• <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 ?

    原位水解沉積制備高效氮化鉭微球太陽能分解水光陽極

    2016-12-05 11:49:24楊立恒羅文俊李明雪鄒志剛
    無機(jī)化學(xué)學(xué)報 2016年10期
    關(guān)鍵詞:南京大學(xué)原位微球

    楊立恒 羅文俊 李明雪 鄒志剛

    (1南京大學(xué)現(xiàn)代工程與應(yīng)用科學(xué)學(xué)院,南京210093)

    (2江蘇省柔性電子重點(diǎn)實(shí)驗(yàn)室,先進(jìn)材料研究院,江蘇先進(jìn)生物與化學(xué)制造協(xié)同創(chuàng)新中心,南京工業(yè)大學(xué),南京211816)

    (3南京大學(xué)環(huán)境材料與再生能源研究中心,固體微結(jié)構(gòu)國家重點(diǎn)實(shí)驗(yàn)室,南京大學(xué)物理學(xué)院,南京210093)

    (4中國礦業(yè)大學(xué)物理學(xué)院,徐州221116)

    原位水解沉積制備高效氮化鉭微球太陽能分解水光陽極

    楊立恒1羅文俊*,2,3李明雪4鄒志剛*,3

    (1南京大學(xué)現(xiàn)代工程與應(yīng)用科學(xué)學(xué)院,南京210093)

    (2江蘇省柔性電子重點(diǎn)實(shí)驗(yàn)室,先進(jìn)材料研究院,江蘇先進(jìn)生物與化學(xué)制造協(xié)同創(chuàng)新中心,南京工業(yè)大學(xué),南京211816)

    (3南京大學(xué)環(huán)境材料與再生能源研究中心,固體微結(jié)構(gòu)國家重點(diǎn)實(shí)驗(yàn)室,南京大學(xué)物理學(xué)院,南京210093)

    (4中國礦業(yè)大學(xué)物理學(xué)院,徐州221116)

    利用一種新的原位水解沉積方法,以在高濕度空氣中老化的甲醇中作為溶劑,通過乙醇鉭水解而成前驅(qū)體微球顆粒沉積,制備出了高效的Ta3N5微球光電極,其1.6 V(vs RHE)電極電位下的光電流值達(dá)到了6.6 mA·cm-2。相反地,在新鮮的甲醇溶液中沒有鉭前驅(qū)體微球顆粒沉積。這表明甲醇中水的含量對Ta3N5微球光電極的形成十分重要。另外,本制備方法也能方便地在其他透明導(dǎo)電襯底上制備出Ta3N5。

    太陽能水分解;Ta3N5光陽極;微球;原位沉積;濕度

    (3Eco-materials and Renewable Energy Research Center(ERERC),National Laboratory of Solid State(Microstructures,Colledge of Physics,Nanjing University,Nanjing 210093,China)

    (4Department of Physics,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)

    0 Introduction

    Since a TiO2-based photoelectrochemical(PEC) cell was reported to split water into H2and O2under illumination,solar water splitting has been considered to be a promising technology to produce H2on a large scale[1].Ta3N5is regarded as one of themost promising candidates due to its high theoretical energy conversion efficiency(15.9%)and suitable band positions[2-3].Many preparation methods,such as thermal oxidation and nitridation of Ta foil,throughmask anodization,anodization combined with hydrothermalmethod,electrophoretic deposition,dropcasting andmagnetron sputtering,havebeen reported to prepare Ta3N5[4-9].However,p-n tandem photoelectrochemical cell requires efficient and translucent/ transparent Ta3N5photoanode,which still remains unfulfilled.Therefore,it isstilldesirable toexplorenew preparation methods of Ta3N5films.In addition, spherical structure can lead to efficient light absorption and improve performance of a photoelectrode[10-11]. However,current preparation methods for spheres are often in the assistance of additional reagents,which increasespreparation cost[12-13].

    Herein,an efficient microsphere Ta3N5photoanode was prepared by a new in situ hydrolysis deposition method without any additional reagents. Microsphere precursor films were firstly deposited on substrates in tantalum ethoxide(Ta(OEt)5)solution of aged methanol.After oxidation and nitridation, microsphere Ta3N5films were obtained.A 6.6 mA· cm-2photocurrent was achieved at 1.6 V vs RHE.In this context,exploration of new preparation method and the synthesis mechanism of Ta3N5film are our research focus and we hope it can give some hints for preparation of efficient and translucent/transparent Ta3N5.

    1 Experimental

    1.1 Preparation of Ta3N5m icrosphere photoanodes

    A typical preparation procedure of Ta3N5microsphere photoanode is as follows.Firstly, methanol(Purity≥99.5%,Nanjing Chemical Reagent Co.,Ltd.)was aged in airwith 7%relative humidity at 25℃for 4 h before use.Secondly,10 mmol·L-1precursor solution of tantalum ethoxide(Purity≥99.95%,Zhuzhou Cemented Carbide Group Corp., Ltd)was prepared with aged methanol.Then,Ta foils (Purity≥99.95%,Zhongnuo Advanced Material Technology Co.,Ltd)were immersed in Ta(OEt)5methanol solution and films were deposited at 7℃for 48 h.Next,the obtained films were rinsed with deionized water and dried in air at room temperature, followed by calcination in air at250℃for 30minutes. Finally,Ta3N5microsphere photoanodes were obtained by nitridation of oxidized samples in a horizontal tube furnace at 850℃for 500 min under 800 mL·min-1NH3flow(Referred as Ta3N5/aged and Ta3N5/aged/Co-Pi for pristine and Co-Pi loaded samples, respectively).In order to investigate the effect of aging methanol,a reference sample was prepared in fresh methanol as solvent under the same conditions (Referred as Ta3N5/fresh and Ta3N5/fresh/Co-Pi for pristine and Co-Pi loaded samples,respectively).

