• <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 ?

    High-performance bulk heterojunction-based photocathode with facile architecture for photoelectrochemical water splitting

    2023-03-14 06:52:08YnlingWuDeyuLiuHunglongZhungJiboLeYongboKung
    Chinese Chemical Letters 2023年1期

    Ynling Wu,Deyu Liu,Hunglong Zhung,Jibo Le,Yongbo Kung,*

    a Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,Ningbo 315201,China

    b University of Chinese Academy of Sciences,Beijing 100049,China

    c Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials,Ningde Normal University,Ningde 352100,China

    Keywords:Photocathodes Ruthenium oxide Bulk heterojunctions Hydrogen evolution Photoelectrochemical cells

    ABSTRACT Organic semiconductors are promising candidates as photoactive layers for photoelectrodes used in photoelectrochemical (PEC) cells due to their excellent light absorption and efficient charge transport properties with the help of interfacial materials.However,the use of multilayers will make the charge transfer mechanism more complicated and decrease the PEC performance of the photoelectrode caused by the increased contact resistance.In this work,a PM6:Y6 bulk heterojunction (BHJ)-based photocathode is fabricated for efficient PEC hydrogen evolution reaction (HER) in an acidic aqueous solution.With RuO2 as an interfacial modification layer,the photocathode with a simple structure (fluorine-doped tin oxide(FTO)/PM6:Y6/RuO2) generates a maximum photocurrent density up to -15 mA/cm2 at 0 V vs. reference hydrogen electrode (RHE),outperforming all previously reported BHJ-based photocathodes in terms of PEC performance.The highest ratiometric power-saved efficiency of 3.7% is achieved at 0.4 V vs. RHE.

    The pursuit of low-cost,renewable,and environmental-friendly energy sources especially hydrogen fuel has received tremendous attention in recent decades to meet the growing global energy demand and achieve carbon-neutral energy supplies [1,2].Photoelectrochemical (PEC) water splitting is a prospective pathway to converting solar energy into green hydrogen fuel [3–7].Solutionprocessed organic semiconductors,including single polymers and donor-acceptor mixed bulk heterojunction materials,represent a class of promising photoactive materials for cost-effective,largescale,and high-efficiency solar-driven water splitting [8].

    Since the blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was used as the photoactive layer of photocathodes in PEC cell for the first time,a series of research work based on P3HT:PCBM has been carried out to optimize the onset potential,photocurrent and durability by introducing interfacial layers with well-matched energy levels,including hole transporting layer (HTL,such as CuI,MoO3,PEDOT:PSS,and graphene oxide),electron transfer layer (ETL,such as TiO2) and catalytical layer (such as Pt,MoSx,and RuO2) [9–11].However,the optimized photocurrent of photocathode based on P3HT:PCBM was only obtained to -8 mA/cm2at 0 Vvs.reference hydrogen electrode (RHE) with an onset potential of 0.7 Vvs.RHE [12].In recent years,the performance of bulk heterojunction (BHJ) based photocathode for hydrogen evolution reaction (HER) has made great progress,benefiting from the rapid development of novel nonfullerene acceptors,which possess significant advantages including broad absorption band,high crystallinity,and tunable energy levels [13].For example,by using the non-fullerene acceptor,Li and coworkers have improved the photocurrent density of BHJ-based photocathodes to -11.7 and 11.98 mA/cm2at 0 Vvs.RHE with onset potentials of 0.8 and 0.87 Vvs.RHE,respectively [13,14].

    Since the organic semiconductor,Y6 ((2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile)),was first reported by Zou’ group in 2019,PM6 (poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8–dione))]):Y6 based BHJ device has achieved a high PCE of 15.7% in organic solar cells (OSCs)[15].After that,PM6 (electron donor):Y6 (electron acceptor) based BHJ has attracted tremendous interest in OSCs applications in virtue of their recombination losses,small dissociation barrier,long diffusion length,beneficial morphology,and excellent light absorption properties [16,17].They have not yet been investigated as photocathodes for PEC water reduction.The rapid development of PM6:Y6 BHJ for organic photovoltaics provides an opportunity to take it as a photoactive layer for solar water reduction.

    Fig.1.(a) Chemical structures of PM6 and Y6.(b) Absorption spectra of the PM6,Y6,and the BHJ (PM6:Y6) film.(c) The energy-level diagram of semiconductors and photocathodes with different architectures that used in this work.

    Although the interfacial layers are commonly required to boost charge separation and reduce recombination [18],the multilayer structure will increase the contact resistances hence lowering the PEC performance and making the charge transfer mechanism more complicated [10].In addition,the electrochemical degradation of the HTLs (PEDOT:PSS,MoO3) has a negative impact on both the PEC performance and the long-term stability of the photocathodes[19].It has been suggested the large potential difference between the Fermi levels of the HTL and the electrolyte is responsible for the high onset potential and photocurrent of the photocathode[20].We assumed that utilizing a donor material with low-lying highest occupied molecular orbital (HOMO) level and high hole mobility might make an HTL unnecessary [21].Moreover,it has been proven that charge transfer at the BHJ/electrolyte interface is a rate-limiting process.Due to its supercapacitive nature,excellent catalytical properties,and good conductivity,RuO2can be decorated on the BHJ surface as an interfacial layer,resulting in effective charge extraction,charge transfer,and catalyzing H+to H2[22,23].

