稀土氧化物及孔道材料改性NaAlH₄吸放氢性能的研究

【作者】 马俊；

【导师】 李洁；

【作者基本信息】 中南大学 ， 工业催化， 2011， 硕士

【摘要】 针对目前储氢材料普遍存在的储氢容量低、放氢速率慢和吸放氢条件苛刻等问题,本文采用机械球磨为制备方法,从材料的结构、形貌、热力学行为和吸放氢特性等方面分别考察了稀土氧化物和孔道材料单独改性及二者复合改性NaAlH4的吸放氢性能。首先研究了稀土氧化物Sm2O3、Er2O3和Tm203对NaAlH4的改性,发现复合了三种稀土氧化物的NaAlH4均具有可逆的吸放氢性能,在150℃条件下NaAlH4-Sm2O3、NaAlH4-Er2O3和NaAlH4-Tm2O3体系的放氢量从纯NaAlH4的1 wt%分别增加到了3.90、4.40和4.59wt%。其中Tm2O3对NaAlH4循环吸放氢性能的改善作用最为明显,NaAlH4-Tm2O3体系的5次循环放氢量分别为4.59,1.96,1.51,1.86和1.39 wt%。以Tm203为例,当球磨时间为1 h, Tm2O3含量为10 wt%时,样品的放氢量最大。此外,还发现NaAlH4-Tm2O3体系在120℃条件下也可放氢,放出氢气的量为4.30 wt%。其次以大孔Al2O3和介孔SiO2材料为改性剂,研究了单独复合孔道材料NaAlH4的储氢性能。NaAlH4-SiO2体系150℃条件下的放氢量为3.59 wt%,高于NaAlH4-Al2O3体系的3.37 wt%。在此基础上,进一步研究了孔道材料和稀土氧化物复合改性NaAlH4的吸放氢性能,NaAlH4-Tm2O3-SiO2、NaAlH4-Tm2O3和NaAlH4体系的放氢量分别为4.73,4.59和4.36 wt%。孔道材料和稀土氧化物复合对NaAlH4进行改性时,体系表现出相同的放氢规律,即NaAlH4-SiO2-(MxOy,M=Sm,Tm,Er)>NaAlH4-(MxOy,M=Sm,Tm,Er)> NaAlH4-Al2O3-(MxOy,M=Sm,Tm,Er)。更多还原

【Abstract】 To solve the problems of low storage capacity, low hydrogen release speed, and harsh hydrogen absorption conditions of hydrogen storage materials, we investigated the hydrogen storage capacity of NaAlH4 doped/and co-doped by lanthanide oxides and porous materials from the aspects of structure, morphology, thermoactivity, and hydrogen de/-reabsorption using the ball milling method.The catalytic effects of Sm2O3, Er2O3, and Tm2O3 on NaAlH4 were investigated, founding that all lanthanide oxides added can make hydrogen storage of NaAlH4 reversible, and samples could release hydrogen at 150℃with a higher speed. For pristine NaAlH4, NaAlH4-Sm2O3, NaAlH4-Er2O3, and NaAlH4-Tm2O3, the amount of hydrogen released within 8 h increased from less than 1 wt% to 3.90,4.40, and 4.59 wt%, respectively. The addition of Tm2O3 improved the hydrogen storage capacity of NaAlH4 at the maximum extent, reversible hydrogen desorption capacity of NaAlH4-Tm2O3 among five cycles was 4.59,1.96,1.51,1.86 and 1.39 wt%, respectively. The optimum milling time and catalyst dosage is 1 h and weight ratio of 10 wt%. Unexpectedly, NaAlH4-Tm2O3 can also release hydrogen at 120℃with a lower amount of 4.30 wt%.In addition, the effects of macroporous Al2O3 and mesoporous silica on NaAlH4 were investigated. The hydrogen storage capacity of NaAlH4-SiO2 and NaAlH4-Al2O3 was 3.59 wt% and 3.37 wt%, respectively. Then the co-effects of lanthanide oxides and porous materials were explored, and the hydrogen storage capacity of NaAlH4-Tm2O3-SiO2, NaAlH4-Tm2O3 and NaAlH4-Tm2O3-Al2O3 was 4.73,4.59 and 4.36 wt%, respectively. Samples co-doped by macroporous Al2O3/mesoporous silca and different lanthanide oxides showed similar hydrogen desorption speed and capacity trend, which was NaAlH4-SiO2-(MxOy,M=Sm,Tm,Er)>NaAlH4-(MxOy,M=Sm,Tm,Er)> NaAlH4-Al2O3-(MxOy,M=Sm,Tm,Er).更多还原