• <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 ?

    Defect engineering for high-selection-performance of NO reduction to NH3 over CeO2(111)surface:A DFT study

    2022-03-14 09:30:36ChaozhengHeRishengSunLingFuJinrongHuoChenxuZhaoXiuyuanLiYanSongSuminWang
    Chinese Chemical Letters 2022年1期

    Chaozheng He,Risheng Sun,Ling Fu,Jinrong Huo,Chenxu Zhao,Xiuyuan Li,Yan Song,Sumin Wang

    aShaanxi Key Laboratory of Optoelectronic Functional Materials and Devices,School of Materials Science and Chemical Engineering,Xi’an Technological University,Xi’an 710021,China

    bInstitute of Environmental and Energy Catalysis,School of Materials Science and Chemical Engineering,Xi’an Technological University,Xi’an 710021,China

    cCollege of Resources and Environmental Engineering,Tianshui Normal University,Tianshui 741001,China

    dSchool of Sciences,Xi’an Technological University,Xi’an 710021,China

    ABSTRACT To reduce the greenhouse effect caused by the surgery of nitrogen-oxides concentration in the atmosphere and develop a future energy carrier of renewables,it is very critical to develop more efficient,controllable,and highly sensitive catalytic materials.In our work,we proposed that nitric oxide(NO),as a supplement to N2 for the synthesis of ammonia,which is equipped with a lower barrier.And the study highlighted the potential of CeO2(111)nanosheets with La doping and oxygen vacancy(OV)as a highperformance,controllable material for NO capture at the site of Vo site,and separation the process of hydrogenation.We also reported that the Eads of -1.12 eV with horizontal adsorption and the Bader charge of N increasing of 0.53|e| and O increasing of 0.17|e| at the most active site of reduction-OV predicted.It is worth noting that ΔG of NORR(NO reduction reaction)shows good performance(thermodynamically spontaneous reaction)to synthesize ammonia and water at room temperature in the theoretical calculation.

    Keywords:La-doping CeO2 Bader analysis Oxygen vacancy(OV)Single atom catalysis Synergistic effect NO reduction reaction(NORR)

    Ammonia(NH3),as a future carrier of renewable energy and a source of fertilizer in agriculture,is the key aspects and anticipated stages in promising technologies for decades,which is provided with large hydrogen content and high energy density[1–3].Although electrosynthesis of NH3from N2composing of 78%of the atmosphere,which is a fertile source for synthetic ammonia,it exists in chemically and biologically unusable gaseous form.Haber,who break through the triple bond of dinitrogen with hydrogen in the presence of the Fe and discovered the process by high temperatures and pressures,explained that his main motivation for the study of synthesizing ammonia was the growing demand for food,and is awarded a Nobel Prize in 1931[4].Recently,more and more researchers are paying attention to the approach to replace the Haber-Bosch process by searching for the befitting catalyst support of ceria under ambient conditions.Doping single metals of chromium(Cr),copper(Cu),iron(Fe),molybdenum(Mo)and rubidium(Ru)can enhance the performance of electrocatalytic N2to NH3in comparison to the pure CeO2(111)surfaces efficiently,which the single Mo atoms in Mo-N3C are also reported for the reason of the best capability of N2adsorption for further electrochemical N2reduction[5–9].Lee and co-workers explored the new way called the reticular chemistry approach which exploiting MOFs water-repelling and molecular-concentrating effects to overcome HER-imposed bottlenecks to accelerate synthesis yield of ammonia in theory[10].Also,Guoet al.focus on the atomically dispersed Bi-catalysts for nitrogen reduction reaction to tackle the activity and selectivity[11].As well as Mxene-based materials,which have been noticed as highlighted catalysts for electrochemical N2reduction recently,are investigated rapidly due to satisfactory catalytic activity[12].Analogously,the process of Ammonia borane(AB)hydrolysis generates H2and NH3on the transition metal Fe@Co coreshell structure has been obtained[13,14].

