• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    B-incorporated,N-doped hierarchically porous carbon nanosheets as anodes for boosted potassium storage capability

    2022-03-14 09:30:10YuHuChengTngHitoLiAijunDuWeiLuoMinghongWuHijioZhng
    Chinese Chemical Letters 2022年1期

    Yu Hu,Cheng Tng,Hito Li,Aijun Du,Wei Luo,Minghong Wu,Hijio Zhng,?

    aInstitute of Nanochemistry and Nanobiology,Shanghai University,Shanghai 200444,China

    bSchool of Chemistry,Physics and Mechanical Engineering,Science and Engineering Faculty,Queensland University of Technology,Brisbane QLD 4001,Australia

    cSchool of Environmental and Chemical Engineering,Shanghai University,Shanghai 200444,China

    dState Key Laboratory for Modification of Chemical Fibers and Polymer Materials,College of Materials Science and Engineering,Donghua University,Shanghai 201620,China

    ABSTRACT Carbonaceous nanomaterials with porous structure have become the highly promising anode materials for potassium-ion batteries(PIBs)due to their abundant resources,low-cost,and excellent conductivity.Nevertheless,the sluggish reaction kinetics and inferior cycling life caused by the large radius of K ions severely restrict their commercial development.Herein,B,N co-doped hierarchically porous carbon nanosheets(BNPC)are achieved via a facile template-assisted route,followed by a simple one-step carbonization process.The resultant BNPC possesses a unique porous structure,large surface area,and high-level B,N co-doping.The structural features endows it with remarkable potassium storage performances,which delivers a high reversible capacity(242.2 mAh/g at 100 mA/g after 100 cycles),and long cycling stability(123.1 mAh/g at 2000 mA/g and 62.9 mAh/g at 5000 mA/g after 2000 cycles,respectively).Theoretical simulations further validate that the rich B doping into N-modified carbon configuration can greatly boost the potassium storage capability of the BNPC anode.

    Keywords:Carbon nanosheets Hierarchical nanostructure B,N co-doping Anode materials Potassium-ion batteries

    Currently,the development and application of new energy have aroused significant attention along with the massive consumption of fossil fuels[1].Although lithium-ion batteries(LIBs)still dominate the overall energy storage markets[2],the overuse of Li resources and their uneven distribution on the earth further obstruct their large-scale applications[3].Thus,it is very imperative to explore the low-cost battery system with ideal electrochemical performances[4,5].Recently,potassium-ion batteries(PIBs)have been adapted as a highly appealing replaceable for LIBs owing to rich natural reserves,low redox potential,and similar electrochemical properties to Li[6-8].Nonetheless,in comparison to Li+(0.76 ?A)and Na+(1.02 ?A),the larger radius of K+(2.72 ?A)generally means the worse reaction kinetics and greater volume expansions during charge-discharge process,thereby causing low capacity,inferior rate performance,and dissatisfied cycling life[9,10].Therefore,it remains significantly desirable to develop advanced electrode materials for PIBs,especially for anode hosts.

    In these potential anodes,carbonaceous materials show an unparalleled advantage because of economic benefits,chemical stability,and superior conductivity[11,12].Significant attempts have been made to modulate the structure and composition of carbon anodes for optimizing their K+storage capabilities[13].Of them,the construction of three-dimensional(3D)hierarchical nanostructures composed of two-dimensional(2D)nanosheets has been confirmed to a direct and scalable method[14,15].Such a unique 2D/3D heterostructure can shorten the transmission path of electrons/ions and promote their diffusion kinetics in the electrochemical process,thus achieving the superior performance.For example,Yuet al.reported the 3D mesoporous carbon nanosheets with excellent energy storage properties[16].Jiet al.prepared Bicontinuous porous carbon spheres,showing a fast transmission behavior of K ions[17].Besides,the doping of heteroatoms such as N,S,B,is another popular protocol[18,19],which can not only improve the conductivity of carbon materials,but also provide more defects for potassium storage.Our recent work also demonstrates the advantages ofin-situN-doping into Ti3C2Txnanosheets,in favor of Na+storage[20].Compared with the single element doping,the co-doping of dual atoms(e.g.,B and N)is more attractive by fully taking advantage of their merits.Moreover,the doping process can also induce the enlargement of interlayer spacing of carbon materials[21].However,the current research mainly focuses on one or two directions for the carbon nanostructure regulating.Hence,exploring carbon electrodes with multiple structural meritsviaa facile and controllable strategy is highly desirable.

    Fig.1.(a)Schematic illustration of synthetic procedures of BNPC.(b,c)SEM images,(d-f)TEM images,(g)HRTEM image,and(h)STEM image and the EDX elemental mapping of BNPC.

    Herein,we present the controllable preparation of B,N codoped porous carbon nanosheets(BNPC)by skillfully selecting Nacetylglucosamine and MgO as the carbon precursor and hard template,respectively.The BNPC product shows large surface area,high-level B,N co-doping,distinct hierarchical nanostructure,and increased interlayer spacing.Such an ingenious configuration endows the BNPC anode with a remarkable potassium storage capability.Based on the experimental and theoretical results,the main reason for the excellent electrochemical performance is as follows:(1)High reversible capacity derived from more active sites owing to the co-doping of B and N into the carbon framework and high surface area;(2)Fast charge transfer dynamics caused by the 3D hierarchical nanostructure built by 2D carbon nanosheets and enlarged interlayer spacing;(3)Long cycling stability at high current density benefiting from the highly stable 3D conductive network.