    1.2 Photo-assisted electrodeposition of Co-Pi co-catalyst

    Following previous studies,Co-Pi co-catalyst was electrodeposited on Ta3N5film by chronopotentiometry under illumination with constant current of 50μA for 4 min[5].The electrodeposition was conducted in a three-electrode cell,with the solution of 0.5 mmol·L-1Co(NO3)2·6H2O(Purity≥99.0%,Shanghai Zhenxin Reagent Factory)and 0.1 mol·L-1K2HPO4·3H2O (Purity≥99.0%,Shanghai Lingfeng Chemical Reagent Co.,Ltd.)buffer at pH=7 as electrolyte.Ta3N5was used as working electrode,Pt foil as counter electrode and saturated calomel electrode(SCE)as reference electrode.An AM 1.5G-simulated sunlight simulator (Oriel 92251A-1000,light intensity=100 mW·cm-2) wasused as light source.During the deposition process, Co2+was oxidized into Co3+[14-15].The total amount of charge was about20mC·cm-2.Assuming that Faradaic efficiency was 100%,the amount of deposited Co was calculated as follow:

    Where NCois the amount of Co-Pi deposited on Ta3N5per square centimeter.96 485(C·mol-1)is the Faradaic constant.

    After Co-Pi deposition,the electrode was rinsed with deionized water and dried in air for use.

    1.3 Characterization of sam p les

    The crystal structures of samples were determined by an X-ray diffractometer(XRD,Rigaku UltimaⅢ)with Cu Kαray(λ=0.154 3 nm)at 40 kV and 40 mA.The range is from 10°to 80°. Morphologies of electrodes were observed on a field emission scanning electron microscope(SEM,Zeiss, Ultra 55-44-08)at an accelerating voltage of 15 kV. Water content of methanol was measured on a moisture analyzer(Metrohm,KF787 Titrino). Absorption spectra were investigated on a UV-vis spectrophotometer(Shimadzu,UV-2550).FTIR spectra were obtained on a Nexus870 spectrophotometer in the range of 4 000~400 cm-1.Thermogravimetric analysis was carried out in air with a Netzsch STA 449F3 instrument by increasing temperature from 30 to 600℃with 5℃·min-1.

    1.4 Photoelectrochem icalmeasurements

    Photoelectrochemical performance was measured in a three-electrode cell using an electrochemical analyzer(CHI-633C,Shanghai Chenhua).Ta3N5microsphere electrode was used as working electrode, Pt foil as counter electrode and saturated calomel electrode(SCE)as reference electrode.Aqueous solution of 1 mol·L-1NaOH was employed as electrolyte.A commercial AM 1.5G-simulated sunlight simulator(Oriel 92251A-1000,light intensity=100 mW·cm-2)was used as light source.Current-potential curveswere recorded at a scan rate of 10mV·s-1.The potential of working electrode versus SCE was converted into RHE(reversible hydrogen electrode) potential scale according to the following formula:

    where VRHEis the potential versus RHE(V),VSCEis the potential versus SCE(V),and pH is the pH value of electrolyte.The incident photon-to-current efficiency (IPCE)was determined under the irradiation of differentwavelength light generated bymonochromatic filters according to the following formula:

    where Iphis the photocurrent density(μA·cm-2),P and λare the incident light intensity(μW·cm-2)and wavelength(nm),respectively.The incident light intensity wasmeasured by a photometer(Newport,84 0-C,USA).

    Fig.1 Photographs of precursor solution of(a)fresh and(b)aged methanol before and after deposition

    2 Results and discussion

    Fig.1 shows photographs of Ta(OEt)5solution of fresh and aged methanol before and after deposition, respectively.Both solutions are transparent at the beginning.After depositing at 7℃for 48 h,solution of aged methanol became white(Fig.1(b)).However, solution of fresh methanolwas still transparent.White films were deposited on substrates in solution of aged methanol,whereas there were no samples on substrates in solution of fresh methanol.The results suggest that film deposition comes from hydrolysis of Ta(OEt)5in aged methanol.Since the only difference between the two kinds ofmethanol was the methanol whether exposed in moist air or not,little water in methanol was essential for the formation of films.The water content was measured about 0.15%(w/w)by a moisture analyzer.The detail effect of water will be

    discussed below.

    Fig.2 XRD patterns of Ta3N5/fresh and Ta3N5/aged

    Fig.3 High magnification SEM images of Ta3N5/fresh(a)and Ta3N5/aged(b);Cross-sectional images of Ta3N5/fresh(d)and Ta3N5/aged(d)

    XRD patterns were measured to determine phases and crystal structures of the two samples,as shown in Fig.2.Orthorhombic phase Ta3N5(PDF No. 19-1291)was obtained for Ta3N5/aged.In contrast, Ta3N5/fresh shows no peaks of Ta3N5.Fig.3 shows scanning electron microscopy(SEM)images of Ta3N5/ fresh and Ta3N5/aged.Surface and cross-sectional SEM images in Fig.3(a,c)indicate that Ta3N5/fresh shows only morphology of Ta substrate and no Ta3N5is observed.The result is in agreement with the XRD data.However,Fig.3(b)shows that Ta3N5/aged is composed of spherical particles,with the diameter around 1μm.Discernible roughness,many nanopores and cracks are observed on the surface,which come from volume shrinkage from transition of Ta2O5into Ta3N5and the decomposition of residual organics (Fig.4)during nitridation[12].High magnification SEM image of precursor is displayed in the inset picture of Fig.3(b).The result suggests that microspheres are formed during precipitation.Fig.3(d)is the crosssectional image of Ta3N5/aged.It shows that Ta3N5film electrode is composed of microsphere particles and the thickness is about 7.5μm.From the inset in Fig.3 (d),Ta3N5microsphere is solid and composed of smaller particles,which suggests that Ta3N5microsphere originates from the agglomeration of nanoparticles.

