• <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 ?

    Photo-induced carbon dioxide reduction on hexagonal tungsten oxide via an oxygen vacancies-involved process

    2023-03-14 06:52:36YiWangRunzeLiuMingShiPanwangZhouKeliHanCanLiRenguiLi
    Chinese Chemical Letters 2023年1期

    Yi Wang,Runze Liu,Ming Shi,Panwang Zhou,Keli Han,Can Li,Rengui Li

    a State Key Laboratory of Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian National Laboratory for Clean Energy,Dalian 116023,China

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

    c Institute of Molecular Sciences and Engineering,Shandong University,Qingdao 266235,China

    d State Key Laboratory of Molecular Reaction Dynamics,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,China

    Keywords:Carbon dioxide reduction Oxygen vacancy Photocatalysis Reaction mechanism Tungsten oxide

    ABSTRACT Although converting the greenhouse gasses carbon dioxide (CO2) into solar fuels is regarded as a convenient means of solar energy storage,the intrinsic mechanism on how the high chemical inertness linear CO2 molecules is activated and converted on a semiconductor oxide is still elusive.Herein,by creating the oxygen vacancies on the typical hexagonal tungsten oxide (WO3),we realize the continuous photoinduced CO2 reduction to selectively produce CO under light irradiation,which was verified by isotope labeling experiment.Detailed oxygen vacancies evolution investigation indicates that light irradiation can simultaneously induce the in-situ formation of oxygen vacancies on hexagonal WO3,and the oxygen vacancies promote the adsorption and activation of CO2 molecules,leading to the CO2 reduction to CO on the hexagonal WO3 via an oxygen vacancies-involved process.Besides,the existence of water further promotes the formation of CO2 reduction intermediate,further promote the CO2 photoreduction.Our work provides insight on the mechanism for converting CO2 into CO under light irradiation.

    Converting greenhouse gasses CO2in atmosphere into valueadded chemical products holds promise to address the current and future demand of energy supply and environmental disasters[1,2].Although photo-induced CO2reduction on a semiconductor is appealing and attractive [3–5],the difficulties in thermodynamics and kinetics make its process complicated and challenging.In particular,the adsorption and activation of high chemical inertness of linear CO2on the surface of semiconductor is very difficult [6].Oxygen vacancies are the most prevalent and widely studied anion defects with a relatively lower formation energy on heterogeneous oxide surfaces [7–11].Normally,oxygen vacancies on the catalyst surfaces can effectively modulate both the coordination structures and electronic states of reactive molecules,thus influencing the reaction kinetics and further altering the reaction mechanisms [12–14].However,an in-depth scenario depicting the interactions between oxygen vacancies and reactive molecular in complicated reactions is still unclear,particularly for the challenging CO2reduction reactions [15].Oxygen vacancies can favor the CO2binding and subsequent CO2activation,as well as the final dissociation to promote the catalytic process [16–18].On the other hand,oxygen vacancies have extensively recognized to serve as the activation sites for the thermodynamically stable molecules such as CO2and N2[19–22].However,in a two-step thermochemical CO2reduction process,oxygen vacancies created by endothermic reduction of metal oxides were found to induce the effective dissociation of CO2molecules acting as Lewis basic sites [23].Although oxygen vacancies can facilitate the CO2reduction in numerous reactions,intrinsic mechanism on how the high chemical inertness of linear CO2molecules are activated and converted is inconclusive and has not fully elucidated.

    It is accepted that the CO2adsorption and activation on a heterogeneous photocatalyst involves the formation of a partially charged species CO2δ- to lower the activation barrier,in which process electron transfer from surface atoms to CO2molecules is dominated [24].Subsequent reduction of CO2·–into carboncontaining products involves the electron and proton transfer and breaking C=O bonds [25,26].The complex chemical environment of the photocatalyst surfaces leads to the formation of diverse intermediates,further causing complicated reaction pathways [27].Several possible reaction pathways were proposed such as the formaldehyde pathway [28],the carbene pathway [29],but the mechanism from CO2adsorption to catalytic reaction is still unclear.Furthermore,utilizing water as the electron donor is the ultimate solution of CO2photoreduction,but the oxygen evolution half-reaction involves complicated four-electron transfer process and O=O bond formation,which makes the CO2reduction process coupling with water oxidation more difficult.

    Fig.1.Schematic structure and characterization of as-prepared hexagonal WO3.(a) Scheme illustration of hexagonal WO3 crystal structure.(b) XRD pattern of asprepared WO3.(c) SEM image of hexagonal WO3.(d,e) High-resolution TEM images of hexagonal WO3.

    In this work,taking hexagonal tungsten oxide (WO3),a semiconductor photocatalyst with unfavorable band structure as a prototype,we experimentally demonstrate the continuous CO2reduction to selectively produce CO under light irradiation can be achieved on the hexagonal WO3.Investigations indicate that light irradiation induces thein-situformation of oxygen vacancies on the hexagonal WO3,and the oxygen vacancies promote the absorption and activation of CO2molecules,thus making the photo-induced CO2reduction takes placeviaan oxygen vacanciesinvolved process.

