Mg-TM-Mm（TM=过渡金属，Mm=混合稀土）贮储氢合金的电化学性能

摘要

Eighteen as-cast binary Mg−Ni, Mg−Mm and ternary Mg−Ni−Mm and Mg−Ni−TM (TM=transition metals (Cu, Zn, Mn and Co); Mm = mischmetal containing Ce, La, Nd and Pr) alloys were hydrided by an electrochemical process to determine the alloys with the most potential for electrochemical hydrogen storage. The alloys were hydrided in a 6 mol/L KOH solution at 80 °C for 480 min and at 100 A/m2. To assess the electrochemical hydriding performance of alloys, maximum hydrogen concentrations, hydrogen penetration depths and total mass of absorbed hydrogen in the alloys were measured by glow discharge spectrometry. In addition, the structures and phase compositions of the alloys both before and after hydriding were studied by optical and scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction. It was determined that the highest total amount of hydrogen was absorbed by the Mg−25Ni−12Mm and Mg−26Ni (mass fraction,%) alloys. The maximum hydrogen concentrations in the Mg−25Ni−12Mm and Mg−26Ni alloys were 1.0% and 1.6%, respectively. The main hydriding product was the binary MgH2 hydride, and the ternary Mg2NiH4 hydride was also detected in the Mg−25Ni−12Mm alloy. The electrochemical hydriding parameters achieved are discussed in relation to the structures of alloys, alloying elements and hydriding mechanisms.%　　对18种铸造态合金，包括二元合金Mg−Ni、Mg−Mm和三元合金Mg−Ni−Mm、Mg−Ni−TM(TM=过渡金属(Cu，Zn，Mn和Co)；Mn=含Ce，La，Nd和Pr的混合稀土)，采用电化学方法进行氢化，选取最具有潜力的电化学贮氢材料。将这些合金在80°C的6 mol/L KOH溶液中以电流密度100 A/m2氢化480 min。为了评价合金的电化学氢化性能，采用辉光放电光谱法测定氢化后合金的最大氢气浓度、氢渗透深度、总的吸氢质量。采用光学和扫描电子显微镜、能谱和X射线衍射测试分析合金的结构与相组成。结果表明，Mg−25Ni−12Mm和Mg−26Ni合金具有最大的吸氢质量，其吸附的最大的氢浓度分别为1.0%和1.6%；主要的氢化产品为二元氢化物MgH2，在Mg−25Ni−12Mm合金中也检测到有三元氢化物Mg2NiH4。讨论了电化学氢化参数对合金的结构、合金化元素和氢化机理的影响。