    Fig.1a describes the entire synthetic process of BNPC.First,the MgO template with a particle size of about 50 nm was prepared(Fig.S1 in Supporting information).Second,N-acetylglucosamine precursor was pyrolyzed onto the MgO surface under the hydrothermal condition.After that,the resultant was uniformly mixed with a certain amount of boric acid by grinding,followed by a simple one-step carbonization process.At last,the MgO template was fully removed by acid washing.Here,it should be mentioned that another product was totally solid carbon spheres at the absence of the MgO template(Fig.S2 in Supporting information),indicating the vital role of the template in the formation of porous structures.

    Seen from SEM images(Figs.1b and c),the as-synthesized BNPC product shows a well-defined morphology and unique 3D hierarchical nanostructure,which is well constructed by many thin carbon nanosheets.Meanwhile,these randomly stacked nanosheets are interconnected to each other to produce a large number of open spaces.That will be beneficial for the transmission and diffusion of electrons/ions,and alleviation of the large volume changes during cycles.The TEM image in Fig.1d demonstrates that BNPC is mainly composed of folded interconnected nanosheets,which are well consistent with SEM observations.The detailed structure is further identified by the high magnification TEM images(Figs.1e and f).Interestingly,it is found that many holes exist into the rough surface of carbon nanosheets,as framed by the yellow dash line.That may be caused by the released gas molecules from the decomposition of boric acid during carbonization process,manifesting the abundant porosity.Additionally,the NPC product exhibits a totally different structure(Fig.S3 in Supporting information),suggesting that the B doping process further induces the formation of such a unique hierarchical structure for BNPC.Fig.1g shows the HRTEM image of BNPC.Clearly,it displays a relatively low crystallinity and expanded interlayer spacing of 0.364 nm,corresponding to the(002)crystal plane of carbon,which is larger than 0.335 nm of graphite[22].STEM image and EDX elemental mapping(Fig.1h)affirm the existence and good distributions of B and N elements in BNPC.

    Fig.2a shows XRD patterns of two products.There are two broad diffraction peaks centered at 25.4° and 42.9° in the NPC sample,corresponding to the(002)and(101)planes of carbon.That is the typical feature of amorphous carbon materials.Differently,the(002)broad peak of BNPC is shifted to the low degree at about 24.2°,suggesting an enlarged interlayer spacing.According to the Bragg equation,the layer spacing(002)of BNPC and NPC are calculated to be 0.365 nm and 0.34 nm,respectively,in line with the HRTEM analysis.The expansion reason for BNPC can be resulted from the boron and nitrogen co-doping.Raman spectroscopy is an effective tool to analyze the carbon microstructure.As displayed in Fig.2b,the D band at 1340 cm?1is described as the disordered carbon,whereas the G band at 1570 cm?1is characteristic of graphitization carbon.And their ratioID/IGusually reflects the graphitization degree of carbon materials[23].BNPC shows a higherID/IGof 1.04 than that of NPC(0.97),signifying the presence of more defects owing to the B,N co-doping into the carbon framework.The texture properties of two samples were further analyzed by N2absorption-desorption isotherm.As shown in Fig.2c,Figs.S4a and b(Supporting information),BNPC and NPC both show a type-IV hysteresis loop at the relative pressure ofP/P0=0.5–0.9,indicating the appearance of mesopores[24].The Barrett-Emmett-Teller(BET)surface area of BNPC is 528.5 m2/g,much higher than 361.6 m2/g of NPC.Importantly,the pore size distribution curve(inset of Fig.2c)further illustrates two kinds of different mesopores centered at 3.7 and 15–33 nm,matching well with the SEM/TEM observations.Such a unique hierarchical nanostructure with large mesopores will in favor of the K+fast transport dynamics.

    X-ray photoelectron spectroscopy(XPS)was further applied to detect the chemical state of BNPC.The high-resolution C 1s spectrum in Fig.2d shows five peaks at the binding energy of 283.9,284.81,285.62,286.54 and 289.18 eV,which are ascribed to CB,C–C,C–O,C=O or C=C and O–C=O,respectively[25,26].Additionally,five peaks appear at the binding energy of 530.7,531.6,532.67,533.86 and 535.23 eV in Fig.S5(Supporting information),corresponding to O=N,C=O(O-I),C–OH(O-II),COOH(O-III)and O-B,respectively[25].Impressively,four distinct peaks exist in Fig.2e,which belong to B-C(189.69 eV),B-C2O(190.73 eV),B-N(191.66 eV)and B-O or B-CO2(192.42 eV)[27,28],verifying the successful doping of B atoms.Fig.2f presents the high-resolution N 1s spectrum of BNPC.That is deconvoluted into N-B(397.73 eV),pyridinic N(N-6,398.8 eV),pyrrolic N(N-5,399.7 eV),graphitic N(NQ,401.23 eV)and N–O(403.17 eV),respectively[28].The ratio of pyridine N and pyrrole N is about 43.1% and 34.9%,respectively(Fig.S6 in Supporting information).As reported,the existence of N-5 and N-6 can bring more additional defects,thereby improve the storage of K+[26].The quantitative analysis shows that about 6.79 at% boron and 7.18 at% nitrogen have been successfully incorporated into the carbon configuration(Fig.S7 in Supporting information).Such a high-level B,N co-doping is expected to improve the storage potassium performance thanks to the formation of more defects and increased active sites[29].

    Fig.2.(a)XRD patterns,(b)Raman spectra,(c)N2 sorption isotherm(inset of(c)is its pore size distribution curve).(d-f)High-resolution XPS spectra for C 1s,B 1s and N 1s of BNPC.

