【摘要】：化石能源(煤、石油、天然氣等)有限的儲量及不可再生性,已無法滿足人類的能源需求。面對日益嚴(yán)峻的能源危機和環(huán)境污染的雙重問題,尋求一種新的可再生綠色能源迫在眉睫。在眾多的新能源中氫能釋放能量高達142 MJ Kg-1,其能量密度大,燃燒后的產(chǎn)物為水,安全環(huán)保,是理想能量的優(yōu)質(zhì)載體,但氫氣的可逆存儲是限制氫能大規(guī)模應(yīng)用的重要因素。固態(tài)儲氫技術(shù)被認為是一種極具潛力的儲氫技術(shù)。輕金屬硼氫化物作為固態(tài)儲氫材料的一種,因具有高儲氫容量,備受關(guān)注。其中,Ca(BH4)2具有11.4wt%理論儲氫容量,理論反應(yīng)焓變只有40.6kJ/molH2,是一種極具潛力的高容量儲氫材料,近年被國內(nèi)外儲氫材料研究機構(gòu)作為研究重點,但其實際反應(yīng)的熱力學(xué)、動力學(xué)以及可逆性等方面仍須進一步改善,就目前的放氫熱力學(xué)、動力學(xué)以及可逆性還無法滿足其實用化。本文以Ca(BH4)2研究目標(biāo),通過Mg(AlH4)2與Ca(BH4)2復(fù)合以及采用多孔CaB2H7+0.1TiO2與MgH2復(fù)合的方法,提高體系的儲氫性能,并揭示了促使性能提高的機理。通過球磨不同比例的Ca(BH4)2和Mg(AlH4)2,制備了Ca(BH4)2-xMg(AlH4)2復(fù)合材料,并研究不同Mg(AlH4)2添加量對Ca(BH4)2儲氫性能的影響。結(jié)合XRD射線、紅外光譜以及DSC熱重分析,揭示了Mg(AlH4)2-Ca(BH4)2體系的分解機制及其性能改善的機理。結(jié)果表明,較單一Ca(BH4)2,復(fù)合體系的吸放氫性能得到明顯提高。研究發(fā)現(xiàn),Mg(AlH4)2分解后產(chǎn)生MgH2與Al產(chǎn)生的Mg-Al固溶體對Ca(BH4)2放氫起到重要作用。形成的MgH2在一定程度上保證了體系具有較高的容量和改善其可逆性。通過在多孔結(jié)構(gòu)的CaB2H7+0.1TiO2基礎(chǔ)上,球磨引入MgH2后制備出CaB2H7+0.1TiO2+2MgH2復(fù)合體系,并研究其的吸放氫性能。研究發(fā)現(xiàn),CaB2H7+ 0.1TiO2+2MgH2復(fù)合體系相對Ca(BH4)2-2MgH2體系其峰值放氫溫度降低了約70℃,且其放氫動力學(xué)性能得到提高。相比與CaB2H7+0.1TiO2體系,添加MgH2后,復(fù)合體系的可逆性提到改善,可逆吸氫量由原先的3.9wt%提高到6.1 wt%。結(jié)果分析,除了Ti02給體系熱力學(xué)動力學(xué)帶來改善的以外,由XRD圖譜得知復(fù)合體系升溫至320℃保溫1小時的過程中產(chǎn)生的新相MgCaH3.72是促進體系可逆性提高的重要因素,該相高度可逆,作為中間產(chǎn)物出現(xiàn),高溫區(qū)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，

本文編號：2269133