Adding a small amount of nanocrystalline TiO2@C （TiO2 supported on nano- porous carbon） composite dramatically decreases the operating temperatures and improves the reaction kinetics for hydrogen storage in NaAlH4. ...Adding a small amount of nanocrystalline TiO2@C （TiO2 supported on nano- porous carbon） composite dramatically decreases the operating temperatures and improves the reaction kinetics for hydrogen storage in NaAlH4. The nano- crystalline TiO2@C composite synthesized at 900 ℃ （referred as TiO2@C-900） exhibits superior catalytic activity to other catalyst-containing samples. The onset dehydrogenation temperature of the TiO2@C-900-containing sample is lowered to 90 ℃; this is 65 ℃ lower than that of the pristine sample. The dehydrogenated sample is completely hydrogenated at 115 ℃ and 100 bar of hydrogen pressure with a hydrogen capacity of 4.5 wt.%. Structural analyses reveal that the Ti undergoes a reduction process of Ti^4＋→Ti^3＋→Ti^2＋→Ti during the ball milling and heating processes, and further converts to Ti hydrides or forms Ti-Al species after rehydrogenation. The catalytic activities of Ti-based catalytic species decrease in the order Al-Ti-species 〉 TiH0.71 〉 TiH2 〉 TiO2. This understanding guides further improvement in hydrogen storage properties of metal alanates using nanocrvstalline transition metal-based additives.展开更多
In this paper,the microstructure and hydrogen storage properties of the（NaH/Al）+x（molar fraction,%） Ti（x=0,4,6, 10） composites were investigated.It was found that the reversible hydrogen storage properties can b...In this paper,the microstructure and hydrogen storage properties of the（NaH/Al）+x（molar fraction,%） Ti（x=0,4,6, 10） composites were investigated.It was found that the reversible hydrogen storage properties can be improved by mechanically ball-milling the（NaH/Al） mixture together with Ti powder.H2 is a better ball-milling atmosphere than Ar,because a part of NaH is consumed during the ball-milling under an Ar atmosphere.As the Ti content increases,the hydrogen storage properties are enhanced gradually.In case of x=10,the reversible hydrogen absorption/desorption capacities of the composites milled for 6 h under the H2 atmosphere reach 4.01% and 3.93%（mass fraction）,respectively.The catalytic mechanism of the Ti-doped NaH/Al composites system is discussed briefly.展开更多
文摘Adding a small amount of nanocrystalline TiO2@C （TiO2 supported on nano- porous carbon） composite dramatically decreases the operating temperatures and improves the reaction kinetics for hydrogen storage in NaAlH4. The nano- crystalline TiO2@C composite synthesized at 900 ℃ （referred as TiO2@C-900） exhibits superior catalytic activity to other catalyst-containing samples. The onset dehydrogenation temperature of the TiO2@C-900-containing sample is lowered to 90 ℃; this is 65 ℃ lower than that of the pristine sample. The dehydrogenated sample is completely hydrogenated at 115 ℃ and 100 bar of hydrogen pressure with a hydrogen capacity of 4.5 wt.%. Structural analyses reveal that the Ti undergoes a reduction process of Ti^4＋→Ti^3＋→Ti^2＋→Ti during the ball milling and heating processes, and further converts to Ti hydrides or forms Ti-Al species after rehydrogenation. The catalytic activities of Ti-based catalytic species decrease in the order Al-Ti-species 〉 TiH0.71 〉 TiH2 〉 TiO2. This understanding guides further improvement in hydrogen storage properties of metal alanates using nanocrvstalline transition metal-based additives.
文摘In this paper,the microstructure and hydrogen storage properties of the（NaH/Al）+x（molar fraction,%） Ti（x=0,4,6, 10） composites were investigated.It was found that the reversible hydrogen storage properties can be improved by mechanically ball-milling the（NaH/Al） mixture together with Ti powder.H2 is a better ball-milling atmosphere than Ar,because a part of NaH is consumed during the ball-milling under an Ar atmosphere.As the Ti content increases,the hydrogen storage properties are enhanced gradually.In case of x=10,the reversible hydrogen absorption/desorption capacities of the composites milled for 6 h under the H2 atmosphere reach 4.01% and 3.93%（mass fraction）,respectively.The catalytic mechanism of the Ti-doped NaH/Al composites system is discussed briefly.
基金National Natural Science Foundation Funded Projects(50806007)Central Key Projects of Scientific Research in Colleges and Universities Operating Costs(CHD2011ZD008)
基金National Natural Science Foundation of China (50806007)Central Key Projects Of Scientific Research in Colleges and Universities Operating Costs (CHD2011ZD008, CHD2010ZY015)
