Effect of Pore Packing Defects in 2-D Ordered Mesoporous Carbons on Ionic Transport

Effect of Pore Packing Defects in2-D Ordered Mesoporous Carbons on Ionic Transport

Da-Wei Wang,?Feng Li,?Hai-Tao Fang,?,?Min Liu,?Gao-Qing Lu,§and Hui-Ming Cheng*,?

Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of

Sciences,72Wenhua Road,Shenyang110016,China,Materials Science and Engineering School,Harbin

Institute of Technology,92West Dazhi Street,Harbin150001,China,and Australian Research Council Centre

for Functional Nanomaterials,School of Engineering,The Uni V ersity of Queensland,QLD4072,Australia

Recei V ed:December13,2005;In Final Form:March12,2006

Ordered mesoporous materials show great importance in energy,environmental,and chemical engineering.

The diffusion of guest species in mesoporous networks plays an important role in these applications,especially

for energy storage,such as supercapacitors based on ordered mesoporous carbons(OMCs).The ion diffusion

behavior in two different2-D hexagonal OMCs was investigated by using cyclic voltametry and electrochemical

impedance spectroscopy.In addition,transmission electron microscopy,small-angle X-ray diffraction,and

nitrogen cryosorption methods were used to study the pore structure variations of these two OMCs.It was

found that,for the OMC with defective pore channels(termed as pore packing defects),the gravimetric

capacitance was greatly decayed when the voltage scan rate was increased.The experimental results suggest

that,for the ion diffusion in2-D hexagonal OMCs with similar mesopore size distribution,the pore packing

defect is a dominant dynamic factor.

1.Introduction

Ordered mesoporous materials have shown great potential in many important applications,such as chemical catalysis, environmental separation,and energy storage.1-3All these applications involve the transportation of guest species(gas/ liquid)in the mesoporous networks.Therefore,it is extremely vital to understand the effect of ordered mesopores on the dynamic processes of these guest species with respect to design of new ordered mesoporous structures.

Electrical double layer capacitors(EDLCs),in which the electrical energy storage/release depends on ion transport in the framework composed of nanometer-sized pores(mainly meso-pores),have been considered as a promising energy storage device in many fields.2-5,8-12Understanding the influence of different mesoporous materials(ordered or disordered arrange-ment)on ion diffusion behavior is fundamental to enhancing EDLC’s performance.However,in the past,the diverse and uncontrollable intrinsic microporous structure of physically or chemically activated carbons has made it impossible to precisely investigate the relations between mesoporous textures and ion diffusion behavior.Recently,Ryoo and co-workers have synthesized ordered mesoporous carbons(OMCs).6,7These OMCs,with mesopore size tailorable and regularly intercon-nected mesoporous channels,are considered to be very promis-ing materials for investigating the impact of ordered mesopores on ion diffusion behavior,which determines the energy density of EDLCs under large current operations.

A few groups have studied the impact of ordered mesopores on ion diffusion behavior by evaluating the performance of EDLCs based on OMCs.8-12Their experiments show that2-D hexagonal OMCs exhibit better EDL capacitive performance than3-D cubic OMCs,which is believed to be attributed to the favorable ion diffusion in larger mesopores existing in2-D hexagonal OMCs.8,9,12Nevertheless,it is clear that only one-dimension diffusion is available in2-D hexagonal OMCs.It can be assumed that if the single diffusion direction is blocked, no other diffusion routes will be available.Consequently,it is quite important to understand to what extent the blockage of the single diffusion direction will influence the ion diffusion ability of2-D hexagonal OMCs.

A simple method was developed in this paper to control the blockage conditions in2-D hexagonal OMCs.The capacitance-decaying trends of two different2-D OMCs were investigated by cyclic voltammogram(CV)at different voltage sweep rates. Moreover,electrochemical impedance spectroscopy(EIS),which is a powerful method for obtaining information on the dynamic ion diffusion behavior,13-16has been utilized to evaluate the influence of blockage conditions on the ion diffusion behavior in2-D hexagonal https://www.wendangku.net/doc/0e13300138.html,bined with mesopore structure characterizations,the present results clearly demonstrate that defective2-D ordered mesoporous channels dramatically reduce the ion diffusivity in mesopores.

2.Experimental Section

2.1.Synthesis and Characterization of OMCs.The2-D hexagonal OMCs materials were obtained by a templating procedure for which ordered mesoporous silica SBA-15was chosen as a template.The SBA-15templates were prepared according to the method described by Jun et al.7However,the final calcination process,which is used to remove the surfactant embedded in SBA-15,was altered to adjust the remaining surfactant amount.For Condition1,the silica template was calcined in an oxygen-poor atmosphere and dark brown powder was obtained;for Condition2,the silica template was calcined in an oxygen-rich atmosphere yielding pure white powder.The oxygen-poor atmosphere was realized simply by air-proofing the volume-limited oven tube,because the available oxygen

*Address correspondence to this author.E-mail:cheng@https://www.wendangku.net/doc/0e13300138.html,.

Fax:86-24-2390-3126.

?Chinese Academy of Sciences.

?Harbin Institute of Technology.

§The University of Queensland.

8570J.Phys.Chem.B2006,110,8570-8575

10.1021/jp0572683CCC:$33.50?2006American Chemical Society

Published on Web04/08/2006

amount in the volume-limited oven tube was exhausted during calcination.The oxygen-rich atmosphere was realized by controlling the inner pressure of the oven tube to be about double that of the atmospheric pressure under a flowing air stream. The effect of oxygen-poor atmosphere was to remove the surfactant in primary mesopores of the silica template,while keeping the surfactant in secondary mesopores.In the case of an oxygen-rich atmosphere,the surfactant in both primary and secondary mesoproes was removed.