    Fig.3.(a)CV curves of the first three cycles at 0.1 mV/s.(b)GDC curves of BNPC electrode at 100 mA/g.(c)Cycling performances at 100 mA/g.(d)Rate capabilities at different current densities ranging from 50 mA/g to 2000 mA/g.(e)Capacity retention of BNPC and NPC electrodes.(f)GDC curves at different current densities.(g)Long cycling stabilities of BNPC electrode at 2000 mA/g and 5000 mA/g over 2000 cycles,respectively.

    The electrochemical performances of BNPC and NPC electrodes as PIBs anodes were systemically studied.Fig.3a illustrates the CV curves of the BNPC electrode for the initial three cycles at 0.1 mV/s.The CV curve of the first cycle exhibits anodic peak at 0.5 V,and cathodic peaks at 0.6 V.The cathodic peak at 0.6 V is attributed to the decomposition of the electrolyte and the generation of a solid electrolyte intermediate phase(SEI)[30],which obviously weakens in the second cycle.The broad anodic peak at near 0.5 V is related to the step potassiation process in carbonbased electrodes[31].Importantly,CV curves almost overlap in the subsequent two cycles,indicating its excellent electrochemical reversibility.Fig.3b shows charge/discharge profiles of BNPC electrode for the first three cycles within the voltage window of 0.01–3.0 Vvs.K/K+at 0.1 A/g.The initial discharge and charge capacities are 1135.5 and 269.5 mAh/g,respectively,showing an initial coulomb efficiency(ICE)of 23.7%.The initial large capacity loss is mainly due to the electrolyte decomposition and the SEI film formation[32].Meanwhile,the low ICE can be enhanced by prepotassiation strategy.In the second cycle,the CE value is increased to 58.9%,and then maintained at about 99.0% after 100 cycles,indicating that the irreversible capacity loss can be relieved during cycling.

    Fig.4.(a)CV curves of BNPC electrode at different scan rates.(b) b-values plotted for the anodic peak and cathodic peak.(c)Capacitive behavior(yellow region)and diffusion behavior(green region)contributions of BNPC at 0.6 mV/s.(d)Normalized contribution ratio of capacitive behavior and diffusion behavior capacities at different scan rates of BNPC.(e)Electrochemical impedance spectra of BNPC and NPC electrodes(inset of(e))is the corresponding equivalent circuit).(f)K diffusion coefficients of BNPC and NPC electrodes.(g)Comparison of the potassium storage performances between the BNPC anode with previously reported carbonaceous materials.(h)Schematic illustration of possible potassium storage mechanism for BNPC.

    Fig.3c displays the cycling stability of two electrodes.Obviously,the BNPC demonstrates a higher reversible capacity and better cycling stability than the control NPC.The charge capacity of BNPC still maintains to be 242.4 mAh/g and nearly 100% coulombic efficiency after 100 cycles at 0.1 A/g,while NPC only provides the capacity of 160 mAh/g.The rate performance of BNPC and NPC electrodes at current density from 0.05 A/g to 2 A/g are presented in Fig.3d.Notably,BNPC exhibits high reversible specific capacities of 314.5,301.2,255.4,227.1 and 176.1 mAh/g at current densities of 50,100,200,500 and 1000 mA/g,respectively.Even at 2000 mA/g,a large reversible specific capacity of 134.5 mAh/g can still be reached.Moreover,when the current density was reset to 100 mA/g,a discharge capacity was recovered to 274.7 mAh/g for BNPC,illustrating an outstanding reversible stability at high current densities.That corresponds to the capacity retention of 100,84.9,75.5,58.5,44.7 and 91.7,respectively(Fig.3e).In comparison,NPC has low reversible capacities of 259.5 and 36.1 mAh/g at current densities of 50 and 2000 mA/g,respectively.Fig.3f shows the charge-discharge curves of BNPC at different current densities,implying capacitive-controlled storage processes.To better show the superiority of BNPC as anodes for PIBs,we also investigate its long-term cycling performance at 2000 mA/g and 5000 mA/g.As shown in Fig.3g,BNPC still keeps a high reversible capacity of 123.1 mAh/g and 62.9 mAh/g after 2000 cycles,respectively,and large coulombic efficiency of nearly 100%.In contrast,NPC only delivers a low capacity of 58.0 mAh/g after 500 cycles at 2000 mA/g(Fig.S8 in Supporting information).Moreover,the BNPC electrode retains the 3D nanostructure well after cycling,which verifies its good structural stability(Fig.S9 in Supporting information).As listed in Table S1(Supporting information),the BNPC anode for PIBs developed in the work outperforms most of the reported carbon-based anodes,highlighting the superiority of B,N co-doping.

    CV measurements at various scan rates ranging from 0.1 mV/s to 2.0 mV/s were further measured to investigate the potassium storage kinetics of BNPC and NPC(Fig.4a and Fig.S10a in Supporting information).As shown in these curves,BNPC maintains the original shape,which becomes broader with increasing scan rates.Furthermore,even the scan rate reaches as high as 2.0 mV/s,the basic characteristics remain well,indicating that BNPC possesses a superior response capability to PIBs.

    The K+storage contribution including the surface capacitive and diffusion contribution was investigated according to the power-law formula[33]:

    Theb-value can be obtained to determine the electrochemical behavior predominated by semi-infinite diffusion(b~0.5)or capacitive process(b~1.0).In Fig.4b,the anodic process exhibitsb-value of 0.88,while cathodic process is 0.73.As a result,the electrochemical process is mainly determined by the surface capacitance,resulting from the high surface area and rich defects owing to the co-doping of B and N.