    However,we will have to admit and should not ignore that the difficulty of a strong N-N bond is the biggest problem in the synthesis of ammonia.In a word,it makes us provide the ideas for seeking another supplementary scheme.As a nitrogen supplement,nitric oxide(NO)has the advantage of bond energy over nitrogen molecules,which consumes much less energy to synthesize ammonia.Especially on the surfaces of CeO2(111),oxygen vacancies play an important role in good catalytic performance,which comes from the interconversion between Ce(III)and Ce(IV)oxidation states with the storage and release of 4f electronic orbits[14–19].In this work,our study demonstrates that we built a 3 × 3 × 1 supercell of CeO2(111)surface by doping La atom with oxygen vacancy for adsorbing NO molecules to study geometry,electronic structures,and NO reduction reaction coordinate to propose a new idea of N-element reduction reaction(NORR):

    The calculations were performed by a spin-polarized DFT + U approach using the Vienna ad initio simulation package(VASP)[20],which employing the generalized gradient approximation(GGA)with Perdew-Burke-Ernzerh of(PBE)function.Also,we use DFT-D2 to describe the van der Waals bonds.For guaranteeing a good convergence of total energies,the plane-wave cutoff was 400 eV,which uses the Brillouin zone sampled with 5 × 5 × 1 of k-points with allowing the convergence of total energy to set 0.01 eV,and the Part valence-electron configurations include Ce(5s,5p,6p,5d,4f),La(5d,6s)and O(2s,2p).And we consider the 4f states of the reduced cerium and doped-La atoms,where the value of the Hubbard U terms was used as 5.0 eV and 7.5 eV effectively[21],and we first predicted bulk lattice constant of the pure CeO2is 5.42 ?A,which compared it and the agreement with the experimental value(5.41 ?A)and the theoretical results(5.43 ?A)[22,23].For the surface selection,we studied only the surface(111)among the low-index surfaces of CeO2(111),(110)and(100),which surface(111)is the most stable[24,25].As depicted in Fig.S1(Supporting information),the circular area of the dotted line represents the possible NO adsorption sites of Ce-top,O-top,Ce-O-bridge and hollow sites.

    For purpose of better understanding the transition metal(TMs)doped CeO2(111)surfaces the formation energies of each surface slab by using the following equation:

    whereEM?CeO2andECeO2are total energies of TMs doped and stoichiometric CeO2(111)surface,respectively.ECeandEMare the energies of single Ce atom and the selected metal atom(M=K,Ca,Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,Mo,Cs,Ba,La,Pr,Nd and Sm),respectively.Clearly,the negative value presents the exothermic process,leading to the stable structure.When the values were calculated to be positive,it explained that doping process is thermodynamically unfavorable.

    As shown in Fig.S2(Supporting information),all the formation energies of the metal-doped CeO2(111)surfaces are plotted,we actually see that except Cs elements,the dopant formation energies of K to Ba atoms(>2 eV)are higher than those(<1.5 eV)which doped with rare metals(La,Pr,Nd and Sm).To further compare with rare metals,La-doped CeO2(111)surface with the lowest formation energy of 0.67 eV indicating that the syntheses of La-doped-CeO2(111)systems are relatively easy in the experiment.Our results are completely consistent with the radii between the M and Ce atoms,that the larger the size difference is,the larger the formation energy is[26].

    Generally,oxygen vacancy(OV)plays an important role in good catalytic performance,which coming from the interconversion between Ce(III)and Ce(IV)oxidation states with the storage and release of 4f electronic orbits.Thus,for investigating the formation energy of oxygen vacancies(OVs)on the CeO2(111)surface,the defect energyEvacis defined as following[27,28]:

    The adsorption energy(Eads)is defined as[33,36]:

    whereEadsorbate/sub,EadsorbateandEsubare the total energies of adsorbate-substrate,isolated adsorbate and substrate system,respectively.And the negative value ofEadsindicates the better stable configuration and exothermic process.