OMCs were hence synthesized by first templating the pretreated SBA-15with sucrose as carbon precursor and then carbonizing by a prescribed heating procedure in argon atmo-sphere.7The resultant silica/carbon composites were washed with NaOH dissolved in a deionized water/ethanol(volume ratio 1:1)(0.1M)solution at373K for3h to remove the silica template.The remaining carbon was then filtered and rinsed until the pH was7.Thereafter,the wet powder was dried under vacuum at373K for12h.The resultant carbon powders were denoted as CS-1and CS-2to differentiate the respective calcination conditions of the corresponding SBA-15templates. The OMCs were characterized by TEM(JEOL2010,200 kV).The OMCs samples were mixed in absolute ethanol and ultrasonically dispersed for several seconds.Then,the dispersed homogeneous solution was dropped onto a microgrid and dried

for TEM observations.The small-angle X-ray diffraction (SAXRD)patterns were collected with use of an RINT2200 (Cu K R,λ)1.5406?)at a step scan rate of0.02°from1.5°to10°.Nitrogen cryosorption was conducted on a Micrometrics ASAP2010M;before measurements,all the OMC samples were evacuated at473K until the manifold pressure was lower than 2Pa.The external surface specific surface area(SSA)is the difference between BET specific surface area(BET-SSA)and micropore surface SSA.The BET-SSA was calculated based on the BET method.The micropore surface SSA was calculated based on the t-plot method.All these calculations were accomplished with the software provided along with the ASAP2010M instrument.

2.2.Electrochemical Measurements.The electrochemical measurements were carried out in a three-electrode system. Nickel foam covered with a composite of activated carbon powders and poly(tetrafluoroethylene)(PTFE)was used as counter electrode(CE).Hg/HgO was chosen as reference electrode(RE)in an alkaline electrolyte of6M KOH.The preparation of the working electrode(WE)for the three-electrode system was as follows.The active materials,CS-1 and CS-2,5.5mg each,were mixed with1mg of PTFE in absolute ethanol and spread onto nickel foam with a size of10 mm×10mm,respectively.Then,the nickel foam covered with 5.5mg of active materials was used as the WE.The electrolyte was6M KOH aqueous solution.The cyclic voltammogram and electrochemical impedance spectroscope were collected on Solartron1287/1260electrochemical systems.The potential range for CV was-1to0V vs Hg/HgO.The bias potential applied to the electrode during EIS was0V vs Hg/HgO,the frequency range was10mHz to100kHz,and the AC signal amplitude was10mV.

3.Results and Discussion

3.1.Pore Structure Characterization of OMCs.The TEM images of CS-1and CS-2perpendicular to their pore channels are illustrated in Figure1a-d.It can be seen that the pore channels of CS-1were far from parallel and straight compared to those of CS-2.During the TEM observations,it was found that most of the CS-1samples possessed similar defective pore structure.In fact,sections2and3(2and3in Figure1a)indeed possess more defective pore structure than section1(1in Figure 1a)because of the absence of distinct localized regular pore structure.However,considering the easy identification of defective pore structure,we chose to show the HRTEM of section1(1in Figure1a)to provide a distinct comparison between the regular pore structure and the defective pore structure,as observed in https://www.wendangku.net/doc/0e13300138.html,pared with the straight parallel mesopore channels in Figure1d,the mesopores in Figure 1b comprise a large number of randomly distributed defective sites.The irregular defective sites in the mesopore channels mainly include(i)collapse of the primary mesopores and(ii) blockage of the primary mesopores.

It is accepted that the ordered hexagonal mesoporous framework composed of primary carbon rods in2-D OMCs is supported by many smaller secondary carbon nanorods7,12and obviously the absence of these short nanorods would cause an irregularly collapsed primary mesopore texture,as in the case of CS-1,which results from the unstable packing conditions of mesopore channels.The detailed formation mechanism of the irregularly collapsed mesopore channels of CS-1can be explained as follows.As mentioned above,the SBA-15template used for the preparation of CS-1was calcined in an oxygen-poor atmosphere and showed a dark brown color after calcina-tion,indicating incomplete removal of the surfactant,and the content of the carbon residue from surfactant was determined to be6wt%by TG in air up to1273K,shown in Figure1S (see the Supporting Information).It is important to mention that both SBA-15templates possessed similar primary mesopore sizes,which probably resulted from complete removal of surfactant existing in the primary mesopores.Hence,the brown-looking carbon residue from surfactant must exist in the smaller secondary mesopores inside the silica walls.Consequently, during the preparation of CS-1,a large number of smaller inner-wall mesopores could not be impregnated by sucrose molecules due to the blockage by the carbon residue from surfactant.That condition would have led to a shortage of smaller secondary carbon nanorods to support the ordered mesoporous structure of resultant OMCs,and hence resulted in the irregular collapsing defects observed in the TEM images.Furthermore,the

carbon Figure1.Typical TEM images of2-D hexagonal OMCs:(a,b)CS-1;(c,d)CS-2.Panels b and d are the HRTEM images of the corresponding square areas in panels a and c,respectively;the white arrows in panel b show the pore packing defects in mesopore textures; the dark arrows in panel d show regularly packed mesopores;white arrow1points out the collapsed mesoporous channels and white arrow 2points out the blockage of mesopore channels by carbon residue from surfactant.

Effect of Pore Packing Defects on Ionic Transport J.Phys.Chem.B,Vol.110,No.17,20068571

residue from surfactant also blocked the mesopore channels of CS-1after the silica template was dissolved,as shown in Figure 1b by the arrows.Because the formation of mesopore channels resulted from the package of primary carbon rods,and the defective packing conditions of mesopore channels (including the collapse of primary carbon rods and blockage of primary mesopores by carbon residue from surfactant)gave rise to these defective sites,it is reasonable to define these defects as pore packing defects (PPDs).