    The following formula can be analyzed the contribution value of the capacitance control process:

    Fig.4c shows a 70.7% of capacitive contribution(yellow region)from the total capacity at 0.6 mV/s for BNPC.Meanwhile,the capacitance contribution rate gradually increases as the scan rate increasing(Fig.4d).When the scan rate is added from 0.2 mV/s to 1 mV/s,the capacitance contribution rate increases from 61.5% to 79.8%,much higher than those of NPC(Fig.S10b in Supporting information).The above results reveal that the capacitance-guided and diffusion-controlled processes are both embodied in the electrochemical reaction of BNPC,and the contribution rate of the surface dominant behavior is in a larger proportion.This high capacitance contribution is mainly due to the presence of many defects in the BNPC anode.

    Fig.5.The top and side views of K+ adsorption on(a)graphitic,(e)pyridinic- and(i)pyrrolic N-functionalized carbon(N–C).The corresponding K adsorbed geometries of B-doped(b-d)graphitic,(f-h)pyridinic- and(j-m)pyrrolic-N functionalized carbon(B-N-C)at marked I,II,III and IV sites,respectively.The adsorption energies and bond lengths of N-K and B-K are listed below each geometry.Purple,brown,gray,green and white spheres represent K,C,N,B and H atoms,respectively.(n,o)Charge density difference(isovalue of 0.001 e/?A3)for K adsorbed pyridinic-N functionalized carbon without and with B(II)substitution.Cyan and yellow areas reflect the electron depletion and accumulation.Blue and red circles show the charge difference around doped N and B center,respectively.

    The electrochemical impedance spectra(EIS)of BNPC and NPC were also measured for further analysis of their diffusion kinetics.Fig.4e shows the initial Nyquist plots of BNPC and NPC electrodes.The impedance spectrum contains an inclined line at the low frequency range and a concave semicircle at the high frequency range,which are assigned to the resistance to charge transfer(Rct)and Warburg impedance(Zw),respectively.The Z-view software analysis indicates that BNPC has a smaller resistance of 331.4Ωthan that of NPC(839.5Ω),revealing a better conductivity and faster diffusion kinetics.

    Galvanostatic intermittent titration(GITT)was applied to identify the K+diffusion coefficient(D)of two electrodes under different voltages.DKvalue can be calculated by the following formula[34]:

    From the GITT results(Fig.4f and Fig.S11),we can see that the D value of BNPC is 10?9cm2/s to 10?12cm2/s,while the NPC is 10?10to 10?13,further verifying the faster diffusivity of K+for BNPC.Impressively,the superior rate performance for potassium storage is comparable to most of previous carbon-based anodes,as summarized in Fig.4g[35-39].Fig.4h describes the schematic diagram of possible storage potassium mechanism of BNPC.Considering that K ions tend to form K-intercalated carbon compounds(KICs)at defect sites[39],more additional defects brought by the B,N co-doping are favorable for the adsorption of K ions,and the unique hierarchical nanostructure can facilitate the rapid transport of K ions and electrons,thus boosting the potassium storage performance for BNPC anode.

    For the sake of clarifying the superior potassium storage performance,we then examine the adsorbed behavior of K ions on Nfunctionalized carbon(N–C)layers with and without the B doping.According to previous work[40],three types of N–C nanosheets are adopted in our calculations.As illustrated in Figs.5a,e,i,the adsorption energies of K+are ?0.84,?1.69 and ?2.54 eV for graphitic,pyridinic and pyrrolic N–C layer,respectively.The bond length of K-N in graphitic N case is significantly larger than other two cases,leading to much weaker K+adsorption performance.As a result,K ions prefer to adsorb onto the pyrrolic N–C layer compared with graphilic and pyridinic ones.

    The K+adsorption on N–C layer after B doping(B-N-C)was further evaluated.Fig.5 gives the corresponding adsorption energies and bond lengths of K-N and K-B for each K adsorbed B-N-C layer.Generally,the different B-doped sites show the small impact on the following K adsorption.For B-graphitic N–C case,the absolute values of the adsorption energies reach up to 1.60 eV,which is remarkably larger than that of graphilic N–C layer(0.84 eV),indicating the enhanced K+adsorption performance.Despite of the initial position set for K+adsorption,it largely shifts towards B side during relaxation,suggesting that B sites are more attractive for K+adsorption than N sites.Besides,such enhanced performance also happens when B doping into the pyridinic and pyrrolic N–C nanosheets.In two cases,doped N and B atoms simultaneously work on and balances the K+adsorption.Additionally,we also calculate the charge density difference of the K adsorbed pyridinic N–C with and without B(II)doping.As displayed in Figs.5n and o,the charge density around N site(blue circle)almost remains unchanged with and without the existence of B.However,the accumulated electrons around B(red circle)are remarkably increased in comparison to those around C or N,mainly resulting in the enhanced K+adsorption performance.Taken together,the doping of B atoms will greatly improve the K+capability of N-modified carbon layers.

    To sum up,we have developed a scalable structural engineering technique for synthesis of B,N co-doped porous carbon nanosheets through a facile template-assisted route and simple carbonization process.Such a unique architecture can facilitate the transmission of ions/electrons,and the co-doping of B and N can increase the conductivity and offer more defects for K ions storage.All of the structural merits together account for the outstanding potassium storage capability.The constructed BNPC anode delivers a high reversible capacity(242.2 mAh/g at 100 mA/g after 100 cycles)and an outstanding long-term cycling stability(123.1 mAh/g at 2000 mA/g and 62.9 mAh/g at 5000 mA/g after 2000 cycles,respectively).The present study proposed can also provide a scalable feasibility for the development and design of advanced carbonbased electrode materials.

