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1、INTRODUCTIONMostoftheoildailyextractedisconsumedintransportation(approximately66.6%inAmerica)http://www.bts.gov/publications/national_transportation_statistics/html/table_04_03.html.Oftheenergyusedinthissector,approximately65%isconsumedbygasoline-poweredvehicles.Diesel-poweredtranspor
2、t(trains,merchantships,heavytrucks,etc.)consumesabout20%,andairtrafficconsumesmostoftheremaining15%USDept.ofEnergy,"AnnualEnergyOutlook"(February2006),TableA2.InItaly,civilmobilityaccountsforabout74%oftotalconsumption,halfofwhichcorrespondingtoabout30%ofthenationaltotalconsumptionontr
3、ansportation,insideurbanandsuburbanzones.Intheseenvironmenttherefore,caremissionsrepresentsthemainpollutionsource.Hydrogencars,byeliminatingCO2emissions,coulddrasticallyreduceinshorttimespollution,especiallyinourlivingareas.Themainobstacle,hinderingtheintroductionintothemarketofhydrog
4、encars,isrepresentedbythelowefficiencyofhydrogenstoragesystem.Figure1.Energydensity,bothvolumetricandgravimetric,ofvarioussystemsforhydrogenstorage.The2010and2015DOEtargetscorrespondto6.0and9.0%wt.Wecanassumethatafuelcellequippedcarwouldrunabout100kmperkgofhydrogenburned.Consequentlya
5、standardof400kmwouldbefulfilledby4kgofhydrogen.Fig.1showsvariousstoragesystemsdimensionedtodeliver4kgofhydrogen.Amongthedifferentstoragesystems,thehydrolysisofhydrideseemsthebestpromisingone(Fig.2).Thereactioncanberepresentedas:2MeHn+nH2O→Me2On+2nH2(1)Thehydrideshouldnecessarilyberege
6、neratedoff-board.AmongthedifferentmetalhydrideNaBH4showsahydrogencontenthigherthan10%wt.Thehighhydrogencontentandthesimplicityofsynthesismakesthesaltaperfectcandidatetostorehydrogenformobileapplication.AsafuelNaBH4islessflammableandlessvolatilethangasoline.Itisrelativelyenvironmentall
7、yfriendlybecauseitwillquicklydegradeintoinertsaltswhenreleasedintotheenvironment.Figure2.Weightpercentofhydrogenevolvedfromhydrolysisofvariouscomplexmetalhydrides.Thehydrogenweightwasreferredonlytotheweightofthemetalhydrideanditdoesnottakeintoaccounttheweightofwaterusedforthehydrolysi
8、s.The
