EXAFS Study of the Structure of Amorphous Nickel Borate(1)

November[Article]

物理化学学报(WuliHuaxueXuebao)

ActaPhys.-Chim.Sin.2014,30(11),1979-1986

doi:10.3866/PKU.WHXB201409251

1979

http://doc.guandang.net

非晶态镍硼酸盐结构的EXAFS研究

刘红艳1,2

房春晖1,*戈海文1

房艳1,*杨子祥1,2

周永全1唐玉玲1,2

2

朱发岩1

中国科学院大学,北京100049)

(1中国科学院青海盐湖研究所,中国科学院盐湖资源与化学重点实验室,西宁810008;

摘要:

由摩尔比分别为1:2和1:8的NiCl2 6H2O和Na2B4O7 10H2O作为反应物,合成两种非晶态镍硼酸盐,同

时通过水热法合成β-Ni(OH)2.化学分析和热重-微商热重法(TG-DTG)分析结果确定两种非晶态镍硼酸盐的分子组成分别为NiO 0.8B2O3 4.5H2O和NiO B2O3 3H2O.激光拉曼(Raman)实验结果表明镍硼酸盐样品中主要

2-2-存在的硼氧阴离子为B3O3(OH)5和B2O(OH)6.同步辐射扩展X射线吸收精细结构(EXAFS)方法对样品进行结

构解析,通过数据拟合给出样品中Ni原子周围近邻配位原子种类、配位数以及原子间距离.用不同晶体结构作为标准对两种非晶态镍硼酸盐进行拟合的结果表明,样品中Ni原子周围局域结构与Ni3B2O6晶体(ICSDNo.31387)中的吻合较好.Ni原子周围配位原子为O、B和Ni,对于NiO 0.8B2O3 4.5H2O,配位数分别为5.7、3.8和3.8,配位距离分别为0.208、0.263和0.311nm;对于NiO B2O3 3H2O,配位数分别为6.0、4.0和4.0,配位距离分别为0.207、0.262和0.310nm.关键词:

硼酸镍;氢氧化镍;扩展X射线吸收精细结构;局域结构;配位原子

O641

中图分类号:

EXAFSStudyoftheStructureofAmorphousNickelBorate

LIUHong-Yan1,2

ZHUFa-Yan1

FANGChun-Hui1,*FANGYan1,*GEHai-Wen1YANGZi-Xiang1,2

ZHOUYong-Quan1

TANGYu-Ling1,2

(1CASKeyLaboratoryofSaltLakeResourcesandChemistry,QinghaiInstituteofSaltLakes,ChineseAcademyofSciences,

Xining810008,P.R.China;2UniversityofChineseAcademyofSciences,Beijing100049,P.R.China)Abstract:Inthiswork,twoamorphoushydratednickelboratesweresynthesizedwithnickelchloridehexahydrateandboraxasreactantsatmoleratiosof1:2and1:8,respectively.ThechemicalcompositionsofthesenickelboratesweredeterminedtobeNiO 0.8B2O3 4.5H2OandNiO B2O3 3H2Othroughthermogravimetry-derivativethermogravimetry(TG-DTG)andchemicalanalysis,inwhichthemainanionsweredeterminedto

2-2-beB3O3(OH)5andB2O(OH)6,respectively,byRamanspectroscopy.ThelocalstructureofthesesampleswasstudiedbysynchrotronradiationextendedX-rayabsorptionfinestructure(EXAFS).BasedontheprocessingandfittingoftheEXAFSexperimentaldata,theneighboringcoordinationatomstype,theinteratomicdistances,andtheatom-pairnumbersofNiweredetermined.ThefittingresultsoftheamorphousnickelborateshowthatthelocalstructurearoundtheNiatomhasasimilarstructuretothatoftheNi3B2O6crystal.TheneighboringcoordinationatomsofNiintheseamorphousnickelboratesareO,B,andNi.ForNiO 0.8B2O3 4.5H2O,theinteratomicdistancesforNi―O,Ni―B,andNi―Niare0.208,0.263,and0.311nm,andtheatom-pairnumbersare5.7,3.8,and3.8,respectively.TheinteratomicdistancesofNiO B2O3 3H2Oare0.207,0.262,and0.310nm,andtheatom-pairnumbersare6.0,4.0,and4.0,respectively.ThefirstshellsofNi2+inNiO 0.8B2O3 4.5H2OandNiO B2O3 3H2Oareoctahedralwithsixoxygenatoms.