    Hexagonal tungsten trioxide (WO3) has been intensively studied as a candidate photocatalyst thanks to its advantages in light harvesting properties and chemical stabilities over a wide range of acidity [7-10,12,30].It is widely-held that the conduction band edge of hexagonal WO3locates at ~0.2 eVvs.RHE,which is more positive than CO2reduction to carbon-containing products energy levels,namely,its conduction band is thermodynamically unfavorable to drive the direct reduction of CO2molecules.Analyzing from the microstructure,hexagonal WO3is composed of WO6octahedral unit cells which share its corner oxygen atom to construct a defect perovskite-like ReO3structure (Fig.1a).The intrinsic structure of hexagonal WO3leads to incidental oxygen atom leakage,creating oxygen vacancies.Correspondingly,the decrease ratio of structural W=O double bonds in the unit cell to single bonds is proposed to correlate the oxygen vacancies generation process [31].Chromic properties result from the color centers is common in the WO3material,generally being attributed to electron excess localized on W ions (W5+),which is closely related to the oxygen vacancies [32].

    The hexagonal WO3was employed in this work and preparedviaa hydrothermal process as reported [33].Detailed synthesis,characterization and CO2photoreduction process was shown in Supporting information.All the XRD diffraction peaks of assynthesized sample can be well indexed to hexagonal phase WO3with no characteristic peak of sub stoichiometric WO3or hydrates was observed (Fig.1b).The morphology of the hexagonal WO3exhibits a rod-like shape with diameter of ~50 nm and rod length of 1–2 μm (Figs.1c and d,Figs.S1 and S2 in Supporting information).A regular lattice fringe spacing about 0.39 nm was shown in high-resolution TEM image,which can be attributed to the representative (001) plane of the hexagonal WO3,demonstrating that the prepared WO3nanorod grew along the [001] crystal direction(Fig.1e).Mott-Schottky analysis was applied to determine the conduction band edge of as-prepared WO3(Fig.S3 in Supporting information).As an n-type semiconductor,the conduction band edge of hexagonal WO3was estimated to be 0.07 eV,similar to the results previously reported [34].The band gap (Eg) was calculated to be 2.68 eV (Figs.S4 and S5 in Supporting information).

    Fig.2.(a) Photocatalytic activities of CO2 reduction on hexagonal WO3.(b) Control experiments of CO2 reduction under light and dark conditions.(c) CO2 photoreduction to CO on hexagonal WO3 under different wavelengths.(d) The comparison of CO2 photoreduction with or without introducing H2O vapor.(e,f) Mass spectra extracted from GC–MS analysis of product with isotope labeling using 13CO2 and H218O.

    Photo-induced CO2reduction on the hexagonal WO3was examined under CO2atmosphere with the presence of water vapor using Xe lamp as light source.As shown in Fig.2a,surprisingly,we observed that the continuous producing of CO gas can be obviously detected under light irradiation,which means that CO2can be reduced to CO under this condition.As contrast,no CO product was detected in the same condition without light irradiation,illustrating that the CO2reduction should be responsive to the lightinduced photoreduction process (Fig.2b).Furthermore,we verified that either no CO was detected in the case when the hexagonal WO3was absence (Fig.S6 in Supporting information).Structural evolution under the illumination condition was further confirmed by Raman spectroscopy (Fig.S7 in Supporting information).Moreover,CO2reduction performance was also examined under different wavelength ranges.As depicted in Fig.2c,CO2photoreduction towards CO is significantly correlated with the light absorption ranges of hexagonal WO3,confirming that the CO2reduction is associated with the photo excitation of hexagonal WO3catalyst and the subsequent charge-involved photoreduction process.Additionally,comparative experiments with or without introducing H2O vapor were conducted.As can be seen from Fig.2d,a remarkable difference of the performance was clearly observed under the cases with or without H2O.When the H2O vapor was introduced into the reactor,the photoreduction activity was more than an order of magnitude of that without H2O,indicating that H2O molecules exactly participate in the CO2photoreduction process.

    Besides,the photocatalytic activity of CO2reduction in gas and liquid phase were also estimated.Under the same irradiation condition,the photocatalytic activity in gas phase is slightly higher than that in liquid phase,which may due to the weak solubility of CO2(Fig.S8 in Supporting information).

    To certify that the reliable product comes from CO2photoreduction rather than other contaminants,isotope labeling experiment was performed using13CO2as the reactant,while the product was analyzed by GC–MS.As shown in Fig.2e,for non-labeled CO2,molecular ion peak atm/z=28 indicates that the product is CO,while replacing the reactant by13CO2,molecular ion peak atm/z=29 evidently showed up without any other products,indicating the selective formation of13CO,giving clear evidence that the produced CO is originated from the CO2input with a high selectivity.To verify the attendance of water,control experiment with18O labeling H2O was also examined.In the mass spectrum shown in Fig.2f,two peaks appeared atm/zvalues of 34 and 36,which can be attributed to the ionic16O18O and18O2,respectively.The detected O2undoubtedly confirms that the water oxidation takes place during CO2photoreduction.Therefore,we can come to a conclusion that the CO2photoreduction can be realized on the hexagonal WO3.It should be noted that although H2O molecules were confirmed to participate in the reaction process,no detectable H2was observed in the experiment,which may be due to fact that the hydrogen species formed in the reaction adsorb on the surface of the catalyst.To investigate the phenomenon,examination of H2adsorption was conducted for the hexagonal WO3with or without light treatment (Fig.S9 in Supporting information).As expected,we found that the hexagonal WO3after photocatalytic reaction under light irradiation shows a drastically enhanced H2adsorption capability compared to the fresh WO3,which is proposed to be the reason why no H2but only CO was detected in the experiment.