    Based on these different observations,together with the low HOMO level (-5.54 eV) of PM6,we used PM6:Y6 as the photoactive layer with RuO2as an interfacial modification layer to fabricate a simplified BHJ based photocathode,resulting in the highest photocurrent density of -15 mA/cm2at a bias of 0 Vvs.RHE,compared with a lower photocurrent density of -12 mA/cm2with TiO2and Pt as interfacial modification layers.The single RuO2layer significantly lowers the device resistance,and the morphology and thickness of RuO2play key roles in promoting the PEC performance.Moreover,the fabrication of the photocathodes could be carried out from the solution and at temperatures never going over 150°C.

    The chemical structures of PM6 and Y6 were depicted in Fig.1a.Both the donor and the accepter have largeπ-conjugated skeletons,resulting in broad absorption in the UV-vis spectra.As shown in Fig.1b,the absorption spectra of PM6 film are well complementary with Y6 film,resulting in a very high spectral response in the range of 300–900 nm.The suitable light absorption and energy levels of PM6:Y6 make it an excellent candidate photoactive layer that can be designed as a photocathode.Since lack of reactive sites on pristine BHJ for driving water splitting,a catalytic layer is indispensable to transfer photo-generated electrons.Pt and RuO2are the most efficiently and commonly used cocatalysts for reducing H+to H2[24].TiO2was selected as an ETL to enhance charge extraction and reduce recombination from BHJ [25].Fig.1c depicts three configurations of photocathodes studied in this work based on PM6:Y6 blends and different interfacial layers: (1)fluorine-doped tin oxide (FTO)/BHJ/Pt,(2) FTO/BHJ/TiO2/Pt,and (3)FTO/BHJ/RuO2.

    Fig.2.SEM images of photocathodes with different architectures.Top-view SEM images of (a) FTO/BHJ/TiO2/Pt and (b) FTO/BHJ/RuO2 photocathodes.Cross-sectional images of the photocathodes with different interfacial layers.From bottom to top:(c) FTO,BHJ,TiO2 and Pt layers; (d) FTO,BHJ and RuO2 layers.Scale bar: 100 nm.

    To meet the requirements of low-cost fabrication and highthroughput industrial implementation,all the three architectures are fabricated by solution-processed methods under ambient atmosphere.The experimental procedures are described in Supporting information.The Pt nanoparticles were loaded by photoassisted electrodeposition.The active layer (BHJ) and interfacial layers (TiO2or RuO2) were spin-coated orderly on the FTO to fabricated facile photocathodes.The surface morphology and thickness of photocathode layers were characterized by high-resolution scanning electron microscopy (SEM).The Pt nanoparticles decorated on the BHJ surface by photo-assisted electrodeposition with a particle size of 5–20 nm can be clearly observed (Fig.S1 in Supporting information).As shown in Figs.2a and b,the TiO2,and RuO2nanoparticles are covered uniformly on the BHJ with an average thickness of about 70 and 100 nm (Figs.2c and d),respectively.In fact,the RuO2layer consists of a porous layer of nanoparticle aggregates,thus its roughness is much higher than that of TiO2,thus not only offering a higher amount of reaction sites originating from the enhanced surface area but also shortening the diffusion length of charge carriers.Well-defined interfaces are observed from the cross-sectional SEM images,except for the Pt nanoparticles,whose small size and sparse distribution make them difficult to be distinguished.Therein,the optimized thickness of BHJ is about 80–150 nm.

    Fig.3.(a) J-V curves of FTO/BHJ,FTO/BHJ/Pt,FTO/BHJ/TiO2/Pt and FTO/BHJ/RuO2 photocathodes under solar spectrum AM1.5 G at 100 mW/cm2 with chopped light illumination in 0.5 mol/L Na2SO4 aqueous solution (pH 1).(b) Summary of the onset potential and current density (at 0 V vs. RHE) of state-of-the-art BHJ-based photocathodes.(c) Identification of the maximum power point (mpp) of the different photocathodes according to their J-V curves: FTO/BHJ/Pt,FTO/BHJ/TiO2/Pt,and FTO/BHJ/RuO2.(d) IPCE spectra of FTO/BHJ/RuO2 and FTO/BHJ/TiO2/Pt photocathodes in 0.5 mol/L Na2SO4 (pH 1) electrolyte with an applied potential of 0 V vs. RHE.