    Spherical structure is one of favorable microstructures in both photoelectrochemical and solar cells[10-11].Usually,spherical Ta3N5particles obtained by solution methods are assisted with additional agents[12-13].Though the distribution size of Ta3N5spheres can be narrowed,introduction of additional reagents actually increases the possibility of inclusion of impurities,as well as experimental difficulties and preparation cost.In our study,however,Ta3N5microsphere was prepared in a more simple way, without any additional agents,and thus those shortcomings are avoided.

    FTIR spectra were used to investigate formation process of microsphere,and the results are shown in Fig.4.Peaks below 1 000 cm-1are attributed to stretching,bending and torsion modes of Ta-O[16-17].

    The broad absorption between 800 and 1 000 cm-1corresponds to the presence of Ta suboxides[18].A peak at~3 342 cm-1is assigned to OH stretching modes, and peak at~1 626 cm-1is associated with OH bending modes[17,19].Both of them are weakened after calcination at 250℃.The existence of-OH group confirms that microsphere is from the hydrolysis of tantalum ethoxide.

    Fig.4 FTIR spectra ofmicrosphere precursor before and after calcined at250℃for 30min in air

    Fig.5 Thermogravimetric spectrum ofmicrosphere precursor

    Fig.6 Schematic illustration of formation process of Ta3N5m icrosphere film

    In order to further investigate composition of asdeposited microsphere precursor before calcination, thermogravimetric(TG)ismeasured and the result is shown in Fig.5.The endothermic peak under 100℃comes from evaporation of adsorbed water.Weight loss with exothermic peak ended at around 500℃arises from the decomposition of organics in microsphere, which comes from the organic group-CH2CH3of Ta (OEt)5[16-17].However,organic compounds cannot be removed completely when calcined at 250℃and thus lead to the formation of Ta suboxides.

    According to the above discussion,formation process of Ta3N5microsphere can be concluded as followswith the simplified chemical reactions[20-21]:

    Hydrolysis:

    Polycondensation:

    Water content in methanol is a key factor to trigger the whole reaction.Actually,the two reactions proceed simultaneously once the hydrolysiscondensation reaction is triggered.As long as a critical radius is reached,nucleation will take place. And nanocrystalline will agglomerate into spherical particle due to its lowest surface energy.Finally,when the spherical particles are big enough,sedimentation happens and a film is deposited on the substrate. After oxidation and nitridation,Ta3N5microsphere film is obtained.A schematic diagram of formation process of Ta3N5microsphere is illustrated in Fig.6.

    Fig.7 indicates UV-Vis absorption spectrum of Ta3N5microsphere photoanode.The Ta3N5microsphere film shows a high absorption,which comes from light scattering ofmicrospheres.Contribution from substrate is excluded through the absorption spectrum of Ta3N5/ fresh.Ambiguous ERERC can be identified through the Ta3N5microsphere film on quartz substrate in the inset(II)of Fig.7,which suggests that in situ hydrolysis deposition method can be used to prepare a translucent Ta3N5microsphere electrode.

    Photoelectrochemical properties of Ta3N5micro-

    sphere photonodes weremeasured and the results are shown in Fig.8.In order to exclude contribution of Ta substrate on photocurrent,Ta3N5/fresh was also measured as a reference.Dark currents of both electrodes are negligible.The photocurrent of Ta3N5/ fresh and Ta3N5/fresh/Co-Pi ismuch lower than that of a Ta3N5microsphere photonode.Therefore, photocurrents of Ta3N5/aged and Ta3N5/aged/Co-Pi entirely come from Ta3N5microsphere,rather than from substrate.Generally,a bare Ta3N5photoanode suffers from severe photo-corrosion in aqueous solution and surface combination,which can be remarkably suspressed by depositing a co-catalyst. Among different co-catalysts,Co-Pi is low-cost and operable undermild conditions[14,22].Therefore,in this study,Co-Pi(2μmol·cm-2)was electrodeposited on the Ta3N5film to improve the performance of the Ta3N5microsphere electrode.After deposition of Co-Pi,the photocurrent of Ta3N5/aged/Co-Pi is about 3 times as high as that of Ta3N5/aged.Current density of Ta3N5microsphere electrode by in situ hydrolysis deposition method is~2.34 mA·cm-2at 1.23 V vs RHE,and~6.6 mA·cm-2at 1.6 V vs RHE.A Ta3N5photoanode prepared by EPD indicated 3.18 mA·cm-2photocurrent at 1.23 V vs RHE and about 6 mA·cm-2at 1.6 V vs RHE[23].High photocurrents of 5.5 mA· cm-2and 6.7 mA·cm-2at 1.23 V vs RHE have been achieved by direct oxidation and nitridation of Ta foil[4-5].The photocurrent in this study is comparable to samples by EPD and oxidation and nitridation of Ta foil,butmuch lower than 12.1 mA·cm-2obtained by Ta3N5with integration of hole-storage layer,coupled molecular catalysts and TiOxblocking layer[6]. However,in this study,preparation conditions and cocatalysts have not yet been optimized.And thus it is promising to further improve Ta3N5microsphere photoanode by in situ hydrolysis deposition method in future work.

