Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydr...Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of alloys were systematically investigated.The hydrogen desorption properties were studied by Sievert apparatus and a differential scanning calorimeter(DSC).Thermodynamic parameters(△H and ΔS) for the hydrogen absorption and desorption of alloys were calculated by Van't Hoff equation.Hydrogen desorption activation energy of alloy hydride was estimated by Arrhenius and Kissinger methods.The increase in Ni content has a slight effect on the thermodynamic properties of alloys,but it significantly enhances the hydrogen absorption and desorption kinetics performance of alloys.Moreover,variation of milling time clearly affects the hydrogen storage properties of alloys.Hydrogen absorption capacity(C(100)~a) and hydrogen absorption saturation ratio(R(10)~a)(a ratio of the hydrogen absorption capacity at 10 min to the saturated hydrogen absorption capacity) have maximum values with milling time varying.But hydrogen desorption ratio(R(20)~d)(a ratio of the hydrogen desorption capacity at 20 min to the saturated hydrogen absorption capacity) always increases with milling time prolonging.Particularly,prolonging milling time from 5 to 60 h makes R(20)~d increase from 10.89% to 16.36% for the x=100 alloy and from 13.93% to 21.68% for the x=200 alloy,respectively.展开更多
The nanocrystalline and amorphous LaMg11Ni ＋ x wt% Ni （x = 100, 200） composites were synthesized by the mechanical milling, and their gaseous and electrochemical hydrogen storage kinetics performance were systemati...The nanocrystalline and amorphous LaMg11Ni ＋ x wt% Ni （x = 100, 200） composites were synthesized by the mechanical milling, and their gaseous and electrochemical hydrogen storage kinetics performance were systematically investigated, The results indicate that the as-milled composites exhibit excellent hydrogen storage kinetic performances, and increasing Ni content significantly facilitates the improvement of the hydrogen storage kinetics properties of the composites. The gaseous and electrochemical hydrogen storage kinetics of the composites reaches a maximum value with the variation of milling time. Increasing Ni content and milling time both make the hydrogen desorption activation energy lower, which are responsible for the enhancement in the hydrogen storage kinetics properties of the composites. The diffusion coefficient of hydrogen atom and activation enthalpy of charge transfer on the surface of the as-milled composites were also calculated, which are considered to be the dominated factors for the electrochemical high rate discharge ability.展开更多
Nanocrystalline and amorphous LaMg_（12）-type LaMg_（11）Ni ＋ x wt% Ni（x = 100, 200） alloys were synthesized by mechanical milling. Effects of Ni content and milling time on the gaseous and electrochemical hydroge...Nanocrystalline and amorphous LaMg_（12）-type LaMg_（11）Ni ＋ x wt% Ni（x = 100, 200） alloys were synthesized by mechanical milling. Effects of Ni content and milling time on the gaseous and electrochemical hydrogen storage kinetics of as-milled alloys were investigated systematically. The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galvanostatic system. And the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter（DSC） connected with a H_2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. It is found that the increase of Ni content significantly improves the gaseous and electrochemical hydrogen storage kinetic performances of as-milled alloys. Furthermore, as ball milling time changes, the maximum of both high rate discharge ability（HRD） and the gaseous hydriding rate of as-milled alloys can be obtained. But the hydrogen desorption kinetics of alloys always increases with the extending of milling time. Moreover, the improved gaseous hydrogen storage kinetics of alloys are ascribed to a decrease in the hydrogen desorption activation energy caused by increasing Ni content and milling time.展开更多