    It has been proved that the FTO/BHJ/RuO2photocathode demonstrates the highest performance for PEC HER in acidic solution than in neutral and alkali solution (Fig.S2 in Supporting information).The PEC performance of photocathodes with different architectures was then examined and compared under 1 sun (AM 1.5 G) in a 0.5 mol/L Na2SO4electrolyte (pH 1).The bare FTO/BHJ exhibits neglect photocurrent when the photocathode was conducted by cycle voltammetry at a scan rate of 20 mV/s in the potential range of 0.8 to 0 Vvs.RHE under chopped light illumination.The current-potential (J-V) curves of four different photocathodes are plotted in Fig.3a.After Pt deposition,the photocurrent density (j) of FTO/BHJ/Pt is effectively improved due to the existence of reactive sites for HER.However,the discrete distribution of Pt nanoparticles leads to limited charge extraction.The addition of TiO2overlayer significantly promotes charge separation and electron transfer,therefore,the FTO/BHJ/TiO2/Pt photocathode is capable of delivering a high photocurrent of -12 mA/cm2at 0 Vvs.RHE.Nevertheless,the additional interface will increase the resistance toward the charge flow and thus is harmful to the PEC performances [26].An interfacial layer that undertakes the tasks of charge extraction,electron transfer,and catalysis is urgently desired.RuO2is a good alternative.In comparison with that of FTO/BHJ/TiO2/Pt photocathode,the saturation photocurrent density of FTO/BHJ/RuO2is greatly enhanced and reaches a record photocurrent value of -15 mA/cm2at 0 Vvs.RHE with an onset potential of 0.8 Vvs.RHE (at 0.1 mA/cm2).To the best of our knowledge,thejat 0 Vvs.RHE is the highest value among the previously reported BHJ-based photocathodes (Fig.3b).In addition,the performance of the FTO/BHJ/TiO2/RuO2photocathode is not superior to FTO/BHJ/RuO2photocathode (Fig.S3 in Supporting information),indicating that the RuO2could efficiently promote charge transfer.The ideal ratiometric power-saved efficiency (Φsaved,ideal,see Supporting information for details) of the photocathodes could be obtained according to their maximum power point (mpp) calculated from theJ-Vcurves(Fig.3c).TheΦsaved,idealof FTO/BHJ/RuO2photocathode is determined to be 3.7% at 0.4 Vvs.RHE,which is nearly twice higher than that of FTO/BHJ/TiO2/Pt photocathode (1.9% at 0.3 Vvs.RHE),while the value of FTO/BHJ/Pt photocathode is below 0.2%.Thanks to the broad light absorption range,the incidentphoton-to-current efficiency (IPCE) spectra of the photocathodes at 0 Vvs.RHE show a wide and high-efficiency response in the whole range of 300–900 nm.The highest IPCEs of 76% and 69% are achieved at about 620 nm for FTO/BHJ/RuO2and FTO/BHJ/TiO2/Pt photocathodes,respectively (Fig.3d).

    To identify the feasibility of the FTO/PM6:Y6/RuO2photocathode with an HTL-free structure,HTL was introduced to investigate its effect on the PEC performance of the photocathode.We chose two commonly used HTL materials (NiO and CuOx)to fabricate FTO/NiO/BHJ/RuO2and FTO/CuOx/BHJ/RuO2photocathodes.As shown in Fig.S4 (Supporting information),due to the low hole mobility and conductivity of NiO,the onset potential of FTO/NiO/BHJ/RuO2is only 0.5 Vvs.RHE with a photocurrent density of -10.5 mA/cm2at 0 Vvs.RHE,indicating that an unsuitable HTL might block the hole transport.Previous studies suggest that CuOxis a favorable material for extracting photo-generated holes[13,14,27].However,the onset potential and photocurrent are not improved compared with the HTL-free photocathode.We inferred that the invalidation of HTL might be ascribed to the high energy difference between the HOMO level of PM6 and the electrolyte(1.1 Vvs.Vacuum).

    The thickness and morphology of RuO2that impact the carrier transport behavior are critical to achieving high PEC performance[28].As plotted in Fig.S5 (Supporting information),when the RuO2layer is not thick enough (below 100 nm),the BHJ surface could not be fully covered by RuO2.Hence the active sites and electron extraction are insufficient.On the contrary,too thick a RuO2layer causes a dramatic increase in charge transfer resistance and decreases in both photocurrent and onset potential.Therefore,a moderate thickness of the RuO2layer is a key point to obtain a saturatedJ-Vcurve.Meanwhile,the photocathode with the thickness of both BHJ and RuO2below 100 nm exhibits similar charge separation efficiency under the front and the back side illumination (Fig.S6 in Supporting information).The mass ratio of PM6:Y6 was also explored in Fig.S7 (Supporting information),and the optimized mass ratio is 1:1.2.It is worth mentioning that the PEC performance of the photocathode is insensitive to the variation of temperature,which means the device has a good working characteristic (Fig.S8 in Supporting information).

    To test the durability of the photocathodes,chronoamperometry(CA) measurements were carried out at a bias of 0.1 Vvs.RHE in a 0.5 mol/L Na2SO4electrolyte (pH 1).As shown in Fig.4a,the photocathode based on TiO2and Pt interlayers degrades rapidly,the photocurrent decreases by 90% in less than 5 min.This is caused by the poor contact between the BHJ and TiO2nanoparticles and the loose structure of the TiO2layer.As a result,the TiO2layer was detached from the BHJ surface,accompanied by the Pt layer.In comparison,with RuO2as the interlayer,~50% of the photocurrent loss occurred after 30 min.The reason for the moderate degradation speed of the FTO/BHJ/RuO2photocathode might be that although exfoliation occurred on the RuO2layer as well,the newly exposed RuO2interface continued to undertake the task of electron transfer and catalysis.The chemical structures of pristine PM6,Y6,BHJ,and BHJ after the CA test were characterized by microscopic infrared spectroscopy (Micro-FTIR) using the attenuated total reflectance (ATR) method at room temperature.The spectra of BHJ after the PEC test is consistent with that as-prepared (Fig.4b),which exhibits the main characteristic peak signals of both pristine PM6 and Y6.The results indicate that the chemical structure of BHJ has not been damaged during the PEC process.As a result,the low stability of the BHJ-based photocathodes may be caused by delamination of overlayers from the BHJ surface or exfoliation of BHJ from FTO substrates,erosion of electrolyte,and electrochemical polarization.The continuous evolution of H2bubbles was observed over the surface of the FTO/BHJ/RuO2photocathode for about 1 h with a faradaic efficiency of nearly 100% (Fig.S9 in Supporting information).

