• <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 ?

    Copper-induced formation of heterostructured Co3O4/CuO hollow nanospheres towards greatly enhanced lithium storage performance

    2024-04-05 02:28:58JunjunZhngHuiyingLuTinhoYoXinJiQingmioZhngLingjieMengJinminFengHongkngWng
    Chinese Chemical Letters 2024年2期

    Junjun Zhng ,Huiying Lu ,Tinho Yo ,Xin Ji ,Qingmio Zhng ,Lingjie Meng ,Jinmin Feng,Hongkng Wng,*

    a College of Geography & Environment,Xianyang Normal University,Xianyang 712000,China

    b State Key Lab of Electrical Insulation and Power Equipment,Center of Nanomaterials for Renewable Energy (CNRE),School of Electrical Engineering,Xi’an Jiaotong University,Xi’an 710049,China

    c School of Chemistry,Xi’an Key Laboratory of Sustainable Energy Material Chemistry,and Instrumental Analysis Center,Xi’an Jiaotong University,Xi’an 710049,China

    Keywords: Lithium-ion batteries Co/Cu-glycerate Hollow nanospheres Co3O4/CuO heterostructure Electrochemical properties

    ABSTRACT We report a facile template-free fabrication of heterostructured Co3O4/CuO hollow nanospheres using pre-synthesized Co/Cu-glycerate as conformal precursor.The introduction of copper nitrate in the solvothermal reaction system of glycerol/isopropanol/cobalt nitrate readily induces the conversion from solid Co-glycerate to hollow Co/Cu-glycerate nanospheres,and the effect of the Co/Cu atomic ratio on the structure evolution of the metal glycerates as well as their corresponding oxides were investigated.When examined as anode materials for lithium-ion batteries,the well-defined Co3O4/CuO hollow nanospheres with Co/Cu molar ratio of 2.0 demonstrate excellent lithium storage performance,delivering a high reversible capacity of 930 mAh/g after 300 cycles at a current density of 0.5 A/g and a stable capacity of 650 mAh/g after 500 cycles even at a higher current density of 2.0 A/g,which are much better than their counterparts of bare CuO and Co3O4.The enhanced lithium storage performance can be attributed to the synergistic effect of the CuO and Co3O4 heterostructure with hollow spherical morphology,which greatly enhances the charge/electrolyte transfer and effectively buffers the volume changes upon lithiation/delithiation cycling.

    Lithium-ion batteries (LIBs) have been considered as one of the most promising electrochemical energy storage devices owing to their high energy/power density,environmental friendliness and long lifespan [1-7].However,with the increasing demand for higher energy density and better safety in large-scale energy storage fields such as electric vehicles and smart-grid,the current graphite anode of commercial LIBs could not meet these requirements due to its lower theoretical capacity (372 mAh/g) and the safety problem arising from the lithium dendrite in the low working potential (vs.Li/Li+) [8-12].Therefore,it is highly desired to explore high-performance anode materials for next-generation LIBs.

    As a kind of promising alternative anode for LIBs,transition metal oxides (TMOs) have received considerable attention owing to their high theoretical capacities,abundant reserve,high safety and affordable cost [13-15].Especially,Co3O4(890 mAh/g) and CuO (674 mAh/g) have attracted many interests because of their high theoretical capacities,easy preparation and wide availability[16-19].Nevertheless,the poor electrical conductivity and large volume expansion hinder their practical application,as the large volume changes upon lithiation/delithiation processes usually lead to electrode pulverization and thus resulting in fast capacity fading with poor cycling stability,while the poor electrical conductivity would result in the unsatisfied rate capability [20].To address these drawbacks,nanostructure engineering with dimensional/morphological control and heterostructure construction has been widely adopted,as the well-designed nanostructures,such as nanofibers,nanosheets and nanospheres with hollow/porous interiors,could efficiently shorten the lithium-ion diffusion paths,expose more ion storage sites,and facilitate the fast electron/ion transport [21,22].For instance,Wangetal.fabricated hollow Co3O4nanoparticle-assembled nanofibersviaelectrospinning and subsequent annealing,which displayed excellent cycle stability of~871.5 mAh/g after 500 cycles at 0.2 A/g [23].Jietal.developed a porous hollow carbon scaffold to anchor ultrafine Co3O4nanoparticles,which showed enhanced cycling stability and lithium storage capacity compared to bare Co3O4[24].

    Heterostructured hybrid electrodes consisting of different active materials usually exhibit enhanced reaction kinetics,which could efficiently improve the electrochemical performance [25,26].To date,various Co3O4/CuO hybrids with well-defined microstructures have been developed to enhance their lithium storage performance by virtue of their synergistic enhancement effect of the two components.For example,Wuetal.designed and prepared graphene quantum dots modified yolk-shell Co3O4@CuO microspheres,which displayed a high reversible capacity of 1054 mAh/g after 200 cycles at 0.1 A/g [27].Wangetal.prepared heterostructured core/shell arrays of Co3O4nanosheets decorated CuO nanowire on nickel foam,which demonstrated good cycle performance and high reversible capacity (1191 mAh/g with 90.9% capacity retention after 200 cycles at 0.2 A/g) and excellent rate capability (810 mAh/g after 500 cycles at 1 A/g) [28].Even though greatly enhanced lithium storage performances have been achieved,these fabrication processes are complicated and not easy for scale-up production.Herein,we developed a facile one-pot route to synthesize hollow Co3O4/CuO nanospheres by using solvothermally prepared Co/Cu-glycerate as conformal precursor and studied the effect of Co/Cu atomic ratio on the microstructure evolution of the metal glycerates and their derivate oxides obtained by calcination method.When investigated as an anode material for LIBs,the hollow Co3O4/CuO nanospheres displayed excellent lithium storage performance including high reversible capacity,outstanding cycling stability and superior rate capability (930 mAh/g after 300 cycles at 0.5 A/g and 650 mAh/g after 500 cycles even at 2.0 A/g),which is owing to the unique hollow heterogeneous nanostructure.

