CeO_2/石墨烯的合成及其在光催化制氢中的应用
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摘要
采用具有丰富分级多孔结构的豆芽为模板,经水热法合成仿生形态的纳米CeO_2/石墨烯催化剂。使用XRD、拉曼光谱(Raman)、TEM、场发射扫描电子显微镜(FESEM)、紫外-可见漫反射光谱(UV-Vis/DRS)、N2吸附-脱附仪和光解水制氢系统等分析表征手段对CeO_2/石墨烯催化剂的结构、形貌及光催化性能进行分析。结果表明,所制备的CeO_2/石墨烯光催化剂不仅继承了豆芽模板高孔隙率和大比表面积的特点,而且保持了豆芽的形态和微观特征。该催化剂是由约5.6nm CeO_2纳米晶与具有生物形态的仿生石墨烯片层结构结合而成。制得的CeO_2/石墨烯复合材料内部存在大量由CeO_2/石墨烯催化剂纳米颗粒堆积而成的纳米孔,其孔径集中分布于15~45nm左右,这种微观结构使CeO_2/石墨烯催化剂具有超大的比表面积,提高了催化剂对光生电子空穴对的捕获能力。由紫外-可见漫反射吸收光谱可知,CeO_2/石墨烯复合材料的可见光利用率显著增强,光解水制氢效率6h后可达到671μmol(h·g)-1,远高于标样CeO_2的51.67μmol(h·g)-1。
The nano-sized CeO_2/graphene catalyst was synthesized by hydrothermal method using bean sprouts with rich and graded porous structure as template.XRD,Raman spectroscopy,TEM,field emission scanning electron microscopy(FESEM),UV-Vis diffuse reflectance spectroscopy(UV-Vis/DRS)were adopted to characterize the structure and morphology of CeO_2/graphene catalyst,as well as the photocatalytic performance.The results show that the prepared CeO_2/graphene photocatalyst not only inherits the characteristics of high porosity and large specific surface area of bean sprouts,but also maintains the morphological and microscopic characteristics of bean sprouts.The catalyst is composed of about 5.6 nm CeO_2 nanocrystals combined with a biologically morphic bionic graphene sheet structure.The as-prepared CeO_2/graphene composite possesses a large number of nanopores formed by the accumulation of catalyst nanoparticles,and their pore sizes distribute at about 15-45 nm,which makes the CeO_2/graphene catalyst have large specific surface area and improves the capture of the photo-generated electronhole pairs ability.The visible light utilization efficiency of CeO_2/graphene composites is significantly enhanced by the UV-visible diffuse reflectance spectrum,and 671μmol(h·g)-1 is obtained after 6 hof photolytic water,which is much higher than that of the standard CeO_2 of 51.67μmol(h·g)-1.
The nano-sized CeO_2/graphene catalyst was synthesized by hydrothermal method using bean sprouts with rich and graded porous structure as template.XRD,Raman spectroscopy,TEM,field emission scanning electron microscopy(FESEM),UV-Vis diffuse reflectance spectroscopy(UV-Vis/DRS)were adopted to characterize the structure and morphology of CeO_2/graphene catalyst,as well as the photocatalytic performance.The results show that the prepared CeO_2/graphene photocatalyst not only inherits the characteristics of high porosity and large specific surface area of bean sprouts,but also maintains the morphological and microscopic characteristics of bean sprouts.The catalyst is composed of about 5.6 nm CeO_2 nanocrystals combined with a biologically morphic bionic graphene sheet structure.The as-prepared CeO_2/graphene composite possesses a large number of nanopores formed by the accumulation of catalyst nanoparticles,and their pore sizes distribute at about 15-45 nm,which makes the CeO_2/graphene catalyst have large specific surface area and improves the capture of the photo-generated electronhole pairs ability.The visible light utilization efficiency of CeO_2/graphene composites is significantly enhanced by the UV-visible diffuse reflectance spectrum,and 671μmol(h·g)-1 is obtained after 6 hof photolytic water,which is much higher than that of the standard CeO_2 of 51.67μmol(h·g)-1.
引文
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[18]FRACKOWIK E,BEGUIN F.Carbon materials for supercapacitor application[J].Physical Chemistry Chemical Physics,2007,9(15):1774-1785.
[19]DOLGOPOLOVA E,IVANOVA O,IVANOV V,et al.Microwave-hydrothermal synthesis of gadolinium-doped nanocrystalline ceria in the presence of hexamethylenetetramine[J].Russian Journal of Inorganic Chemistry,2012,57(10):1303-1307.
[20]QIAN J,CHEN Z,LIU C,et al.Improved visible-lightdriven photocatalytic activity of CeO2 microspheres obtained by using lotus flower pollen as biotemplate[J].Materials Science in Semiconductor Processing,2014,25:27-33.
[21]KRISHNAN R,LU T M,KORATKAR N.Functionally strain-graded nanoscoops for high power Li-ion battery anodes[J].Nano Letters,2010,11(2):377-384.
