Hydrogen energy is one of the ideal energy alternatives and the upstream of the hydrogen industry chain is hydrogen production,which can be achieved via the reaction of inorganic materials with water,known as hydrolys...Hydrogen energy is one of the ideal energy alternatives and the upstream of the hydrogen industry chain is hydrogen production,which can be achieved via the reaction of inorganic materials with water,known as hydrolysis.Among inorganic materials,the high hydrogen capacity for hydrolysis of MgH_(2)(15.2 wt%)makes it a promising material for hydrogen production via hydrolysis.However,the dense Mg(OH)_(2) passivation layer will block the reaction between MgH_(2) and the solution,resulting in low hydrogen yield and sluggish hydrolysis kinetics.In this work,the hydrogenyield and hydrogen generation rate of MgH_(2) are considerably enhanced by adding Ti-Zr-Fe-Mn-Cr-V high-entropy alloys(HEAs) for the first time.In particular.the MgH_(2)-3 wt% TiZrFe_(1.5)MnCrV_(0.5)(labelled as MgH_(2)-3 wt% Fe_(1.5)) composite releases 1526.70 mL/g H_(2) within 5 min at 40℃,and the final hydrolysis conversion rate reaches 95.62% within 10 min.The mean hydrogen generation rate of the MgH_(2)-3 wt% Fe_(1.5) composite is 289.16 mL/g/min,which is 2.38 times faster than that of pure MgH_(2).Meanwhile,the activation energy of the MgH_(2)-3 wt% Fe_(1.5) composite is calculated to be 12.53 kJ/mol. The density functional theory(DFT) calculation reveals that the addition of HEAs weakens the Mg-H bonds and accelerates the electron transfer between MgH_(2) and HEAs,Combined with the cocktail effect of HEAs as well as the formation of more interfaces and micro protocells,the hydrolysis performance of MgH_(2) is considerably improved.This work provides an appealing prospect for real-time hydrogen supply and offers a new effective strategy for improving the hydrolysis performance of MgH_(2).展开更多
Ni and carbon materials exhibit remarkable catalysis for the hydriding reaction of Mg.But the underlying mechanism of Ni/C hybrid catalysis is still unclear.In this work,density functional theory(DFT)calculation is ap...Ni and carbon materials exhibit remarkable catalysis for the hydriding reaction of Mg.But the underlying mechanism of Ni/C hybrid catalysis is still unclear.In this work,density functional theory(DFT)calculation is applied to investigate the effect of Ni/C co-incorporation on the hydriding reaction of Mg crystal.The morphology and crystal structure of the Ni/C co-incorporated Mg sample show that the coincorporated structure is credible.The transition state searching calculation suggests that both the incorporations of Ni and C are beneficial for the H_(2) dissociation.But Ni atom has a dramatic improvement for H_(2) dissociation and makes the H diffusion become limiting step of the hyriding reaction.The Ni dz_(2)orbit and H s orbit accept the electrons and combine together compactly,while the Ni d_(xy) orbit is half-occupied.The catalytic effect of Ni on H_(2) dissociation can be ascribed to the bridging effect of Ni d_(xy) orbit.The incorporation of C can weaken the over-strong interaction between Ni and H which hindered the H diffusion on Mg(0001).The Ni/C co-incorporated Mg(0001)shows the best performance during hyriding reaction compared with the clean and single incorporated Mg(0001).展开更多
The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydro...The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydrogenation properties of MgH_(2)@Ni-CNTs was studied by DFT simulation,and the corresponding models were constructed based on MS.The dehydrogenation process of MgH_(2)can be regarded as the dissociation of Mg-H and desorption of H_(2)from the MgH_(2)surface.In view of the whole dehydrogenation,the dissociation of H^(−)is the rate-determining step,which is the main reason for restricting the dehydrogenation kinetics.Compared with vacancy vacancy-defective MgH_(2)(001)surface,the appearance of vacancy defects on the(110)surface substantially reduces the energy barrier required for H dissociation to 0.070 Ha.The reason is that vacancy defects accelerate the transition of electrons from the H^(−)s orbit to the Mg^(2+)3s orbit,resulting in a decrement of the Mg-H bond strength,which makes H atoms more easily dissociated from the MgH_(2)(110)surface.Therefore,the existence of vacancy defects improves the dehydriding kinetic of MgH_(2).Most importantly,this research offers crucial directions for developing hydrogen storage materials as well as a potential fix for the slow dehydrogenation kinetics of nano-confined MgH_(2).展开更多
