Optimization and Regulation of Catalytic Activity and Stability: Pt-Ni Diamond-Shaped Pearl Nanochains with Core-Shell Structure as High-Efficient Oxygen Reduction Reaction Catalysts

Abstract

The low utilization efficiency and poor stability of carbon-supported Pt nanoparticles (Pt/C) catalyst are two main problems of proton exchange membrane fuel cells (PEMFC), which can improve the catalytic performance by forming alloys and precisely regulating morphology and structures. Here, we introduced a simple and direct method for synthesizing Pt-Ni diamond-shaped pearl nanochains (Pt-Ni DP-NCs) as efficient electrocatalyst for oxygen reduction reaction (ORR). The alloying with Ni could enhance the catalytic activity, but because of leaching out of Ni during the cathodic reaction process, which causes a poor stability. To achieve the optimal point for both high activity and robust stability, a portion of Ni is selectively etched from Pt-Ni DP-NCs precursor in advance. During the process of de-alloying, Pt atoms with high catalytic activity are exposed to the surface of the nanochain after atomic rearrangement, thus obtaining Pt-Ni etched diamond-shaped pearl nanochains (Pt-Ni EDP-NCs) with 1D core-shell structure, which consisted of Pt-Ni as the core and Pt as the shell. Benefitting from the unique 1D core-shell structure and composition, Pt-Ni EDP-NCs-9 (etched for 9h) exhibits high catalytic activity and robust stability for ORR. The mass activity of the sample Pt-Ni EDP-NCs-9 is 0.35 A/mgPt, which is 1.4 times higher than that of the Pt-Ni DP-NCs (0.25 A/mgPt), and 2.2 times higher than that of commercial Pt/C (0.16 A/mgPt). In addition, the 1D core-shell structure enables Pt-Ni EDP-NCs to be highly stable, which only lost by 8.6% of mass activity after 10,000 long cycles, whereas Pt-Ni DP-NCs suffers from a 34% loss under the same conditions. This work provides a strategic approach for designing efficient Pt-based catalysts that simultaneously modulate activity and stability.

Keywords: Pt-Ni Catalyst, De-alloying, Oxygen Reduction Reaction, Stability, Electrocatalytic Activity