    Fig.8(a)Current-potential curves of Ta3N5/fresh,Ta3N5/fresh/Co-Pi,Ta3N5/aged and Ta3N5/aged/Co-Pi in the dark(dash lines) and under AM 1.5G simulated sunlight irradiation(100mW·cm-2)(solid lines),respectively;(b)IPCE curves of Ta3N5/ fresh/Co-Piand Ta3N5/aged/Co-Piat 1.23 V vs RHE

    Fig.8(b)is the incident photon-to-current efficiency(IPCE)of Ta3N5/fresh/Co-Pi and Ta3N5/aged/ Co-Pi.The IPCE of Ta3N5/fresh/Co-Pi is nearly zero in the spectrum range from 350 to 610 nm,which further excludes contribution of substrate on photocurrent. The IPCE of Ta3N5/aged/Co-Pi is~26%at 400 nm, but decreases at longer wavelength[24].The integrated

    photocurrent(~2.35 mA·cm-2)shown in Fig.9 is very close to themeasured value(~2.34 mA·cm-2),which suggests that the measured photocurrent is reliable. The photocurrent response of Ta3N5/aged/Co-Pi in IPCE also agrees well with the absorption edge, suggesting that the photocurrent originates from the band gap transition of Ta3N5.The stability of Ta3N5/ aged and Ta3N5/aged/Co-Piwas alsomeasured and the result is shown in Fig.10.As we can see,the photocurrent of Ta3N5/aged declines over 50%after only 3~4 s under illumination,but the time was extended to about 2 000 s for Ta3N5/aged/Co-Pi. Though photocurrent of Ta3N5/aged/Co-Pi decreases obviously,nonzero photocurrent can still be observed. The stability of Ta3N5microsphere electrode should be further improved in future.

    Fig.9 Integrated solar photocurrent at 1.23 V vs RHE from the standard solar spectrum

    Fig.10 Current-time curves of Ta3N5/aged and Ta3N5/ aged/Co-Pimeasured at 1.23 V vs RHE

    3 Conclusions

    In summary,we synthesized an efficient Ta3N5microsphere photoanode by a new and facile in situ hydrolysis deposition method.A Ta3N5microsphere film was formed on Ta substrate in Ta(OEt)5solution of aged methanol.The microsphere is formed by hydrolysis of Ta(OEt)5and subsequentagglomeration of nanoparticles.Water content in solvent was indispensable to in situ deposition of Ta3N5film.High photocurrent density was obtained on the Ta3N5microsphere electrode,~2.34 mA·cm-2at 1.23 V vs RHE and~6.6 mA·cm-2at 1.6 V vs RHE under AM 1.5G simulated sunlight irradiation(100 mW·cm-2).In addition,in situ hydrolysis deposition method is a promising method to prepare efficient Ta3N5photoanodes on other transparent conducting substr ates.

    [1]Fujishima A,Honda K.Nature,1972,238:37-38

    [2]Wang L,Zhou X,Nguyen N T,et al.Adv.Mater.,2016,28 (12):2432-2438

    [3]Fu G,Yan S,Yu T,et al.Appl.Phys.Lett.,2015,107(17): 171902

    [4]LiM,LuoW,Cao D,etal.Angew.Chem.Int.Ed.,2013,52 (42):11016-11020

    [5]Li Y,Zhang L,Torres-Pardo A,et al.Nat.Commun.,2013, 4:2566

    [6]Liu G,Ye S,Yan P,et al.Energy Environ.Sci.,2016,9: 1327-1334

    [7]Khan S,Zapata M JM,Pereira M B,et al.Phys.Chem. Chem.Phys.,2015,17:23952-23962

    [8]Wang Z,Qi Y,Ding C,et al.Chem.Sci.,2016,7(7):4391-4399

    [9]Cong Y,Park H S,Dang H X,et al.Chem.Mater.,2012,24 (3):579-586

    [10]Pan JH,Wang Q,Bahnemann D W.Catal.Today,2014, 230:197-204

    [11]Deepak T G,Anjusree G S,Thomas S,et al.RSC Adv., 2014,4(34):17615-17638

    [12]Cao J,Ren L,Li N,et al.Chem.Eur.J.,2013,19(38): 12619-12623

    [13]Liu X,Zhao L,Domen K,et al.Mater.Res.Bull.,2014,49: 58-65

    [14]Kanan M W,Nocera D G.Science,2008,321(5892):1072-1075

    [15]Lutterman D A,Surendranath Y,Nocera D G.J.Am.Chem. Soc.,2009,131(11):3838-3839

    [16]Ndiege N,Subramanian TW V,Shannon M A,et al.Chem. Mater.,2007,19(13):3155-3161

    [17]Zhao D,Jiang H,Gong H,et al.Transition Met.Chem., 2010,36(1):119-123

    [18]Fang Q,Zhang J Y,Wang Z,et al.Thin Solid Films, 2003,428(1):248-252

    [19]Antonelli D M,Ying JY.Chem.Mater.,1996,8(4):874-881

    [20]Sun Y,Sermon P,Vong M.Thin Solid Films,1996,278(1): 135-139

    [21]Wolf C,Rüssel C.J.Mater.Sci.,1992,27(14):3749-3755

    [22]Pramanik M,LiC,Imura M,etal.Small,2016,12(13):1709-1715

    [23]Liao M,Feng J,Luo W,et al.Adv.Funct.Mater.,2012,22 (14):3066-3074

    [24]Hisatomi T,Kubota J,Domen K.Chem.Soc.Rev.,2014,43 (22):7520-7535

    In Situ Hydrolysis Deposition of an Efficient Ta3N5M icrosphere Photoanode for Solar W ater Sp litting

    YANG Li-Heng1LUOWen-Jun*,2,3LIMing-Xue4ZOU Zhi-Gang*,3

    (1College of Engineering and Applied Science,Nanjing University,Nanjing 210093,China)

    (2Key Laboratory of Flexible Electronics&Institute of Advanced Materials,Jiangsu National Synergetic Innovation

    Center for Advanced Materials,Nanjing Tech University,Nanjing 211816,China)

    A new in situ hydrolysis deposition method was used to prepare a Ta3N5microsphere photoanode, which indicates a high photocurrent of 6.6 mA·cm-2at1.6 V vs RHE.Microsphere precursor films are formed by hydrolysis of Ta(OEt)5and subsequent deposition on substrates,which is achieved by aging methanol solvent in air with high humidity.In contrast,no precursor films were obtained on substrates with fresh methanol.The results suggest thatwater in solvent is very essential to in situ depositing Ta3N5photoanode.In addition,the facile method can be used to deposit Ta3N5on other transparent conducting substrates.