Magnesium is one of the most promising candidates of light metal materials for hydrogen production by hydrolysis due to its efficient and economical properties.Various modification methods have been investigated to im...Magnesium is one of the most promising candidates of light metal materials for hydrogen production by hydrolysis due to its efficient and economical properties.Various modification methods have been investigated to improve the hydrolytic properties of Mg.However,the direction of the design of efficient catalysts is unclear and needs to be guided by a richer catalytic mechanism of hydrolysis.In this work,a simple approach was used to synthesize Few Layer Graphene(FLG)-loaded ultra-fine highly dispersed Ni/Sc_(2)O_(3)nanocatalyst,which achieves impressive catalytic hydrolysis results.Here,the addition of 4 wt%Ni/Sc_(2)O_(3)@FLG catalyst allows Mg to produce 833 mL g^(-1)of H_(2) in 20 s at 30℃.There is an initial hydrogen release rate as high as 5942 mL g^(-1)min^(-1),a final hydrogen yield of 859 mL g^(-1)(99.13%),and almost complete conversion of Mg to Mg(OH)_(2).Furthermore,surprisingly,even with only 0.2 wt%catalysts added,Mg still has an initial hydrogen generation rate of 3627 mL g^(-1)min^(-1),which is over 20 times faster than that of Mg.It also produces 690 mL g^(-1)of H_(2) in 30 s at 30℃.Hydrolysis kinetic curves and microscopic morphology tests show that FLG could shape and hold Mg into thin sheets,giving them an ultra-high hydrolysis rate and conversion rate.The formation of micro-galvanic cells between Ni and Mg accelerates the electrochemical corrosion of Mg and greatly enhances electron transfer during hydrolysis.This work provides a new strategy for the preparation of efficient nanocatalysts,which is expected to make“Mg-efficient catalyst”the most ideal light metal-based material for hydrogen production by hydrolysis.展开更多
MgH_(2)has a high theoretical hydrogen production capacity and mild conditions for hydrogen production by hydrolysis,so it is suitable as an ideal hydrogen source for fuel cells.However,with the progress of the hydrol...MgH_(2)has a high theoretical hydrogen production capacity and mild conditions for hydrogen production by hydrolysis,so it is suitable as an ideal hydrogen source for fuel cells.However,with the progress of the hydrolysis reaction,MgH_(2)is impeded from reacting further by the continuous deposition of magnesium hydroxide on its surface,resulting in low hydrogen yield and slow reaction kinetics.In the present work,a highly efficient NiCo bimetallic synergistic catalysis is developed to improve the hydrolysis performance of MgH_(2).The MgH_(2)-8 wt%NiCo@C composite ball-milled for 5 h achieves nearly 100%hydrogen desorp-tion efficiency within 15 min in 0.05 mol L^(-1)MgCl_(2)solution.Because the interaction between Ni and Co on the surface of MgH_(2)can form a channel for rapid hydrogen evolution,which hinders the continuous formation of the Mg(OH)_(2)passivation layer and promotes the hydrolysis reaction of MgH_(2).This is very important for the implementation of MgH_(2)hydrolysis to produce hydrogen in the future.展开更多
Metal borohydride ammoniates have become one of the most promising hydrogen storage materials due to their ultrahigh capacities.However,their application is still restricted by the high temperature of hydrogen desorpt...Metal borohydride ammoniates have become one of the most promising hydrogen storage materials due to their ultrahigh capacities.However,their application is still restricted by the high temperature of hydrogen desorption and the release of ammonia.Here,to promote the dehydrogenation evolution and suppress the ammonia release,different amounts of NbF 5 were introduced into Mg(BH4)2·2NH3.Compared to the pure Mg(BH_(4))_(2)·2NH_(3),the Mg(BH_(4))_(2)·2NH_(3)-NbF_(5) composites exhibit lower onset dehydriding temperatures(53–57℃)and higher dehydriding capacities(5.6 wt.%–8.2 wt.%)at below 200℃,with the complete suppression of ammonia.In addition,7.4 wt.%H_(2) could be released from Mg(BH_(4))_(2)·2NH_(3)–5 mol%NbF5 composite at 200℃ within 20 min and the apparent activation energy is calculated to be 60.28 kJ mol^(-1),which is much lower than that of pure Mg(BH_(4))_(2)·2NH_(3)(92.04 kJ mol^(-1)).Mg(BH_(4))_(2)·2NH_(3) should mechanochemically react with NbF5,forming dual-metal(Mg,Nb)borohydride ammoniate and spherical MgF2.The introduction of electronegative Nb cation results in-situ formation of(Mg,Nb)borohydride ammoniate towards a lower dehydrogenation temperature and a higher hydrogen release purity.The increased phase boundaries among the Mg(BH_(4))_(2)·2NH_(3),dual-metal(Mg,Nb)borohydride ammoniate,and MgF2 phases further facilitate the hydrogen diffusion during the dehydrogenation of the composites.展开更多
