Mg_2FeH_6纳米晶的制备及储氢性能

Preparation and Hydrogen Storage Properties of Mg_2FeH_6 Nanocrystals

在室温和氩气气氛下,以MgH2和纳米Fe为原料,采用机械合金化(球磨法)制备了Mg2FeH6纳米晶.考察了球磨参数(时间、转速)对产物的影响,对所制备的Mg2FeH6纳米晶的组成、结构和形貌进行了表征,并对其储氢性能进行了测试.结果表明,所制备的Mg2FeH6纳米晶为立方结构,纯度较高(91.4%),其晶粒尺寸较小,约为10～30 nm,但团聚现象较为严重.Mg2FeH6纳米晶具有较低的活化能和较好的吸放氢动力学性能,其放氢的脱附焓和脱附熵分别为(-42.8±2)kJ/mol和(-72.0±3)J/(mol.K).在503 K和6 kPa的氢气压力下,Mg2FeH6纳米晶在70 min内放氢量达到2.5%(质量分数);在2 MPa的氢气压力下,上述放氢产物具有较快的起始吸氢速率.

The preparation of Mg2FeH6 nanocrystals and their hydrogen storage properties were reported.Mg2FeH6 nanocrystals were prepared by mechanical ball-milling the mixture of MgH2 and Fe nanoparticles at room temperature under an argon atmosphere.The processing parameters（time,milling speed）,crystal structure,morphologies,and hydrogen storage properties of the as-prepared Mg2FeH6 nanocrystals were investigated.The results show that the cubic Mg2FeH6 nanocrystals have a yield ratio around 91.4%,and a grain size between 10—30 nm in the powder.However,the agglomeration of particles are more serious.Mg2FeH6 nanocrystals show fast absorption/desorption kinetics.The desorption enthalpy and entropy for Mg2FeH6 are（-42.8±2） kJ/mol and（-72.0±3） J/（mol·K）,respectively.At 503 K,the as-prepared Mg2FeH6 nanocrystals can release about 2.5%（mass fraction） hydrogen in 70 min under an initial hydrogen pressure of 6 kPa.Under 2 MPa hydrogen pressure,the rehydrogenation rate for the Mg2FeH6 decomposed product is fast.