    Declaration of competing interest

    The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

    Acknowledgments

    The work was supported by Shuguang Program from Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.18SG035),and State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University(No.KF2015).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2021.06.063.

    久久久久久久久久久久大奶| 91老司机精品| 欧美中文综合在线视频| svipshipincom国产片| 欧美另类亚洲清纯唯美| 级片在线观看| 精品熟女少妇八av免费久了| 亚洲五月天丁香| 亚洲欧美一区二区三区黑人| 一个人免费在线观看的高清视频| 国产亚洲精品久久久久5区| 日日干狠狠操夜夜爽| 久久人妻熟女aⅴ| 国产熟女午夜一区二区三区| 欧美一级a爱片免费观看看 | 欧美色视频一区免费| 99久久综合精品五月天人人| 搞女人的毛片| 亚洲成人精品中文字幕电影| 亚洲狠狠婷婷综合久久图片| 99riav亚洲国产免费| 色av中文字幕| 国产乱人伦免费视频| 亚洲美女黄片视频| 黄色视频,在线免费观看| 久久香蕉激情| 亚洲 欧美一区二区三区| 久久香蕉精品热| 一a级毛片在线观看| 国产av精品麻豆| 别揉我奶头~嗯~啊~动态视频| 级片在线观看| 中文亚洲av片在线观看爽| 男女下面进入的视频免费午夜 | 最近最新中文字幕大全免费视频| 亚洲人成电影免费在线| 免费一级毛片在线播放高清视频 | 美女 人体艺术 gogo| 亚洲欧美日韩高清在线视频| 老汉色∧v一级毛片| 色综合亚洲欧美另类图片| 两个人视频免费观看高清| 欧美色欧美亚洲另类二区 | 免费观看人在逋| 国产麻豆成人av免费视频| 久久人人爽av亚洲精品天堂| 999精品在线视频| 欧美黑人欧美精品刺激| 麻豆国产av国片精品| 久久午夜综合久久蜜桃| 国产午夜福利久久久久久| 色综合亚洲欧美另类图片| a级毛片在线看网站| 色av中文字幕| 欧美激情久久久久久爽电影 | 日韩大码丰满熟妇| 国产亚洲精品久久久久5区| 久久婷婷成人综合色麻豆| 激情在线观看视频在线高清| 国产精品免费视频内射| 免费在线观看影片大全网站| 波多野结衣高清无吗| 啦啦啦 在线观看视频| 亚洲色图 男人天堂 中文字幕| 亚洲欧洲精品一区二区精品久久久| 又黄又爽又免费观看的视频| 波多野结衣av一区二区av| 国产亚洲欧美在线一区二区| av福利片在线| 欧美日本视频| 亚洲国产精品sss在线观看| 丝袜美腿诱惑在线| 国产区一区二久久| 一级毛片女人18水好多| 亚洲中文字幕日韩| 亚洲熟妇熟女久久| 国产欧美日韩综合在线一区二区| 看片在线看免费视频| 悠悠久久av| 中文字幕人妻丝袜一区二区| 久久九九热精品免费| 国产日韩一区二区三区精品不卡| 黄色 视频免费看| 亚洲成av片中文字幕在线观看| 两性夫妻黄色片| 久久人妻av系列| 夜夜看夜夜爽夜夜摸| 日本在线视频免费播放| 亚洲男人的天堂狠狠| 成人国产综合亚洲| 1024香蕉在线观看| 69精品国产乱码久久久| 免费一级毛片在线播放高清视频 | 桃红色精品国产亚洲av| 欧美国产日韩亚洲一区| 手机成人av网站| avwww免费| 69av精品久久久久久| 婷婷丁香在线五月| 国产视频一区二区在线看| 日韩欧美一区二区三区在线观看| 在线观看午夜福利视频| 国产亚洲欧美98| 美女扒开内裤让男人捅视频| 97碰自拍视频| 国产亚洲精品久久久久久毛片| 婷婷精品国产亚洲av在线| 亚洲三区欧美一区| 欧美亚洲日本最大视频资源| 亚洲成人免费电影在线观看| 好男人电影高清在线观看| av在线播放免费不卡| 天堂√8在线中文| 久久中文字幕一级| 丰满人妻熟妇乱又伦精品不卡| 久热爱精品视频在线9| 黄色女人牲交| 真人一进一出gif抽搐免费| 黄色a级毛片大全视频| 国产精品综合久久久久久久免费 | av福利片在线| 女性被躁到高潮视频| 日韩成人在线观看一区二区三区| 国产午夜精品久久久久久| 香蕉丝袜av| bbb黄色大片| 50天的宝宝边吃奶边哭怎么回事| 在线观看免费视频日本深夜| 精品久久久久久,| 男女床上黄色一级片免费看| 51午夜福利影视在线观看| 别揉我奶头~嗯~啊~动态视频| www.