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 9 h) exhibits high catalytic activity and robust stability for ORR. The mass activity of the sample Pt–Ni EDP-NCs-9 is 0.43 A/mgPt, which is 1.65 times higher than that of the Pt–Ni DP-NCs (0.26 A/mgPt), and 2.05 times higher than that of commercial Pt/C (0.21 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.