    The results above evidently demonstrate the occurrence of photo-induced CO2reduction to CO on the hexagonal WO3,however,how the reaction takes place is still unclear.Considering the structure of hexagonal WO3,each oxygen atom bounds to two W atoms in the lattice,whereas there may be missing oxygen atoms at the boundary or corner sites on the surface.In addition,the photogenerated holes with high oxidation potential may oxidize the lattice oxygen of the hexagonal WO3and create oxygen vacancies on the surface,which attends the CO2reduction and activation subsequently.As depicted in Fig.3a,when the hexagonal WO3was irradiated under light,the apparent color gradually changes from light gray to dark blue with irradiation time prolonging.UV–vis diffusion reflection spectroscopy was then employed to investigate the absorbance during this color-changing process (Fig.3b).Obviously,the absorption in the region of 500–800 nm dramatically increases,while the absorption at the band edge keeps nearly constant.In general,the light absorption increase in visible light region for semiconductors can be attributed to the formation of lowvalued metal species [35].Here,the increase in light absorption can be attributed to the generation of pentavalent tungsten (W5+),which also correlates the generation of oxygen vacancies during the CO2photoreduction reaction on the hexagonal WO3.Electron spin resonance (ESR) spectra were therefore employed to further verify the formation of oxygen vacancies.As depicted in Fig.3c,no significant signal was observed in dark condition,whereas an obvious signal atg=2.002 appears once light irradiated,which clearly evidenced the formation of single-electron-trapped oxygen vacancies.Furthermore,the hexagonal WO3samples before and after irradiation exhibit comparable XRD diffraction peaks and intensities (Fig.3d),indicating the maintained crystallinity of the hexagonal WO3with light-induced formation of oxygen vacancies,which was also supported by the unchanged lattice spacing of the hexagonal WO3compared with the fresh ones (Fig.S10 in Supporting information).Fig.3e depicts the Raman spectra of the hexagonal WO3before and after light irradiation.The bands with Raman shift at 760 cm-1and 817 cm-1can be ascribed to O-W-O stretching mode,whilst peaks at 250 and 324 cm-1belong to the stretching mode of W-O-W [36].The Raman peak at 940 cm-1can be assigned to the W=O double bond stretching mode located at the boundaries.After light irradiation to generate oxygen vacancies,the intensity of all characteristic peaks dramatically decreases.Besides,the defects of nanocrystals can be reflected on the width of Raman shift [37].The peak width at half-height at around 806 cm-1decreased obviously after irradiation,which supports the formation of oxygen vacancies laterally.

    To further build a connection between the oxygen vacancies formation and CO2photoreduction and provide an unambiguous interpretation of the water function of in the reaction process,insitutransient Fourier transform infrared spectroscopy (FTIR) experiment were conducted (Figs.3f-h).The spectra were obtained by subtracting WO3background in Ar atmosphere.When sole CO2was introduced to the reaction system,no obvious weak was shown in Fig.3f,which can be attributed to the weak absorption of CO2.When WO3was under irradiation,two negative peaks corresponding to COOH-and HOCOO-were shown,which may due to the reduction of chemical absorbed CO2[38].As for the situation that CO2purged through the water (Fig.3g),a broaden peak at around 1650 cm-1arose,which belongs to the–OH,besides,a weak peak at 1425 cm-1assigned to HCO3-occurred,which indicate that attendance of water promotes the formation of HCO3-intermediate.Besides,under the same irradiation condition,the peaks corresponding to COOH-and HOCOO-decrease with a larger magnitude,which support the inference above.It is noticeable that after irradiation the peak around 1425 cm-1reoccurred,suggesting that HCO3-can be formed with the help of water.In addition,the formation and decomposition of the HCO3-keeps dynamic balance during the irradiation.

    To figure out the function of oxygen vacancies,the catalyst was pre-irradiated in Ar to induce oxygen vacancies formation,followed by the same experiment steps as above (Fig.3h).The spectra were normalized according to the transmittance.It is noticeable that when the catalyst was kept in the dark state under humid CO2atmosphere,no peak corresponding to CO2reaction intermediate was found,which imply that photo-generated electrons and holes are indispensable.Different from the fresh catalyst,the spectrum of the catalyst containing oxygen vacancies shows a small peak corresponding to HOCOO-species after CO2adsorption.A plausible explanation for is that one oxygen atom of CO2fills the oxygen vacancy and the other oxygen atom bind with hydroxy group on the surface to form a bending structure [39].Compared with the spectrum of intrinsic WO3under same condition,a larger hydroxyl peak was shown.During the irradiation,the peak belongs to COOH-decreases but is different from that HOCOO-species.With the help of H2O molecules,the oxygen vacancies facilitate the formation of HOCOO-,namely HCO3-intermediate and consequently promote CO2reduction.

    Fig.3.(a) Photographs of the hexagonal WO3 under light irradiation.(b) UV–visible spectra of the hexagonal WO3 before and after light irradiation.(c) In-situ EPR spectra of the hexagonal WO3 before and after light irradiation.(d) XRD pattern of the hexagonal WO3 before and after the photocatalytic reaction.(e) In-situ Raman spectra of the hexagonal WO3 before and after light irradiation. In-situ FTIR spectra of (f) CO2 and (g) CO2 and water vapor interaction with fresh WO3 in the dark and under photoirradiation subsequently.(h) CO2 and water vapor interaction with pre-irradiated WO3 in the dark and under photoirradiation subsequently.

