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采用Sievert’s体积法、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)和差示扫描量热仪(DSC)等分析手段研究暴露空气前后Mg(NH_2)_2-2Li H-0.07KOH储氢材料的放氢性能及其影响机制。研究表明,粉末状样品经空气暴露后,其中的Mg(NH_2)_2和LiH与空气中的O_2和H_2O发生剧烈反应,生成MgO,LiNH_2,Li_2O和Li2Mg(NH)_2,各产物之间不能够发生放氢反应,样品放氢容量几乎为零。而压实体样品经空气暴露后,仅样品表面的Mg(NH_2)_2和LiH可与空气中的O_2和H_2O反应生成Mg O,LiNH_2和Li_2O。样品的放氢容量由暴露空气前的4.68%降至3.32%(质量分数),放氢反应动力学也相应减慢,这是由于新生成的Mg O,Li NH_2和Li2O能够减慢Mg(NH_2)_2和LiH之间界面反应的传质过程,阻碍放氢过程中氢气的扩散,样品放氢反应激活能提高,放氢反应速率减慢。压制成型使Mg(NH_2)_2-2Li H-0.07KOH材料的应用安全性能显著提高。
Sievert’s volumetric method, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to study the effect of Mg (NH_2) _2-2Li H-0.07 KOH Hydrogen storage performance of hydrogen storage material and its influence mechanism. The results show that MgO, LiNH_2, Li_2O and Li_2Mg (NH_) _2 react with Mg (NH_2) _2 and LiH and react with O_2 and H_2O in the air, respectively, after air exposure. Hydrogen release reaction occurred, the sample discharge capacity is almost zero hydrogen. However, only the Mg (NH_2) _2 and LiH on the sample surface after exposure to air in the compacted samples can react with O_2 and H_2O in the air to form MgO, LiNH_2 and Li_2O. The hydrogen desorption capacity of the sample decreased from 4.68% before exposure to air to 3.32% (mass fraction), and the kinetics of the hydrogen desorption reaction also slowed down accordingly. This is because the newly formed MgO, LiNH_2 and Li2O can slow down the Mg (NH_2 ) _2 and LiH interfacial reaction between the mass transfer process, hinder hydrogen diffusion process of hydrogen release, the sample discharge hydrogen activation reaction can increase the rate of hydrogen release reaction slowed down. Compression molding makes the application of Mg (NH_2) _2-2Li H-0.07KOH material safety significantly improved.