    Fig.4.(a) Stability test of FTO/BHJ/TiO2/Pt and FTO/BHJ/RuO2 photocathodes under solar spectrum AM1.5 G at 100 mW/cm2 at a bias of 0.1 V vs. RHE in 0.5 mol/L Na2SO4 aqueous solution (pH 1) with trace of H2PtCl4.(b) FTIR-ATR characterization of PM6,Y6,FTO/BHJ (PM6:Y6)/RuO2,and FTO/BHJ/RuO2 after CA test for 20 min.

    Fig.5.(a) Open circuit potentials were tested in a 0.5 mol/L H3BO3-KOH buffer solution with 0.5 mol/L Na2SO3 at pH 9 under chopped light illumination.(b) CA curve of FTO/BHJ/RuO2 photocathode under different light irradiation conditions at 0 V vs. RHE.(c) Nyquist plots of as-prepared FTO/BHJ,FTO/BHJ/Pt,FTO/BHJ/TiO2/Pt,and FTO/BHJ/RuO2 photocathodes at a bias of 0.25 V vs. RHE in 0.5 mol/L Na2SO4 aqueous solution (pH 1) under light illumination.Inset: original magnification 25×.(d)Distribution of relaxation times (DRT) curves converted from impedance spectra of(c).

    Open-circuit potential (OCP) measurements were performed to estimate the relative photovoltages of the different photoelectrodes,their OCP curves are shown in Fig.5a.Under illumination,the OCP for FTO/BHJ/Pt,FTO/BHJ/TiO2/Pt,and FTO/BHJ/RuO2photocathodes move toward the positive direction,indicating ptype semiconductor properties,and the photovoltages are 50 mV,100 mV,and 200 mV,respectively.The result corresponds to the tendency of the onset potential values of the photocathodes.Compared with FTO/BHJ/Pt and FTO/BHJ/TiO2/Pt,the more positive shift in the OCP under illumination for FTO/BHJ/RuO2suggests that the RuO2overlayer enables higher conversion efficiency of the incident light to sufficiently available photogenerated electrons,leading to improved PEC activity of PM6:Y6 based photocathode [13].

    It is worth mentioning that the value of photocurrent simultaneously irradiated under 590 nm and 810 nm monochromatic LED light is equal to the sum of photocurrent values that separately irradiated,indicating that there is no synergetic interaction between PM6 and Y6 (Fig.5b).

    To further study the electron transport kinetics in the four kinds of photocathodes and at their interfaces of photocathode/electrolyte,electrochemical impedance spectroscopy (EIS)measurements were conducted under light illumination at the bias from 0.05 V to 0.65 Vvs.RHE (Figs.S10a–h in Supporting information).As shown in Fig.5c,the EIS plots of the four kinds of photocathodes differ from one another.The arc radii of the FTO/BHJ photocathode is much larger than the other photocathodes,indicating its photo-generated charge separation and transfer is very difficult without an interfacial layer.From the high-magnification of the EIS plots in Fig.5c (upper right inset),it is clearly observed that the photocathodes modified by interfacial layers show two or more arcs.The radius values of these photoelectrodes follow the order of FTO/BHJ/RuO2<FTO/BHJ/TiO2/Pt<FTO/BHJ/Pt<FTO/BHJ,which are perfectly consistent with their corresponding photocurrent density.The resistances of FTO/BHJ/RuO2and FTO/BHJ/TiO2/Pt photocathodes are decreased at both high and low-frequency regions due to their efficient electron extraction and transfer,increased conductivity,and enhanced interface kinetics.However,it is hard to distinguish all these contributions.Distribution of relaxation times (DRT) converted from impedance spectra was introduced to effectively separate polarization processes more clearly than in common Nyquist or Bode plots [29].From the DRT plots(Fig.5d),peaks can be characterized to different polarization processes based on their relaxation time (τ) in the order of series resistances (low-τ)<charge transfer (mid-τ)<interfacial reactions(high-τ) [30].The peak intensity of FTO/BHJ/Pt and FTO/BHJ photocathodes at mid-τand high-τregions dramatically increases,indicating that their HER performances are hampered due to their inefficient charge transfer and limited reaction sites (Figs.S10e and f).The FTO/BHJ/TiO2/Pt photocathode obtained the weakest peak intensity in the high-τregion might be due to the excellent conductivity and catalytical properties of Pt.The weakest peak intensity of the FTO/BHJ/RuO2photocathode in the low-τregion indicates it possesses the smallest series resistances ascribes to the simplified architecture.In addition,the loading of RuO2effectively promotes the charge transfer in BHJ bulk and decreases the series resistance that mass transfer was the dominant process for FTO/BHJ/RuO2photocathode (Fig.S10h) [31].

    In conclusion,through the selection of PM6:Y6 BHJ as the photoactive layer and RuO2as the interfacial layer,a facile photocathode was fabricated by the all-solution processed method.The asobtained photocathode achieves the highest photocurrent density of -15 mA/cm2at 0 Vvs.RHE for HER compared with previous reported BHJ-based photocathodes.The value ofΦsaved,idealis up to 3.7% at 0.4 Vvs.RHE.The IPCE value reaches 76% at about 620 nm.By utilizing RuO2as an interfacial layer,an electron transfer layer is unnecessary,thus the interfacial recombination and excessive series resistances of the simplified photocathode are effectively reduced.Moreover,the positive shift of OCP of FTO/BHJ/ RuO2photocathode is responsible for the enhancement of its onset potential.Our work provides an easy and efficient fabrication technique that can meet the requirement of high-throughput industrial implementation.

    Declaration of competing interest

    The authors declare no competing financial interest.