    The aforementioned results proved the creation of oxygen vacanciesviathe light-induced process during photocatalytic reactions on the hexagonal WO3while the photogenerated electrons will reduce W6+to W5+.It should be emphasized that such oxygen vacancies generation process is reversible when the catalyst was exposed to O2-containing atmosphere.The created oxygen vacancies on the surface of hexagonal WO3can be eliminated by O2(Figs.S11 and S12 in Supporting information),and the oxygen vacancies can be recovered again after irradiated by light,completing the oxygen vacancies-containing chemical redox loop on the surface.The recyclable CO2photoreduction during this reversible oxygen vacancies-containing process were also confirmed,further confirming the indispensable role of oxygen vacancies in this process (Fig.S13 in Supporting information).It can be therefore concluded that irradiation of WO3created the oxygen vacancies on the surface,which serves as the activation site of CO2reduction.The existence of light-induced oxygen vacancies makes it possible for hexagonal WO3to drive CO2reduction,whereas an appropriate amount of oxygen vacancies is needed.To further verify the essential role oxygen vacancies on the photo-induced CO2reduction on the hexagonal WO3,we synthesized a series of oxygen vacanciescontaining samplesviatreating the hexagonal WO3under the atmosphere of H2gas (Fig.S14 in Supporting information).The reduction of WO3to produce oxygen vacancies were confirmed by the UV–vis spectra of the samples treated under different conditions.The photocatalytic activities increase obviously with increasing the content of oxygen vacancies to reach the maximum.Excess amount of the oxygen vacancies may destroy the structure of hexagonal WO3and result in a decline in photocatalytic activities.

    DFT calculation was also utilized to verify the function of oxygen vacancies.We first simulated the most possible oxygen vacancy sites on the hexagonal WO3surface.As shown in Fig.S15a(Supporting information),the comparison of three modes of oxygen vacancy were presented on the representative (100) surface.The relative defect formation energy was calculated during removing an oxygen atom from the corresponding location,the structure of Type III with lowest defect formation energy was found to be the most stable oxygen vacancy site.The adsorption mode of CO2molecules on the perfect (100) and defective (100) surfaces was then calculated (Figs.S15b-e in Supporting information).When CO2molecule adsorbs on a perfect (100) surface (Figs.S15b and d),the adsorption energy is -0.37 eV.Compared with the C=O in CO2molecule,the C=O in adsorbed CO2is not significantly elongated compared with the non-absorbed case (1.25 ?Avs.1.17 ?A).In addition,the C atom in CO2molecule forms a weak link with the surface oxygen atom,causing a bending configuration with a 136°carbon-oxygen double bond angle.In contrast,the adsorption energy of CO2molecule adsorbed on the oxygen vacancy-containing(100) surface is -2.09 eV,which is much larger in magnitude than that on the perfect (100) surface (Figs.S15c and e).The results illustrate that CO2molecules can be easily adsorbed on the oxygen vacancy sites.Moreover,the C=O bond in absorbed CO2is obviously elongated from 1.17 ?A to 1.457 ?A and the bond angle of C=O was reduced to 124.8°.It is acceptable that the O atom in CO2adsorbed onto the oxygen vacancy promotes the electron transfer from low-value W5+to the O sites,leading to the elongation of C=O bond,which further intensifies the electron cloud mismatching between C and O atoms.The elongated C=O bond at this scale is much easier to break,signifying that C=O is weakened by the presence of oxygen vacancies,which effectively promotes the activation of CO2molecules.

    Scheme 1.Schematic illustration of the proposed mechanism for photo-induced CO2 reduction on the hexagonal WO3.

    Based on the results above,oxygen vacancies can be induced on the surface of hexagonal WO3under irradiation,which serves as the activation sites of CO2.When CO2and water were introduced with light irradiation on WO3,a plausible reaction mechanism involved the formation of oxygen vacancies and intermediate on the hexagonal WO3photocatalyst was proposed (Scheme 1).Initially,oxygen vacancies were induced to generate on the surface of the hexagonal WO3by the irradiation of light.Then,oxygen atom in CO2molecule adsorbed on the light-induced oxygen vacancies of the hexagonal WO3surface to form bended*CO2,following by protonated by–OH adsorbed on the adjacent W atom to form adsorbed HCO3-and HCOO-intermediate.Differ from the mechanism previously reported on hydrated WO3·0.33H2O [29],since the attendance of water will lead to the formation of adsorbed H,the H species will form a hydrogen bond with the O atom in CO2.Combining with the electron transfer from the adjacent W5+,the breaking of C-O band induces filling an oxygen vacancy and formation of CO and H2O.The following irradiation will regenerate the oxygen vacancies and drive the successive reaction.The existence of photo-induced oxygen vacancies is a double-edged sword,since the presence of a small amount of oxygen vacancies will promote CO2activation,but a large amount of that will destroy the surface structure.

    In summary,we experimentally realize the photo-induced CO2reduction to CO on the hexagonal WO3viaan oxygen vacanciesinvolved process.Isotope labeling experiments verified the formation of oxygen with the attendance of water and lattice oxygen.The photo-induced formation of oxygen vacancies was demonstrated to closely correlate the activities of CO2photoreduction.Combining with thein-situFTIR,a mechanism involved oxygen vacancy was proposed that with the assistance of adsorbed water,CO2adsorbed on oxygen vacancy was protonated to HCO3-intermediate and finally reduce to CO.Our work provides insight on the mechanism for carbon dioxide reduction on oxygen vacancy sites.