Figure 2shows the SAXRD patterns of CS-1and CS-2.It can be seen that CS-1possessed a low degree of periodic order with a weak intensity from (110)planes.CS-2exhibited a high degree of periodic order with a strong intensity from both (110)and (200)planes.The visible high index peak (200)indicates a high periodic order in the arrangement of symmetry cells (here the symmetry cell is the carbon cylinder).6,7It can be deduced,then,that the low degree of arrangement order in CS-1resulted from pore packing defects in the hexagonal carbon honeycomb structure,in agreement with the TEM observations.7

The nitrogen adsorption -desorption isotherms,which are shown in Figure 3a,are used to determine the specific surface area (SSA)and pore size distribution (PSD)of the OMCs.The isotherms for CS-1and CS-2are typical Type IV isotherms and show an obvious capillary condensation step (hysteresis loop),as is characteristic of OMCs.7However,the capillary-condensation relative pressure ranges (P /P 0)for CS-1and CS-2are different.The pressure range for CS-1is 0.5to 0.7,which is higher than that of CS-2(0.4to 0.6).This result corresponds to the existence of larger mesopores in CS-1(5.5nm)than in CS-2(4.8nm)based on Density Functional Theory (DFT)analysis,as shown in Figure 3b.The BET-SSA and external surface SSA are listed in Table 1.From the nitrogen isotherms,the external surface area is mainly composed of mesopore surface area,and the ratio of macropores is quite small.On the basis of the data in Table 1,it can be seen that although CS-2has a higher BET surface area,the percentage of mesopores is quite close to that of CS-1.Therefore,the pore structure deviations between CS-1and CS-2are mainly (1)CS-1possesses a defective mesoporous structure with lower periodic

order compared with that of the regular mesoporous channels of CS-2and (2)CS-1has a larger mesopore size than that of CS-2.

3.2.Electrochemical Performance of OMCs.The influence of ordered mesoporous structure on ion transport bahavior can be characterized by the CV method based on the evaluation of capacitive performance of EDLC based on OMCs.8-12Gener-ally,the desired capacitive performance requires a rectangular shaped voltammogram.Besides,the capacitive behavior can also be studied by changing the voltage sweep rates to estimate the applicability for quick charge -discharge operations.12

The cyclic voltammograms of CS-1and CS-2are presented in Figure 4,panels a and b,respectively,for different voltage scan rates.The voltammograms of these two carbons maintained the desired rectangular shape at voltage scan rates of 5mV/s,where the charging and discharging curves were parallel with the voltage axis.When the voltage scan rate was increased to 50mV/s,a quasirectangular shape can still remain for CS-2,indicating excellent capacitive behavior even at high current intensity.However,the voltammogram of CS-1exhibited a triangular shape at 50mV/s,indicating the absence of capacitive behavior at high current density.This means that CS-1would be less suitable for quick charge -discharge operations than CS-2.The absolute gravimetric capacitance and specific surface capacitance (capacitance per unit surface area)are listed in Tables 2and 3,respectively.From Table 3,it can be seen that CS-1has higher specific surface capacitance than CS-2.This probably comes from the superior active surface of CS-1,as suggested by DSC results shown in Figure 2S (see the Supporting Information).As the voltage scan rates increased,the difference of gravimetric capacitance and specific surface capacitance between CS-1and CS-2decreased.The same trend was also observed from the results in a two-electrode system,as shown in Tables 1S and 2S (see the Supporting Information).This probably originates from the absence of capacitive behavior of CS-1at high current density.To evaluate the capacitive behavior of CS-1and CS-2,the ratio of retained gravimetric capacitance vs increased voltage scan rates is plotted in Figure 5.CS-2maintains 82%of its capacitance at a high voltage scan rate of 50mV/s,which is more than the ratio of 74%for CS-1.These unexpected results show a better capacitive behavior for CS-2despite its smaller mesopore size than that of CS-1.Generally,the faster the penetration of electrolyte ions into electrochemically active porous surface,the better the capacitive behavior at high voltage scan https://www.wendangku.net/doc/0e13300138.html,paring CS-1with CS-2,the inferior capacitive behavior of CS-1is unexpected because of its relatively larger mesopore size.However,as mentioned previously,the pore channel packing defects (PPDs)in CS-1are much different from those in CS-2.To account for the larger mesopore size and inferior capacitive behavior for CS-1,it is believed that the different PPDs for CS-1and CS-2must have played a dominant role in determining the capacitive behavior at high voltage scan rates.

3.3.Electrochemical Impedance Spectroscopy of OMCs.Although the CV method can be utilized to estimate the ion transport behavior in ordered mesoporous structure by

varying

Figure 2.Small angle XRD patterns of CS-1and

CS-2.

Figure 3.(a)Nitrogen cryosorption isotherms and (b)DFT pore size distributions of CS-1and CS-2.

TABLE 1:Specific Surface Area and Pore Diameter of CS-1and CS-2

carbon S BET (m 2/g)S ext (m 2/g)a

pore diameter (nm)b

CS-11089822 5.5CS-2

1222

904

4.8

a

Specific surface area of the external surface,calculated from the t-plot method.b Peak value of the mesopore diameter distribution curves based on the DFT method.