精华液| 欧美乱码精品一区二区三区| 成人国产一区最新在线观看| 欧美在线黄色| 亚洲,欧美精品.| 天天添夜夜摸| 国产成人av教育| 国产成人av激情在线播放| 老熟妇乱子伦视频在线观看| 亚洲一区二区三区色噜噜| 天天躁狠狠躁夜夜躁狠狠躁| 18禁国产床啪视频网站| 老汉色av国产亚洲站长工具| 中国美女看黄片| 久久久国产成人精品二区| 黑人欧美特级aaaaaa片| 亚洲三区欧美一区| 久久中文字幕一级| 制服人妻中文乱码| 黄色 视频免费看| 叶爱在线成人免费视频播放| 多毛熟女@视频| 成人特级黄色片久久久久久久| 国产黄a三级三级三级人| 非洲黑人性xxxx精品又粗又长| 国产亚洲精品av在线| 亚洲中文字幕一区二区三区有码在线看 | 天堂影院成人在线观看| 国产亚洲精品综合一区在线观看 | 少妇裸体淫交视频免费看高清 | 激情视频va一区二区三区| 丰满的人妻完整版| 99精品久久久久人妻精品| 欧美乱码精品一区二区三区| 亚洲男人天堂网一区| 中文字幕人妻熟女乱码| 少妇熟女aⅴ在线视频| 婷婷六月久久综合丁香| 中文字幕人妻熟女乱码| 两性午夜刺激爽爽歪歪视频在线观看 | 黄色丝袜av网址大全| 亚洲国产高清在线一区二区三 | 欧美黑人欧美精品刺激| 欧美丝袜亚洲另类 | 香蕉国产在线看| 波多野结衣巨乳人妻| 久久久久亚洲av毛片大全| 91成人精品电影| 免费在线观看日本一区| 中文字幕久久专区| 黄色a级毛片大全视频| 精品欧美一区二区三区在线| 亚洲av片天天在线观看| 欧美亚洲日本最大视频资源| 18禁国产床啪视频网站| 久久亚洲真实| 亚洲国产中文字幕在线视频| 99久久99久久久精品蜜桃| 亚洲国产精品sss在线观看| 一边摸一边抽搐一进一小说| 精品高清国产在线一区| 国产xxxxx性猛交| 18禁裸乳无遮挡免费网站照片 | 我的亚洲天堂| 美女午夜性视频免费| 国产精品久久视频播放| 欧美日韩乱码在线| 正在播放国产对白刺激| 身体一侧抽搐| cao死你这个sao货| 99国产精品99久久久久| 国产精品久久久人人做人人爽| av福利片在线| 亚洲人成网站在线播放欧美日韩| 极品教师在线免费播放| 久久人人爽av亚洲精品天堂| 一a级毛片在线观看| 99在线视频只有这里精品首页| 咕卡用的链子| 国产私拍福利视频在线观看| 国产精品亚洲av一区麻豆| 一级a爱视频在线免费观看| АⅤ资源中文在线天堂| 亚洲精品国产一区二区精华液| 精品国产亚洲在线| 日本免费a在线| 久久久久精品国产欧美久久久| ponron亚洲| cao死你这个sao货| 国产熟女xx| 免费av毛片视频| 操出白浆在线播放| 亚洲国产高清在线一区二区三 | 视频在线观看一区二区三区| 麻豆一二三区av精品| 亚洲国产看品久久| 两人在一起打扑克的视频| 国语自产精品视频在线第100页| 长腿黑丝高跟| svipshipincom国产片| 好男人电影高清在线观看| 久久久久久久久久久久大奶| 在线国产一区二区在线| www.999成人在线观看| 在线av久久热| 动漫黄色视频在线观看| 男女之事视频高清在线观看| 丁香六月欧美| 美女高潮喷水抽搐中文字幕| 国产激情久久老熟女| 少妇粗大呻吟视频| 亚洲av熟女| 日韩大尺度精品在线看网址 | 精品第一国产精品| 国产成人系列免费观看| 国产极品粉嫩免费观看在线| 国产精品野战在线观看| 波多野结衣高清无吗| 亚洲 欧美一区二区三区| 超碰成人久久| 国产视频一区二区在线看| 韩国精品一区二区三区| 黄色视频,在线免费观看| 国产精品久久电影中文字幕| 国产精品一区二区精品视频观看| 欧美激情 高清一区二区三区| 久久精品人人爽人人爽视色| 中亚洲国语对白在线视频| 欧美日韩亚洲国产一区二区在线观看| 9191精品国产免费久久| 国产亚洲精品综合一区在线观看 | 一进一出抽搐动态| 老司机福利观看| 国产人伦9x9x在线观看| 激情在线观看视频在线高清| 亚洲全国av大片| 女生性感内裤真人,穿戴方法视频| 国产精品久久视频播放| 看免费av毛片| 在线观看免费视频日本深夜| 欧美亚洲日本最大视频资源| 国产午夜精品久久久久久| x7x7x7水蜜桃| 国产精品亚洲美女久久久| 丰满人妻熟妇乱又伦精品不卡| 国产乱人伦免费视频| 黄色 视频免费看| 变态另类丝袜制服| 男人操女人黄网站| 50天的宝宝边吃奶边哭怎么回事| 精品一区二区三区av网在线观看| 99久久久亚洲精品蜜臀av| 天堂动漫精品| 中亚洲国语对白在线视频| 国产日韩一区二区三区精品不卡| 搞女人的毛片| 两个人免费观看高清视频| 免费在线观看完整版高清| 99国产精品一区二区蜜桃av| 久久人妻av系列| 在线观看www视频免费| 