    Fig.1 illustrates the formation of hollow Co/Cu-glycerate and the derivate Co3O4/CuO nanospheres,which are preparedviasolvothermal method with subsequent calcination treatment (see more details in Supporting information).Typically,Co(NO3)2·6H2O and Cu(NO3)2·2.5H2O are dissolved in the mixture solution of isopropanol and glycerol,serving as precursor solution which is encapsulated in a Teflon vessel and reacted at 180 °C for 6 h.In this process,the Cu2+/Co2+metal ions are complexed with organic ligands through metal-hydroxyl interaction,forming uniform Co/Cu glycerate hollow nanospheres.As revealed by the thermogravimetric analysis (TGA),the Co/Cu-glycerate is thermally unstable and shows abrupt decomposition at around 260 °C with a total weight loss of~36.3 wt% (Fig.S1a in Supporting information),suggesting the organic component undergoes complete and fast combustion into gaseous species.Even further increasing the testing temperature,the weight still keeps constant and the residual is confirmed as Co3O4/CuO hybrid (Fig.S1b in Supporting information).

    Fig.1.Schematic illustration of the fabrication processes of the Co/Cu-glycerate and the resulting Co3O4/CuO hybrid with conformal hollow spherical morphology.

    To verify the effect of Cu ions on the formation of the hollow spherical structure,pure Co and Co/Cu ions were reacted with glycerol under solvothermal condition,forming spherical Co-glycerate with solid interiors and Co/Cu glycerate with hollow interiors,suggesting the introduction of Cu ions induce the formation of welldefined hollow nanospheres,which will be in favor of enhanced charge transferability and cycling stability.Fig.2a shows the scanning electron microscope (SEM) image of the Co-glycerate spheres,which display an average diameter of around 500 nm with smooth surface.Fig.2b shows the high-angle annular dark field (HAADF)scanning transmission electron microscopy (STEM) image of a single Co-glycerate sphere with solid structure,in which the Co and O elements are well distributed and overlapped within the sphere(Figs.2c and d).Interestingly,when substituting part of Co ions with Cu ions,the solid-to-hollow evolution is observed.As shown in Figs.2e and f,the as-prepared Co/Cu glycerate with Co/Cu molar ratio of 2.0 shows well-defined monodispersed hollow spherical morphology,and the hollow Co/Cu glycerate spheres show an average diameter of around 500 nm and a shell thickness of around 100 nm but with rough surface,which is composed of downy species.In addition,the corresponding elemental energydispersive X-ray spectrometer (EDS) maps of the single Cu/Coglycerate sphere intuitively illustrate the well-overlapped distribution of Cu and Co,indicating the uniform formation of the Co/Cuglycerol complex (Figs.2g and h).Moreover,Table S1 (Supporting information) compares the structure evolution upon varying the molar ratio of Co/Cu.Note that the pure Cu-glycerate displays irregular aggregate morphology,which consists of randomly packed nanoparticles.With increasing the Co/Cu molar ratio from 0.5 to 1.0,the as-prepared Co/Cu-glycerates show hollow spherical morphology but with poor uniformity and broken/opened structure.These results demonstrate that the Co-glycerol complex is prone to form spherical aggregation,while the Cu-glycerol complex would preferentially aggregate loosely,thus the synergistic interaction of Co-Cu ions and glycerol induces the hollowing of the Co/Cu-glycerate.

    The metal-glycerol complex can be an ideal conformal template to synthesize the oxide counterpart,and the bare Co,Cu and various Co/Cu glycerates readily converted into oxide phases with almost the same morphology (Table S1 and Fig.3).Fig.3a shows the SEM image of the well-defined Co3O4/CuO hollow spheres with uniform diameter and monodispersing.The transmission electron microscope (TEM) image reveals the hollow spheres show a shell thickness of~80 nm,which is composed of densely packed nanoparticles (Figs.3b and c).Figs.3d and e show the high-resolution TEM (HRTEM) images with different lattice fringes,which can be ascribed to the Co3O4and the CuO,respectively.In Fig.3d,two sets of lattice fringes showd-spacings of 0.47 and 0.28 nm,which are correspondingly indexed to the (111) and(ˉ220) planes of cubic Co3O4(JCPDS No.43-1003) with an angle of 90° [29,30],consistent with the theoretical value.Fig.3e shows another two sets of lattice fringes with the same d spacing of 0.30 nm and an angle of around 120°,which can be well ascribed to the (113)1/2and (11ˉ3)1/2of monoclinic CuO (JCPDS No.48-1548)[31].Note that the (113)1/2and (11ˉ3)1/2reflect the 1/2 positions of (113) and (11ˉ3) which is two times as much as that of (113)plane [32].Fig.3f shows the HAADF STEM image of a single hollow sphere,whose EDS maps are correspondingly shown in Figs.3g-j.It is noteworthy that the Co and O elements are well overlapped,while accumulation of Cu element can be observed,suggesting the phase separation of Co3O4and CuO to some extent.