    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

    This work was performed by the Fundamental Research Center of Artificial Photosynthesis (FReCAP),and supported by National Natural Science Foundation of China (No.22088102).This work was also supported by National Natural Science Foundation of China (No.22090033).R.Li would like to thank the support from Youth Innovation Promotion Association of Chinese Academy of Sciences and Dalian Institute of Chemical Physics,CAS.

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2022.02.006.

    国内精品美女久久久久久| 婷婷色麻豆天堂久久| 在线观看av片永久免费下载| 七月丁香在线播放| 18禁裸乳无遮挡免费网站照片| 热re99久久精品国产66热6| 亚洲丝袜综合中文字幕| 欧美日韩综合久久久久久| 自拍偷自拍亚洲精品老妇| 一边亲一边摸免费视频| 国产精品嫩草影院av在线观看| 中文字幕人妻熟人妻熟丝袜美| 国产成人freesex在线| 午夜福利高清视频| 夫妻午夜视频| 在线免费十八禁| 日本一本二区三区精品| 国产成人精品久久久久久| 国产成人91sexporn| 午夜亚洲福利在线播放| 女的被弄到高潮叫床怎么办| 岛国毛片在线播放| 日韩不卡一区二区三区视频在线| 大片免费播放器 马上看| 欧美 日韩 精品 国产| 欧美日本视频| 国产精品偷伦视频观看了| 97在线视频观看| 成年人午夜在线观看视频| 国产色爽女视频免费观看| 人人妻人人澡人人爽人人夜夜| 免费观看a级毛片全部| 久久人人爽av亚洲精品天堂 | 成年免费大片在线观看| 亚洲在久久综合| 久久久午夜欧美精品| 日韩av免费高清视频| 2021少妇久久久久久久久久久| 高清在线视频一区二区三区| 全区人妻精品视频| 自拍欧美九色日韩亚洲蝌蚪91 | 午夜免费鲁丝| 亚洲国产成人一精品久久久| 久久女婷五月综合色啪小说 | 国产亚洲一区二区精品| 日韩成人伦理影院| 26uuu在线亚洲综合色| 日韩成人av中文字幕在线观看| 99热这里只有是精品在线观看| 国产午夜精品一二区理论片| 少妇人妻一区二区三区视频| 国产免费一区二区三区四区乱码| 久久久久久久亚洲中文字幕| 最近中文字幕2019免费版| 国产伦精品一区二区三区视频9| 久久6这里有精品| 如何舔出高潮| 国产精品一区二区在线观看99| 又大又黄又爽视频免费| 亚洲精品影视一区二区三区av| 亚洲av不卡在线观看| 一个人看视频在线观看www免费| 亚洲欧美日韩无卡精品| 欧美成人a在线观看| 亚洲精品国产av蜜桃| 日韩国内少妇激情av| 国产精品无大码| 少妇裸体淫交视频免费看高清| 欧美3d第一页| 夫妻性生交免费视频一级片| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | 亚洲国产精品999| 日产精品乱码卡一卡2卡三| 男女国产视频网站| 国产一级毛片在线| 欧美最新免费一区二区三区| av又黄又爽大尺度在线免费看| 免费观看的影片在线观看| 国产色爽女视频免费观看| 国产成人精品久久久久久| 2018国产大陆天天弄谢| 久久人人爽人人片av| 亚洲精华国产精华液的使用体验| 精华霜和精华液先用哪个| 欧美激情在线99| 中文字幕亚洲精品专区| 五月开心婷婷网| freevideosex欧美| 日本色播在线视频| 日韩av不卡免费在线播放| 特大巨黑吊av在线直播| 熟妇人妻不卡中文字幕| 成人漫画全彩无遮挡| 亚洲成人精品中文字幕电影| 黄片无遮挡物在线观看| 精品国产乱码久久久久久小说| 免费看a级黄色片| 26uuu在线亚洲综合色| 国产黄a三级三级三级人| 黄色怎么调成土黄色| 禁无遮挡网站| 超碰97精品在线观看| 一级爰片在线观看| 亚洲欧美日韩东京热| 日本黄大片高清| 五月伊人婷婷丁香| 亚洲欧洲日产国产| 日日摸夜夜添夜夜爱| 狂野欧美白嫩少妇大欣赏| 中文字幕免费在线视频6| 亚洲经典国产精华液单| 亚洲内射少妇av| 久久久久国产精品人妻一区二区| 黄色配什么色好看| 大码成人一级视频| 