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| Effect of Rare Earth Elements on the Microstructure and Electrochemical Properties of Mg-Free R-Y-Ni Based A2B7-Type Hydrogen Storage Alloys |
| Author Name | Affiliation | E-mail | | JIANG Wan-Ting | Department of Materials Science and Engineer, Lanzhou University of Technology, Lanzhou 730050, China | | | LUO Yong-Chun | Department of Materials Science and Engineer, Lanzhou University of Technology, Lanzhou 730050, China
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China | luoyc@lut.cn | | ZHAO Lei | Department of Materials Science and Engineer, Lanzhou University of Technology, Lanzhou 730050, China | | | DEN An-Qiang | Department of Materials Science and Engineer, Lanzhou University of Technology, Lanzhou 730050, China | | | ZHANG Guo-Qing | Department of Materials Science and Engineer, Lanzhou University of Technology, Lanzhou 730050, China | |
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| Abstract: The R-Y-Ni based A2B7-type R0.3Y0.7Ni3.25Mn0.15Al0.1 (R=Y, La, Pr, Ce, Nd, Gd, Sm) alloys were prepared by vacuum arc melting and followed by annealing treatment. The effects of rare earth element R on the microstructure, hydrogen storage and electrochemical properties of the alloys were investigated systematically. XRD and SEM-EDS analysis showed that the annealed alloys mainly composed of Ce2Ni7-type main phases, minor PuNi3-type and CaCu5-type phases. The lattice constants a, c and cell volume V of the Ce2Ni7-type main phases decreased in sequence with the decreasing radius of R atoms. The annealed alloys obviously presented a hydrogen absorption/desorption platform, the maximum hydrogen storage capacities and the equilibrium hydrogen absorption pressures (Peq) at room temperature were in the range of 1.17%~1.48% (w/w) and 0.037~0.194 MPa, respectively. Electrochemical analysis showed that the electrochemical activation performance was excellent. The heterogeneity of microstructure and electrochemical oxidation corrosion of rare earth elements were main reason that affected the cycling stability of alloy electrodes. For all the alloys, the R=La alloys exhibited the highest electrochemical discharge capacity of 389.2 mAh·g-1 and the best cyclic stability S100=85.7% (charge/discharge after 100 cycles). The high rate discharge ability HRD900 (current density was 900 mA·g-1) of the alloys was 71.05%~86.94% and the control step of the reaction kinetics was mainly controlled by the diffusion rate of the hydrogen atom in the alloys. |
| Keywords: R-Y-Ni based A2B7-type hydrogen storage alloys rare earth elements microstructure hydrogen storage electrochemical properties |
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| JIANG Wan-Ting,LUO Yong-Chun,ZHAO Lei,DEN An-Qiang,ZHANG Guo-Qing.Effect of Rare Earth Elements on the Microstructure and Electrochemical Properties of Mg-Free R-Y-Ni Based A2B7-Type Hydrogen Storage Alloys[J].Chinese Journal of Inorganic Chemistry,2018,34(10):1817-1825. |
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