    Fig.3.(a) SEM,(b) TEM and (c) STEM images of the Co3O4/CuO hollow spheres.HRTEM images taken at different areas showing the lattice fringes of (d) Co3O4 and (e)CuO.(f) HAADF STEM image of a single hollow sphere with corresponding EDS maps of (g) Co,(h) Cu,(i) O and (j) the overlapping map of Co/Cu elements.

    X-ray diffraction (XRD) measurements were also conducted to verify the phase structure of the products.As shown in Fig.S2a(Supporting information),the products prepared with single metal source show typical diffraction peaks of Co3O4(JCPDS No.43-1003) and CuO (JCPDS No.48-1548),respectively,suggesting their pure phase.Fig.S2b (Supporting information) depicts the XRD patterns of Co3O4/CuO with different molar ratios,where the typical peaks for both Co3O4and CuO can be detected,suggesting their hybrid structure.As the Co/Cu molar ratio gradually decreases from 2/1 to 1/2,the peaks at 31.3° and 36.8° (Co3O4) become weaker,and the typical peaks for CuO (35.5° and 38.7°) become much more prominent,which is in good agreement with the content ratio in preparation.

    The chemical compositions and oxidation states of the asprepared Co3O4/CuO hollow spheres were revealed by X-ray photoelectron spectroscopy (XPS) analysis,and the survey spectrum clearly indicates the presence of Co,Cu and O elements (Fig.S3a in Supporting information).As shown in the high-resolution Co 2p XPS spectrum (Fig.S3b in Supporting information),two prominent peaks at 779.7 and 794.6 eV are typically assigned to the Co 2p3/2and Co 2p1/2of the Co3O4phase,respectively.In addition,two shake-up satellite peaks (“Sat”) appear at 789.4 and 803.6 eV.The Co 2p spectrum can be further fitted into two spin-orbit doublets,in which the peaks at around 779.7 and 794.6 eV are ascribed to Co3+,while the peaks at 781.9 and 796.6 eV relate to Co2+[33-36].Fig.S3c (Supporting information) shows the Cu 2p XPS spectrum,in which the two peaks at 933.9 and 953.5 eV are correspondingly assigned to the Cu 2p3/2and Cu 2p1/2,while three fitted satellite peaks appear at 941.0,943.4 and 961.8 eV,indicating the oxidation state of Cu2+as CuO in the hybrid [37,38].In the O 1s XPS spectrum (Fig.S3d in Supporting information),three characteristic peaks can be fitted and located at 529.6,531.2 and 532.9 eV,which can be ascribed to metal-oxygen bonds,the lattice oxygen,and the surface oxygen originated from the physically/chemically adsorbed water,respectively [39].

    To verify the efficacy of the Co3O4/CuO heterostructure as anode for LIBs,the lithium storage properties of Co3O4,CuO and various Co3O4/CuO were examined in half-cells using lithium metal as counter/reference electrode.Cyclic voltammograms (CV) were performed to investigate the lithium storage mechanism,and Fig.4a shows the typical CV curves of Co3O4/CuO for the first five cycles at 0.2 mV/s.In the first cathodic scan,three peaks are observed,and the minor cathodic peaks at 1.64 V can be attributed to the reduction of CuO into Cu2O [40],while the prominent peak at 0.96 V accompanied by a minor peak at 0.70 V can be ascribed to the reduction of Co3O4into Co and reduction of Cu2O into Cu,as well as the formation of solid electrolyte interface (SEI) film [41,42],in which the prominent peak at 0.96 V disappears in the following cycles,indicating the irreversible capacity loss owing to the structure destruction and the formation of SEI film [43,44].In the following four cycles,two newly merged cathodic peaks steadily appear at 0.92/1.16 V,corresponding to the highly reversible reduction of the Co/Cu oxides.In the anodic sweep,a broad peak at 2.07 V can be attributed to the oxidation of the metallic Cu and Co to CuO and Co3O4,respectively [45,46].The anodic peak in the following cycles remains similar,suggesting good reversibility for the redox reaction.Moreover,the CV curves for the bare Co3O4and CuO are provided in Fig.S4 (Supporting information),and the Co3O4/CuO electrode displays a smaller potential difference (0.94 V) between the anodic/cathodic peaks (ΔE) than those for the bare Co3O4(1.07 V) and the bare CuO (1.34 V) electrodes(Fig.4b),suggesting the faster kinetics of Co3O4/CuO [47].

    Fig.4.(a) CV curves of the Co3O4/CuO electrode for the first five cycles at 0.2 mV/s,and (b) comparison of the 5th CV curves for the CuO,Co3O4 and Co3O4/CuO electrodes.(c) Galvanostatic discharge/charge profiles of the Co3O4/CuO electrode at 0.2 A/g.(d) Rate performance at different current densities for the CuO,Co3O4 and Co3O4/CuO electrodes with different Co/Cu molar ratios.(e) Cycle performances of the optimized Co3O4/CuO electrode at 0.5 and 2.0 A/g.

