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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,固体表面化学 Chemistry on Solid Surfaces,王 野,wangye,Tel:2186156,化学楼209,第1页,参考书,1.G.A.Somorjai,Introduction to Surface Chemistry and Catalysis,1994,John Wiley&Sons Inc.,New York.,2.丁莹如，秦关林，,固体表面化学,，1988，上海科技出版社,3.吴清辉，,表面化学与多相催化,，1991，化学工业出版社,4.G.A.Somorjai,Chemistry in Two Dimensions,Surfaces,Cornell University Press,1981.,第2页,第一章 引言,Chapter 1 Surfaces-An Introduction,第二章 固体化学基础,Chapter 2 An Introduction to Solid State Chemistry,第三章 表面结构,Chapter 3 Surface Structure,第四章 表面热力学,Chapter 4 Surface Thermodynamics,第五章 表面动态学,Chapter 5 Surface Dynamics,第六章 表面电性质,Chapter 6 Electrical Properties of Surfaces,第七章 表面化学键,Chapter 7 Chemical Bonding on Surfaces,第八章 表面催化作用,Chapter 8 Catalysis on Surfaces,内 容Contents,第3页,Chapter 1 Surfaces-An Introduction,1.1 Historical perspectives,1.2 Concepts related to solid surfaces,1.Surface density,2.Dispersion,3.Thin films,4.Internal surface,5.Adsorption,1.3 Unique features of solid surfaces,1.4 Methods for surface characterizations,第4页,1.1 Historical Perspective,第5页,Berzelius first used the“catalysis”in 1836,认为是一未知力(catalytic force),J.J.Berzelius(17791848),1823年J.W.Dbereiner用Pt表面催化H,2,和O,2,反应,（较早表面技术）,第6页,Wilhelm Ostwald(18351932),Ostwald(1909 Nobel Prize),比较清楚地提出催化作用概念，并预言催化将在化学各领域得到广泛认知，在工业中得到广泛应用,第7页,第8页,Josiah Willard Gibbs,1839-19,化学热力学和统计热力学奠基人,Gibbs,1877年提出适合用于表面相热力学理论,Ostwald称赞Gibbs:从内容到形式，他赋予物理化学整整一百年,康乃狄格(Connecticut)科学院院报:,论非均相物质之平衡(323页）,第9页,第10页,Irving Langmuir,1881-1957,Nobel Prize(1932),它主要贡献是：（1）创造了充惰性气体灯泡，延长了灯泡寿命；（2）创造了人工降雨；（3）,提出了单分子层吸附理论，设计出研究表面张力“表面天平”,；（4）,首创了表面化学和等离子体物理学等新学科,；（5）创造了高真空计和水银扩散泵等。,第11页,第12页,电镜下观察到半导体硅表面硅原子,第13页,The Nobel Prize in Chemistry,Prof.Dr.Gerhard Ertl,Dept.of Physical Chemistry,Fritz-Haber-Institut der,Max-Planck-Gesellschaft,Berlin,b.1936,“The father of modern surface chemistry”,www.berkeley.edu/news/media/releases/05/10_somorjai.html,Prof.Gabor A.Somorjai,University of California,Berkeley,nobelprize.org/nobel_prizes/chemistry/laureates/sci.html,for his studies of chemical processes on solid surfaces,第14页,Ertl has developed a general methodology that can be applied to the important problems in molecular surface science.He has applied the methodology to some of the most central previously unanswered questions concerning molecules on surfaces.The investigations have been carried out with the greatest elegance in the experimental approach.His work is characterized by the ambition to always use the method best suited to solve