Complex metal oxide catalysts greatly accelerate the hydrogen sorption rates in the magnesium hydride system.In this study,the graphene-supported Sc_(2)O_(3)/TiO_(2) catalyst is synthesized by means of a simple method...Complex metal oxide catalysts greatly accelerate the hydrogen sorption rates in the magnesium hydride system.In this study,the graphene-supported Sc_(2)O_(3)/TiO_(2) catalyst is synthesized by means of a simple method,and a surprisingly synergetic effect of the Sc_(2)O_(3)-TiO_(2) cocatalyst on the hydrogen storage performance of MgH_(2) is observed.The MgH_(2)-Sc_(2)O_(3)/TiO_(2)@Gn composite starts to release hydrogen at 140°C and reaches the peak dehydrogenation temperature at 239.9°C.It absorbs 6.55 wt%of H_(2) in 1 min and desorbs 5.71 wt%of H_(2) in 10 min at 300°C,showing excellent hydrogen absorption and desorption performance.Furthermore,with the decrease of the grain size and changes in the structure,the activity of the catalyst is greatly improved.The low-valent titanium and scandium and oxygen vacancies formed in the process of dehydrogenation facilitate hydrogen diffusion and electron transfer,and further improve the kinetic performance of the Mg/MgH_(2)-Sc_(2)O_(3)/TiO_(2)@Gn system.This study aims to provide insights into studying complex metal oxides as catalysts to improve hydrogen storage performance,and shed light on other catalysis-related research.展开更多
基金financed by the National Key Research and Development Program of China [2022YFB3803703]the National Natural Science Foundation of China [52071141, 52271212, 52201250, 51771056]the Interdisciplinary Innovation Program of North China Electric Power University [XM2112355]。
文摘Hydrogen energy is one of the ideal energy alternatives and the upstream of the hydrogen industry chain is hydrogen production,which can be achieved via the reaction of inorganic materials with water,known as hydrolysis.Among inorganic materials,the high hydrogen capacity for hydrolysis of MgH_(2)(15.2 wt%)makes it a promising material for hydrogen production via hydrolysis.However,the dense Mg(OH)_(2) passivation layer will block the reaction between MgH_(2) and the solution,resulting in low hydrogen yield and sluggish hydrolysis kinetics.In this work,the hydrogenyield and hydrogen generation rate of MgH_(2) are considerably enhanced by adding Ti-Zr-Fe-Mn-Cr-V high-entropy alloys(HEAs) for the first time.In particular.the MgH_(2)-3 wt% TiZrFe_(1.5)MnCrV_(0.5)(labelled as MgH_(2)-3 wt% Fe_(1.5)) composite releases 1526.70 mL/g H_(2) within 5 min at 40℃,and the final hydrolysis conversion rate reaches 95.62% within 10 min.The mean hydrogen generation rate of the MgH_(2)-3 wt% Fe_(1.5) composite is 289.16 mL/g/min,which is 2.38 times faster than that of pure MgH_(2).Meanwhile,the activation energy of the MgH_(2)-3 wt% Fe_(1.5) composite is calculated to be 12.53 kJ/mol. The density functional theory(DFT) calculation reveals that the addition of HEAs weakens the Mg-H bonds and accelerates the electron transfer between MgH_(2) and HEAs,Combined with the cocktail effect of HEAs as well as the formation of more interfaces and micro protocells,the hydrolysis performance of MgH_(2) is considerably improved.This work provides an appealing prospect for real-time hydrogen supply and offers a new effective strategy for improving the hydrolysis performance of MgH_(2).
基金This work is supported by the National Key R&D Program of China(Grant No.2017YFB0103002)National Natural Science Foundation of China(Grant Nos.51771056,51371056,51701043 and 52071141)+4 种基金Equipment Preresearch Field Foundation(Grant No.6140721040101)Equipment Preresearch Sharing Technology(No.41421060201)Changzhou Leading Talents Project(Grant No.CQ20183020)333 Project in Jiangsu Province and the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,Fundamental Research Funds for the Central Universities(Grant No.2021MS051)Interdisciplinary Innovation Program of North China Electric Power University(grant number XM2112355).
