Surface Evolution of a Pt-Pd-Au Electrocatalyst for Stable Oxygen Reduction
Update: 2018-02-24 09:37:20      Author:

The exploration of new technologies for efficient energy management is attractive in order to reduce our dependence on environmentally unfriendly fossil fuels. Proton-exchange membrane fuel cells (PEMFCs) are thought to be an ideal solution for energy conversion because of their high efficiency, high reliability and low or zero carbon emissions1. Unfortunately, the sluggish reaction kinetics of the oxygen reduction reaction (ORR) at PEMFC cathodes and the poor durability of conventional ORR electrocatalysts have seriously hindered the development and commercial application of PEMFCs on a large scale1. As the most active metal electrocatalyst for ORR, Pt and Pt-based nanocatalysts have attracted substantial research interests over the past decade. The demonstrated approaches for achieving higher catalytic activities include exposing highly active lattice planes on their surfaces, alloying with other suitable metals to increase their intrinsic activity, and constructing hollow or core-shell1 structures to improve Pt utilization. Regarding improving catalyst durability, the addition of stabilizing elements and the optimization of crystallinity have been shown to be feasible.

Recently, Dr. Li-Min Liu in CSRC worked with Dr. Yi Ding and Jun Luo’s group at Tianjin University of Technology, designed an unsupported nanoporous catalyst with a sub-nanometer-thick PtPd shell on Au by theory and experiment, which demonstrates a high ORR activity (1.140 A mgPt-1 at 0.9 V) and stability (1.471 A mgPt-1 until 100,000 cycles). The DFT and experiment unveil the origin of the activity change: the atomic-scale evolution of the shell from an initial PtPd alloy into a bilayer structure with a Pt-rich trimetallic surface and finally into a uniform and stable PtPdAu alloy. First-principles calculations further revealed that the surface atomic composition of the finally obtained PtPdAu decreases the free energy change of the final water formation from the *OH on the catalyst surface and thereby enhances the ORR catalytic activity. 


FIG. 1 Left: Atomically-resolved elemental mapping of the surfaces of NPG-Pd-Pt10,000 and NPG-Pd-Pt30,000 electrocatalysts. Right: Calculated adsorption configurations of the intermediate species of ORR on the surfaces of the PtPdAu(111) and the pure Pt(111) models and the calculated free energy profiles of the ORR steps.



Jian Li#, Hui-Ming Yin#, Xi-Bo Li#, Eiji Okunishi, Yong-Li Shen, Jia He, Zhen-Kun Tang, Wen-Xin Wang, Emrah Yucelen, Chao Li, Yue Gong, Lin Gu, Shu Miao, Li-Min Liu*, Jun Luo*, Yi Ding*. Nature Energy2017DOI10.1038/nenergy.2017.111.

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