the problem at hand.Ertl is never satisfied with an isolated interesting observation.Instead the studies are brought to their logical conclusions.Through his accurate studies he has provided a firm basis for our thinking about molecular processes at surfaces.,Scientific Background on the Nobel Prize in Chemistry,Chemical Processes on Solid Surfaces,Hkan Wennerstrm,Professor of Theoretical Physical Chemistry,Lund University,Member of the Nobel Committee for Chemistry,Sven Lidin,Professor of Inorganic Chemistry,Stockholm University,Member of the Nobel Committee for Chemistry,第15页,Evolution of Surface Sciencein recent 40 years,Somorjai,et al.,JACS,131,16589(Perspective),第16页,Surface and Interface in nature or our daily life,第17页,Surface and Interface in nature or our daily life,第18页,Surface and Interface in nature or our daily life,第19页,1.2 Concepts related to surfaces-1,1.Surface concentration(density),体相密度,bulk:1 g/cm,3,分子密度,r,510,22,molecules/cm,3,表面密度,分子密度,s,r,2/3,110,15,molecules/cm,2,依据所研究面不一样可能会相差2个数量级,M,(g/mol）,r,(g/cm,3,),s,(cm,-2,),Hg 200 13.61.210,14,Cu 63.5 8.91.910,15,C,6,H,6,78 0.8793.610,14,例子,第20页,1.2 Concepts related to surfaces-2,2.Dispersion（分散度）,考虑简单立方堆积,D,number of surface atoms/total number of atoms,n=8,n=27,n=64,n=125,n=216,D,=1,D,=26/27=0.963,D,=56/64=0.875,D,=98/125=0.784,D,=152/216=0.704,第21页,Dispersion and particle size,第22页,随粒子尺寸减小，分散度快速增大，表面效应十分显著。,Nano Science&Surface Science,包含多相催化在内许多表面过程仅与表面原子相关，因而这些体系中经常有必要减小活性粒子大小，增加分散度。,第23页,1.2 Concepts related to surfaces-3,3.Thin films（薄膜）,第24页,4.Internal Surface,孔 大小 例,大孔(macropore)50 nm,多孔玻璃,煤炭,介孔(mesopore)250 nm,气凝胶(10nm),层状粘土(1-10nm),介孔分子筛(MCM-41,SBA-15),(2-30nm),微孔(micropore)2nm,沸石分子筛,(63 kJ mol,-1,(15 kcal mol,-1,),t,1 s,吸附分子表面浓度,s,=,F,t,F,:,单位时间单位面积上流过气体量(通量),第30页,1 Surface heterogeneity,2 Clean surface and ultra high vacuum(UHV),1.3 Unique features of solid surfaces,第31页,1.Surface heterogeneity,A.表面并不平坦,SEM picture of Zn crystal surface,第32页,B.更微观地看表面,STM picture of the(0001)face of Re over a 4000-A,2,area,第33页,描述表面不均匀性惯用模型,第34页,2.Clean Surface,固体表面原子浓度为10,15,/cm,2,数量级，为保持表面清洁,必须保持同表面碰撞分子数低于某水准,依据气体分子运动论,在一定,T,一定,P,下,单位时间单位面积上流过气体量(通量)为,F,=,P,(2,p,mk,B,T,),1/2,=,N,A,P,2,p,M,(mol/g),RT,1/2,P,(Pa),M,(mol/g),T,1/2,=2.6310,20,P,(torr),M,(mol/g),T,1/2,=3.5110,22,假定,M,=28,T,=300 K,P,=3,10,-6,torr,F,=1.15,10,15,molecule cm,-2,s,-1,第35页,换言之,在,P,3,10,-6,torr 时,假如每一次碰撞都可使分子在表面吸附话,固体表面在1s之内就被吸附物所覆盖。因而要在研究时间内，如1h，保持表面清洁，则真空度必须小于10,-9,torr。