8572J.Phys.Chem.B,Vol.110,No.17,2006Wang et al.

the voltage sweep rates,it is still unable to precisely describe the actual electrochemical diffusion process.Hence,it is quite important to further investigate the influence of ordered meso-porous structure on ion diffusion based on EIS,which has been considered as a powerful method to obtain dynamic ion diffusion information.13-16

The formation of EDL capacitance under an alternative electric field for a mesoporous/microporous electrode should involve three processes:(a)a high-frequency region where mass transfer is inhibited,so charge aggregation at the surface of carbon powder electrode in contact with the bulk electrolyte would be dominant;(b)a medium-frequency region where the dominant process would be ion diffusion in mesoporous channels which contributes the most to the development of capacitive behavior;and (c)a low-frequency region where inhomogeneous diffusion in the less-accessible sites (like

micropores)may govern the impedance.13Thus,the inferior dynamic capacitive performance of CS-1at high voltage scan rates ought to be related to the ion diffusion ability in mesoporous channels which is identified as the medium-frequency region in both Nyquist and Bode plots.

The complex -plane impedance plots (Nyquist plots)for CS-1and CS-2are given in Figure 6a.The knee frequencies are illustrated in the inset of Figure 6a,and the values for CS-1and CS-2are 39.8and 63.1Hz,respectively.Generally,the knee frequency is considered to be the critical frequency where EDLC begins to exhibit capacitive behavior.In the impedance plots,when the frequency is less than the knee frequency,a straight line,nearly vertical to the realistic impedance axis (Z ′),was observed,characteristic of an admirable capacitive behavior.Deviation from the vertical line is attributable to inner-mesopore diffusion resistance for electrolyte ions,which is strongly dependent on the detailed mesoporous structure of the different samples.Therefore,it is possible to investigate the dynamic process of ion diffusion in ordered mesopores based on EIS.In the phase angle plot,the approach to pure capacitive behavior at low frequency is usually identified with phase angle approaching to the negative 90degree.14Accordingly,the value of the phase angle can be used to evaluate the effectiveness of ion diffusion in mesopores at the medium-frequency region.That is,the smaller the phase angle,the better the capacitive performance and,hence,the faster the ions diffuse.The frequency dependent behaviors of the phase angle,Φ,are illustrated in Figure 6b (Bode plots).When the frequency is lower than 1.6Hz,where the impedance behavior of both CS-1and CS-2would be ion-diffusion controlled,the phase angle of CS-2is always smaller than that of CS-1.This result indicates more rapid diffusion of ions in the ordered mesoporous channels of CS-2,regardless of its smaller mesopore size than that

of

Figure 4.Cyclic voltammograms for (a)CS-1and (b)CS-2in 6M KOH at different voltage scan rates.

TABLE 2:The Gravimetric Capacitance of CS-1and CS-2under Different Measurement Conditions in a Three-Electrode System

gravimetric capacitance at different voltage scan rates (F/g)

capacitor type sample 5mV/s 10mV/s 20mV/s 30mV/s 40mV/s 50mV/s 3-electrode

CS-1122.5109.7102.796.995.790.4CS-2

99.5

94.5

89.6

86.1

83.8

81.5

TABLE 3:The Specific Surface Capacitance of CS-1and CS-2under Different Measurement Conditions in a Three-Electrode System

specific surface capacitance at different voltage scan rates (F/m 2)a

capacitor type sample 5mV/s 10mV/s 20mV/s 30mV/s 40mV/s 50mV/s 3-electrode

CS-10.1120.10.0940.0890.0880.083CS-2

0.081

0.077

0.073

0.07

0.069

0.067

a

The specific surface capacitance (C s )was calculated by the equation C s )C g /S BET ,where C g is the gravimetric capacitance listed in Table 2and S BET is the BET specific surface area listed in Table

1.

Figure 5.The retained capacitance change of CS-1and CS-2with voltage scan rates.

Effect of Pore Packing Defects on Ionic Transport J.Phys.Chem.B,Vol.110,No.17,20068573

CS-1.Therefore,CS-2shows a closer approach to pure capacitive behavior,which means that the ions are able to access more electrochemically active mesoporous surfaces in CS-2than in CS-1at the same AC frequency in the medium region.3.4.Impact of Pore Packing Defects on Ion Transport.Both the CV and EIS methods clearly demonstrate that CS-2exhibits a superior capacitive performance to CS-1,which means that the mesoporous structure of CS-2favors ion diffusion.To account for the inferior mesopore size of CS-2to that of CS-1,the intense negative impact of PPDs on ion diffusion must be clarified.

Impedance behavior on porous electrodes can be understood by ion penetrability:at higher penetrability most of the electrode surface should be detected,while at lower penetrability,only part of the porous electrode surface would be detected.15On this basis,CS-2should possess a higher penetrability than CS-1does,as discussed previously.

The ion penetrability R can be expressed by the following formula:16

where r is the pore radius,l p is the pore length,R is the inner-pore electrolyte resistance,C d is the specific surface EDL capacitance at the interface between the carbon phase and the electrolytes,and ωis the angular frequency.

It can be seen that the value of penetrability is directly proportional to r 1/2,l p -1,and R -1/2.As the mesopore diameter for CS-1is 5.5nm,larger than that of CS-2,the values of l p -1

and R -1/2for CS-1should be much smaller than those of CS-2,which would,in turn,give a lower penetrability value for CS-1in order to be consistent with its poor capacitive behavior as determined by CV and EIS.

As observed from TEM images,the morphology of 2-D OMCs was rodlike particles with length at the micrometer scale and the primary mesopores running through the OMC rods.Therefore,it should be possible to estimate the primary mesopore length by evaluating the OMC rod length.From the OMC rod length distribution illustrated in Figure 7,CS-1and CS-2possess a similar rod length distribution with their peak values located between 0.8and 1.2μm,which indicates a similar primary mesopore length and hence a similar l p -1value for both CS-1and CS-2.