    As shown in Fig.1a and Fig.S1,in order to further elucidate and study the nature of the CeO2systems for NO activation,we have testedEadsof and bond length of NO,thex-axis coordinates indicate the possible adsorption locations,which are Ce-top,O-top,bridge,hollow and OV sites and they-axis is the energy of adsorption.Also,we can see that red and black lines,which show NO molecule can be adsorbed over different sites through its O and N atom,respectively.The bar chart shows the bond length of NO after adsorption through N atom,and the date by O atom is listed in Table S1(Supporting information)due to the minor change.Our computations demonstrated that NO chemisorption occurs on the N site preferably,which the value of N-site shows better adsorption than O-site withEadsunder ?0.40 eV in general.Moreover,when the OV occurs on the surface,the adsorption energy is significantly reduced,and the bond length is also increased of 1.211 ?A.In all,the results indicate that the existence of OV can well improve the ability of NO activation.Especially,adsorption energy and bond length are significantly improved when metals are doped with oxygen vacancy.By comparison of different adsorption energyEadsof NO and bond length after different metals doping on MxCe1-xO2-δsurfaces(M=K,Ca,Sc,Ti,V,Cr,Mn,Fe,Cu,Zn,Mo,Cs,Ba,La,Pr,Nd and Sm),what is noteworthy is that the bond length of NO molecule increased to 1.245 ?A from its original length of 1.117 ?A and the adsorption energy decreased to ?1.12 eV by activating over La-doping with OV surface(Fig.1b).

    In a word,according to Fig.1,Tables S1 and S2(Supporting information),we found that direct generation of OV can also achieve the result of NO activation(the formation energy of oxygen vacancy(Eads)is 3.01 eV,the bond length of NO is 1.211 ?A and theEadsis–0.85 eV),except the system of low formation energy doping La atom with OV(the formation energy of oxygen vacancy(Eads)is 2.85 eV,the bond length of NO is 1.245 ?A and theEadsis–1.12 eV).As shown in Fig.S4(Supporting information),NO molecule prefers to adopt an end-on way with Ce-N bonding distance of 2.491 ?A on the OV surface and a side-on mode with Ce-O,Ce-N and La-N bonding distances of 2.703,2.542 and 2.661 ?A.It is obvious that the defect area is large,the distance of Ce3+-O is too far to bond on pure OV surface.Conversely,duo to the La ion is bigger that the Ce and the defect area is smaller,N and O atom can contact with more reductive active sites at the same time to pull the NO bond.Therefore,in order to further study the difference between them for NORR,we carried out the HER study over La doped CeO2(111)surface with an oxygen vacancy and CeO2(111)surface only with OV,respectively(Fig.S5 in Supporting information),which is an important side reaction to hinder the process of NORR.Ulteriorly,we can see that the first hydrogen is adsorbed on the La doped CeO2(111)surface with an oxygen vacancy and CeO2(111)surface only with Vo with the free energy change of?0.73 and ?0.81 eV,respectively,which the calculated equation isΔGH=Eads+ 0.24[36].In other words,the results reveal the practical free energies change of?H are ?0.97 eV over La-doped CeO2with Vo,which is smaller than that of?NO(?1.12 eV)and theEadsof?H are ?1.05 eV over pure CeO2with Vo,which is bigger than that of?NO(?0.85 eV).The calculation indicates that the La-doped CeO2(111)with OV can dominantly attract more NO than H,where the defected surface can expose more active sites for NORR.

    Fig.1.(a)The adsorption energy of NO(Eads)for different sites and corresponding bond length on the clean CeO2 surface and CeO2-δ urface with an oxygen vacancy,as well as the calculation of the value on the MxCe1-xO2-δ surfaces(M=K,Ca,Sc,Ti,V,Cr,Mn,Fe,Cu,Zn,Mo,Cs,Ba,La,Pr,Nd and Sm).Thus the results for Co and Ni doping are not shown in the work because of nonconvergent.

    Fig.2.(a)Difference charge density of CeO2(111)surface with defect,and red color(0.003 eV/?A3)in the plot indicates electron density increase after formation,and blue represents the opposite.(b)The calculated geometries of dCe-O, dLa-O and dCe?M(M=Ce and La)are shown to compare with pure CeO2(111)surfaces.(c)The spin-polarized density of states(DOS)of the optimized stoichiometric ceria.The fermi level is set at 0 eV.