    Acknowledgments

    We acknowledge the financial support by the National Natural Science Foundation of China (NSFC,21905288,and 51904288),the Zhejiang Provincial Natural Science Foundation (No.LZ21B030017),K.C.Wong Education Foundation (No.GJTD-2019-13),Ningbo Major Special Projects of the Plan “Science and Technology Innovation 2025” (Nos.2018B10056,and 2019B10046),and Ningbo 3315 Program,and Natural Science Foundation of Fujian Province (No.2021J011150).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2022.04.078.

    亚洲久久久国产精品| 1024香蕉在线观看| 叶爱在线成人免费视频播放| av福利片在线| 成人18禁高潮啪啪吃奶动态图| 国产在视频线精品| av天堂在线播放| 精品人妻熟女毛片av久久网站| 在线观看午夜福利视频| 制服人妻中文乱码| 在线观看www视频免费| 搡老岳熟女国产| 国产男女超爽视频在线观看| 女人精品久久久久毛片| av不卡在线播放| 亚洲伊人色综图| 人人妻人人爽人人添夜夜欢视频| 波多野结衣一区麻豆| 欧美国产精品一级二级三级| 精品少妇一区二区三区视频日本电影| 亚洲视频免费观看视频| 嫁个100分男人电影在线观看| 18禁裸乳无遮挡动漫免费视频| 黑人操中国人逼视频| 国产欧美日韩一区二区三区在线| 亚洲精品国产精品久久久不卡| 制服诱惑二区| 日日爽夜夜爽网站| 成人av一区二区三区在线看| 亚洲精品美女久久av网站| 在线观看免费日韩欧美大片| 国产精品一区二区在线不卡| 国产无遮挡羞羞视频在线观看| 国产91精品成人一区二区三区| 电影成人av| 91麻豆av在线| 在线十欧美十亚洲十日本专区| 村上凉子中文字幕在线| 男女免费视频国产| 国内久久婷婷六月综合欲色啪| 成年版毛片免费区| 精品一区二区三卡| a级毛片在线看网站| 久久久国产一区二区| 欧美精品啪啪一区二区三区| 久久精品国产亚洲av香蕉五月 | 啦啦啦在线免费观看视频4| 动漫黄色视频在线观看| 日韩三级视频一区二区三区| 99久久国产精品久久久| 成人永久免费在线观看视频| 国产淫语在线视频| 十八禁人妻一区二区| 国产aⅴ精品一区二区三区波| 国产在线精品亚洲第一网站| 黄片小视频在线播放| 久久影院123| 国产精品偷伦视频观看了| 麻豆国产av国片精品| 亚洲成国产人片在线观看| 成人影院久久| 少妇猛男粗大的猛烈进出视频| 色婷婷久久久亚洲欧美| 日韩中文字幕欧美一区二区| 亚洲精品在线观看二区| 精品国产美女av久久久久小说| 亚洲熟妇中文字幕五十中出 | 亚洲av成人av| 在线看a的网站| 热99re8久久精品国产| 电影成人av| 手机成人av网站| 成年人午夜在线观看视频| 中文亚洲av片在线观看爽 | 久久久久久久精品吃奶| 国产熟女午夜一区二区三区| 成年女人毛片免费观看观看9 | 激情视频va一区二区三区| 人人妻,人人澡人人爽秒播| 91麻豆精品激情在线观看国产 | 老鸭窝网址在线观看| 操出白浆在线播放| 91老司机精品| 建设人人有责人人尽责人人享有的| 巨乳人妻的诱惑在线观看| 欧美老熟妇乱子伦牲交| 黄片大片在线免费观看| 成人精品一区二区免费| 国产精品 国内视频| 下体分泌物呈黄色| 黄网站色视频无遮挡免费观看| 在线十欧美十亚洲十日本专区| 国产淫语在线视频| 天天躁狠狠躁夜夜躁狠狠躁| 亚洲精品在线观看二区| 男女之事视频高清在线观看| 天天影视国产精品| 国产不卡av网站在线观看| 91精品三级在线观看| 亚洲精品美女久久久久99蜜臀| 18禁美女被吸乳视频| 亚洲熟女精品中文字幕| 精品午夜福利视频在线观看一区| 丁香六月欧美| 曰老女人黄片| 亚洲精品国产区一区二| 在线观看免费视频网站a站| 欧美av亚洲av综合av国产av| 精品一品国产午夜福利视频| 满18在线观看网站| 精品熟女少妇八av免费久了| 校园春色视频在线观看| 老司机在亚洲福利影院| 日韩 欧美 亚洲 中文字幕| 午夜福利在线免费观看网站| 国产一区二区三区在线臀色熟女 | 亚洲欧美一区二区三区黑人| 久久久久视频综合| 一区二区三区国产精品乱码| 校园春色视频在线观看| 