LaMg11Ni+x wt.%Ni(x=100,200)alloys were prepared by ball milling and researched by various methods to study their structure and electrochemical hydrogen storage property.The outcomes reveal that increasing Ni content ...LaMg11Ni+x wt.%Ni(x=100,200)alloys were prepared by ball milling and researched by various methods to study their structure and electrochemical hydrogen storage property.The outcomes reveal that increasing Ni content contributes to improving its electrochemical performance.Particularly,the discharge capacity of as-milled(40 h)alloy will be increased from 157.3 to 1053.5 mAh/g through enhancing Ni percentage from 100 to 200 wt.%when discharging at 60 mAh/g.Ball milling obviously affects the electrochemical performanee of alloys.With milling duration prolonging,the discharge capacity of x=100 alloy keeps increasing,while that of the x=200 alloy has a maximum value.Milling time also affects the cycle stability of experimental alloys.Extendi ng milli ng duration clearly decreases the cycle stability of x=100 alloy but weakens that of the x=200 alloy at first and strengthens it later.In addition,prolonging milling time makes the milling prepared x=100 and 200 alloys get the maximal values of high rate discharge ability of 81.60%and 84.52%,respectively.展开更多
Solid solutions between LaNbON_(2)and LaMg_(2/3)Nb_(1/3)O_(3),i.e.(LaNbON_(2))_(1−x)(LaMg_(2/3)Nb_(1/3)O_(3))_(x)(0.0≤x≤1.0),have been investigated as photocatalysts for water oxidation into oxygen under visible lig...Solid solutions between LaNbON_(2)and LaMg_(2/3)Nb_(1/3)O_(3),i.e.(LaNbON_(2))_(1−x)(LaMg_(2/3)Nb_(1/3)O_(3))_(x)(0.0≤x≤1.0),have been investigated as photocatalysts for water oxidation into oxygen under visible light illumination(λ≥420 nm).Many important parameters are strongly correlated with solid solution levels,including band gap,nitrogen content,defect concentration,band edge alignments,etc.This offers us a useful tool to steer photocatalytic performance among these solid solutions.Much improved photocatalytic activity is noticed for(LaNbON_(2))_(0.8)(LaMg_(2/3)Nb_(1/3)O_(3))_(0.2)(x=0.2),which gives an AQE as high as 0.53%at 420±20 nm.This useful strategy by forming solid solutions opens new playgrounds full of opportunities for the design and development of efficient photocatalysts for solar energy conversions.展开更多
利用第一原理赝势平面波方法计算了C aM g2N i9,L aM g2N i9贮氢合金的电子结构,分析了合金中原子间的相互作用以及对合金稳定性的影响.结果表明:L aM g2N i9中N i-N i间的作用比C aM g2N i9中相应的原子间的作用强,使得C aM g2N i9比L ...利用第一原理赝势平面波方法计算了C aM g2N i9,L aM g2N i9贮氢合金的电子结构,分析了合金中原子间的相互作用以及对合金稳定性的影响.结果表明:L aM g2N i9中N i-N i间的作用比C aM g2N i9中相应的原子间的作用强,使得C aM g2N i9比L aM g2N i9易于完成由N i-N i键到N i-H的转移,是导致L aM g2N i9合金吸氢量比C aM g2N i9合金吸氢量少的原因之一.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51371094 and 51471054)
文摘Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of alloys were systematically investigated.The hydrogen desorption properties were studied by Sievert apparatus and a differential scanning calorimeter(DSC).Thermodynamic parameters(△H and ΔS) for the hydrogen absorption and desorption of alloys were calculated by Van't Hoff equation.Hydrogen desorption activation energy of alloy hydride was estimated by Arrhenius and Kissinger methods.The increase in Ni content has a slight effect on the thermodynamic properties of alloys,but it significantly enhances the hydrogen absorption and desorption kinetics performance of alloys.Moreover,variation of milling time clearly affects the hydrogen storage properties of alloys.Hydrogen absorption capacity(C(100)~a) and hydrogen absorption saturation ratio(R(10)~a)(a ratio of the hydrogen absorption capacity at 10 min to the saturated hydrogen absorption capacity) have maximum values with milling time varying.But hydrogen desorption ratio(R(20)~d)(a ratio of the hydrogen desorption capacity at 20 min to the saturated hydrogen absorption capacity) always increases with milling time prolonging.Particularly,prolonging milling time from 5 to 60 h makes R(20)~d increase from 10.89% to 16.36% for the x=100 alloy and from 13.93% to 21.68% for the x=200 alloy,respectively.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51161015 and 51371094)
文摘The nanocrystalline and amorphous LaMg11Ni ＋ x wt% Ni （x = 100, 200） composites were synthesized by the mechanical milling, and their gaseous and electrochemical hydrogen storage kinetics performance were systematically investigated, The results indicate that the as-milled composites exhibit excellent hydrogen storage kinetic performances, and increasing Ni content significantly facilitates the improvement of the hydrogen storage kinetics properties of the composites. The gaseous and electrochemical hydrogen storage kinetics of the composites reaches a maximum value with the variation of milling time. Increasing Ni content and milling time both make the hydrogen desorption activation energy lower, which are responsible for the enhancement in the hydrogen storage kinetics properties of the composites. The diffusion coefficient of hydrogen atom and activation enthalpy of charge transfer on the surface of the as-milled composites were also calculated, which are considered to be the dominated factors for the electrochemical high rate discharge ability.