成人免费观看视频高清| 精品欧美国产一区二区三| 国产在线精品亚洲第一网站| 国产一级毛片七仙女欲春2 | 久久久久久久精品吃奶| 欧美色欧美亚洲另类二区 | 久久中文字幕一级| 香蕉国产在线看| 亚洲欧美日韩高清在线视频| 亚洲精品中文字幕在线视频| 叶爱在线成人免费视频播放| 久久影院123| 好男人电影高清在线观看| 一a级毛片在线观看| 91国产中文字幕| 美女扒开内裤让男人捅视频| 国产亚洲精品久久久久久毛片| 在线天堂中文资源库| 18美女黄网站色大片免费观看| 在线播放国产精品三级| 亚洲欧美精品综合一区二区三区| 亚洲第一av免费看| 狠狠狠狠99中文字幕| 熟女少妇亚洲综合色aaa.| 9热在线视频观看99| 91麻豆精品激情在线观看国产| 欧美激情高清一区二区三区| 国产单亲对白刺激| 成人永久免费在线观看视频| 亚洲第一av免费看| www.www免费av| 亚洲色图 男人天堂 中文字幕| 无限看片的www在线观看| 91字幕亚洲| 免费在线观看完整版高清| 午夜老司机福利片| 真人做人爱边吃奶动态| 国产高清激情床上av| 午夜精品久久久久久毛片777| 9191精品国产免费久久| 久久久久久免费高清国产稀缺| 亚洲精品国产精品久久久不卡| 亚洲精品国产一区二区精华液| 久久久久久人人人人人| а√天堂www在线а√下载| 国产97色在线日韩免费| 亚洲专区字幕在线| 精品乱码久久久久久99久播| 黄色片一级片一级黄色片| 国语自产精品视频在线第100页| 欧美日韩中文字幕国产精品一区二区三区 | 两个人视频免费观看高清| 高清在线国产一区| 天天躁夜夜躁狠狠躁躁| 亚洲九九香蕉| 国产人伦9x9x在线观看| 女同久久另类99精品国产91| 岛国视频午夜一区免费看| 亚洲欧美激情综合另类| 亚洲自偷自拍图片 自拍| 成人三级黄色视频| 国产亚洲av嫩草精品影院| 真人做人爱边吃奶动态| 12—13女人毛片做爰片一| 亚洲中文av在线| 亚洲精品国产一区二区精华液| 欧美一区二区精品小视频在线| 69av精品久久久久久| 久久 成人 亚洲| 精品国产一区二区三区四区第35| 国产成人精品久久二区二区91| 亚洲国产精品久久男人天堂| 国产亚洲精品久久久久久毛片| 久久久久久久午夜电影| 多毛熟女@视频| 悠悠久久av| videosex国产| 99精品久久久久人妻精品| 黄色丝袜av网址大全| 国产亚洲精品一区二区www| 黑人巨大精品欧美一区二区蜜桃| 久久精品国产亚洲av香蕉五月| 日韩大码丰满熟妇| 色综合婷婷激情| 一二三四在线观看免费中文在| 国产精品久久久av美女十八| 后天国语完整版免费观看| 欧美乱码精品一区二区三区| 亚洲第一青青草原| 成人手机av| 精品国内亚洲2022精品成人| 天天躁狠狠躁夜夜躁狠狠躁| 久久精品人人爽人人爽视色| 操美女的视频在线观看| 熟妇人妻久久中文字幕3abv| 国产xxxxx性猛交| 精品熟女少妇八av免费久了| 色播在线永久视频| 18禁观看日本| 一级片免费观看大全| 国产精品久久电影中文字幕| 老司机在亚洲福利影院| 美女高潮到喷水免费观看| 女人精品久久久久毛片| 亚洲成人免费电影在线观看| 亚洲久久久国产精品| 亚洲成a人片在线一区二区| 中文亚洲av片在线观看爽| 亚洲欧美一区二区三区黑人| 91麻豆av在线| 老司机靠b影院| 亚洲狠狠婷婷综合久久图片| 国产人伦9x9x在线观看| 免费少妇av软件| 香蕉国产在线看| 国产精品国产高清国产av| 亚洲男人天堂网一区| 性欧美人与动物交配| 精品国产超薄肉色丝袜足j| 欧美黄色片欧美黄色片| 性少妇av在线| 91在线观看av| 999久久久精品免费观看国产| 欧美成人性av电影在线观看| 级片在线观看| 女人高潮潮喷娇喘18禁视频| 久久中文字幕人妻熟女| 国产片内射在线| 999久久久国产精品视频| 亚洲人成电影观看| 国产成人精品久久二区二区免费| 国产精品久久久av美女十八| 最近最新免费中文字幕在线| 9191精品国产免费久久| 国产一卡二卡三卡精品| 亚洲第一欧美日韩一区二区三区| 亚洲精品中文字幕在线视频| 国产精品av久久久久免费| 中亚洲国语对白在线视频| 日本vs欧美在线观看视频| 亚洲午夜理论影院| 日韩精品中文字幕看吧| 丁香欧美五月| 精品国产乱码久久久久久男人| 色综合欧美亚洲国产小说| 超碰成人久久| 最好的美女福利视频网| 亚洲成人国产一区在线观看| 国产伦人伦偷精品视频| 好男人在线观看高清免费视频 | 99riav亚洲国产免费| 精品日产1卡2卡| 精品一区二区三区av网在线观看| 99国产精品一区二区三区| 亚洲精品美女久久久久99蜜臀| 日韩三级视频一区二区三区| 