午夜激情福利司机影院| 岛国毛片在线播放| 欧美日韩一区二区视频在线观看视频在线 | 全区人妻精品视频| 我要看日韩黄色一级片| 午夜精品国产一区二区电影 | 精品少妇久久久久久888优播| 18禁动态无遮挡网站| 久久久久久久久久久免费av| 免费不卡的大黄色大毛片视频在线观看| 热99国产精品久久久久久7| 免费少妇av软件| 91午夜精品亚洲一区二区三区| 国产视频首页在线观看| 丝瓜视频免费看黄片| 国产av码专区亚洲av| 中文精品一卡2卡3卡4更新| 国产片特级美女逼逼视频| 国产又色又爽无遮挡免| 少妇被粗大猛烈的视频| 精品久久久久久久末码| 午夜免费男女啪啪视频观看| 国产精品av视频在线免费观看| 亚洲四区av| 80岁老熟妇乱子伦牲交| eeuss影院久久| 少妇猛男粗大的猛烈进出视频 | 欧美性猛交╳xxx乱大交人| 嘟嘟电影网在线观看| 久久女婷五月综合色啪小说 | 极品少妇高潮喷水抽搐| 大话2 男鬼变身卡| 亚洲精品久久午夜乱码| 日韩电影二区| 欧美bdsm另类| 麻豆成人午夜福利视频| 岛国毛片在线播放| 97在线视频观看| 国产精品久久久久久久久免| 亚洲av日韩在线播放| 国产亚洲午夜精品一区二区久久 | 亚洲国产精品专区欧美| 午夜激情福利司机影院| 国产av码专区亚洲av| 欧美少妇被猛烈插入视频| 又爽又黄无遮挡网站| 一个人看的www免费观看视频| 国产欧美另类精品又又久久亚洲欧美| 91精品国产九色| 色网站视频免费| 高清av免费在线| 超碰97精品在线观看| 九九在线视频观看精品| 欧美性感艳星| 在线观看一区二区三区激情| 亚洲av中文av极速乱| 亚洲怡红院男人天堂| 毛片女人毛片| 国产成人精品一,二区| 熟女电影av网| 少妇裸体淫交视频免费看高清| 高清在线视频一区二区三区| 欧美日韩在线观看h| 王馨瑶露胸无遮挡在线观看| 91狼人影院| 日韩制服骚丝袜av| 国产精品一二三区在线看| 成人亚洲精品一区在线观看 | 国产黄片视频在线免费观看| 免费人成在线观看视频色| 国产精品成人在线| 国产精品久久久久久精品电影小说 | 国产精品.久久久| 国产一区亚洲一区在线观看| 亚洲av不卡在线观看| 在线看a的网站| 18禁在线播放成人免费| 男人添女人高潮全过程视频| 日韩不卡一区二区三区视频在线| 99热这里只有是精品在线观看| 国产高清不卡午夜福利| 青青草视频在线视频观看| 国产乱人偷精品视频| 男人舔奶头视频| 91精品伊人久久大香线蕉| 欧美97在线视频| 亚洲天堂av无毛| 热99国产精品久久久久久7| 麻豆成人av视频| 免费不卡的大黄色大毛片视频在线观看| 麻豆精品久久久久久蜜桃| 大陆偷拍与自拍| 成人特级av手机在线观看| 国产91av在线免费观看| 日本与韩国留学比较| 成人无遮挡网站| 国产精品不卡视频一区二区| 高清av免费在线| 狠狠精品人妻久久久久久综合| 1000部很黄的大片| 亚洲婷婷狠狠爱综合网| 日韩国内少妇激情av| 国产成人精品婷婷| 中文在线观看免费www的网站| 一区二区三区精品91| 亚洲婷婷狠狠爱综合网| 久久鲁丝午夜福利片| 麻豆国产97在线/欧美| 亚洲成人久久爱视频| 免费人成在线观看视频色| 欧美97在线视频| 秋霞在线观看毛片| 国产大屁股一区二区在线视频| 在线a可以看的网站| 少妇人妻一区二区三区视频| 在线免费十八禁| 成年版毛片免费区| 高清av免费在线| 国产黄色视频一区二区在线观看| 国产在视频线精品| 一区二区三区四区激情视频| 男人和女人高潮做爰伦理| 欧美日韩亚洲高清精品| 精品酒店卫生间| 亚洲av.av天堂| 日韩强制内射视频| 国产老妇伦熟女老妇高清| 久久久久久久亚洲中文字幕| 人体艺术视频欧美日本| 亚洲国产精品专区欧美| 王馨瑶露胸无遮挡在线观看| 亚洲精品国产av蜜桃| 欧美激情久久久久久爽电影| 日韩精品有码人妻一区| 亚洲婷婷狠狠爱综合网| 亚洲人成网站在线播| 久久久久久久久久久免费av| 日韩精品有码人妻一区| 久久韩国三级中文字幕| 久久精品国产鲁丝片午夜精品| 一个人看视频在线观看www免费| 国产男人的电影天堂91| 啦啦啦啦在线视频资源| 午夜福利在线观看免费完整高清在| 偷拍熟女少妇极品色| 97在线人人人人妻| 日韩伦理黄色片| 国产精品一区www在线观看| 五月开心婷婷网| 舔av片在线| 欧美一级a爱片免费观看看| 男女下面进入的视频免费午夜| 狂野欧美激情性bbbbbb| 国产成人精品久久久久久| 亚洲国产精品成人综合色| 亚洲精品一二三| 国产欧美另类精品又又久久亚洲欧美| av黄色大香蕉| 国产精品福利在线免费观看| 麻豆乱淫一区二区| 亚洲精品乱码久久久久久按摩| 婷婷色综合www| 国产成人精品福利久久| 国产精品精品国产色婷婷| 又黄又爽又刺激的免费视频.