硼基和氮基化学储氢材料研究进展.pdf
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1、RECENT PROGRESS IN BORON-AND NITROGEN-BASEDCHEMICAL HYDROGEN STORAGEZHANG-HUI LU and QIANG XU*National Institute of Advanced Industrial Science and Technology(AIST)Ikeda,Osaka 563-8577,Japan,and Graduate School of EngineeringKobe University,Nada Ku,Kobe,Hyogo 657-8501,Japan*q.xuaist.go.jpReceived 27
2、 November 2011;Accepted 25 December 2011;Published 6 April 2012Boron-and nitrogen-based chemical hydrogen storage materials,such as metal borohydrides,ammonia borane,hydrazine borane,metal-nitrogen-hydrogen systems,ammonia,and hydrazine,have been extensively investigated in the past years.A variety
3、ofmethods have been developed to decrease the reaction temperature and enhance the reaction kinetics of these systems.This featurearticle is to serve as an up to date account of the recent progress in chemical hydrogen storage with the boron-and nitrogen-basedmaterials.Keywords:Hydrogen storage;boro
4、n-based chemical hydrides;nitrogen-based chemical hydrides;dehydrogenation.1.IntroductionThere is an increasing and impending demand for sufficientenergy supply along with the continuously growing popu-lation and the rising standards of living in the world.Hydrogen has attracted considerable attenti
5、on as a globallyaccepted clean energy carrier.The use of hydrogen fuel cellsin portable electronic devices or vehicles requires lightweighthydrogen storage or on-board hydrogen generation.Cur-rently,the search of safe and efficient hydrogen storagematerials is one of the most difficult challenges fo
6、r thetransformation to hydrogen-powered society as a long-termsolution for a secure energy future.1Vehicular applications and off-board uses enforce scien-tific efforts to discover hydrogen storage materials that canstore and release hydrogen in a safe and efficient way.Forvehicular applications,the
7、 U.S.Departments of Energy(DOE)has set storage targets;the gravimetric(volumetric)system targets for near-ambient temperature(?40C?85C)and moderate pressure(100bar)are 6.0wt.%(45g/L)forthe year 2010 and 9.0wt.%(81g/L)for 2015.2In order tomeet the targets set by the U.S.DOE,different storagesolutions
8、 have been developed and a large number of litera-tures on hydrogen storage materials,such as metal hydrides,1on-board reforming of hydrocarbon into hydrogen,3metalorganic frameworks,4,5and organic hydrides,6have beenreported.However,big challenges still remain.Chemical storage materials with high h
9、ydrogen contentsare highly promising as hydrogen sources for fuel cells.Among them,boron-and nitrogen-based compounds,such asmetal borohydrides,7ammonia borane,8hydrazine bor-ane,9,10metal-nitrogen-hydrogen systems,11ammonia,12andhydrazine,13,14have been extensively investigated in the pastyears.Thi
10、s feature article is to serve as an up to date accountof the recent progress in chemical hydrogen storage withthese boron-and nitrogen-based compounds.2.Boron-based Chemical Hydrides2.1.Metal borohydridesMetal borohydrides have received considerable researchinterest as potential hydrogen storage mat
11、erials owing to theirhigher gravimetric and volumetric hydrogen capacity.7,15?17Lithium borohydride(LiBH4,LB)is a stable white solid witha hydrogen content of 18.5wt.%and reacts slowly with waterto produce H2but relatively stable in dry air.Hydrogendesorption from LB is highly endothermic and the hi
12、ghtemperature(400C)was required for the dehydrogenationof pure LB.18A number of approaches have been adopted todestabilize LB for hydrogen storage.Ball milling LB 2LiNH2gave a composite with a chemical compositionof Li3BN2H8,which is capable of releasing more than10wt.%of H2in the temperature range