    Fig.4c shows the galvanostatic discharge/charge profiles of the Co3O4/CuO electrode at different cycles at 0.2 A/g.The first discharge/charge capacities are 1900/1058 mAh/g with an initial Coulombic efficiency (CE) of 55.7%.The capacity loss in the first cycle is due to the reversible formation of SEI film [48].In the 2nd/3rdcycles,the CEs increase to 93.0%/95.0%,indicating the gradually increased reversibility of the redox reaction.With further increasing the cycling to the 50thand 100thcycles,the charge/discharge capacities increase,which is consistent with the rate test.Fig.4d displays the rate performance of the CuO,Co3O4and Co3O4/CuO electrodes with different Co/Cu molar ratios with current densities ranging from 0.2 A/g to 5.0 A/g,among which the Co3O4/CuO(Co/Cu=2/1) demonstrates the highest lithium storage capacity,delivering high reversible capacities of 1023,974,930,870 and 760 mAh/g each after 5 cycles at 0.2,0.5,1.0,2.0 and 5.0 A/g,respectively.When cycling again at 0.2 A/g,the Co3O4/CuO (Co/Cu=2/1)electrode shows steadily increased reversible capacity,delivering a high discharge capacity of 1156 mAh/g after another 20 cycles.However,the pure Co3O4and Co3O4/CuO (Co/Cu=1/1 and 1/2)electrodes suffer from capacity fading as the current increases,suggesting their poor rate capability.It is worth noting that the initial capacity of the Co3O4/CuO electrodes shows a downward trend as the Co concentration decreases,as the Co3O4counterpart would offer more theoretical capacity than that for CuO.Interestingly,the Co3O4/CuO (Co/Cu=2/1 and 1/1) almost show similar initial capacity compared to pure Co3O4electrode,which suggests that the heterostructured Co3O4/CuO with hollow structure would provide more lithium storage sites.In contrast,the pure CuO electrode displays the worst cycle and rate performances with the lowest discharge capacity of 390 mAh/g at 0.2 A/g and only 50 mAh/g at 5.0 A/g.Furthermore,Fig.S5 (Supporting information) compares the cycling performances of the CuO,Co3O4and Co3O4/CuO electrodes with different Co/Cu molar ratios at high current density,displaying the trend of descending in the initial cycles and then ascending,which can be seen in most transition metal oxide electrodes.The phenomena with continuous capacity increase can be widely observed in the transition metal-based anodes,which was generally attributed to the continuous activation of the electrode materials and the reversible formation/decomposition of electrolytederived surface layer,thus bringing additional charge storage capacity [49,50].When cycling at 0.5 A/g (Fig.4e),the Co3O4/CuO electrode exhibits a high reversible capacity of 883.5 mAh/g in the 2ndcycle and then the lowest capacity of 797.5 mAh/g at the 57thcycle,which may be due to the formation of thick SEI layer that retards electron transport and extends the diffusion length for lithium ions [31,51,52].In the subsequent cycles,the capacity increases to 938.6 mAh/g with a capacity retention of 106.2% after 300 cycles.Even cycling at 2.0 A/g (Fig.4e),the discharge capacity retains 693.4 mAh/g after 500 cycles,which is higher than most of other previously reported Co3O4or CuO-based anodes (Table S2 in Supporting information).Electrochemical impedance spectroscopy (EIS) measurements were also conducted to reveal the charge transfer kinetics of these electrodes,which clearly reveals that the Co3O4/CuO electrode exhibits the smallest charge transfer resistance (Rct) of 71.4Ω(Fig.S6 and Table S3 Supporting information),as compared with the CuO (109.1Ω) and Co3O4(267.4Ω) electrodes.

    The structural stability of the hollow Co3O4/CuO nanospheres upon lithiation/delithiation cycling was also examined byex-situTEM analysis (Fig.S7 in Supporting information),revealing that the hollow spherical shape of the discharged and charged Co3O4/CuO electrode in the initial cycle is well preserved,even after 300 cycles at 0.5 A/g.In addition,EDS maps clearly display that the Co and Cu elements are uniformly distributed and well overlapped with the discharged/charged Co3O4/CuO.These results demonstrate that the hollow Co3O4/CuO heterostructure can efficiently buffer the volume changes upon cycling,indicating its robust structure stability as an anode material for LIBs.

    In summary,we demonstrated a facile way to construct heterostructured Co3O4/CuO with well-defined hollow spherical morphology,using the solvothermally pre-synthesized Co/Cu-glycerate as the conformal template.The introduction of Cu species not only induced the formation of hollow Co/Cu-glycerate nanospheres from solid Co-glycerate nanospheres but also greatly enhanced the lithium storage performance of the Co/Cu-glycerate derived Co3O4/CuO.When examined as LIB anode,the optimized Co3O4/CuO hollow heterostructure displayed excellent lithium storage performance with high specific capacity (1156 mAh/g at 0.2 A/g),superior rate performance and outstanding cycling stability(930 mAh/g after 300 cycles at 0.5 A/g and 650 mAh/g after 500 cycles even at 2.0 A/g).Electrochemical analyses revealed that the Co3O4/CuO heterostructure demonstrated the synergistic enhancement effect with higher charge transfer rate and faster reaction kinetics as compared with the bare Co3O4and CuO counterparts,while the unique hollow spherical structure exhibited robust structural stability and effectively buffered the volume changes upon lithiation/delithiation cycling.More importantly,we developed a novel synthetic strategy to fabricate well-defined hollow spherical metal glycerates/oxides,which can be promising for the development of high-performance electrode materials for energy-related applications.