大码成人一级视频| 久久人人爽av亚洲精品天堂| 亚洲一区中文字幕在线| 人人妻,人人澡人人爽秒播| 亚洲久久久国产精品| 中国美女看黄片| 婷婷丁香在线五月| 中文字幕高清在线视频| 热re99久久精品国产66热6| 在线观看免费视频网站a站| 亚洲性夜色夜夜综合| 制服诱惑二区| 女人精品久久久久毛片| 一级毛片精品| 精品国产亚洲在线| 免费黄频网站在线观看国产| 交换朋友夫妻互换小说| 国产成人免费无遮挡视频| 亚洲成人免费av在线播放| 国产成人精品久久二区二区91| 色尼玛亚洲综合影院| 丰满饥渴人妻一区二区三| 国产精品九九99| 两人在一起打扑克的视频| 成人18禁在线播放| 99久久综合精品五月天人人| 国产高清视频在线播放一区| 日日摸夜夜添夜夜添小说| 9191精品国产免费久久| 久久香蕉精品热| 黄网站色视频无遮挡免费观看| www.精华液| 大码成人一级视频| 久久影院123| 亚洲欧美日韩另类电影网站| av中文乱码字幕在线| 天堂动漫精品| 亚洲九九香蕉| 久久午夜亚洲精品久久| 亚洲精品国产一区二区精华液| www.999成人在线观看| 欧美乱码精品一区二区三区| 手机成人av网站| 国产xxxxx性猛交| 久久国产精品大桥未久av| 欧美色视频一区免费| 久久国产精品人妻蜜桃| 亚洲精品一卡2卡三卡4卡5卡| 欧美在线黄色| 亚洲专区中文字幕在线| 91老司机精品| 国产1区2区3区精品| 亚洲精品久久午夜乱码| av电影中文网址| 纯流量卡能插随身wifi吗| 天堂√8在线中文| 中文欧美无线码| 亚洲精品久久午夜乱码| 乱人伦中国视频| 欧美日韩亚洲综合一区二区三区_| 国产亚洲精品久久久久5区| 欧美成人免费av一区二区三区 | 91精品三级在线观看| 最新在线观看一区二区三区| 日本黄色视频三级网站网址 | 午夜激情av网站| 亚洲av成人av| 成熟少妇高潮喷水视频| 大型黄色视频在线免费观看| 99riav亚洲国产免费| 亚洲av片天天在线观看| 亚洲男人天堂网一区| 欧美丝袜亚洲另类 | 一本综合久久免费| 丝袜在线中文字幕| √禁漫天堂资源中文www| 香蕉丝袜av| 色精品久久人妻99蜜桃| 99国产精品一区二区蜜桃av | 纯流量卡能插随身wifi吗| 国产一卡二卡三卡精品| 亚洲五月婷婷丁香| 亚洲人成电影免费在线| 国内久久婷婷六月综合欲色啪| 在线观看66精品国产| 91精品三级在线观看| 狂野欧美激情性xxxx| 精品国产超薄肉色丝袜足j| 久久国产精品大桥未久av| av一本久久久久| 日韩制服丝袜自拍偷拍| 中国美女看黄片| 黑人操中国人逼视频| 久久天堂一区二区三区四区| 色综合欧美亚洲国产小说| 免费在线观看影片大全网站| 中亚洲国语对白在线视频| 一级毛片女人18水好多| av视频免费观看在线观看| 很黄的视频免费| 亚洲欧美日韩另类电影网站| 最近最新中文字幕大全免费视频| 在线国产一区二区在线| 亚洲视频免费观看视频| 高清av免费在线| 午夜精品国产一区二区电影| 高清毛片免费观看视频网站 | 又紧又爽又黄一区二区| 少妇裸体淫交视频免费看高清 | 中文字幕高清在线视频| 中文字幕人妻丝袜一区二区| 少妇的丰满在线观看| 在线观看免费高清a一片| 国内久久婷婷六月综合欲色啪| 一级毛片高清免费大全| av不卡在线播放| 欧美亚洲日本最大视频资源| 精品国产一区二区三区四区第35| 国产伦人伦偷精品视频| 欧美丝袜亚洲另类 | 国产麻豆69| 建设人人有责人人尽责人人享有的| 91av网站免费观看| 成人精品一区二区免费| 日本精品一区二区三区蜜桃| 99久久综合精品五月天人人| 国产日韩欧美亚洲二区| 国产成人av教育| 又黄又爽又免费观看的视频| 精品国产一区二区三区久久久樱花| 最近最新中文字幕大全电影3 | 国产极品粉嫩免费观看在线| 久久久久久免费高清国产稀缺| 久久99一区二区三区| 啦啦啦在线免费观看视频4| 少妇被粗大的猛进出69影院| 91麻豆av在线| ponron亚洲| 精品久久久久久久毛片微露脸| 一级a爱视频在线免费观看| 久久久久久久久免费视频了| 精品久久久久久久久久免费视频 | 亚洲精品乱久久久久久| 人妻 亚洲 视频| 狠狠狠狠99中文字幕| 一级,二级,三级黄色视频| 国产精品永久免费网站| 欧美成人午夜精品| www.999成人在线观看| 欧美日韩福利视频一区二区| 午夜日韩欧美国产| 少妇粗大呻吟视频| 久久亚洲真实| 国产高清videossex| 岛国毛片在线播放| 久久久久久久午夜电影 | 电影成人av| 欧美久久黑人一区二区| 纯流量卡能插随身wifi吗| 国产成人精品在线电影| 一区二区三区精品91| 男人舔女人的私密视频| 亚洲国产看品久久| 欧美日韩亚洲综合一区二区三区_| 女人被狂操c到高潮| 