Thursday, 15 December 2016

Biaxially strained PtPb/Pt core/shell nanoplate boosts oxygen reduction catalysis

Source: "Biaxially strained PtPb/Pt core/shell nanoplate boosts oxygen reduction catalysis", Science  16 Dec 2016: Vol. 354, Issue 6318, pp. 1410-1414, DOI: 10.1126/science.aah6133

Author Affiliations

Lingzheng Bu1, Nan Zhang1, Shaojun Guo2,3,4,*, Xu Zhang5, Jing Li6, Jianlin Yao1, Tao Wu1, Gang Lu5, Jing-Yuan Ma1, Dong Su6,*, Xiaoqing Huang1,*

1College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Jiangsu 215123, China.
2Department of Materials Science and Engineering, and Department of Energy and Resources Engineering, College of Engineering, Peking University, Beijing 100871, China.
3The Beijing Innovation Center for Engineering Science and Advanced Technology (BIC-ESAT), College of Engineering, Peking University, Beijing 100871, China.
4Key Laboratory of Theory and Technology of Advanced Batteries Materials, College of Engineering, Peking University, Beijing 100871, China.
5Department of Physics and Astronomy, California State University, Northridge, CA 91330, USA.
6Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA.
7Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
*Corresponding author. Email: (S.G.); (D.S.); (X.H.)

An activity lift for platinum

Platinum is an excellent but expensive catalyst for the oxygen reduction reaction (ORR), which is critical for fuel cells. Alloying platinum with other metals can create shells of platinum on cores of less expensive metals, which increases its surface exposure, and compressive strain in the layer can also boost its activity (see the Perspective by Stephens et al.). Bu et al. produced nanoplates—platinum-lead cores covered with platinum shells—that were in tensile strain. These nanoplates had high and stable ORR activity, which theory suggests arises from the strain optimizing the platinum-oxygen bond strength. Li et al. optimized both the amount of surface-exposed platinum and the specific activity. They made nanowires with a nickel oxide core and a platinum shell, annealed them to the metal alloy, and then leached out the nickel to form a rough surface. The mass activity was about double the best reported values from previous studies.

Science, this issue p. 1410, p. 1403; see also p. 1378


Compressive surface strains have been necessary to boost oxygen reduction reaction (ORR) activity in core/shell M/platinum (Pt) catalysts (where M can be nickel, cobalt, or iron). We report on a class of platinum-lead/platinum (PtPb/Pt) core/shell nanoplate catalysts that exhibit large biaxial strains. The stable Pt (110) facets of the nanoplates have high ORR specific and mass activities that reach 7.8 milliampere (mA) per centimeter squared and 4.3 ampere per milligram of platinum at 0.9 volts versus the reversible hydrogen electrode (RHE), respectively. Density functional theory calculations reveal that the edge-Pt and top (bottom)–Pt (110) facets undergo large tensile strains that help optimize the Pt-O bond strength. The intermetallic core and uniform four layers of Pt shell of the PtPb/Pt nanoplates appear to underlie the high endurance of these catalysts, which can undergo 50,000 voltage cycles with negligible activity decay and no apparent structure and composition changes.

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