硼氢化钙基复合材料储氢行为及其机理
发布时间：2018-10-13 15:39
【摘要】：化石能源(煤、石油、天然气等)有限的储量及不可再生性,已无法满足人类的能源需求。面对日益严峻的能源危机和环境污染的双重问题,寻求一种新的可再生绿色能源迫在眉睫。在众多的新能源中氢能释放能量高达142 MJ Kg-1,其能量密度大,燃烧后的产物为水,安全环保,是理想能量的优质载体,但氢气的可逆存储是限制氢能大规模应用的重要因素。固态储氢技术被认为是一种极具潜力的储氢技术。轻金属硼氢化物作为固态储氢材料的一种,因具有高储氢容量,备受关注。其中,Ca(BH4)2具有11.4wt%理论储氢容量,理论反应焓变只有40.6kJ/molH2,是一种极具潜力的高容量储氢材料,近年被国内外储氢材料研究机构作为研究重点,但其实际反应的热力学、动力学以及可逆性等方面仍须进一步改善,就目前的放氢热力学、动力学以及可逆性还无法满足其实用化。本文以Ca(BH4)2研究目标,通过Mg(AlH4)2与Ca(BH4)2复合以及采用多孔CaB2H7+0.1TiO2与MgH2复合的方法,提高体系的储氢性能,并揭示了促使性能提高的机理。通过球磨不同比例的Ca(BH4)2和Mg(AlH4)2,制备了Ca(BH4)2-xMg(AlH4)2复合材料,并研究不同Mg(AlH4)2添加量对Ca(BH4)2储氢性能的影响。结合XRD射线、红外光谱以及DSC热重分析,揭示了Mg(AlH4)2-Ca(BH4)2体系的分解机制及其性能改善的机理。结果表明,较单一Ca(BH4)2,复合体系的吸放氢性能得到明显提高。研究发现,Mg(AlH4)2分解后产生MgH2与Al产生的Mg-Al固溶体对Ca(BH4)2放氢起到重要作用。形成的MgH2在一定程度上保证了体系具有较高的容量和改善其可逆性。通过在多孔结构的CaB2H7+0.1TiO2基础上,球磨引入MgH2后制备出CaB2H7+0.1TiO2+2MgH2复合体系,并研究其的吸放氢性能。研究发现,CaB2H7+ 0.1TiO2+2MgH2复合体系相对Ca(BH4)2-2MgH2体系其峰值放氢温度降低了约70℃,且其放氢动力学性能得到提高。相比与CaB2H7+0.1TiO2体系,添加MgH2后,复合体系的可逆性提到改善,可逆吸氢量由原先的3.9wt%提高到6.1 wt%。结果分析,除了Ti02给体系热力学动力学带来改善的以外,由XRD图谱得知复合体系升温至320℃保温1小时的过程中产生的新相MgCaH3.72是促进体系可逆性提高的重要因素,该相高度可逆,作为中间产物出现,高温区又消失。
[Abstract]:The limited reserves and non-renewable fossil energy (coal, oil, natural gas, etc.) can no longer meet the energy needs of human beings. Facing the dual problems of energy crisis and environmental pollution, it is urgent to seek a new renewable green energy. Hydrogen energy release energy is as high as 142 MJ Kg-1, in many new energy sources. Its energy density is high, the product after combustion is water, safe and environmental protection, and it is a good carrier of ideal energy. However, the reversible storage of hydrogen is an important factor limiting the large-scale application of hydrogen energy. Solid state hydrogen storage technology is considered as a potential hydrogen storage technology. As a kind of solid hydrogen storage material, light metal borohydride has attracted much attention because of its high hydrogen storage capacity. , Ca (BH4) 2 has a theoretical hydrogen storage capacity of 11.4 wt%, and the theoretical reaction enthalpy change is only 40.6 kJ / mol H _ 2, which is a potential high capacity hydrogen storage material. In recent years, Ca (BH4) _ 2 has been regarded as the research focus of hydrogen storage materials at home and abroad, but the thermodynamics of its actual reaction is very important. The kinetics and reversibility still need to be further improved. The present hydrogen desorption thermodynamics, kinetics and reversibility can not meet its practical requirements. In this paper, the hydrogen storage performance of Ca (BH4) 2 system is improved by Mg (AlH4) 2 and Ca (BH4) 2 composite and porous CaB2H7 0.1TiO2 and MgH2 composite, and the mechanism of improving performance is revealed. Ca (BH4) 2-xMg (AlH4) 2 composites were prepared by ball milling with different ratios of Ca (BH4) 2 and Mg (AlH4) 2. The effects of different Mg (AlH4) 2 contents on the hydrogen storage properties of Ca (BH4) 2 were investigated. The decomposition mechanism of Mg (AlH4) 2-Ca (BH4) 2 system and the mechanism of improving its performance were revealed by XRD ray, infrared spectroscopy and DSC thermogravimetric analysis. The results show that compared with the single Ca (BH4) 2, the hydrogen absorption and desorption properties of the composite system are obviously improved. It is found that the Mg-Al solid solution produced by, Mg (AlH4) 2 decomposes into MgH2 and Al plays an important role in the dehydrogenation of Ca (BH4) 2. To a certain extent, the formed MgH2 ensures the high capacity of the system and improves its reversibility. On the basis of porous CaB2H7 0.1TiO2, the composite system of CaB2H7 0.1TiO2 2MgH2 was prepared by introducing MgH2 into ball mill, and its hydrogen absorption and desorption properties were studied. It is found that the peak desorption temperature of CaB2H7 0.1TiO2 2MgH2 composite system is about 70 鈩，