It has been deduced that the penetrability for CS-1could be smaller than that for CS-2only in the case of a smaller value of l p -1and R -1/2for CS-1than for CS-2.However,the l p -1value has been proved to be similar for both CS-1and CS-2.Consequently,the value of R -1/2for CS-1must be greatly smaller than that for CS-2.As a result,the electrolyte ion resistance,R ,in the mesoporous channels of CS-1must be much larger than that of CS-2.The large ion diffusion resistance R must have had a serious negative effect on reducing the ion diffusion ability,which,in turn,would have lowered the ion penetrability for CS-1.

As determined by TEM and SAXRD,CS-1is believed to have possessed much more pore packing defects than CS-2.In other words,the PPDs for CS-1are greater than that for CS-2and,hence,will contribute to a large inner-pore electrolyte resistance,as deduced

above.

Figure 6.The Nyquist plots (a)and Bode plots (b)of CS-1and

CS-2.

Figure 7.Statistical length distributions of the OMC rod from SEM images:(a)CS-1and (b)CS-2(inset figures are the corresponding SEM images for CS-1and CS-2,respectively).

R )

12l p

r Cd ωR

(1)

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When electrolyte ions transport into a pore under the stimulation of an AC signal,the ions will penetrate deeper along the porous channel with decreasing frequency until they have accessed the entire pore surface.14,15Unfortunately,ion diffusion is intensely dependent on the actual pore channel conditions rather than an ideally cylindrical pore without any defects.14,15 The distributed pore packing defects along the mesoporous channels will constrict the mesopores to some extent.When the PPDs are severe and lead to a confined effect on pore diameters,as pointed out by the arrows in Figure1b,the electrolyte ions will be restricted in the narrowed parts of the channels,and will transport more slowly than in the regular defect free mesopores(Figure1d).This phenomenon would certainly increase the transport resistance in the mesoporous channels and hence result in a decrement of the ion penetrability, as observed for CS-1.Therefore,the capacitive behavior of CS-1 at high voltage scan rates was inferior to that for CS-2. Evidently,for2-D hexagonal OMCs with similar PSD,the dynamic ion diffusion behavior in mesoporous channels will be strongly controlled by pore packing defects rather than by pore size distributions.

4.Conclusion

The capacitive behaviors of two different2-D hexagonal OMCs were investigated based on CV and EIS.It was found that for an OMC with a larger mesopore size the capacitive behavior was inferior to that of an OMC with a smaller mesopore size.The reason is believed to lie in the difference between their ordered mesoporous structures.Pore packing defects have been proposed as the basis for interpreting these unexpected results.It is considered that for2-D OMCs with similar mesopore diameters,the pore packing defects will determine the ion diffusion process in ordered mesopores at high current intensity.It is believed that a defect-free stable ordered mesoporous system will enable the electrolyte ion to transport more efficiently and will ultimately enhance the total EDLC system performance.

Acknowledgment.This work was supported by NFSC (50328204,50472084)and the Hi-Tech Research and Develop-ment Program of MOST(2004AA302090),China

Supporting Information Available:Electrochemcial mea-surement results in a two-electrode system and TG/DSC results, including the TG curves of silica templates(Figure1S),the DSC curves of OMCs(Figure2S),the gravimetric capacitance values in a two-electrode system(Table1S),and the specific surface capacitance values in a two-electrode system(Table2S). This material is available free of charge via the Internet at http:// https://www.wendangku.net/doc/0e13300138.html,.

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(8)Vix-Guterl,C.;Saadallah,S.;Jurewicz,K.;Frackowiak,E.;Reda, M.;Parmentier,J.;Patarin,J.;Be′guin,F.Mater.Sci.Eng.B2004,108, 148.

(9)Jurewicz,K.;Vix-Guterl,C.;Frackowiak,E.;Saadallah,S.;Reda, M.;Parmentier,J.;Patarin,J.;Be′guin,F.J.Phys.Chem.Solids2004,65, 287.

(10)Liu,H.Y.;Wang,K.P.;Teng,H.Carbon2004,43,559.

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Effect of Pore Packing Defects on Ionic Transport J.Phys.Chem.B,Vol.110,No.17,20068575

英语中的比较级与最高级 详解

比较级与最高级 1.as...as 与(not) as(so)...as as...as...句型中，as的词性 第一个as是副词，用在形容词和副词的原级前，常译为“同样地”。第二个as是连词，连接与前面句子结构相同的一个句子(相同部分常省略)，可译为“同..... He is as tall as his brother is (tall) . (后面的as 为连词) 只有在否定句中，第一个as才可换为so 改错: He is so tall as his brother.（X） 2.在比较状语从句中，主句和从句的句式结构一般是相同的 与as...as 句式中第二个as一样，than 也是连词。as和than这两个连词后面的从句的结构与前面的句子大部分情况下结构是相同的，相同部分可以省略。 He picked more apples than she did. 完整的表达为: He picked more apples than she picked apples. 后而的picked apples和前面相同，用did 替代。 He walked as slowly as she did.完整表达为: He walked as slowly as she walked slowly. she后面walked slowly与前面相同，用did替代。

