered structure with a low Pt fraction is a promising substrate for building high-performance Pt-skin catalysts for ORR.

The size of nanocrystals (NCs) is regarded as one of the vital factors determining their electrochemical performance. To achieve high electrochemical activity and durability at the same time still remains a big challenge. This work has demonstrated the successful synthesis of Pt 3 Ni nanocrystals of large size with porous characteristics (PNC-Pt 3 Ni). The mass and specific activity of the as-prepared catalyst are 6 and 6.6 times more than those of commercial Pt/C at 0.9 volts versus the reversible hydrogen electrode (RHE), respectively. More importantly, PNC-Pt 3 Ni prevails against a durability test (23.7% loss of mass activity after 10 000 potential cycling) with little change to the porous morphology under harsh experimental conditions. Density functional theory calculations show a much lower activation energy for PNC-Pt 3 Ni during the process of dissociation of the oxygen molecule adsorbed on the surface of the catalyst, which may account for the improvement in the catalytic activity. The lower series resistance for PNC-Pt 3 Ni is also verified by electrochemical impedance spectroscopy (EIS) data, resulting from fewer grain boundaries for nanocrystals with large sizes. This exciting work contributes a new strategy for the optimization of electrochemical performance and durability. ; Tel: +86 021 64250996; +86 021 6425094 † Electronic supplementary information (ESI) available: DFT models and calculations, XRD and XPS patterns of PNC-Pt 3 Ni, morphology change with different doses of DTAC, structural analysis recorded under different precursor ratios, structure of Pt-Ni alloy with different ratios of solvent, TEM images of PNC-Pt 3 Ni/C and Pt/C, TEM images aer 10k potential cycles, and the illustration of O 2 * adsorption. See