欧美国产精品va在线观看不卡| 国产高清激情床上av| 国产精品偷伦视频观看了| 亚洲 欧美一区二区三区| 黄色女人牲交| 国产精品 欧美亚洲| 精品亚洲成国产av| 日本撒尿小便嘘嘘汇集6| 少妇粗大呻吟视频| 69精品国产乱码久久久| 国产无遮挡羞羞视频在线观看| 母亲3免费完整高清在线观看| 成人永久免费在线观看视频| 成人免费观看视频高清| 久久人人爽av亚洲精品天堂| 国产精品免费一区二区三区在线 | 欧美国产精品va在线观看不卡| 人人妻人人澡人人爽人人夜夜| 黄片播放在线免费| 人人妻人人爽人人添夜夜欢视频| 两个人看的免费小视频| 日韩欧美三级三区| av天堂久久9| 免费在线观看影片大全网站| 交换朋友夫妻互换小说| 久久精品亚洲熟妇少妇任你| 黑丝袜美女国产一区| 国精品久久久久久国模美| 国产蜜桃级精品一区二区三区 | 老司机靠b影院| a级毛片在线看网站| 久久人人爽av亚洲精品天堂| 天天躁狠狠躁夜夜躁狠狠躁| 精品一区二区三区四区五区乱码| 欧美+亚洲+日韩+国产| 欧美日韩视频精品一区| 亚洲三区欧美一区| 一级,二级,三级黄色视频| 久久久久国产精品人妻aⅴ院 | 欧美成人午夜精品| 十八禁人妻一区二区| 亚洲精品一卡2卡三卡4卡5卡| 男女免费视频国产| 成年人午夜在线观看视频| 欧美激情高清一区二区三区| 免费观看a级毛片全部| 亚洲午夜精品一区,二区,三区| 欧美日韩乱码在线| 热99国产精品久久久久久7| 久久中文字幕一级| av电影中文网址| 一个人免费在线观看的高清视频| 99国产精品99久久久久| videosex国产| 美女福利国产在线| 国产精品九九99| 久久青草综合色| 精品乱码久久久久久99久播| 两个人看的免费小视频| 中文字幕人妻丝袜一区二区| 免费在线观看日本一区| 男女床上黄色一级片免费看| 50天的宝宝边吃奶边哭怎么回事| 日本黄色日本黄色录像| 免费一级毛片在线播放高清视频 | 精品人妻在线不人妻| 校园春色视频在线观看| 一区二区日韩欧美中文字幕| svipshipincom国产片| 久久狼人影院| 国内久久婷婷六月综合欲色啪| 国产不卡一卡二| 中出人妻视频一区二区| 成年动漫av网址| 校园春色视频在线观看| 日韩欧美一区二区三区在线观看 | 搡老岳熟女国产| 欧美丝袜亚洲另类 | 中文字幕制服av| 如日韩欧美国产精品一区二区三区| 国产亚洲一区二区精品| 欧美色视频一区免费| 身体一侧抽搐| 国产国语露脸激情在线看| 天天躁夜夜躁狠狠躁躁| 久久久精品国产亚洲av高清涩受| 免费看a级黄色片| x7x7x7水蜜桃| 精品亚洲成国产av| 亚洲综合色网址| 丁香欧美五月| 欧洲精品卡2卡3卡4卡5卡区| 热99久久久久精品小说推荐| 成人18禁高潮啪啪吃奶动态图| 亚洲成人国产一区在线观看| 人人澡人人妻人| 深夜精品福利| 一级毛片精品| 黄色视频,在线免费观看| 好看av亚洲va欧美ⅴa在| 国内毛片毛片毛片毛片毛片| 在线观看舔阴道视频| 天天添夜夜摸| 国产精品久久久久成人av| 亚洲精品中文字幕一二三四区| 岛国在线观看网站| 视频在线观看一区二区三区| 国产亚洲一区二区精品| 99精品久久久久人妻精品| 欧美日韩亚洲高清精品| 免费在线观看黄色视频的| 亚洲专区中文字幕在线| 最新在线观看一区二区三区| 一a级毛片在线观看| 日韩欧美在线二视频 | 日日爽夜夜爽网站| 99精国产麻豆久久婷婷| 在线十欧美十亚洲十日本专区| 欧美在线一区亚洲| 国产亚洲精品久久久久久毛片 | 涩涩av久久男人的天堂| 精品午夜福利视频在线观看一区| 国产免费av片在线观看野外av| 中文字幕最新亚洲高清| 天堂动漫精品| 色播在线永久视频| 日本a在线网址| 一边摸一边抽搐一进一出视频| 欧美在线一区亚洲| 变态另类成人亚洲欧美熟女 | 日韩人妻精品一区2区三区| 国产精品免费大片| 女人被躁到高潮嗷嗷叫费观| 免费观看人在逋| 精品久久久久久久久久免费视频 | 一级黄色大片毛片| 中文字幕另类日韩欧美亚洲嫩草| 脱女人内裤的视频| 国产蜜桃级精品一区二区三区 | 搡老岳熟女国产| 一进一出抽搐动态| 妹子高潮喷水视频| 一级片免费观看大全| 91九色精品人成在线观看| 精品人妻熟女毛片av久久网站| 国产精品永久免费网站| 国产精品久久久av美女十八| x7x7x7水蜜桃| 女人被躁到高潮嗷嗷叫费观| 超色免费av| 精品福利观看| 欧美日韩乱码在线| 亚洲中文日韩欧美视频| 一本综合久久免费| 80岁老熟妇乱子伦牲交| a在线观看视频网站| 欧美性长视频在线观看| 午夜视频精品福利| av在线播放免费不卡| 99精品久久久久人妻精品| 精品福利观看| 香蕉丝袜av| 黄色怎么调成土黄色| 国产黄色免费在线视频| 侵犯人妻中文字幕一二三四区| 青草久久国产| 99国产极品粉嫩在线观看| 