    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.

    Acknowledgment

    This work was supported by the National Natural Science Foundation of China (No.52077175).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2023.108450.

    中文字幕av成人在线电影| 久久精品国产亚洲av涩爱| 成人鲁丝片一二三区免费| 成人漫画全彩无遮挡| 欧美日韩视频精品一区| 久久精品国产亚洲av涩爱| 别揉我奶头 嗯啊视频| 婷婷色综合www| xxx大片免费视频| 交换朋友夫妻互换小说| 免费av观看视频| 国产精品久久久久久精品古装| 免费观看性生交大片5| 菩萨蛮人人尽说江南好唐韦庄| 国产极品天堂在线| 久久精品国产亚洲av涩爱| 高清在线视频一区二区三区| 国产精品嫩草影院av在线观看| 青青草视频在线视频观看| 在线观看美女被高潮喷水网站| 亚洲精品国产成人久久av| 2021天堂中文幕一二区在线观| 国产成人精品福利久久| 欧美一级a爱片免费观看看| 秋霞在线观看毛片| 日韩免费高清中文字幕av| 久久人人爽av亚洲精品天堂 | 黄色一级大片看看| 亚洲在久久综合| 国产精品99久久久久久久久| 欧美高清成人免费视频www| 看十八女毛片水多多多| 五月开心婷婷网| 国产精品一区二区在线观看99| 夜夜看夜夜爽夜夜摸| 欧美日韩一区二区视频在线观看视频在线 | 日产精品乱码卡一卡2卡三| 色视频www国产| 国产精品一区www在线观看| 久久午夜福利片| 大片免费播放器 马上看| av网站免费在线观看视频| 亚洲欧美日韩另类电影网站 | 哪个播放器可以免费观看大片| 男的添女的下面高潮视频| 制服丝袜香蕉在线| 制服丝袜香蕉在线| 国产午夜福利久久久久久| 一个人看的www免费观看视频| 国产黄片美女视频| 午夜视频国产福利| 久热这里只有精品99| 老女人水多毛片| 日日啪夜夜爽| 晚上一个人看的免费电影| 建设人人有责人人尽责人人享有的 | 久久久久久九九精品二区国产| 大香蕉久久网| 黄色配什么色好看| 亚洲欧美日韩东京热| 色5月婷婷丁香| 国产伦在线观看视频一区| 岛国毛片在线播放| 成人高潮视频无遮挡免费网站| 久久亚洲国产成人精品v| 午夜视频国产福利| 国产淫语在线视频| 观看免费一级毛片| 国产色爽女视频免费观看| 老女人水多毛片| 中文在线观看免费www的网站| 女的被弄到高潮叫床怎么办| 国产视频内射| 精品人妻熟女av久视频| 乱系列少妇在线播放| 最近2019中文字幕mv第一页| 中文乱码字字幕精品一区二区三区| 国产亚洲av嫩草精品影院| 王馨瑶露胸无遮挡在线观看| 久久人人爽av亚洲精品天堂 | 777米奇影视久久| 99久久精品热视频| 日韩欧美精品v在线| 精品国产乱码久久久久久小说| 午夜福利高清视频| 欧美最新免费一区二区三区| 中国美白少妇内射xxxbb| 联通29元200g的流量卡| 中文在线观看免费www的网站| 特大巨黑吊av在线直播| 亚洲欧美日韩另类电影网站 | 嫩草影院新地址| 欧美bdsm另类| 欧美人与善性xxx| 精品国产一区二区三区久久久樱花 | 国产视频内射| 免费黄网站久久成人精品| 狠狠精品人妻久久久久久综合| 亚洲欧美一区二区三区国产| 国产亚洲精品久久久com| 国产69精品久久久久777片| 97在线人人人人妻| 国产伦在线观看视频一区| 国产黄片美女视频| 国产精品偷伦视频观看了| 熟女电影av网| 国产白丝娇喘喷水9色精品| 伦精品一区二区三区| 美女被艹到高潮喷水动态| av黄色大香蕉| 中文字幕人妻熟人妻熟丝袜美| 久久久久精品性色| av在线播放精品| 久久久精品欧美日韩精品| 精品一区二区免费观看| 国产黄色免费在线视频| 美女脱内裤让男人舔精品视频| 99re6热这里在线精品视频| tube8黄色片| 啦啦啦啦在线视频资源| 婷婷色综合www| 九草在线视频观看| 日本三级黄在线观看| 国产成人a区在线观看| 热re99久久精品国产66热6| 亚洲va在线va天堂va国产| 成人漫画全彩无遮挡| 国产欧美另类精品又又久久亚洲欧美| 国产真实伦视频高清在线观看| 1000部很黄的大片| 国产高清不卡午夜福利| 国产毛片在线视频| 精品久久久久久久人妻蜜臀av| 尤物成人国产欧美一区二区三区| 韩国高清视频一区二区三区| 99久国产av精品国产电影| 