文摘Ni and carbon materials exhibit remarkable catalysis for the hydriding reaction of Mg.But the underlying mechanism of Ni/C hybrid catalysis is still unclear.In this work,density functional theory(DFT)calculation is applied to investigate the effect of Ni/C co-incorporation on the hydriding reaction of Mg crystal.The morphology and crystal structure of the Ni/C co-incorporated Mg sample show that the coincorporated structure is credible.The transition state searching calculation suggests that both the incorporations of Ni and C are beneficial for the H_(2) dissociation.But Ni atom has a dramatic improvement for H_(2) dissociation and makes the H diffusion become limiting step of the hyriding reaction.The Ni dz_(2)orbit and H s orbit accept the electrons and combine together compactly,while the Ni d_(xy) orbit is half-occupied.The catalytic effect of Ni on H_(2) dissociation can be ascribed to the bridging effect of Ni d_(xy) orbit.The incorporation of C can weaken the over-strong interaction between Ni and H which hindered the H diffusion on Mg(0001).The Ni/C co-incorporated Mg(0001)shows the best performance during hyriding reaction compared with the clean and single incorporated Mg(0001).
基金financed by the National Key Research and Development Program of China(Grant No.2021YFB3802400)the National Natural Science Foundation of China(Grants Nos.52071141,52271212,52201250,and 51771056)+1 种基金the Natural Science Foundation of Hebei Province(Grant No.E2018502054)the Fundamental Research Funds for the Central Universities(Grant No.2023MS148).
文摘The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydrogenation properties of MgH_(2)@Ni-CNTs was studied by DFT simulation,and the corresponding models were constructed based on MS.The dehydrogenation process of MgH_(2)can be regarded as the dissociation of Mg-H and desorption of H_(2)from the MgH_(2)surface.In view of the whole dehydrogenation,the dissociation of H^(−)is the rate-determining step,which is the main reason for restricting the dehydrogenation kinetics.Compared with vacancy vacancy-defective MgH_(2)(001)surface,the appearance of vacancy defects on the(110)surface substantially reduces the energy barrier required for H dissociation to 0.070 Ha.The reason is that vacancy defects accelerate the transition of electrons from the H^(−)s orbit to the Mg^(2+)3s orbit,resulting in a decrement of the Mg-H bond strength,which makes H atoms more easily dissociated from the MgH_(2)(110)surface.Therefore,the existence of vacancy defects improves the dehydriding kinetic of MgH_(2).Most importantly,this research offers crucial directions for developing hydrogen storage materials as well as a potential fix for the slow dehydrogenation kinetics of nano-confined MgH_(2).
基金supported by the National Key R&D Program of China(No.2022YFB3803700)the National Natural Science Foun-dation of China(Grant Nos.52071141,52271212,52201250,and 51771056)+1 种基金Interdisciplinary Innovation Program of North China Electric Power University(No.XM2112355)the Double-First Class project for the NCEPU.
文摘Magnesium is one of the most promising candidates of light metal materials for hydrogen production by hydrolysis due to its efficient and economical properties.Various modification methods have been investigated to improve the hydrolytic properties of Mg.However,the direction of the design of efficient catalysts is unclear and needs to be guided by a richer catalytic mechanism of hydrolysis.In this work,a simple approach was used to synthesize Few Layer Graphene(FLG)-loaded ultra-fine highly dispersed Ni/Sc_(2)O_(3)nanocatalyst,which achieves impressive catalytic hydrolysis results.Here,the addition of 4 wt%Ni/Sc_(2)O_(3)@FLG catalyst allows Mg to produce 833 mL g^(-1)of H_(2) in 20 s at 30℃.There is an initial hydrogen release rate as high as 5942 mL g^(-1)min^(-1),a final hydrogen yield of 859 mL g^(-1)(99.13%),and almost complete conversion of Mg to Mg(OH)_(2).Furthermore,surprisingly,even with only 0.2 wt%catalysts added,Mg still has an initial hydrogen generation rate of 3627 mL g^(-1)min^(-1),which is over 20 times faster than that of Mg.It also produces 690 mL g^(-1)of H_(2) in 30 s at 30℃.Hydrolysis kinetic curves and microscopic morphology tests show that FLG could shape and hold Mg into thin sheets,giving them an ultra-high hydrolysis rate and conversion rate.The formation of micro-galvanic cells between Ni and Mg accelerates the electrochemical corrosion of Mg and greatly enhances electron transfer during hydrolysis.This work provides a new strategy for the preparation of efficient nanocatalysts,which is expected to make“Mg-efficient catalyst”the most ideal light metal-based material for hydrogen production by hydrolysis.
基金This work was financially supported by the National Key Re-search and Development Program of China(No.2021YFB3802400)the National Natural Science Foundation of China(Nos.51771056,51371056,51701043,and 52071141)+1 种基金the Interdisciplinary Innovation Program of North China Electric Power University(No.XM2112355)the Double-First Class project for the NCEPU.