少妇的丰满在线观看| 80岁老熟妇乱子伦牲交| 国产99久久九九免费精品| 免费高清在线观看日韩| 亚洲色图av天堂| 桃红色精品国产亚洲av| 亚洲专区中文字幕在线| 欧美成人免费av一区二区三区 | 久久亚洲真实| 亚洲国产欧美日韩在线播放| aaaaa片日本免费| 免费少妇av软件| 欧美精品av麻豆av| 成年人免费黄色播放视频| 亚洲午夜理论影院| 老鸭窝网址在线观看| 国产无遮挡羞羞视频在线观看| 99久久国产精品久久久| 国产不卡一卡二| 国产精品一区二区免费欧美| 黑丝袜美女国产一区| 一边摸一边抽搐一进一出视频| 亚洲一区二区三区欧美精品| 成人av一区二区三区在线看| 可以免费在线观看a视频的电影网站| av视频免费观看在线观看| 精品少妇久久久久久888优播| 91成年电影在线观看| 久久精品亚洲熟妇少妇任你| 久久性视频一级片| 99久久人妻综合| 久久久国产一区二区| 人人妻人人爽人人添夜夜欢视频| 在线观看舔阴道视频| 国产精品 国内视频| 每晚都被弄得嗷嗷叫到高潮| 十分钟在线观看高清视频www| 午夜福利一区二区在线看| 欧美最黄视频在线播放免费 | 99riav亚洲国产免费| 精品电影一区二区在线| 在线观看舔阴道视频| 国产精品久久久久久人妻精品电影| 亚洲三区欧美一区| 日本撒尿小便嘘嘘汇集6| 久久精品aⅴ一区二区三区四区| 精品久久久久久久久久免费视频 | 久久精品91无色码中文字幕| 18禁观看日本| 国产激情久久老熟女| 亚洲av成人av| 亚洲va日本ⅴa欧美va伊人久久| 超色免费av| 精品人妻1区二区| 日韩欧美在线二视频 | 老司机亚洲免费影院| 国产精品成人在线| 韩国精品一区二区三区| 国产亚洲欧美精品永久| 亚洲熟妇中文字幕五十中出 | 美女午夜性视频免费| 国产日韩一区二区三区精品不卡| 黄色视频,在线免费观看| 亚洲欧美精品综合一区二区三区| 视频区图区小说| 国产精品香港三级国产av潘金莲| 一级毛片女人18水好多| 最近最新中文字幕大全免费视频| 欧美亚洲日本最大视频资源| 欧美一级毛片孕妇| 久久久久精品人妻al黑| www日本在线高清视频| 成人手机av| 天天躁狠狠躁夜夜躁狠狠躁| 亚洲在线自拍视频| 国产伦人伦偷精品视频| 欧美日韩黄片免| 亚洲成国产人片在线观看| 日韩欧美三级三区| 一本大道久久a久久精品| 最新的欧美精品一区二区| 亚洲av成人不卡在线观看播放网| www.精华液| 视频区欧美日本亚洲| 超碰成人久久| 麻豆国产av国片精品| 一级a爱片免费观看的视频| 50天的宝宝边吃奶边哭怎么回事| 18禁美女被吸乳视频| 999精品在线视频| 婷婷丁香在线五月| 19禁男女啪啪无遮挡网站| 亚洲午夜精品一区,二区,三区| 精品熟女少妇八av免费久了| 国产主播在线观看一区二区| 看黄色毛片网站| 麻豆av在线久日| 国产精品综合久久久久久久免费 | 交换朋友夫妻互换小说| 亚洲 国产 在线| 在线播放国产精品三级| 久久国产精品大桥未久av| 久久香蕉精品热| 十分钟在线观看高清视频www| 人人妻人人爽人人添夜夜欢视频| 热99国产精品久久久久久7| 69精品国产乱码久久久| 午夜福利乱码中文字幕| 亚洲国产欧美网| 超色免费av| 在线视频色国产色| 亚洲精品久久午夜乱码| 交换朋友夫妻互换小说| 老熟女久久久| 欧美久久黑人一区二区| 亚洲国产精品一区二区三区在线| 午夜精品国产一区二区电影| www.熟女人妻精品国产| 国产有黄有色有爽视频| 999精品在线视频| 国产男女内射视频| 90打野战视频偷拍视频| 亚洲成人免费电影在线观看| 亚洲第一欧美日韩一区二区三区| 19禁男女啪啪无遮挡网站| 黄色成人免费大全| 国产成人免费观看mmmm| 亚洲精品美女久久久久99蜜臀| 一边摸一边抽搐一进一出视频| 黄色片一级片一级黄色片| 国产蜜桃级精品一区二区三区 | 日韩大码丰满熟妇| 无遮挡黄片免费观看| 欧美最黄视频在线播放免费 | 18禁黄网站禁片午夜丰满| 国产高清激情床上av| 韩国av一区二区三区四区| 如日韩欧美国产精品一区二区三区| 国产又色又爽无遮挡免费看| 亚洲av片天天在线观看| 国产精品成人在线| 国产精品香港三级国产av潘金莲| 精品卡一卡二卡四卡免费| 成人手机av| 久久精品熟女亚洲av麻豆精品| 亚洲中文日韩欧美视频| 久久精品亚洲av国产电影网| 天天影视国产精品| 男男h啪啪无遮挡| 91国产中文字幕| 国产一区在线观看成人免费| 国产成人精品久久二区二区免费| 国产精华一区二区三区| 巨乳人妻的诱惑在线观看| 看黄色毛片网站| 欧美成狂野欧美在线观看| 久热这里只有精品99| 欧美乱色亚洲激情| 又大又爽又粗| 亚洲av成人不卡在线观看播放网| 老司机福利观看| 亚洲欧美激情在线| videosex国产|