3.谓语的替代 在as和than 引导的比较状语从句中，由于句式同前面 主句相同，为避免重复，常把主句中出现而从句中又出现的动词用do的适当形式来代替。 John speaks German as fluently as Mary does. 4.前后的比较对象应一致 不管后面连词是than 还是as,前后的比较对象应一致。The weather of Beijing is colder than Guangzhou. x than前面比较对象是“天气”，than 后面比较对象是“广州”，不能相比较。应改为: The weather of Bejing is colder than that of Guangzhou. 再如: His handwriting is as good as me. 应改为: His handwriting is as good as mine. 5.可以修饰比较级的词 常用来修饰比较级的词或短语有: Much,even,far,a little,a lot,a bit,by far,rather,any,still,a great deal等。 by far的用法: 用于强调，意为“...得多”“最最...”“显然”等，可修饰形容词或副词的比较级和最高级，通常置于其后，但是若比较级或最高级前有冠词，则可置于其前或其后。

人教版(新目标)初中英语形容词与副词的比较级与最高级

人教版（新目标）初中英语形容词与副词的比较级与最高级 （一）规则变化： 1．绝大多数的单音节和少数双音节词，加词尾-er ，-est tall—taller—tallest 2．以不发音的e结尾的单音节词和少数以-le结尾的双音节词只加-r，-st nice—nicer—nicest , able—abler—ablest 3．以一个辅音字母结尾的重读闭音节词或少数双音节词，双写结尾的辅音字母，再加-er，-est big—bigger—biggest 4．以辅音字母加y结尾的双音节词，改y为i再加-er，-est easy—easier—easiest 5．少数以-er，-ow结尾的双音节词末尾加-er，-est clever—cleverer—cleverest, narrow—narrower—narrowest 6．其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 easily—more easily—most easily （二）不规则变化 常见的有： good / well—better—best ; bad (ly)/ ill—worse—worst ; old—older/elder—oldest/eldest many / much—more—most ; little—less—least ; far—farther/further—farthest/furthest

用法： 1．原级比较：as + adj./adv. +as（否定为not so/as + adj./adv. +as）当as… as中间有名字时，采用as + adj. + a + n.或as + many / much + n. This is as good an example as the other is . I can carry as much paper as you can. 表示倍数的词或其他程度副词做修饰语时放在as的前面 This room is twice as big as that one. 倍数+as+adj.+as = 倍数+the +n.+of Your room is twice as larger as mine. = Your room is twice the size of mine. 2．比较级+ than 比较级前可加程度状语much, still, even, far, a lot, a little, three years. five times,20%等 He is three years older than I (am). 表示“（两个中）较……的那个”时，比较级前常加the（后面有名字时前面才能加冠词） He is the taller of the two brothers. / He is taller than his two brothers. Which is larger, Canada or Australia? / Which is the larger country, Canada or Australia? 可用比较级形式表示最高级概念，关键是要用或或否定词等把一事物（或人）与其他同类事物（或人）相分离 He is taller than any other boy / anybody else.

英语中的比较级和最高级

大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和 -est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加 -er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。

英语比较级和最高级的用法归纳

英语比较级和最高级的用法归纳 在学习英语过程中，会遇到很多的语法问题，比如比较级和最高级的用法，对于 这些语法你能够掌握吗？下面是小编整理的英语比较级和最高级的用法，欢迎阅读！ 英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级 在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：bea utiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词 the，副词最高级前可不用。 例句： The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem.

英语比较级和最高级的用法

More than的用法 A. “More than+名词”表示“不仅仅是” 1)Modern science is more than a large amount of information. 2)Jason is more than a lecturer; he is a writer, too. 3) We need more than material wealth to build our country.建设我们国家，不仅仅需要物质财富. B. “More than+数词”含“以上”或“不止”之意，如： 4)I have known David for more than 20 years. 5)Let's carry out the test with more than the sample copy. 6) More than one person has made this suggestion. 不止一人提过这个建议. C. “More than+形容词”等于“很”或“非常”的意思，如： 7)In doing scientific experiments, one must be more than careful with the instruments. 8)I assure you I am more than glad to help you. D. more than + (that)从句，其基本意义是“超过（=over）”，但可译成“简直不”“远非”.难以，完全不能（其后通常连用情态动词can） 9) That is more than I can understand . 那非我所能懂的. 10) That is more than I can tell. 那事我实在不明白。 11) The heat there was more than he could stand. 那儿的炎热程度是他所不能忍受的 此外，“more than”也在一些惯用语中出现，如： more...than 的用法 1. 比……多，比……更 He has more books than me. 他的书比我多。 He is more careful than the others. 他比其他人更仔细。 2. 与其……不如 He is more lucky than clever. 与其说他聪明，不如说他幸运。 He is more （a）scholar than （a）teacher. 与其说他是位教师，不如说他是位学者。 注：该句型主要用于同一个人或物在两个不同性质或特征等方面的比较，其中的比较级必须用加more 的形式，不能用加词尾-er 的形式。 No more than/not more than 1. no more than 的意思是“仅仅”“只有”“最多不超过”，强调少。如： --This test takes no more than thirty minutes. 这个测验只要30分钟。 --The pub was no more than half full. 该酒吧的上座率最多不超过五成。-For thirty years，he had done no more than he （had）needed to. 30年来，他只干了他需要干的工作。 2. not more than 为more than （多于）的否定式，其意为“不多于”“不超过”。如：Not more than 10 guests came to her birthday party. 来参加她的生日宴会的客人不超过十人。 比较： She has no more than three hats. 她只有3顶帽子。（太少了） She has not more than three hats. 她至多有3顶帽子。（也许不到3顶帽子） I have no more than five yuan in my pocket. 我口袋里的钱最多不过5元。（言其少） I have not more than five yuan in my pocket. 我口袋里的钱不多于5元。（也许不到5元） more than, less than 的用法 1. （指数量）不到，不足 It’s less than half an hour’s drive from here. 开车到那里不到半个钟头。 In less than an hour he finished the work. 没要上一个小时，他就完成了工作。 2. 比……（小）少 She eats less than she should. 她吃得比她应该吃的少。 Half the group felt they spent less than average. 半数人觉得他们的花费低于平均水平。 more…than,/no more than/not more than (1)Mr．Li is ________ a professor; he is also a famous scientist． (2)As I had ________ five dollars with me, I couldn’t afford the new jacket then． (3)He had to work at the age of ________ twelve． (4)There were ________ ten chairs in the room．However, the number of the children is twelve． (5)If you tel l your father what you’ve done, he’ll be ________ angry． (6)－What did you think of this novel? －I was disappointed to find it ________ interesting ________ that one． 倍数表达法 1. “倍数+形容词（或副词）的比较级+than+从句”表示“A比B大（长、高、宽等）多少倍” This rope is twice longer than that one.这根绳是那根绳的三倍（比那根绳长两倍）。The car runs twice faster than that truck.这辆小车的速度比那辆卡车快两倍（是那辆卡车的三倍）。 2. “倍数+as+形容词或副词的原级+as+从句”表示“A正好是B的多少倍”。