| av免费观看日本| 亚洲欧美日韩另类电影网站 | 最近中文字幕2019免费版| 69人妻影院| 人人妻人人看人人澡| 免费不卡的大黄色大毛片视频在线观看| 国产欧美日韩一区二区三区在线 | 亚洲美女搞黄在线观看| 精品久久久久久久久亚洲| 少妇人妻精品综合一区二区| 纵有疾风起免费观看全集完整版| 午夜福利视频1000在线观看| 大陆偷拍与自拍| 久久6这里有精品| av在线亚洲专区| 日本猛色少妇xxxxx猛交久久| 国产综合懂色| 草草在线视频免费看| 日本黄色片子视频| 午夜日本视频在线| 国产美女午夜福利| 欧美精品一区二区大全| 男人和女人高潮做爰伦理| 99精国产麻豆久久婷婷| av国产久精品久网站免费入址| 尾随美女入室| 偷拍熟女少妇极品色| 精品久久久久久久人妻蜜臀av| 日韩三级伦理在线观看| 精品亚洲乱码少妇综合久久| 国产精品av视频在线免费观看| 国产一级毛片在线| 日产精品乱码卡一卡2卡三| 午夜爱爱视频在线播放| 国产永久视频网站| 精品人妻熟女av久视频| 亚洲av欧美aⅴ国产| 一本一本综合久久| 麻豆久久精品国产亚洲av| 丰满少妇做爰视频| 熟女电影av网| 2021少妇久久久久久久久久久| 色网站视频免费| 狂野欧美激情性xxxx在线观看| 亚洲国产成人一精品久久久| 精品酒店卫生间| 街头女战士在线观看网站| 深爱激情五月婷婷| 久久久久精品性色| 97超碰精品成人国产| 亚洲精品乱久久久久久| 在线观看一区二区三区激情| 国产精品人妻久久久影院| 狠狠精品人妻久久久久久综合| 亚洲精品日韩在线中文字幕| 亚洲精品日本国产第一区| 最近中文字幕2019免费版| 嫩草影院入口| 欧美变态另类bdsm刘玥| 五月伊人婷婷丁香| av卡一久久| 联通29元200g的流量卡| 国产真实伦视频高清在线观看| 简卡轻食公司| 国产精品久久久久久久电影| 欧美性感艳星| 亚洲丝袜综合中文字幕| 婷婷色综合大香蕉| 偷拍熟女少妇极品色| 老师上课跳d突然被开到最大视频| 亚洲自拍偷在线| 国产视频内射| 亚洲天堂av无毛| 热re99久久精品国产66热6| 免费看a级黄色片| 日韩一区二区三区影片| 91aial.com中文字幕在线观看| 少妇 在线观看| 国产av码专区亚洲av| 日韩av免费高清视频| 日韩欧美精品免费久久| 看黄色毛片网站| 久久久成人免费电影| 最近中文字幕高清免费大全6| 中文字幕亚洲精品专区| 日韩人妻高清精品专区| 嫩草影院新地址| 老师上课跳d突然被开到最大视频| 亚洲av日韩在线播放| 久久久久久国产a免费观看| 中文字幕制服av| 欧美日韩一区二区视频在线观看视频在线 | 国产精品久久久久久精品电影| 热99国产精品久久久久久7| 国产成人一区二区在线| 亚洲国产精品专区欧美| 欧美xxxx性猛交bbbb| 欧美激情久久久久久爽电影| 一级片'在线观看视频| 亚洲成人一二三区av| 高清午夜精品一区二区三区| av在线天堂中文字幕| 国产 一区 欧美 日韩| 欧美日韩在线观看h| 国产片特级美女逼逼视频| 少妇高潮的动态图| 男男h啪啪无遮挡| 久久女婷五月综合色啪小说 | 成人高潮视频无遮挡免费网站| av在线播放精品| 色综合色国产| 插阴视频在线观看视频| 日本-黄色视频高清免费观看| 久久久久九九精品影院| 九九在线视频观看精品| 精品一区二区三区视频在线| 国内少妇人妻偷人精品xxx网站| 亚洲人与动物交配视频| 久久99精品国语久久久| 国产一级毛片在线| 国产伦精品一区二区三区视频9| 高清在线视频一区二区三区| 大码成人一级视频| 赤兔流量卡办理| 狂野欧美激情性xxxx在线观看| 中国美白少妇内射xxxbb| 色视频在线一区二区三区| 国产精品99久久久久久久久| 91精品伊人久久大香线蕉| 成人亚洲欧美一区二区av| 午夜老司机福利剧场| 全区人妻精品视频| 黄色视频在线播放观看不卡| 日本与韩国留学比较| 如何舔出高潮| 国产成人免费观看mmmm| 精品一区二区三卡| 久久久精品欧美日韩精品| av在线亚洲专区| av在线播放精品| h日本视频在线播放| 亚洲va在线va天堂va国产| 肉色欧美久久久久久久蜜桃 | 国产真实伦视频高清在线观看| 中文字幕制服av| 精品久久久久久电影网| 欧美97在线视频| 丰满乱子伦码专区| 亚洲av电影在线观看一区二区三区 | 99热网站在线观看| 国产成人a区在线观看| 2018国产大陆天天弄谢| 国产伦理片在线播放av一区| 国产免费视频播放在线视频| 精品熟女少妇av免费看| 亚洲人与动物交配视频| 97人妻精品一区二区三区麻豆| 亚洲美女搞黄在线观看| 在线观看三级黄色| 国产又色又爽无遮挡免| 欧美国产精品一级二级三级 | 中文字幕免费在线视频6| 亚洲国产av新网站| 