    solarwater splitting;Ta3N5photoanodes;microsphere;in situ deposition;humidity

    O614.51+3

    A

    1001-4861(2016)10-1839-08

    10.11862/CJIC.2016.330

    2016-04-26。收修改稿日期:2016-08-18。

    國家重點(diǎn)基礎(chǔ)研究發(fā)展計劃(973計劃,No.2013CB632404,2014CB239303)、江蘇省自然科學(xué)基金(No.15KJB150010,BK20140197)、南京大學(xué)納米技術(shù)江蘇省重點(diǎn)實(shí)驗(yàn)室開放研究基金資助項(xiàng)目。

    *通信聯(lián)系人。E-mail:iamwjluo@njtech.edu.cn,zgzou@nju.edu.cn

    猜你喜歡
    南京大學(xué)原位微球
    物歸原位
    幼兒100(2024年19期)2024-05-29 07:43:34
    我校黨委書記柴林一行赴南京大學(xué)交流學(xué)習(xí)
    《南京大學(xué)學(xué)報數(shù)學(xué)半年刊》征稿簡則
    懸浮聚合法制備窄尺寸分布聚甲基丙烯酸甲酯高分子微球
    未培養(yǎng)微生物原位培養(yǎng)技術(shù)研究進(jìn)展
    TiO2/PPy復(fù)合導(dǎo)電微球的制備
    Comprendre et s'entendre
    échange humain sous le contexte de la mondialisation
    可吸收止血微球在肝臟部分切除術(shù)中的應(yīng)用
    復(fù)凝法制備明膠微球
    河南科技(2014年22期)2014-02-27 14:18:07
    热re99久久国产66热| 国产69精品久久久久777片| 观看免费一级毛片| 国产欧美亚洲国产| 边亲边吃奶的免费视频| 一级毛片 在线播放| 免费观看无遮挡的男女| 97在线视频观看| 亚洲精品久久午夜乱码| 极品教师在线视频| 国产精品.久久久| 亚洲精品乱码久久久久久按摩| 精品国产一区二区久久| 少妇裸体淫交视频免费看高清| 黄色视频在线播放观看不卡| 老熟女久久久| 18禁动态无遮挡网站| 少妇被粗大猛烈的视频| 天天操日日干夜夜撸| 国产日韩欧美亚洲二区| 日本黄色片子视频| 亚洲国产最新在线播放| 久久青草综合色| 校园人妻丝袜中文字幕| 又粗又硬又长又爽又黄的视频| 精华霜和精华液先用哪个| 久久免费观看电影| 成年美女黄网站色视频大全免费 | videossex国产| 久热久热在线精品观看| 欧美+日韩+精品| 国产黄色免费在线视频| 青春草亚洲视频在线观看| 欧美日韩av久久| 国产高清三级在线| 久久人妻熟女aⅴ| 日韩制服骚丝袜av| 美女cb高潮喷水在线观看| 精品亚洲乱码少妇综合久久| 全区人妻精品视频| 大片电影免费在线观看免费| 亚洲国产色片| 国产精品不卡视频一区二区| 五月伊人婷婷丁香| 美女福利国产在线| 中文在线观看免费www的网站| 老司机影院毛片| 亚洲av成人精品一二三区| 一二三四中文在线观看免费高清| av在线app专区| 人体艺术视频欧美日本| 亚洲伊人久久精品综合| 欧美 亚洲 国产 日韩一| 极品少妇高潮喷水抽搐| 九九在线视频观看精品| 久久人人爽人人爽人人片va| 少妇人妻精品综合一区二区| 中国美白少妇内射xxxbb| 亚洲av国产av综合av卡| 久久精品久久精品一区二区三区| 丝瓜视频免费看黄片| 少妇高潮的动态图| 十分钟在线观看高清视频www | 久久亚洲国产成人精品v| 国产精品国产三级专区第一集| 国产精品免费大片| 久久人人爽人人片av| 另类亚洲欧美激情| 久久国产乱子免费精品| 中文字幕av电影在线播放| 中文字幕制服av| 欧美激情极品国产一区二区三区 | 永久网站在线| 观看av在线不卡| 久久精品久久精品一区二区三区| 亚洲人与动物交配视频| 国产精品麻豆人妻色哟哟久久| 亚洲国产日韩一区二区| 内射极品少妇av片p| 又黄又爽又刺激的免费视频.