少妇猛男粗大的猛烈进出视频 | 亚洲精品国产av蜜桃| 国产片特级美女逼逼视频| av卡一久久| 国产高清有码在线观看视频| 一级毛片久久久久久久久女| 听说在线观看完整版免费高清| 久久久久久国产a免费观看| 少妇的逼好多水| 免费观看性生交大片5| 少妇猛男粗大的猛烈进出视频 | 十八禁网站网址无遮挡 | 国精品久久久久久国模美| 欧美zozozo另类| 少妇猛男粗大的猛烈进出视频 | 黄色一级大片看看| 白带黄色成豆腐渣| 美女脱内裤让男人舔精品视频| 国产免费福利视频在线观看| 日韩av不卡免费在线播放| 午夜福利在线在线| 国产真实伦视频高清在线观看| 日韩精品有码人妻一区| 最近最新中文字幕免费大全7| 午夜激情久久久久久久| 亚洲精品国产色婷婷电影| av国产精品久久久久影院| 欧美日韩国产mv在线观看视频 | 国产淫片久久久久久久久| 最近2019中文字幕mv第一页| 又爽又黄无遮挡网站| 丝瓜视频免费看黄片| 久久久久久久亚洲中文字幕| 亚洲丝袜综合中文字幕| 亚洲国产精品999| 黄色一级大片看看| 欧美三级亚洲精品| 男女啪啪激烈高潮av片| 久久国产乱子免费精品| 国产精品av视频在线免费观看| 日韩大片免费观看网站| 97在线视频观看| av在线播放精品| 亚洲欧美清纯卡通| 熟女人妻精品中文字幕| 免费看日本二区| av黄色大香蕉| 波多野结衣巨乳人妻| 久久鲁丝午夜福利片| 肉色欧美久久久久久久蜜桃 | 男人和女人高潮做爰伦理| 97精品久久久久久久久久精品| 女人被狂操c到高潮| 亚洲天堂国产精品一区在线| 午夜免费观看性视频| 特级一级黄色大片| 国产高清不卡午夜福利| 日韩人妻高清精品专区| 26uuu在线亚洲综合色| 亚洲av福利一区| 中国国产av一级| 天天躁日日操中文字幕| 久久久久网色| 欧美成人精品欧美一级黄| 中文在线观看免费www的网站| 看黄色毛片网站| 网址你懂的国产日韩在线| 亚洲av日韩在线播放| 久久国产乱子免费精品| 18禁裸乳无遮挡动漫免费视频 | 国产精品国产av在线观看| 免费大片黄手机在线观看| av.在线天堂| 国产精品国产三级专区第一集| 国内揄拍国产精品人妻在线| 午夜激情久久久久久久| 亚洲精品久久午夜乱码| 国产亚洲av嫩草精品影院| 性色av一级| 国产综合懂色| 欧美老熟妇乱子伦牲交| 精品国产一区二区三区久久久樱花 | 国产淫片久久久久久久久| 久久热精品热| 亚洲精品亚洲一区二区| 免费播放大片免费观看视频在线观看| 一级片'在线观看视频| 少妇裸体淫交视频免费看高清| 亚洲欧美清纯卡通| 婷婷色av中文字幕| tube8黄色片| 久久精品国产亚洲av涩爱| 亚洲欧美一区二区三区黑人 | 有码 亚洲区| 国产av国产精品国产| 亚洲国产精品成人久久小说| 极品教师在线视频| 国产色婷婷99| www.av在线官网国产| 久久久亚洲精品成人影院| 日韩精品有码人妻一区| 国国产精品蜜臀av免费| 18禁在线无遮挡免费观看视频| 秋霞在线观看毛片| 久久久a久久爽久久v久久| 亚洲在久久综合| 边亲边吃奶的免费视频| 搡女人真爽免费视频火全软件| 久久久久久国产a免费观看| 精品久久久久久久末码| 秋霞在线观看毛片| tube8黄色片| www.av在线官网国产| 男女边摸边吃奶| 99久久中文字幕三级久久日本| 国产综合精华液| 下体分泌物呈黄色| 亚洲国产精品国产精品| 亚洲,欧美,日韩| 国产精品一区二区性色av| 少妇丰满av| 激情 狠狠 欧美| 99久国产av精品国产电影| 99热这里只有精品一区| 亚洲欧美成人精品一区二区| 寂寞人妻少妇视频99o| 日韩不卡一区二区三区视频在线| 欧美国产精品一级二级三级 | 日本黄大片高清| 亚洲av成人精品一二三区| 99九九线精品视频在线观看视频| 免费观看的影片在线观看| 成人亚洲精品av一区二区| 日韩在线高清观看一区二区三区| 99视频精品全部免费 在线| 久久国产乱子免费精品| a级毛片免费高清观看在线播放| 国产在视频线精品| 久久久久久久大尺度免费视频| 欧美变态另类bdsm刘玥| 天堂中文最新版在线下载 | 欧美zozozo另类| a级毛色黄片| 欧美97在线视频| 在线a可以看的网站| 国产一区二区三区av在线| 97在线视频观看| 久久久色成人| 亚洲不卡免费看| 人妻制服诱惑在线中文字幕| 2022亚洲国产成人精品| 国产男女内射视频| 欧美日韩国产mv在线观看视频 | 亚洲精品国产av蜜桃| 国产成人一区二区在线| 精品人妻偷拍中文字幕| 精品午夜福利在线看| 大片免费播放器 马上看| 国产精品久久久久久久久免| 亚洲人成网站在线观看播放| 