国内精品久久久久久久电影| av电影中文网址| 国产又爽黄色视频| 两性夫妻黄色片| 亚洲精品中文字幕在线视频| 青草久久国产| 午夜久久久久精精品| 不卡一级毛片| 久久亚洲真实| 色播在线永久视频| 成人免费观看视频高清| 我的亚洲天堂| 国产精品久久久久久精品电影 | 午夜久久久久精精品| 欧美在线黄色| 在线av久久热| 美女大奶头视频| 女人精品久久久久毛片| 免费看a级黄色片| 女人被狂操c到高潮| 精品电影一区二区在线| 别揉我奶头~嗯~啊~动态视频| 每晚都被弄得嗷嗷叫到高潮| 欧美色视频一区免费| 久久婷婷成人综合色麻豆| 亚洲aⅴ乱码一区二区在线播放 | 亚洲九九香蕉| 一区在线观看完整版| 妹子高潮喷水视频| 男女床上黄色一级片免费看| 久久午夜综合久久蜜桃| 巨乳人妻的诱惑在线观看| 给我免费播放毛片高清在线观看| 一边摸一边抽搐一进一出视频| 香蕉丝袜av| 亚洲专区字幕在线| 国产一区二区三区综合在线观看| www.精华液| 久久亚洲精品不卡| 在线av久久热| 老熟妇仑乱视频hdxx| 久久九九热精品免费| 看免费av毛片| 国产精品久久电影中文字幕| 看免费av毛片| 一区二区三区高清视频在线| 露出奶头的视频| 国产高清videossex| 身体一侧抽搐| 日日干狠狠操夜夜爽| 久久久久精品国产欧美久久久| 在线观看免费视频网站a站| 国内毛片毛片毛片毛片毛片| 丰满人妻熟妇乱又伦精品不卡| 两性午夜刺激爽爽歪歪视频在线观看 | 午夜福利18| 国产精品久久视频播放| 国产伦一二天堂av在线观看| 天堂√8在线中文| 久久香蕉激情| av免费在线观看网站| 国产精品免费一区二区三区在线| 高清毛片免费观看视频网站| xxx96com| 国产xxxxx性猛交| 满18在线观看网站| 国产单亲对白刺激| 欧美日韩精品网址| 老汉色av国产亚洲站长工具| 波多野结衣一区麻豆| 久久国产亚洲av麻豆专区| 在线视频色国产色| 亚洲成av人片免费观看| 两人在一起打扑克的视频| 欧美精品亚洲一区二区| 亚洲熟妇中文字幕五十中出| 久久久精品国产亚洲av高清涩受| 看免费av毛片| 天天躁狠狠躁夜夜躁狠狠躁| 国产精品久久久久久人妻精品电影| 午夜免费鲁丝| 国产精品影院久久| 在线观看免费日韩欧美大片| 亚洲欧美精品综合一区二区三区| 国产一区二区三区在线臀色熟女| 可以在线观看毛片的网站| 成在线人永久免费视频| 国产成+人综合+亚洲专区| 99riav亚洲国产免费| 亚洲国产高清在线一区二区三 | bbb黄色大片| 欧美一区二区精品小视频在线| 校园春色视频在线观看| 国产又爽黄色视频| 99精品在免费线老司机午夜| 99国产精品免费福利视频| 又黄又粗又硬又大视频| 免费女性裸体啪啪无遮挡网站| 妹子高潮喷水视频| 波多野结衣一区麻豆| 国产精品久久久av美女十八| 少妇的丰满在线观看| 88av欧美| 女人爽到高潮嗷嗷叫在线视频| 91成年电影在线观看| 黑人巨大精品欧美一区二区mp4| 日日干狠狠操夜夜爽| 国产高清视频在线播放一区| 99香蕉大伊视频| 亚洲国产看品久久| 91麻豆av在线| 国产一区二区激情短视频| 欧美绝顶高潮抽搐喷水| 高清黄色对白视频在线免费看| 麻豆久久精品国产亚洲av| 久久香蕉激情| 日韩欧美一区视频在线观看| 级片在线观看| 午夜亚洲福利在线播放| 亚洲av五月六月丁香网| 精品无人区乱码1区二区| 99国产极品粉嫩在线观看| 9色porny在线观看| www.999成人在线观看| 美女国产高潮福利片在线看| 亚洲一卡2卡3卡4卡5卡精品中文| 久久久久久人人人人人| 亚洲第一电影网av| 亚洲片人在线观看| 亚洲国产日韩欧美精品在线观看 | 99国产综合亚洲精品| 久久精品91蜜桃| 精品午夜福利视频在线观看一区| 国产精品香港三级国产av潘金莲| 亚洲av片天天在线观看| 国产亚洲av嫩草精品影院| 国产成人欧美| 欧美国产日韩亚洲一区| 久久人妻福利社区极品人妻图片| 欧美绝顶高潮抽搐喷水| 国产欧美日韩综合在线一区二区| 亚洲激情在线av| 久久青草综合色| 人成视频在线观看免费观看| 嫩草影视91久久| 国产单亲对白刺激| 亚洲中文av在线| 亚洲精品一卡2卡三卡4卡5卡| 午夜精品在线福利| 久久精品aⅴ一区二区三区四区| 级片在线观看| 亚洲性夜色夜夜综合| 欧美亚洲日本最大视频资源| 波多野结衣一区麻豆| 午夜福利一区二区在线看| 无限看片的www在线观看| 国产成人精品久久二区二区91| 日韩精品青青久久久久久| 制服人妻中文乱码| av免费在线观看网站| e午夜精品久久久久久久| 国产一区二区三区综合在线观看| 国产精品免费视频内射| www国产在线视频色| 中文字幕人成人乱码亚洲影| 级片在线观看|