即研究清洁表面时，必须保持ultrahigh vacuum conditions,假定:,M,=28,T,=300 K,P,=3,10,-6,torr,F,10,15,molecule cm,-2,s,-1,UHV要求,研究气体分子在清洁表面吸附时，常使用表面覆盖度概念，单位用Langmuir(L),1 L=10,-6,torr s,第36页,1 Adsorption,2 LEED,3 XPS,4 AES,5 EELS(HREELS),6 EXAFS,1.4 Methods for Surface Characterizations,Probe:molecule;atom;electron;X-ray;etc.,What information?,geometric structure;,composition;,chemical state;etc.,Why surface sensitive?,第37页,1.Adsorption,包含物理和化学吸附,其中物理吸附适合用于全部多孔材料。,要求：适当真空度,物理吸附可取得信息为：,表面积、孔道特征,化学吸附可取得信息为：,表面位浓度及分散度,Probe:molecule,第38页,2.Low-Energy Electron Diffraction(LEED),从低能电子（,500 ev电子束,平均自由程(波长),2nm）与表面作用，发生弹性散射研究清洁固体表面或表面吸附几何结构有效伎俩。,要求：超高真空,可取得信息为：,清洁表面原子排列形式（几何结构）,吸附原子或分子在表面排列形式,Probe:electron,C.J.Davisson,G.P.Thomson,(1927年试验）,电子衍射试验贡献1937年获Nobel物理学奖,第39页,3.X-ray Photoelectron Spectroscopy(XPS),X射线激发固体中原子或离子内层电子，经过能量差得出内层电子结合能信息。对于特定原子其结合能是特定，因而可用于表面组成份析。随价态及化学环境改变，结合能会有一定移动，从移动能够判断原子价态及配位环境。,因光电子逃逸深度小于23 nm,所以是表面敏感伎俩。,要求：超高真空,可取得信息为：,表面组成,表面原子价态、配位环境,Probe:X-ray;photoelectron,K.M.Siegbahn,因对电子能谱学贡献1981年获Nobel物理学奖,第40页,4.Auger Electron Spectroscopy(AES),当一个内层芯(K)电子被激发或电离时，其空穴会被一个从较高能级(L1)上下来电子充填，产生光子能量能深入使外层电子电离，产生电子称Auger电子，该双电子过程称Auger过程。,要求：超高真空,可取得信息为：,表面化学组成定量分析,Probe:X-ray;photoelectron,第41页,5.High-Resolution Electron Energy Loss Spectroscopy(HREELS),低能电子束同固体表面相互作用，引发表面吸附物种分子振动发生跃迁，经过测定反射电子束能量，从能量损失情况得到吸附物种振动跃迁信息。HREELS实际上所得信息与IR相同，只不过HREELS使用低能电子，从而所得信息是,高度表面灵敏。对表面吸附物种灵敏程度为IR约100倍。,可取得信息为：,表面吸附物种键合结构,要求：超高真空,Probe:electron,第42页,6.Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS),当X射线透过物质时，假如能激发内层电子就会被吸收。当X射线能量与电子结合能相同时，其吸收为最大，若X射线能量大于电子结合能时，对单个原子系统，吸收会单调减小。但在固体中因为受邻近原子影响，吸收会随能量增加发生摆动，经过研究吸收系数摆动规律，能够得到中心原子邻近原子配位数及键长度信息。,可取得信息为：,短程有序结构测定,纳米尺度材料结构表征,中心原子配位数及键距离,无高真空要求，适合于原位研究,Probe:X-ray,第43页,Surface Science Techniques for Molecular-Level Studies,Surface Composition:,Auger electron spectroscopy(AES),X-ray photoelectron spectroscopy(XPS),Secondary ion mass spectrometry(SIMS),Ion scattering spectroscopy(ISS),Surface Electron Structure:,Second harmonic generation(SHG),Ultraviolet Photoelectron Spectroscopy,X-ray emission spectroscopy,Scanning tunneling spectroscopy(STS),Electron energy loss spectroscopy(EELS),Helium atom scattering,IR spectroscopy,Raman spectroscopy,Sum-frequency generation spectroscopy(SFG),Molecular beam surface scattering,Surface Vibration and Reaction Dynamics:,Surface Structure:,Low-energy electron diffraction(LEED),Transmission electron microscopy(TEM),Atom diffraction,Atomic force microscopy(AFM),Scanning Tunneling microscopy(STM),Surface X-ray diffraction,X-ray absorption fine structure(XAFS),第44页,
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