文摘MgH_(2)has a high theoretical hydrogen production capacity and mild conditions for hydrogen production by hydrolysis,so it is suitable as an ideal hydrogen source for fuel cells.However,with the progress of the hydrolysis reaction,MgH_(2)is impeded from reacting further by the continuous deposition of magnesium hydroxide on its surface,resulting in low hydrogen yield and slow reaction kinetics.In the present work,a highly efficient NiCo bimetallic synergistic catalysis is developed to improve the hydrolysis performance of MgH_(2).The MgH_(2)-8 wt%NiCo@C composite ball-milled for 5 h achieves nearly 100%hydrogen desorp-tion efficiency within 15 min in 0.05 mol L^(-1)MgCl_(2)solution.Because the interaction between Ni and Co on the surface of MgH_(2)can form a channel for rapid hydrogen evolution,which hinders the continuous formation of the Mg(OH)_(2)passivation layer and promotes the hydrolysis reaction of MgH_(2).This is very important for the implementation of MgH_(2)hydrolysis to produce hydrogen in the future.
基金supported by the National Key Research and Development Plan(Grant No.2021YFB3802400)the National Natural Science Foundation of China(Grant Nos.52071141,52271212,52201250)+1 种基金the Equipment Pre-research Field Foundation(Grant No.6140721040101)the Interdisciplinary Innovation Program of North China Electric Power University(Grant No.XM2112355).
文摘Metal borohydride ammoniates have become one of the most promising hydrogen storage materials due to their ultrahigh capacities.However,their application is still restricted by the high temperature of hydrogen desorption and the release of ammonia.Here,to promote the dehydrogenation evolution and suppress the ammonia release,different amounts of NbF 5 were introduced into Mg(BH4)2·2NH3.Compared to the pure Mg(BH_(4))_(2)·2NH_(3),the Mg(BH_(4))_(2)·2NH_(3)-NbF_(5) composites exhibit lower onset dehydriding temperatures(53–57℃)and higher dehydriding capacities(5.6 wt.%–8.2 wt.%)at below 200℃,with the complete suppression of ammonia.In addition,7.4 wt.%H_(2) could be released from Mg(BH_(4))_(2)·2NH_(3)–5 mol%NbF5 composite at 200℃ within 20 min and the apparent activation energy is calculated to be 60.28 kJ mol^(-1),which is much lower than that of pure Mg(BH_(4))_(2)·2NH_(3)(92.04 kJ mol^(-1)).Mg(BH_(4))_(2)·2NH_(3) should mechanochemically react with NbF5,forming dual-metal(Mg,Nb)borohydride ammoniate and spherical MgF2.The introduction of electronegative Nb cation results in-situ formation of(Mg,Nb)borohydride ammoniate towards a lower dehydrogenation temperature and a higher hydrogen release purity.The increased phase boundaries among the Mg(BH_(4))_(2)·2NH_(3),dual-metal(Mg,Nb)borohydride ammoniate,and MgF2 phases further facilitate the hydrogen diffusion during the dehydrogenation of the composites.
基金National Key R&D Program of China(no.2022YFB3803700)National Natural Science Foundation of China(grant nos.52071141,52271212,52201250,and 51771056)+1 种基金Interdisciplinary Innovation Program of North China Electric Power University(no.XM2112355)Double-First Class project for the NCEPU.
文摘Complex metal oxide catalysts greatly accelerate the hydrogen sorption rates in the magnesium hydride system.In this study,the graphene-supported Sc_(2)O_(3)/TiO_(2) catalyst is synthesized by means of a simple method,and a surprisingly synergetic effect of the Sc_(2)O_(3)-TiO_(2) cocatalyst on the hydrogen storage performance of MgH_(2) is observed.The MgH_(2)-Sc_(2)O_(3)/TiO_(2)@Gn composite starts to release hydrogen at 140°C and reaches the peak dehydrogenation temperature at 239.9°C.It absorbs 6.55 wt%of H_(2) in 1 min and desorbs 5.71 wt%of H_(2) in 10 min at 300°C,showing excellent hydrogen absorption and desorption performance.Furthermore,with the decrease of the grain size and changes in the structure,the activity of the catalyst is greatly improved.The low-valent titanium and scandium and oxygen vacancies formed in the process of dehydrogenation facilitate hydrogen diffusion and electron transfer,and further improve the kinetic performance of the Mg/MgH_(2)-Sc_(2)O_(3)/TiO_(2)@Gn system.This study aims to provide insights into studying complex metal oxides as catalysts to improve hydrogen storage performance,and shed light on other catalysis-related research.