基金Funded by the National Natural Science Foundation of China(Nos.51471054,51761032,and 51371094)the Natural Science Foundation of Inner Mongolia,China(No.2015MS0558)
文摘Nanocrystalline and amorphous LaMg_（12）-type LaMg_（11）Ni ＋ x wt% Ni（x = 100, 200） alloys were synthesized by mechanical milling. Effects of Ni content and milling time on the gaseous and electrochemical hydrogen storage kinetics of as-milled alloys were investigated systematically. The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galvanostatic system. And the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter（DSC） connected with a H_2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. It is found that the increase of Ni content significantly improves the gaseous and electrochemical hydrogen storage kinetic performances of as-milled alloys. Furthermore, as ball milling time changes, the maximum of both high rate discharge ability（HRD） and the gaseous hydriding rate of as-milled alloys can be obtained. But the hydrogen desorption kinetics of alloys always increases with the extending of milling time. Moreover, the improved gaseous hydrogen storage kinetics of alloys are ascribed to a decrease in the hydrogen desorption activation energy caused by increasing Ni content and milling time.
基金the National Natural Science Foundations of China(51161015 and 51371094).
文摘LaMg11Ni+x wt.%Ni(x=100,200)alloys were prepared by ball milling and researched by various methods to study their structure and electrochemical hydrogen storage property.The outcomes reveal that increasing Ni content contributes to improving its electrochemical performance.Particularly,the discharge capacity of as-milled(40 h)alloy will be increased from 157.3 to 1053.5 mAh/g through enhancing Ni percentage from 100 to 200 wt.%when discharging at 60 mAh/g.Ball milling obviously affects the electrochemical performanee of alloys.With milling duration prolonging,the discharge capacity of x=100 alloy keeps increasing,while that of the x=200 alloy has a maximum value.Milling time also affects the cycle stability of experimental alloys.Extendi ng milli ng duration clearly decreases the cycle stability of x=100 alloy but weakens that of the x=200 alloy at first and strengthens it later.In addition,prolonging milling time makes the milling prepared x=100 and 200 alloys get the maximal values of high rate discharge ability of 81.60%and 84.52%,respectively.
基金National Natural Science Foundation of China(Grant no.51972233)Natural Science Foundation of Shanghai(Grant no.19ZR1459200)+1 种基金Shanghai Science and Technology Commission(14DZ2261100)Fundamental Research Funds for the Central Universities。
文摘Solid solutions between LaNbON_(2)and LaMg_(2/3)Nb_(1/3)O_(3),i.e.(LaNbON_(2))_(1−x)(LaMg_(2/3)Nb_(1/3)O_(3))_(x)(0.0≤x≤1.0),have been investigated as photocatalysts for water oxidation into oxygen under visible light illumination(λ≥420 nm).Many important parameters are strongly correlated with solid solution levels,including band gap,nitrogen content,defect concentration,band edge alignments,etc.This offers us a useful tool to steer photocatalytic performance among these solid solutions.Much improved photocatalytic activity is noticed for(LaNbON_(2))_(0.8)(LaMg_(2/3)Nb_(1/3)O_(3))_(0.2)(x=0.2),which gives an AQE as high as 0.53%at 420±20 nm.This useful strategy by forming solid solutions opens new playgrounds full of opportunities for the design and development of efficient photocatalysts for solar energy conversions.
文摘利用第一原理赝势平面波方法计算了C aM g2N i9,L aM g2N i9贮氢合金的电子结构,分析了合金中原子间的相互作用以及对合金稳定性的影响.结果表明:L aM g2N i9中N i-N i间的作用比C aM g2N i9中相应的原子间的作用强,使得C aM g2N i9比L aM g2N i9易于完成由N i-N i键到N i-H的转移,是导致L aM g2N i9合金吸氢量比C aM g2N i9合金吸氢量少的原因之一.