1000部很黄的大片| 日韩三级伦理在线观看| 97热精品久久久久久| 亚洲久久久久久中文字幕| 国产伦理片在线播放av一区| 在线观看av片永久免费下载| 又粗又硬又长又爽又黄的视频| 97热精品久久久久久| 免费黄网站久久成人精品| 免费看光身美女| 亚洲成人精品中文字幕电影| 噜噜噜噜噜久久久久久91| 国产精品99久久99久久久不卡 | 高清欧美精品videossex| 久久精品国产鲁丝片午夜精品| 国产精品一区二区三区四区免费观看| 亚洲欧美精品专区久久| 欧美另类一区| 精品一区二区三区视频在线| 国产亚洲av片在线观看秒播厂| 人人妻人人澡人人爽人人夜夜| eeuss影院久久| 69人妻影院| 国产v大片淫在线免费观看| 麻豆成人av视频| 国产精品福利在线免费观看| 国产亚洲最大av| 在线免费观看不下载黄p国产| 国产伦精品一区二区三区四那| 边亲边吃奶的免费视频| 国产亚洲91精品色在线| 国产亚洲av嫩草精品影院| av在线老鸭窝| 亚洲国产高清在线一区二区三| www.色视频.com| 亚洲精品中文字幕在线视频 | 亚洲精品日韩在线中文字幕| 欧美国产精品一级二级三级 | 神马国产精品三级电影在线观看| 麻豆国产97在线/欧美| 熟女人妻精品中文字幕| av专区在线播放| 国产乱人视频| 国产一区二区亚洲精品在线观看| 亚洲精品日本国产第一区| 日韩视频在线欧美| 永久免费av网站大全| 在线观看三级黄色| 男人爽女人下面视频在线观看| 久久久久久久亚洲中文字幕| 日本-黄色视频高清免费观看| 五月玫瑰六月丁香| 中文乱码字字幕精品一区二区三区| 亚洲三级黄色毛片| 日韩欧美 国产精品| 国国产精品蜜臀av免费| 51国产日韩欧美| 免费看不卡的av| 国产黄频视频在线观看| 午夜亚洲福利在线播放| 国产精品久久久久久久久免| 黄色一级大片看看| 草草在线视频免费看| 欧美成人一区二区免费高清观看| 97在线人人人人妻| 天堂中文最新版在线下载 | 在线 av 中文字幕| 午夜免费观看性视频| 久久久午夜欧美精品| 青青草视频在线视频观看| 欧美 日韩 精品 国产| 亚洲av二区三区四区| 日韩大片免费观看网站| 久久久久网色| 亚洲人成网站在线观看播放| av在线观看视频网站免费| 久久久久久久精品精品| 蜜桃久久精品国产亚洲av| 99精国产麻豆久久婷婷| 丰满人妻一区二区三区视频av| 毛片女人毛片| 男人添女人高潮全过程视频| 中文字幕av成人在线电影| 青春草亚洲视频在线观看| 香蕉精品网在线| 午夜免费观看性视频| 2021天堂中文幕一二区在线观| 亚洲,一卡二卡三卡| 伊人久久国产一区二区| 在线看a的网站| 综合色av麻豆| 美女视频免费永久观看网站| 黄片wwwwww| 精品久久久精品久久久| 日韩电影二区| 欧美亚洲 丝袜 人妻 在线| 亚洲欧美日韩卡通动漫| av线在线观看网站| 在线看a的网站| 舔av片在线| 熟妇人妻不卡中文字幕| 欧美三级亚洲精品| 一级毛片电影观看| 国产v大片淫在线免费观看| 久久久久久久久久人人人人人人| 欧美精品国产亚洲| 天堂俺去俺来也www色官网| 亚洲色图av天堂| 爱豆传媒免费全集在线观看| 亚洲欧美日韩另类电影网站 | 欧美高清性xxxxhd video| 天堂中文最新版在线下载 | 亚洲欧美一区二区三区国产| 精品少妇黑人巨大在线播放| 美女国产视频在线观看| 在线 av 中文字幕| 亚洲国产精品999| 久久99热这里只有精品18| 好男人在线观看高清免费视频| 亚洲精品一二三| 视频区图区小说| 99久国产av精品国产电影| 在线播放无遮挡| 少妇人妻 视频| 日韩亚洲欧美综合| 亚洲精品一二三| 亚洲国产av新网站| 好男人在线观看高清免费视频| 91狼人影院| 亚洲国产精品专区欧美| 水蜜桃什么品种好| 岛国毛片在线播放| 欧美精品国产亚洲| 亚洲精品中文字幕在线视频 | 国产精品三级大全| 男人狂女人下面高潮的视频| 高清午夜精品一区二区三区| 噜噜噜噜噜久久久久久91| 日本三级黄在线观看| 在线观看av片永久免费下载| 免费观看无遮挡的男女| 免费少妇av软件| 成人黄色视频免费在线看| 大香蕉97超碰在线| 亚洲国产精品999| 七月丁香在线播放| a级毛色黄片| 精品国产露脸久久av麻豆| 我要看日韩黄色一级片| 高清在线视频一区二区三区| 婷婷色麻豆天堂久久| 性插视频无遮挡在线免费观看| a级一级毛片免费在线观看| 久久久久精品久久久久真实原创| av女优亚洲男人天堂| 看免费成人av毛片| 国产成人福利小说| 欧美成人午夜免费资源| av网站免费在线观看视频| 