| 日日摸夜夜添夜夜爱| 久久久久人妻精品一区果冻| 亚洲伊人久久精品综合| 久久精品国产自在天天线| 免费观看a级毛片全部| 最新的欧美精品一区二区| 三级国产精品欧美在线观看| 国产有黄有色有爽视频| 国产欧美亚洲国产| www.av在线官网国产| 国产成人freesex在线| 少妇高潮的动态图| 高清黄色对白视频在线免费看 | 国产乱来视频区| 少妇的逼水好多| 久久久亚洲精品成人影院| 精品久久久久久久久av| 欧美精品亚洲一区二区| 免费看不卡的av| 日韩av在线免费看完整版不卡| 日本猛色少妇xxxxx猛交久久| 在现免费观看毛片| 人人妻人人看人人澡| 日韩人妻高清精品专区| 亚洲情色 制服丝袜| 国产精品一二三区在线看| 欧美老熟妇乱子伦牲交| 亚洲美女视频黄频| 国产在视频线精品| 大又大粗又爽又黄少妇毛片口| 欧美精品一区二区大全| 狂野欧美激情性xxxx在线观看| 国产精品一区www在线观看| 在线观看免费视频网站a站| 交换朋友夫妻互换小说| 中国国产av一级| 国产日韩欧美视频二区| 亚洲国产精品999| 街头女战士在线观看网站| 亚洲情色 制服丝袜| 免费在线观看成人毛片| 五月开心婷婷网| 日本vs欧美在线观看视频 | 日韩制服骚丝袜av| 国产成人aa在线观看| 人人妻人人看人人澡| 在线观看免费日韩欧美大片 | 亚洲国产成人一精品久久久| 人妻夜夜爽99麻豆av| 免费av中文字幕在线| 亚洲欧美日韩另类电影网站| 亚洲国产日韩一区二区| 国产成人免费观看mmmm| 狂野欧美白嫩少妇大欣赏| 亚洲,欧美,日韩| 少妇丰满av| 亚洲国产最新在线播放| 亚洲丝袜综合中文字幕| 五月伊人婷婷丁香| 日韩免费高清中文字幕av| 欧美97在线视频| 一级,二级,三级黄色视频| 丰满迷人的少妇在线观看| 亚洲av不卡在线观看| av福利片在线观看| 亚洲精品国产色婷婷电影| 久久精品久久久久久久性| 国产成人精品福利久久| 一边亲一边摸免费视频| 亚洲人成网站在线播| 欧美日韩一区二区视频在线观看视频在线| 在线观看国产h片| 欧美成人精品欧美一级黄| 国产有黄有色有爽视频| 国产精品一区二区在线不卡| 亚洲精品国产av蜜桃| 插逼视频在线观看| 少妇裸体淫交视频免费看高清| 精品亚洲乱码少妇综合久久| 亚洲真实伦在线观看| 久久韩国三级中文字幕| 午夜免费观看性视频| 欧美日韩视频精品一区| 一本一本综合久久| 在线播放无遮挡| 国产一区二区在线观看日韩| 亚洲欧美一区二区三区国产| 国产白丝娇喘喷水9色精品| 日韩大片免费观看网站| 美女视频免费永久观看网站| 男的添女的下面高潮视频| 午夜免费鲁丝| 国产一区有黄有色的免费视频| 大话2 男鬼变身卡| 久久久久久久精品精品| 欧美97在线视频| 欧美日韩在线观看h| 在线观看免费高清a一片| 久久久国产欧美日韩av| 日本av免费视频播放| 一二三四中文在线观看免费高清| 人妻 亚洲 视频| 少妇人妻一区二区三区视频| 一本大道久久a久久精品| 国产成人午夜福利电影在线观看| 草草在线视频免费看| 亚洲va在线va天堂va国产| 久久久精品免费免费高清| 少妇人妻一区二区三区视频| 在线 av 中文字幕| 午夜福利,免费看| 99热国产这里只有精品6| 国产免费一区二区三区四区乱码| 欧美+日韩+精品| 亚洲精品乱久久久久久| 男人狂女人下面高潮的视频| 纵有疾风起免费观看全集完整版| videossex国产| 99久久精品一区二区三区| 国产永久视频网站| 精品国产国语对白av| av专区在线播放| 日韩伦理黄色片| 国内精品宾馆在线| 日日摸夜夜添夜夜添av毛片| 视频区图区小说| 精品人妻熟女av久视频| av福利片在线观看| 日本爱情动作片www.在线观看| 99热这里只有是精品50| 国产欧美日韩综合在线一区二区 | 五月开心婷婷网| 有码 亚洲区| 热99国产精品久久久久久7| 乱码一卡2卡4卡精品| 久久精品国产亚洲av涩爱| 高清黄色对白视频在线免费看 | 国产精品一区www在线观看| 啦啦啦啦在线视频资源| 久久久国产欧美日韩av| 国产成人精品福利久久| 久久99精品国语久久久| 一区二区av电影网| 日日爽夜夜爽网站| 青春草国产在线视频| 亚洲丝袜综合中文字幕| 国产女主播在线喷水免费视频网站| 国产欧美日韩综合在线一区二区 | 亚洲国产成人一精品久久久| 久久久欧美国产精品| 国产成人精品福利久久| 国产精品秋霞免费鲁丝片| 嫩草影院入口| 80岁老熟妇乱子伦牲交| 亚洲国产欧美在线一区| 亚洲国产精品国产精品| 亚洲精品亚洲一区二区| 久久久久网色| 国产成人精品福利久久| 欧美日韩视频高清一区二区三区二| 日本91视频免费播放| 亚洲精品,欧美精品| 99久国产av精品国产电影| 十八禁网站网址无遮挡 | 国产伦在线观看视频一区| xxx大片免费视频| 国产欧美日韩一区二区三区在线 | 中文精品一卡2卡3卡4更新| 国产一级毛片在线| 精品人妻偷拍中文字幕| 欧美 亚洲 国产 日韩一| 免费大片黄手机在线观看| 免费av中文字幕在线| 国产亚洲av片在线观看秒播厂| 少妇人妻一区二区三区视频| 国产视频内射| 美女大奶头黄色视频| 黄色毛片三级朝国网站 | 最近中文字幕高清免费大全6| 亚洲国产精品国产精品| 日韩欧美 国产精品| 在线观看美女被高潮喷水网站| 自线自在国产av| 人人妻人人澡人人爽人人夜夜| 国产视频首页在线观看| 亚洲三级黄色毛片| 制服丝袜香蕉在线| 日韩免费高清中文字幕av| 亚洲久久久国产精品| 午夜久久久在线观看| 黑人巨大精品欧美一区二区蜜桃 | 亚洲国产精品一区二区三区在线| av国产精品久久久久影院| 