[2]SARAVANAKUMAR K,RAMJAN M M,SURESH P,et al.Fabrication of highly efficient visible light driven Ag/CeO2photocatalyst for degradation of organic pollutants[J].Journal of Alloys and Compounds,2016,664:149-160.
[3]LYONS D M,AND M G,MORRIS M A.Surface studies of ceria and mesoporous ceria powders by solid-state 1 HMAS NMR[J].Journal of Physical Chemistry B,2003,107(19):4607-4617.
[4]RUPP J L M,SOLENTHALER C,GASSER P,et al.Crystallization of amorphous ceria solid solutions[J].Acta Materialia,2007,55(10):3505-3512.
[5]ZHAI Y,ZHANG S,PANG H.Preparation,characterization and photocatalytic activity of CeO2nanocrystalline using ammonium bicarbonate as precipitant[J].Materials Letters,2007,61(8-9):1863-1866.
[6]SONG S,WANG X,ZHANG H.ChemInform abstract:CeO2-encapsulated noble metal nanocatalysts:Enhanced activity and stability for catalytic application[J].Cheminform,2015,47(43):5315-5319.
[7]IMAGAWA H,SUDA A,YAMAMURA K,et al.Monodisperse CeO2nanoparticles and their oxygen storage and release properties[J].Journal of Physical Chemistry C,2016,115(5):1740-1745.
[8]LEI M,WANG Z B,LI J S,et al.CeO2nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell[J].Scientific Reports,2014,4:7415.
[9]JIANG L,YAO M,LIU B,et al.Controlled synthesis of CeO2/graphene nanocomposites with highly enhanced optical and catalytic properties[J].The Journal of Physical Chemistry C,2012,116(21):11741-11745.
[10]YANG Z,HE B,LU Z,et al.Physisorbed,chemisorbed,and oxidized co on highly active Cu-CeO2(111)[J].The Journal of Physical Chemistry C,2016,114(10):4486-4494.
[11]黄徽,杨平.石墨烯基有序介孔金属氧化物复合材料的制备及研究进展[J].复合材料学报,2015,32(5):1233-1240.HUANG H,YANG P.Preparation and research progress of graphene-based ordered mesoporous metal oxide composites[J].Acta Materiae Compositae Sinica,2015,32(5):1233-1240(in Chinese).
[12]邓凌峰,余开明,严忠,等.CO2+掺杂石墨烯/LiFePO4锂离子电池复合正极材料的制备与表征[J].复合材料学报,2015,32(5):1390-1398.DENG L F,YU K M,YAN Z,et al.Preparation and characterization of Co2+doped graphene/LiFePO4composite cathode materials for lithium battery[J].Acta Materiae Compositae Sinica,2015,32(5):1390-1398(in Chinese).
[13]吴娟霞,徐华,张锦.拉曼光谱在石墨烯结构表征中的应用[J].化学学报,2014,72(3):301-318.WU J X,XU H,ZHANG J.Raman spectroscopy of graphene[J].Acta Chimica Sinica,2014,72(3):301-318(in Chinese).
[14]ROHDER L A,BRANDT T,SIGG L,et al.Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III)on short term effects to the green algae Chlamydomonas reinhardtii[J].Aquatic Toxicology,2014,152(5):121-130.
[15]王新征,李梦青,居荫轩,等.制备方法对活性炭孔结构的影响[J].炭素技术,2002(6):25-30.WANG X Z,LI M Q,JU Y X,et al.Influence of preparation methods on the porosity of activated carbon[J].Carbon Techniques,2002(6):25-30(in Chinese).
[16]李嘉,石峰晖,吕晶,等.电弧法制备石墨烯材料的表征与评价[J].复合材料学报,2015,32(6):1658-1662.LI J,SHI F H,LV J,et al.Characterization and evaluation of electric-arc-produced graphene material[J].Acta Materiae Compositae Sinica,2015,32(6):1658-1662(in Chinese).
[17]WANG J,KASKEL S.KOH activation of carbon-based materials for energy storage[J].Journal of Materials Chemistry,2012,22(45):23710-23725.
[18]FRACKOWIK E,BEGUIN F.Carbon materials for supercapacitor application[J].Physical Chemistry Chemical Physics,2007,9(15):1774-1785.
[19]DOLGOPOLOVA E,IVANOVA O,IVANOV V,et al.Microwave-hydrothermal synthesis of gadolinium-doped nanocrystalline ceria in the presence of hexamethylenetetramine[J].Russian Journal of Inorganic Chemistry,2012,57(10):1303-1307.
[20]QIAN J,CHEN Z,LIU C,et al.Improved visible-lightdriven photocatalytic activity of CeO2 microspheres obtained by using lotus flower pollen as biotemplate[J].Materials Science in Semiconductor Processing,2014,25:27-33.
[21]KRISHNAN R,LU T M,KORATKAR N.Functionally strain-graded nanoscoops for high power Li-ion battery anodes[J].Nano Letters,2010,11(2):377-384.