初中英语比较级和最高级讲解与练习

初中英语比较级和最高级讲解与练习 形容词比较级和最高级 一．绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 1. 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 2. 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基 础上变化的。分为规则变化和不规则变化。 二．形容词比较级和最高级规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 wide (原级) wider (比较级) widest (最高级) 3) 少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和-est构成。 clever(原级) cleverer(比较级) cleverest(最高级)， slow(原级) slower(比较级) slowest (最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该 辅音字母然后再加-er和-est。 原形比较级最高级原形比较级最高级 big bigger biggest hot hotter hottest red redder reddest thin thinner thinnest 6) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构 成。 原形比较级最高级 careful careful more careful most careful difficult more difficult most difficult delicious more delicious most delicious 7)常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best 好的 well better best 身体好的 bad worse worst 坏的 ill worse worst 病的 many more most 许多 much more most 许多 few less least 少数几个 little less least 少数一点儿 （little littler littlest 小的） far further furthest 远（指更进一步，深度。亦可指更远） far farther farthest 远（指更远，路程）

英语比较级和最高级

形容词比较级和最高级的形式 一、形容词比较级和最高级的构成 形容词的比较级和最高级变化形式规则如下 构成法原级比较级最高级 ①一般单音节词末尾加 er 和 est strong stronger strongest ②单音节词如果以 e结尾，只加 r 和 st strange stranger strangest ③闭音节单音节词如末尾只有一个辅音字母， 须先双写这个辅音字母，再加 er和 est sad big hot sadder bigger hotter saddest biggest hottest ④少数以 y, er(或 ure), ow, ble结尾的双音节词， 末尾加 er和 est(以 y结尾的词，如 y前是辅音字母， 把y变成i，再加 er和 est，以 e结尾的词仍 只加 r和 st) angry Clever Narrow Noble angrier Cleverer narrower nobler angriest cleverest narrowest noblest ⑤其他双音节和多音节词都在前面加单词more和most different more different most different 1) The most high 〔A〕mountain in 〔B〕the world is Mount Everest，which is situated 〔C〕in Nepal and is twenty nine thousand one hundred and fourty one feet high 〔D〕 . 2) This house is spaciouser 〔A〕than that 〔B〕white 〔C〕one I bought in Rapid City，South Dakota 〔D〕last year. 3) Research in the social 〔A〕sciences often proves difficulter 〔B〕than similar 〔C〕work in the physical 〔D〕sciences. 二、形容词比较级或最高级的特殊形式：

高中英语的比较级和最高级用法总结

比较级和最高级 1.在形容词词尾加上―er‖ ―est‖ 构成比较级、最高级： bright（明亮的）—brighter—brightest broad（广阔的）—broader—broadest cheap（便宜的）—cheaper—cheapest clean（干净的）—cleaner—cleanest clever（聪明的）—cleverer—cleverest cold（寒冷的）—colder—coldest cool（凉的）—cooler—coolest dark（黑暗的）—darker—darkest dear（贵的）—dearer—dearest deep（深的）—deeper—deepest fast（迅速的）—faster—fastest few（少的）—fewer—fewest great（伟大的）—greater—greatest hard（困难的,硬的）—harder—hardest high（高的）—higher—highest kind（善良的）—kinder—kindest light（轻的）—lighter—lightest long（长的）—longer—longest loud（响亮的）—louder—loudest low（低的）—lower—lowest near（近的）—nearer—nearest new（新的）—newer—newest poor（穷的）—poorer—poorest quick（快的）—quicker—quickest quiet（安静的）—quieter—quietest rich（富裕的）—richer—richest short（短的）—shorter—shortest slow（慢的）—slower—slowest small（小的）—smaller—smallest smart（聪明的）—smarter—smartest soft（柔软的）—softer—softest strong（强壮的）—stronger—strongest sweet（甜的）—sweeter—sweetest tall（高的）-taller-tallest thick（厚的）—thicker—thickest warm（温暖的）—warmer—warmest weak（弱的）—weaker—weakest young（年轻的）—younger—youngest 2.双写最后一个字母,再加上―er‖ ―est‖构成比较级、最高级： big（大的）—bigger—biggest fat（胖的）—fatter—fattest hot（热的）—hotter—hottest red（红的）—redder—reddest sad（伤心的）—sadder—saddest thin（瘦的）—thinner—thinnest wet（湿的）—wetter—wettest mad（疯的）—madder—maddest 3.以不发音的字母e结尾的形容词,加上―r‖ ―st‖ 构成比较级、最高级：able（能干的）—abler—ablest brave（勇敢的）—braver—bravest close（接近的）—closer—closest fine（好的,完美的）—finer—finest large（巨大的）—larger—largest late（迟的）—later—latest nice（好的）—nicer—nicest ripe（成熟的）—riper—ripest