免费看不卡的av| av又黄又爽大尺度在线免费看| 晚上一个人看的免费电影| 久久免费观看电影| 国产 精品1| 黑丝袜美女国产一区| 嫩草影院新地址| 日韩欧美一区视频在线观看 | 97超碰精品成人国产| 成人国产av品久久久| 啦啦啦啦在线视频资源| 久久久午夜欧美精品| 国产片特级美女逼逼视频| 亚洲成色77777| 日本av手机在线免费观看| 在线观看免费视频网站a站| av免费在线看不卡| 亚洲精品国产av蜜桃| 在线观看免费日韩欧美大片 | 精品一品国产午夜福利视频| 日韩三级伦理在线观看| 国产91av在线免费观看| 一区在线观看完整版| 在线免费观看不下载黄p国产| 在线天堂最新版资源| 国产免费视频播放在线视频| 黄色一级大片看看| 欧美日韩视频高清一区二区三区二| 国产在线男女| 亚洲内射少妇av| 一个人免费看片子| 看非洲黑人一级黄片| 少妇熟女欧美另类| 男女边摸边吃奶| av不卡在线播放| 亚洲经典国产精华液单| 高清不卡的av网站| 精品人妻熟女毛片av久久网站| 伦理电影免费视频| 免费看不卡的av| 有码 亚洲区| 黄色欧美视频在线观看| 亚州av有码| 又爽又黄a免费视频| 精华霜和精华液先用哪个| 建设人人有责人人尽责人人享有的| 成人毛片60女人毛片免费| 美女cb高潮喷水在线观看| av福利片在线观看| av国产久精品久网站免费入址| 欧美激情极品国产一区二区三区 | 久久久精品94久久精品| 一级爰片在线观看| 自拍欧美九色日韩亚洲蝌蚪91 | 一级毛片电影观看| 日韩精品免费视频一区二区三区 | 肉色欧美久久久久久久蜜桃| 少妇猛男粗大的猛烈进出视频| 十八禁网站网址无遮挡 | 人人妻人人澡人人爽人人夜夜| 一区二区三区四区激情视频| 国产在线视频一区二区| 亚洲,一卡二卡三卡| 亚洲在久久综合| 欧美性感艳星| 亚洲人成网站在线观看播放| a级毛片免费高清观看在线播放| 欧美精品高潮呻吟av久久| 亚洲国产av新网站| 精品亚洲成a人片在线观看| 国产伦精品一区二区三区视频9| 91精品国产九色| 午夜日本视频在线| 亚洲精品第二区| 日韩人妻高清精品专区| 秋霞在线观看毛片| 2022亚洲国产成人精品| 麻豆乱淫一区二区| 国产精品国产三级专区第一集| 狂野欧美白嫩少妇大欣赏| av网站免费在线观看视频| 麻豆成人午夜福利视频| 纵有疾风起免费观看全集完整版| 日韩 亚洲 欧美在线| 人妻夜夜爽99麻豆av| 日本欧美国产在线视频| 欧美日韩综合久久久久久| 在线观看免费高清a一片| 尾随美女入室| 亚洲国产精品专区欧美| 亚洲精品国产av成人精品| 新久久久久国产一级毛片| 男的添女的下面高潮视频| 9色porny在线观看| 97在线人人人人妻| 在线观看av片永久免费下载| 久久 成人 亚洲| 国产伦精品一区二区三区四那| 日韩不卡一区二区三区视频在线| 欧美xxxx性猛交bbbb| 欧美日本中文国产一区发布| 亚洲内射少妇av| 亚洲图色成人| 亚洲精品日韩在线中文字幕| 最后的刺客免费高清国语| 亚洲性久久影院| 亚州av有码| 午夜精品国产一区二区电影| 欧美精品一区二区大全| 亚洲成人手机| 色5月婷婷丁香| 18禁裸乳无遮挡动漫免费视频| 日本黄色片子视频| 国产精品一区二区性色av| 9色porny在线观看| 国产色婷婷99| 久久国产乱子免费精品| 精品人妻熟女av久视频| 最近中文字幕2019免费版| 丰满迷人的少妇在线观看| 久久精品熟女亚洲av麻豆精品| 九九久久精品国产亚洲av麻豆| 51国产日韩欧美| 高清午夜精品一区二区三区| 青青草视频在线视频观看| 精品视频人人做人人爽| 少妇人妻久久综合中文| 青春草国产在线视频| 亚洲av日韩在线播放| av卡一久久| 久久久久久久久久成人| 精品久久久久久久久av| 涩涩av久久男人的天堂| 精华霜和精华液先用哪个| 51国产日韩欧美| av.在线天堂| 啦啦啦中文免费视频观看日本| 免费人成在线观看视频色| 美女国产视频在线观看| 在线观看www视频免费| 三级国产精品欧美在线观看| 王馨瑶露胸无遮挡在线观看| 99国产精品免费福利视频| √禁漫天堂资源中文www| 精品人妻一区二区三区麻豆| 国产一区二区三区av在线| 久久久久精品性色| 国产高清不卡午夜福利| av国产精品久久久久影院| 人人妻人人看人人澡| 中文精品一卡2卡3卡4更新| 精品亚洲乱码少妇综合久久| 五月伊人婷婷丁香| 三级国产精品片| 人妻夜夜爽99麻豆av| 一级毛片我不卡| 亚洲国产日韩一区二区| 最近手机中文字幕大全| 伦精品一区二区三区| 国产国拍精品亚洲av在线观看| 高清在线视频一区二区三区| 如日韩欧美国产精品一区二区三区 | 美女脱内裤让男人舔精品视频| 国产日韩一区二区三区精品不卡 | 亚洲av综合色区一区| 一个人看视频在线观看www免费| 国产国拍精品亚洲av在线观看| 精品人妻一区二区三区麻豆| 少妇被粗大猛烈的视频| 国产视频内射| 国内少妇人妻偷人精品xxx网站| 