Synthesization, characterization, and highly efficient electrocatalysis of chain-like Pt-Ni nanoparticles
Authors: Xu Ke-Xin , Xia Tian-Yu , Zhou Liang , Li Shun-Fang , Cai Bin , Wang Rong-Ming , Guo Hai-Zhong ,   School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China,   Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China,   Collaborative Innovation Center of Light Manipulations and Applications, Shandong Normal University, Jinan 250358, China
Published: December 2020

Fuel cells are one of the promising energy-conversion devices due to their high efficiency and zero emission. Despite tremendous research works in past decades, there remains a tough challenge in realizing the commercial applications of fuel cell technologies. Therefore, the development of highly efficient and stable fuel cell electrocatalyst is the top priority for practical fuel cells. As we all know, the small-size nanoparticles always have high specific surface area, which can provide more active sites to enhance the catalytic activity, while the one-dimensional nanowires usually own high structural stability. It may provide a possibility for the design of a novel bimetal Pt-based alloy nanostructure by combining the structural superiority of both, which can maintain the high stability and maximize the catalytic activity at the same time. Driven by these purposes, a novel nanostructure constructed by Pt-Ni alloy nanoparticles with a one-dimensional chain structure was designed to balance the contradiction between the activity and stability due to the size effects (the smaller the size, the higher the activity, and the worse the stability of the nanocatalyst; and vice versa). Here, a simple one-step solvothermal method has been adopted to produce the novel nanostructures constructed by the chain-like Pt-Ni nanoparticles (Pt-Ni CNPs) with Pt-rich crystal faces and alloy nature. The structure, component and catalysis were investigated by the combination of X-ray diffraction, transmission electron microscopy, X-ray photoemission spectra, and electrochemical measurements. The results show that the as-synthesized Pt-Ni CNP is constructed from a nanowire (with a diameter of about 3 nm and a length of several hundred nanometers) and the nanoparticles (with an average diameter of about 10 nm). This nanostructure is cleverly integrated the structural advantages of one-dimensional nanowires and zero-dimensional nanoparticles, which can significantly enhance the catalytic activity and stability for the methanol oxidation reaction (MOR) in acidic environment. Specially, the mass activity and specific activity of as-prepared Pt-Ni CNPs are 5.7 and 7.6 times higher than those of the commercial Pt/C, respectively. After 1000 cycles of cyclic voltammetry (CV) measurement, Pt-Ni CNPs still retain 91.2% of the specific activity, while the commercial Pt/C undergoes a drastic loss of MOR activities, retaining only 4.4% of the initial activity. It is particularly noteworthy that this nanostructure of Pt-Ni CNP solves the problem of agglomeration of nanoparticle catalysts in the reaction, and provides a new approach to obtain Pt-based nanocatalysts with high catalytic activity and stability at the same time. Our finding will provide insight into more rational designs of Pt-based bimetallic nanocatalysts with one-dimensional architectures, which is expected to promote the further development and large-scale industrial application of the direct methanol fuel.