国产成人a∨麻豆精品| 小蜜桃在线观看免费完整版高清| 26uuu在线亚洲综合色| 国产精品99久久99久久久不卡 | 熟妇人妻不卡中文字幕| 中文字幕av成人在线电影| 六月丁香七月| 久久精品国产自在天天线| 水蜜桃什么品种好| av福利片在线观看| 在线观看国产h片| av在线老鸭窝| av国产免费在线观看| 人妻少妇偷人精品九色| 亚洲成色77777| av在线天堂中文字幕| 日本一本二区三区精品| 在线免费观看不下载黄p国产| 色综合色国产| 丰满乱子伦码专区| 中文在线观看免费www的网站| 日韩欧美精品v在线| 国产淫片久久久久久久久| 三级经典国产精品| 中国国产av一级| 国产成人a区在线观看| 黄片wwwwww| 免费在线观看成人毛片| 欧美三级亚洲精品| 女人十人毛片免费观看3o分钟| 可以在线观看毛片的网站| 亚洲国产精品专区欧美| 热re99久久精品国产66热6| 纵有疾风起免费观看全集完整版| 国产精品久久久久久av不卡| 日日摸夜夜添夜夜添av毛片| 亚洲一级一片aⅴ在线观看| 中文字幕亚洲精品专区| 婷婷色麻豆天堂久久| 在现免费观看毛片| av福利片在线观看| 日本爱情动作片www.在线观看| 午夜视频国产福利| 亚州av有码| 亚洲不卡免费看| 国产一区二区三区av在线| 简卡轻食公司| 亚洲国产高清在线一区二区三| 亚洲aⅴ乱码一区二区在线播放| 亚洲精品一二三| 一边亲一边摸免费视频| videos熟女内射| 成人国产麻豆网| 又爽又黄无遮挡网站| 亚洲精品自拍成人| 热99国产精品久久久久久7| 人人妻人人澡人人爽人人夜夜| 午夜免费鲁丝| 免费av观看视频| 少妇的逼好多水| 男女那种视频在线观看| 日本wwww免费看| 久久久久久久大尺度免费视频| 国产极品天堂在线| 国产人妻一区二区三区在| 免费观看在线日韩| 美女内射精品一级片tv| 日韩,欧美,国产一区二区三区| 久久久精品欧美日韩精品| 可以在线观看毛片的网站| 亚洲av免费在线观看| 高清在线视频一区二区三区| 看非洲黑人一级黄片| 女人被狂操c到高潮| 亚洲精品久久久久久婷婷小说| 在线免费十八禁| 欧美三级亚洲精品| 一级毛片我不卡| 免费av不卡在线播放| 色播亚洲综合网| 在线精品无人区一区二区三 | 噜噜噜噜噜久久久久久91| 国产欧美日韩精品一区二区| 五月玫瑰六月丁香| 国产高清三级在线| 99久久中文字幕三级久久日本| 别揉我奶头 嗯啊视频| 久久久久精品久久久久真实原创| 久热久热在线精品观看| 黄片无遮挡物在线观看| 国产视频内射| 日产精品乱码卡一卡2卡三| 亚洲精品第二区| 欧美精品人与动牲交sv欧美| 国产淫片久久久久久久久| 国产精品一区二区性色av| 日本欧美国产在线视频| 亚洲第一区二区三区不卡| 亚洲综合精品二区| 高清午夜精品一区二区三区| 国语对白做爰xxxⅹ性视频网站| 三级男女做爰猛烈吃奶摸视频| 欧美成人a在线观看| 黄色日韩在线| 精品久久久久久久末码| 亚洲成色77777| 18禁在线无遮挡免费观看视频| 黄色日韩在线| 国模一区二区三区四区视频| 国产男女超爽视频在线观看| 国产免费一区二区三区四区乱码| 不卡视频在线观看欧美| 嫩草影院新地址| 九草在线视频观看| 少妇猛男粗大的猛烈进出视频 | 日本爱情动作片www.在线观看| 一个人看视频在线观看www免费| 亚洲精品久久午夜乱码| 看免费成人av毛片| 综合色丁香网| 看免费成人av毛片| 色播亚洲综合网| 久久久久久久久久人人人人人人| 能在线免费看毛片的网站| 高清午夜精品一区二区三区| 久久国内精品自在自线图片| 亚洲av日韩在线播放| 人妻少妇偷人精品九色| 亚洲精品自拍成人| 青春草国产在线视频| 亚洲精品,欧美精品| 国产v大片淫在线免费观看| 精品国产乱码久久久久久小说| 蜜桃久久精品国产亚洲av| 亚洲国产精品专区欧美| 久久久a久久爽久久v久久| 一级片'在线观看视频| 80岁老熟妇乱子伦牲交| 在线观看国产h片| 国产成人freesex在线| 卡戴珊不雅视频在线播放| 亚洲经典国产精华液单| 日韩免费高清中文字幕av| 人妻夜夜爽99麻豆av| 最近2019中文字幕mv第一页| av在线观看视频网站免费| 欧美成人精品欧美一级黄| 草草在线视频免费看| av在线老鸭窝| 国产亚洲午夜精品一区二区久久 | 国产成人福利小说| 国产精品不卡视频一区二区| 精品少妇久久久久久888优播| 国产白丝娇喘喷水9色精品| 亚洲va在线va天堂va国产| 成人毛片60女人毛片免费| 秋霞在线观看毛片| 亚洲精品成人久久久久久| 尤物成人国产欧美一区二区三区| 亚洲国产欧美在线一区|