国产精品国产三级国产专区5o| 国产成人精品久久久久久| 国产日韩一区二区三区精品不卡 | 建设人人有责人人尽责人人享有的| 亚洲av日韩在线播放| 五月天丁香电影| 婷婷色麻豆天堂久久| 性色av一级| 69精品国产乱码久久久| videos熟女内射| 久久久国产一区二区| 在线播放无遮挡| 亚洲欧美日韩卡通动漫| 熟女电影av网| 亚洲精品第二区| 精华霜和精华液先用哪个| 十八禁高潮呻吟视频 | 一级爰片在线观看| 爱豆传媒免费全集在线观看| 免费看不卡的av| av在线播放精品| 国产av码专区亚洲av| 黄色视频在线播放观看不卡| 国产黄频视频在线观看| 99久久人妻综合| 各种免费的搞黄视频| 久久毛片免费看一区二区三区| 最近中文字幕高清免费大全6| 99精国产麻豆久久婷婷| 51国产日韩欧美| 国产熟女午夜一区二区三区 | 性高湖久久久久久久久免费观看| 亚洲av免费高清在线观看| 这个男人来自地球电影免费观看 | 亚洲欧美日韩东京热| 一区二区三区乱码不卡18| 我的老师免费观看完整版| 亚洲精品第二区| 精品国产乱码久久久久久小说| 国产高清三级在线| 国产日韩一区二区三区精品不卡 | 三级国产精品欧美在线观看| 天堂俺去俺来也www色官网| 久久精品国产自在天天线| 又黄又爽又刺激的免费视频.| 亚洲av福利一区| 国产伦在线观看视频一区| 国产免费一区二区三区四区乱码| 久久热精品热| 狠狠精品人妻久久久久久综合| 五月玫瑰六月丁香| 欧美+日韩+精品| 人妻人人澡人人爽人人| 汤姆久久久久久久影院中文字幕| 99久久人妻综合| 亚洲欧洲日产国产| 欧美激情国产日韩精品一区| 最近手机中文字幕大全| 自拍偷自拍亚洲精品老妇| 久久久久久久久久久丰满| 国产亚洲欧美精品永久| 伦精品一区二区三区| 最后的刺客免费高清国语| 男人舔奶头视频| 亚洲精品乱码久久久v下载方式| 2018国产大陆天天弄谢| 蜜桃在线观看..| 美女内射精品一级片tv| 日韩av在线免费看完整版不卡| 成年av动漫网址| 免费久久久久久久精品成人欧美视频 | 久久 成人 亚洲| 高清黄色对白视频在线免费看 | 一本色道久久久久久精品综合| 亚洲欧美成人精品一区二区| 丰满少妇做爰视频| 男女边摸边吃奶| 三上悠亚av全集在线观看 | 人人妻人人爽人人添夜夜欢视频 | 伦理电影大哥的女人| av女优亚洲男人天堂| 美女主播在线视频| 成人美女网站在线观看视频| 日韩成人av中文字幕在线观看| 欧美最新免费一区二区三区| 欧美精品亚洲一区二区| 搡女人真爽免费视频火全软件| 99久久精品一区二区三区| 欧美性感艳星| 免费大片黄手机在线观看| 黄色毛片三级朝国网站 | 国产综合精华液| 乱人伦中国视频| 久久久久久伊人网av| 少妇精品久久久久久久| 18禁裸乳无遮挡动漫免费视频| 91成人精品电影| 爱豆传媒免费全集在线观看| 午夜影院在线不卡| 各种免费的搞黄视频| 成人美女网站在线观看视频| 国产成人精品婷婷| 人人妻人人看人人澡| 偷拍熟女少妇极品色| 国产成人一区二区在线| 一级毛片久久久久久久久女| 国产精品人妻久久久久久| 国产精品一区二区在线不卡| 熟女av电影| 一级二级三级毛片免费看| 国产探花极品一区二区| 欧美日韩视频高清一区二区三区二| 两个人免费观看高清视频 | 国产又色又爽无遮挡免| 一级二级三级毛片免费看| 久久久久久久久久成人| 国产高清有码在线观看视频| 女性生殖器流出的白浆| 久久午夜福利片| 黑丝袜美女国产一区| 春色校园在线视频观看| 我的老师免费观看完整版| 日韩亚洲欧美综合| 午夜福利网站1000一区二区三区| 国产精品99久久99久久久不卡 | 日韩熟女老妇一区二区性免费视频| 国产免费一区二区三区四区乱码| 制服丝袜香蕉在线| 亚洲精品成人av观看孕妇| 婷婷色综合大香蕉| 丝瓜视频免费看黄片| 777米奇影视久久| 日韩成人伦理影院| 青青草视频在线视频观看| 日本黄大片高清| 美女视频免费永久观看网站| 精品久久久久久久久av| av福利片在线观看| 久久精品久久久久久久性| 自拍欧美九色日韩亚洲蝌蚪91 | 国产片特级美女逼逼视频| 成人国产麻豆网| 91精品一卡2卡3卡4卡| 国语对白做爰xxxⅹ性视频网站| 亚洲美女黄色视频免费看| 精品人妻一区二区三区麻豆| 视频中文字幕在线观看| 亚洲国产精品一区二区三区在线| 熟妇人妻不卡中文字幕| 多毛熟女@视频| 插逼视频在线观看| 如何舔出高潮| 久久久精品94久久精品| 你懂的网址亚洲精品在线观看| 99热这里只有是精品在线观看| 777米奇影视久久| h日本视频在线播放| 少妇人妻精品综合一区二区| 18禁裸乳无遮挡动漫免费视频| 国产欧美亚洲国产| 秋霞在线观看毛片| 精品午夜福利在线看| 性高湖久久久久久久久免费观看| a级毛色黄片| 一级片'在线观看视频| 欧美最新免费一区二区三区| 免费看av在线观看网站| 国产亚洲欧美精品永久| 成人亚洲欧美一区二区av| 嘟嘟电影网在线观看| 大码成人一级视频|