13、of 250?350CFunctional Materials LettersVol.5,No.1(2012)1230001(9 pages)World Scientific Publishing CompanyDOI:10.1142/S17936047123000101230001-1Review(see Table 1).19,20More than 9wt.%of H2can be releasedfrom the LB 2LiNH2mixture at ca.180C in the presenceof 2.6mol%of Co catalyst.21In particular,it
14、was reportedthat 17.8wt.%of H2can be released from the Co-catalyzedlithium borohydride ammoniate,LiNH343BH4,in thetemperature range of 135C?250C(Table 1),22which isthe highest amount of H2emission in the temperature rangeever reported for hydrogen storage materials.A very prom-ising concept of desta
15、bilization of LB using MgH2asdestabilizing additive was suggested by Vajo et al.23Theaddition of LiAlH4to LB combined with metal halides as acatalyst was reported to have a significant enhancement in thedehydrogenation kinetics.24Recently,it was found that thenanoscale LB exhibited the ultralow onse
16、t temperature forreleasing H2(at?32C).25An alternative way to generatehydrogen from LB was via hydrolysis.Kojima et al.foundthat the gravimetric and volumetric hydrogen densitiesincreased,followed by a decrease,with increasing H2O/LBratio.26However,during the hydrolysis process for hydrogengeneratio
17、n,the agglomeration of the hydrolysis product ofLB limits its full utilization.27Recently,Weng et al.proposedthat full hydrolysis of LB can be achieved by the addition ofMWCNTs and the hydrogen capacity reached 7.5wt.%intotal.28Sodium borohydride(NaBH4,SB)is stable in dry air andstores 10.8wt.%of hy
18、drogen.The thermolysis of SB is notconceivable because it is achieved at too high temperatures(500C).Recent efforts have been devoted to incorporatingadditives,such as MgH2,29LiAlH4,30CaH2and CaBH42,tothermodynamically destabilize SB toward an lowered tem-perature for hydrogen release.31In the absen
19、ce of an alkalinesolution,SB spontaneously reacts slowly with water and itshydrogen generation rate is low.However,the hydrolysis ofSB can effectively liberate H2at room temperature in thepresence of a catalyst via the following reaction:NaBH4 2H2O!NaBO2 4H2:1Since Schlesinger et al.discovered that
20、SB hydrolysis reac-tion can be significantly accelerated by the addition of acid,32a great variety of catalysts have been examined to acceleratethe SB hydrolysis at room temperature.15Kojima et al.reported that by using Pt-LiCoO2catalyst the hydrogengeneration rates were high compared with those usi
21、ng othermetal and metal oxide.33Krishnan et pared thehydrogen release kinetics using IRA-400 anion resin dis-persed Pt,Ru catalysts and LiCoO2-supported Pt,Ru andPtRu catalysts,and they reported the most effective catalystwas 10wt.%PtRu-LiCoO2.34In addition,some non-nobletransition elements also exh
22、ibited high activities.15Cobaltand nickel borides were the most investigated catalysts.Itwas reported that the catalytic performance of Co3O4for thehydrolysis of SB was at par with the noble metal-basedcatalysts at low concentration of SB and far superior to noblemetal-based catalysts at higher conc
23、entration.35Despiteconsiderable efforts in research and development,the U.S.Department of Energy(DOE)recommended a no-go for SBfor on-board automotive hydrogen storage because the aqu-eous solution of SB does not meet DOE criteria in terms ofstorage capacity,spent fuel recycling and cost.36However,N
24、aBH4may still have a potential for portable applications.37The main challenge today is improve catalyst durability.15Magnesium borohydride(MgBH42)has a hydrogencontent of 14.9wt.%.It decomposed to hydrogen at tem-peratures above 340C.38Recently,Soloveichik et al.pro-posedafour-stagepathwayforthether
25、maldecompositionwithformation of intermediate magnesium polyboranes and ulti-mately ends with formation of MgB2.39Other borohydrides,7such as CaBH42and ZnBH42,40,41also decomposed toTable 1.Summary of typical chemical hydrogen storage materials/systems.Dehydrogenation reactionsMass.%Temp.(C)Ref.2LiB
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