Received:August6,2014;Revised:September25,2014;PublishedonWeb:September25,2014.

Correspondingauthors.FANGChun-Hui,Email:fangch@http://doc.guandang.net.FANGYan,Email:fangy8@http://doc.guandang.net.

TheprojectwassupportedbytheNationalNaturalScienceFoundationofChina(21373251)andMainDirectionProgramofKnowledgeInnovationofChineseAcademyofSciences,China(KZCX2-EW-307).

国家自然科学基金项目(21373251)和中国科学院知识创新工程重要方向项目(KZCX2-EW-307)资助

©EditorialofficeofActaPhysico-ChimicaSinica

1980

KeyWords:

ActaPhys.-Chim.Sin.2014

Nickelborate;Nickelhydroxide;ExtendedX-rayabsorptionfinestructure;Vol.30

Localstructure;Coordinationatom

1Introduction

Metalboratesarewidelyappliedinfuelcells,1laserapplica-tions,andnon-linearoptical.2,3Theyarealsoknownfortheirin-terestingmagnetic,catalytic,andphosphorescenceproperties.4-6Inrecentyears,crystallineanhydrousnickelboratewasfoundtobeusedascathodematerial7oflithiumionbattery.Bediakoetal.8,9haveshownthatanhydrousnickelboratecanalsoactasacatalystforsolar-drivenwatersplittingtoH2andO2,andwhichisanat-tractivemethodofaccomplishingthesolar-to-fuelsconversionnecessarytomeetthegrowingglobalenergydemandbyrenew-ablesources.10,11Atpresent,althoughthecrystallinenickelboratestructurewaswelldeveloped,thestructureofamorphoushydratednickelboratehasnotbeenreportedyet.

Withthewealthofexperienceacquiredinthefieldofcrystalandnanometernickelborate,12-15inthepresentwork,wedecidedtostudytheamorphoushydratednickelborateusingacombi-nationofvarioustechniques.TheamorphousnickelborateswerecharacterizedbyX-raydiffraction(XRD),Ramanspectrum,andthethermogravimetry-derivativethermogravimetry(TG-DTG)analysis.Toobtainacomprehensiveunderstandingofthelocalstructureofamorphoushydratednickelborates,wecon-ductedadetailedstudyusingsynchrotronradiation(SR)extendedX-rayabsorptionfinestructure(EXAFS)method.

2Experimental

2.1Materialsandsamplepreparation

NiCl2 6H2O(AR),Na2B4O7 10H2O(GR),H3BO3(AR),NaOH(AR),andNiSO4 6H2O(AR)werecommerciallyavailable.TheamorphoushydratednickelboratesweresynthesizedwithNiCl2 6H2OandNa2B4O7 10H2Oasreactantswithmoleratioof1:1and1:8,respectively.Thereactantsweredissolvedindistilledwaterseparatelyatroomtemperature,mixedtogetherandheatedtoabout50°C.16TheH3BO3solution(10%(w))wasusedtoadjustthepHvalueofsolutionto8.8and7.9,respectively.Thepre-cipitationofnickelborateproductswasobtainedafterreactionfor4handstaticovernight,thentheprecipitationwaswashedwiththeH3BO3solutionanddistilledwaterforseveraltimes.InordertocheckthereliabilityoftheSREXAFSexperimentanddataprocessing,theβ-Ni(OH)2wassynthesizedwithNaOHandNiSO4 6H2Oinaqueoussolutionbydirectprecipitationmethod.17,18El-ementanalysisforNiwasdeterminedbyethylenediaminetet-raaceticacid(EDTA)complexmetrictitrationwithmurexideasindicatorandBbymannitoltitrationmethod.19

2.2Characterizationmethods

Thermalstabilityofthesampleswascharacterizedbyasyn-chronousthermalanalyzer(theUnitedSt …… 此处隐藏：23687字，全部文档内容请下载后查看。喜欢就下载吧 ……