本文编号：2269133
[Abstract]:The limited reserves and non-renewable fossil energy (coal, oil, natural gas, etc.) can no longer meet the energy needs of human beings. Facing the dual problems of energy crisis and environmental pollution, it is urgent to seek a new renewable green energy. Hydrogen energy release energy is as high as 142 MJ Kg-1, in many new energy sources. Its energy density is high, the product after combustion is water, safe and environmental protection, and it is a good carrier of ideal energy. However, the reversible storage of hydrogen is an important factor limiting the large-scale application of hydrogen energy. Solid state hydrogen storage technology is considered as a potential hydrogen storage technology. As a kind of solid hydrogen storage material, light metal borohydride has attracted much attention because of its high hydrogen storage capacity. , Ca (BH4) 2 has a theoretical hydrogen storage capacity of 11.4 wt%, and the theoretical reaction enthalpy change is only 40.6 kJ / mol H _ 2, which is a potential high capacity hydrogen storage material. In recent years, Ca (BH4) _ 2 has been regarded as the research focus of hydrogen storage materials at home and abroad, but the thermodynamics of its actual reaction is very important. The kinetics and reversibility still need to be further improved. The present hydrogen desorption thermodynamics, kinetics and reversibility can not meet its practical requirements. In this paper, the hydrogen storage performance of Ca (BH4) 2 system is improved by Mg (AlH4) 2 and Ca (BH4) 2 composite and porous CaB2H7 0.1TiO2 and MgH2 composite, and the mechanism of improving performance is revealed. Ca (BH4) 2-xMg (AlH4) 2 composites were prepared by ball milling with different ratios of Ca (BH4) 2 and Mg (AlH4) 2. The effects of different Mg (AlH4) 2 contents on the hydrogen storage properties of Ca (BH4) 2 were investigated. The decomposition mechanism of Mg (AlH4) 2-Ca (BH4) 2 system and the mechanism of improving its performance were revealed by XRD ray, infrared spectroscopy and DSC thermogravimetric analysis. The results show that compared with the single Ca (BH4) 2, the hydrogen absorption and desorption properties of the composite system are obviously improved. It is found that the Mg-Al solid solution produced by, Mg (AlH4) 2 decomposes into MgH2 and Al plays an important role in the dehydrogenation of Ca (BH4) 2. To a certain extent, the formed MgH2 ensures the high capacity of the system and improves its reversibility. On the basis of porous CaB2H7 0.1TiO2, the composite system of CaB2H7 0.1TiO2 2MgH2 was prepared by introducing MgH2 into ball mill, and its hydrogen absorption and desorption properties were studied. It is found that the peak desorption temperature of CaB2H7 0.1TiO2 2MgH2 composite system is about 70 鈩，
本文编号：2269133
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