亚洲在线观看片| 久久久久久国产a免费观看| 尾随美女入室| av卡一久久| 永久网站在线| 国产中年淑女户外野战色| 久久国产乱子免费精品| 乱码一卡2卡4卡精品| 少妇的逼好多水| 亚洲国产精品999| 久久6这里有精品| 熟女电影av网| 亚洲精品第二区| 婷婷色综合大香蕉| 国产一区有黄有色的免费视频| 色哟哟·www| 欧美+日韩+精品| 亚洲精品影视一区二区三区av| 午夜福利在线观看免费完整高清在| 日韩 亚洲 欧美在线| 国产一区二区三区av在线| 亚洲久久久久久中文字幕| 一级毛片 在线播放| 成人欧美大片| 久久精品久久精品一区二区三区| 国产老妇女一区| 国产人妻一区二区三区在| 亚洲自拍偷在线| av线在线观看网站| 久久久国产一区二区| 色5月婷婷丁香| 亚洲精品影视一区二区三区av| 亚洲欧美一区二区三区黑人 | 最近2019中文字幕mv第一页| 3wmmmm亚洲av在线观看| 国产日韩欧美在线精品| 国产精品女同一区二区软件| 老司机影院毛片| 国产人妻一区二区三区在| 91aial.com中文字幕在线观看| 直男gayav资源| 国产男女内射视频| 十八禁网站网址无遮挡 | 免费观看性生交大片5| 欧美区成人在线视频| 日韩 亚洲 欧美在线| 亚洲精品成人久久久久久| 免费黄频网站在线观看国产| 舔av片在线| 人人妻人人澡人人爽人人夜夜| 国产片特级美女逼逼视频| 中文欧美无线码| 亚洲图色成人| 久久精品综合一区二区三区| 五月开心婷婷网| 色婷婷久久久亚洲欧美| 亚洲欧美日韩无卡精品| tube8黄色片| 欧美性猛交╳xxx乱大交人| 波野结衣二区三区在线| 久久精品夜色国产| 久久精品久久久久久噜噜老黄| 黄色欧美视频在线观看| 在线观看美女被高潮喷水网站| 欧美区成人在线视频| 午夜激情福利司机影院| 久久99热这里只有精品18| 秋霞伦理黄片| 国产免费视频播放在线视频| 亚洲av欧美aⅴ国产| 欧美成人精品欧美一级黄| 各种免费的搞黄视频| 中国美白少妇内射xxxbb| videossex国产| 亚洲精品视频女| 99久久人妻综合| a级毛片免费高清观看在线播放| 少妇高潮的动态图| 乱系列少妇在线播放| 日韩伦理黄色片| 免费少妇av软件| 色哟哟·www| 97超碰精品成人国产| 嫩草影院精品99| 午夜视频国产福利| 亚洲欧洲日产国产| 老师上课跳d突然被开到最大视频| 免费电影在线观看免费观看| 久久久久久久久久久丰满| 亚洲怡红院男人天堂| av黄色大香蕉| 美女主播在线视频| 特大巨黑吊av在线直播| 久久精品久久久久久噜噜老黄| 中文字幕久久专区| 69av精品久久久久久| 三级国产精品欧美在线观看| 欧美 日韩 精品 国产| 国产成人精品婷婷| 精品酒店卫生间| 精品人妻熟女av久视频| 草草在线视频免费看| 午夜免费男女啪啪视频观看| 亚洲国产最新在线播放| 2022亚洲国产成人精品| 精品人妻一区二区三区麻豆| 欧美性感艳星| 国产成人精品久久久久久| 国产v大片淫在线免费观看| 一级片'在线观看视频| 国产成人精品福利久久| 狂野欧美激情性bbbbbb| 久久久久久伊人网av| 91狼人影院| 在现免费观看毛片| 男女下面进入的视频免费午夜| 久热这里只有精品99| 亚洲aⅴ乱码一区二区在线播放| 天天躁夜夜躁狠狠久久av| 直男gayav资源| 国产精品精品国产色婷婷| 亚洲电影在线观看av| 美女视频免费永久观看网站| 少妇的逼好多水| 亚洲成色77777| 99热全是精品| 黑人高潮一二区| 国产欧美亚洲国产| 狂野欧美激情性bbbbbb| 亚洲av.av天堂| 亚洲在久久综合| 午夜爱爱视频在线播放| 久久久成人免费电影| 亚洲性久久影院| 国产精品熟女久久久久浪| 精华霜和精华液先用哪个| 久久这里有精品视频免费| 天天躁日日操中文字幕| 亚洲真实伦在线观看| 国产成人a区在线观看| 日日摸夜夜添夜夜爱| 午夜日本视频在线| 男女那种视频在线观看| 欧美激情在线99| 国产乱人视频| 免费黄频网站在线观看国产| 一区二区三区四区激情视频| 亚洲精品亚洲一区二区| tube8黄色片| 久久6这里有精品| 神马国产精品三级电影在线观看| 久久久久久久亚洲中文字幕| 亚洲aⅴ乱码一区二区在线播放| 久久久午夜欧美精品| 亚洲人成网站高清观看| 69av精品久久久久久| 2022亚洲国产成人精品| 黄色欧美视频在线观看| 六月丁香七月| 深夜a级毛片| 精品久久久久久久人妻蜜臀av| 国产在视频线精品| 国产一区二区在线观看日韩| 日韩在线高清观看一区二区三区| 国产亚洲精品久久久com| 欧美日韩精品成人综合77777| 人人妻人人看人人澡| 国产精品熟女久久久久浪| 草草在线视频免费看| 搞女人的毛片| 少妇 在线观看| 五月玫瑰六月丁香|