(完整版)初中英语比较级和最高级的用法

英语语法---比较级和最高级的用法 在英语中通常用下列方式表示的词:在形容词或副词前加more(如 more natural,more clearly )或加后缀 -er(newer,sooner )。典型的是指形容词或副词所表示的质、量或关系的增加。英语句子中，将比较两个主体的方法叫做“比较句型”。其中，像“A比B更……”的表达方式称为比较级；而“A最……”的表达方式则称为最高级。组成句子的方式是将形容词或副词变化成比较级或最高级的形态。 一、形容词、副词的比较级和最高级的构成规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音）中，先双写末尾的辅音字母，比较级加-er，最高级加-est； 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily

初中英语形容词比较级和最高级讲解与练习

初中英语形容词比较级和最高级讲解与练习 形容词比较级和最高级 绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。 例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。 wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加-er 和-est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音 字母然后再加-er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不"

(完整)初中英语比较级和最高级

◇下列形容词和副词没有比较级和最高 （即表示“最高程度”或“绝对状态”的形容词和副词没有比较级和最高级） empty, wrong, perfect, unique, extreme, excellent, favourite, true, right, correct, extremely ... 形容词副词比较级最高级使用注意事项 ◇比较应在同类事物之间进行。 误：Your English is better than me. 正：Your English is better than mine. ◇比较级前可以有一个表示程度的状语，最常见的三大修饰词是：a little, much, even。 以下单词也可用来修饰：any, far, still, a lot, yet, rather。 My sister is a little taller than me. Their house is much larger than ours. 另外，名词短语也可修饰比较级，说明程度。 I’m three years older than he. 特别提醒：very, quite, too不可修饰比较级。 ◇避免重复使用比较级。 误：He is more kinder to small animals than I. 正：He is much kinder to small animals than I. 误：He is more cleverer than his brother. 正：He is cleverer than his brother. ◇比较要符合逻辑，在同一范围内比较时，避免将主语含在比较对象中，这时需使用other来排除自身。 误：China is larger that any country in Asia. 正：China is larger than any other country in Asia. 误：John studies harder than any student in his class. 正：John studies harder than any other student in his class. 正：John studies harder than any of the other students in his class. 正：John studies harder than anyone else in his class. ◇比较要遵循前后一致的原则，注意前后呼应。 The population of Shanghai is larger than that of Beijing. It is easier to make a plan than to carry it out. ◇序数词通常只修饰最高级。 Africa is the second largest continent. The Yellow River is the second longest river in China. This is the third most popular song of Michael Jackson. ◇为避免重复，我们通常用that, those, one, ones代替前面出现的名词。that 代替可数名词单数和不可数名词，those代替可数名词复数。one既可指人又可指物，只能 代替可数名词。 The weather in China is different from that in America. The book on the table is more interesting than that(或the one)on the desk. A box made of steel is stronger than one made of wood. 误：In winter, the weather of Beijing is colder than it of Shanghai. 正：In winter, the weather of Beijing is colder than that of Shanghai. ◇“否定词 + 比较级”相当于最高级。

英语比较级和最高级

英语比较级和最高级

一、比较级和最高级的讲解 变化规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest n arrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音） 中，先双写末尾的辅音字母，比较级加-er，最高级加-est；

如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y 改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most d ifferent easily→more easily→most easily 注意： （1）形容词最高级前通常必须用定冠词the，副词最高级前可不用。 例句：The Sahara is the biggest desert in the world. （2）形容词most前面没有the，不表示最高级的含义，只表示"非常"。

英语比较级与最高级的解释和种类

形容词的比较级和最高级: 绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加-er 和-est 构成。 clever(原级) cleverer(比较级) cleverest(最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加-er和-est。 big (原级) bigger (比较级) biggest (最高级) ) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构成。beautiful (原级)? difficult (原级) more beautiful (比较级) more difficult (比较级) 常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best many more most much more most little less least ill worse worst far farther(further) farthest(furthest) 形容词前如加less 和lest 则表示"较不"和"最不" important 重要 less important 较不重要 lest important 最不重要 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。 It is warmer today than it was yesterday. 今天的天气比昨天暖和。 This picture is more beautiful than that one.

英语单词的比较级和最高级

little:形容词比较级littler/less/lesser 形容词最高级littlest/least 副词比较级less 副词最高级least far:形容词比较级farther/further 形容词最高级farthest/furthest 副词比较级farther/further 副词最高级farthest/furthest well:形容词比较级better 形容词最高级best 副词比较级better 副词最高级best ill:形容词比较级worse 形容词最高级worst 副词比较级worse 副词最高级worst many:形容词比较级more 形容词最高级most bad:形容词比较级worse 形容词最高级worst good:形容词比较级better 形容词最高级:best old:形容词比较级:older/elder 形容词最高级:oldest/eldest good:比较级better 最高级the best hot:比较级hotter 最高级the hottest heavy:比较级heavier 最高级the heaviest fine:比较级finer 最高级the finest exciting:比较级more exciting 最高级the most exciting bad:比较级worse 最高级the worst creative:比较级more creative 最高级the most creative boring:比较级more boring 最高级the most boring far:比较级farther/further 最高级the farthest/the furthest near:比较级nearer

英语比较级和最高级的用法

英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：beautiful→more beautiful→most beautiful different→more different→most different easi ly→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词the，副词最高级前可不用。 例句：The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem. 6.有少数形容词、副词的比较级和最高级是不规则的，必须熟记。 如：good→better→best well→better→best bad→worse→worst ill→worse→worst