Abstract:Mg2Ni-Ni-5%RExOy(CeO2, Nd2O3, Tb4O7) composites were synthesized via ball milling method. The microstructure and hydrogen storage properties of the materials were analyzed systematically by XRD, SEM, EDS, the electrochemical and kinetic measurements. The results show that the crystallinities of the composites with rare earth oxides decrease, and the distribution of the rare earth oxide catalysts on the surface of alloys is uniform. The maximum discharge capacities of the composites with rare earth oxides rise evidently,the discharge capacity of the sample containing Tb4O7 reaches to 871mAh·g-1 at room temperature, and the composites can also keep higher cycling stability. The CeO2 and Tb4O7 catalysts can enhance the abilities of charge transfer on the surface of alloys, and improve the transmission rate of H atoms in the bulk of Mg2Ni alloy obviously. The rare earth oxides catalysts can also increase the gaseous hydrogen absorption capacity. The hydrogen storage capacity of the sample with Tb4O7 reaches to 2.02%(mass fraction) at 250℃, which is the maximum hydrogen absorption capacity among these samples, but the hydriding rate is relatively slow at lower temperature. The catalytic effect of the rare earth oxides is mainly related to the changeable valences of the rare earth ions, that is, the more likely of the valences change of the ions, the better the catalytic activities exhibit. The catalytic activities in descending order are Tb4O7, CeO2 and Nd2O3.
[1] 张国芳,翟亭亭,胡锋,等. 纳米CuO催化剂晶粒尺寸对Mg2Ni基复合材料储氢性能的影响[J]. 材料工程,2018,46(7):151-156. ZHANG G F,ZHAI T T, HU F,et al. Effect of different sizes of nano CuO catalysts on hydrogen storage properties of Mg2Ni based composites[J]. Journal of Materials Engineering,2018,46(7):151-156.
[2] 张国芳,张羊换,许剑轶,等. Ni-5%RExOy复合添加剂对Mg2Ni电化学储氢性能的影响[J]. 材料工程,2017,45(11):72-77. ZHANG G F,ZHANG Y H,XU J Y,et al. Effects of Ni-5%RExOy composite additives on electrochemical hydrogen storage performance of Mg2Ni[J]. Journal of Materials Engineering,2017,45(11):72-77.
[3] ZHANG G F,XU J Y,HOU Z H,et al. Research on micro-structure and catalysis properties of nanosized Ce1-x(Fe0.5Eu0.5)xO2-δ solid solutions[J]. Journal of Rare Earths,2017,35(1):63-70.
[4] 张国芳,张羊换,许剑轶,等. Mg2Ni-Ni-xCeO2复合材料储氢性能研究[J].稀有金属,2014,38(6):1035-1042. ZHANG G F,ZHANG Y H,XU J Y,et al. Hydrogen storage properties of Mg2Ni-Ni-xCeO2 composites[J]. Chinese Journal of Rare Metals,2014,38(6):1035-1042.
[5] XIE L,LI J,ZHANG T,et al. Air-stable MgH2-CeO2 composite with facilitated dehydrogenation kinetics synthesized by high energy ball milling[J]. Materials Characterization,2017,133:94-101.
[6] ZHANG Y,HUANG G,YUAN Z,et al. A comparison study of hydrogen storage performances of as-milled YMg11Ni alloy catalyzed by CeO2 and MoS2[J]. Materials Science & Engineering B,2017,225:1-9.
[7] ISMAI E,MEHMET A,SEMRA D A,et al. Phase stability and electric conductivity of Eu2O3-Tb4O7 co-doped Bi2O3 electrolyte[J]. International Journal of Hydrogen Energy,2015,40(30):9485-9490.
[8] ZHANG Y,DENG J,ZHANG H,et al. Three-dimensionally ordered macroporous Pr6O11 and Tb4O7 with mesoporous walls:preparation, characterization, and catalytic activity for CO oxidation[J]. Catalysis Today,2015,245:28-36.
[9] ZHANG Y,YANG T,CAI Y,et al. Structures and electroche-mical performances of RE-Mg-Ni-Mn-based alloys prepared by casting and melt spinning[J]. Jounal of Rare Earths,2016,34(12):1241-1251.
[10] DABAKI Y,BOUSSAMI S,KHALDI C,et al. The effect of ZnO addition on the electrochemical properties of the LaNi3.55Mn0.4Al0.3Co0.2Fe0.55 electrode used in nickel-metal hydride batteries[J]. Journal of Solid State Electrochemistry,2017,21(4):1-8.
[11] KURIYAMA N,SAKAI T,MIYAMURA H,et al. Electro-chemical impedance and deterioration behavior of metal hydride electrodes[J]. Journal of Alloys and Compound,1993,202(1/2):183-197.
[12] KURIYAMA N,SAKAI T,MIYAMURA H,et al. Electro-chemical impedance spectra and deterioration mechanism of metal hydride electrodes[J]. Journal of the Electrochemical Society,1992,139:72-73.
[13] WU M S,WU H R,WANG Y Y,et al. Surface treatment for hydrogen storage alloy of nickel/metal hydride battery[J]. Journal of Alloys and Compoud,2000,302(1/2):248-257.
[14] OELERICH W,KLASSEN T,BORMANN R. Metal oxides as catalysts for improved hydrogen sorption in nanocrystalline Mg-based materials[J]. Journal of Alloys and Compounds,2001,315(1):237-242.
[15] TSUDA M,DINO W A,KASAI H,et al. Mg-H dissociation of magnesium hydride MgH2 catalyzed by 3d transition metals[J]. Thin Solid Films,2006,509(1):157-159.
[16] JANOT R,DAROK X,ROUGIER A,et al. Hydrogen sorption properties for surface treated MgH2 and Mg2Ni alloys[J]. Journal of Alloys and Compoud,2005,404/406(12):293-296.
[17] GULICOVSKI J,RASKOVIC-LOVRE Z,KURKO S,et al. Influence of vacant CeO2 nanostructured ceramics on MgH2 hydrogen desorption properties[J]. Ceramics International,2012,38(2):1181-1186.
[18] MUSTAFA N S,ISMAIL M. Hydrogen sorption improvement of MgH2 catalyzed by CeO2 nanopowder[J]. Journal of Alloys and Compoud,2017,695:2532-2538.
[19] CUI J,WANG H,LIU J,et al. Remarkable enhancement in dehydrogenation of MgH2 by a nano-coating of multi-valence Ti-based catalysts[J]. Journal of Materials Chemistry A,2013,1(18):5603-5611.