    To speculate the mechanism of the adsorption sites of the NOmolecule,it is necessary to calculate the difference charge density after doping La atom and forming an oxygen vacancy.We thus investigate the electronic structures of interaction between NO and defected species and densities of states(DOS)of N and O atoms which guiding us to determine the location of the reduction sites[37].According to the Fig.2a,the charge transference from OV site to La2+(Bader charge of 1.71|e|)and Ce3+(Bader charge of 2.81|e|)sites,respectively.Now therefore,the existence of chemical adsorptive sites may at the position of Ce3+and La2+.

    For defected systems containing a single metal atom doping and an oxygen vacancy,only the lanthanide element is used,which the value ofEadsis lowest and degree of NO bond activation shows the best performance of 1.245 ?A,giving smaller to the volume of dopant hole,where is enclosed by i,ii and iii in Fig.S1,which considering the reason of the similar ion radius sizes between Ce and La atom.Thus,the combination of Ce3+and La2+active reduced sites together can accelerate NO molecules activation,were reacting on a finite scale.As shown in Fig.2b,the red and blue patterns indicate the distances of neighboring atoms each other on the pure surface and defective surfaces,respectively.The distances between M and Ox(x=I,II and III)atoms(M=Ce and La)are 2.371,2.369,2.339 and 2.241 ?A as shown in Fig.S1 and Fig.2b,which are closed to the distance of pure surface(2.348 ?A)[38–40].To better describe the situation of the active sites,it is worth mentioning that the density of states(DOS)to study the influence of doping La atom with an oxygen vacancy on the electronic structure of defected CeO2surface.Fig.2c shows that the orbital electronics of Ce(f)contributed between ?0.2 eV and 0 eV,and La(d)orbital electronics contributed between ?1.85 eV and 0 eV apparently with both VB occupied by states in spin up closed to the Fermi level,that the result is well consistent with the value[41].

    For further understanding activation of NO molecule,we make the Bader charge analysis that N atom accepts the charge of 0.53|e|from the Ce and La cation and O atom receives the charge of 0.17|e|(Fig.2b).The evidence of chemical adsorption can be confirmed by the charge density difference and is calculated using the expression[42–46]:

    Fig.3.All calculation for electronic structure analysis.(a,b)Optimized structure of adsorption configurations and charge density differences about NO chemisorbed on the CeO2(111)partial slab models from the top views.The isosurfaces value is 0.003 eV/?A3.(c–e)The simplified schematic with bonding in NO molecule and metal atoms(La and Ce)on the defective surfaces.(f,g)The projected electronic of states(PDOS)with spin-polarized density.The fermi level is set at 0 eV.

    whereρtotal,ρsurandρNOare the charge densities of the NO adsorption on the OV site with metal-La doping,the charge density of the pure surface,and the charge density of studied gas molecule-NO,respectively[33].

    The Gibbs free energy change(ΔG)for each elementary step was obtained using the computational hydrogen electrode(CHE)model by the following equation[45]:

    whereΔE,ΔEZPEandΔSare the reaction energy by the DFT calculation and the changes in zero-point energy and entropy,respectively.Tis the temperature(298.15 K).

    In a word,the adsorption energy of NO on the OV site indicates that the CeO2(111)surface is modified by metal La and vacancy of O atom with a synergistic effect.Charge density difference plots(Figs.3a and b)show that adsorbed NO can interact with these active and occupied orbitals of La and Ce atoms,in which the lone pair electrons from the Ce3+and La2+are injecting into the electrons from the Ce3+and La2+are injecting into the antibonding orbitals of NOviaN and O atoms by the so-called as the “push” hypothesis.The more interaction is thus for the lower dissociation barrier than NO adsorption on the pure surface.Our calculation is further performed to provide more details of such chemical change between isolated La and NO by fragment orbital analysis as shown in Figs.3c–g[11,46–52].Also,the projected densities of states(PDOS)of NO adsorption on defected species show thatα-,β- andαβ-spin states represent pure substrate surface,a gaseous NO molecule,and the adsorption configuration for comparison(Figs.3f and g)[53].

    For the interaction between the two main states of 4f-5d for Ce3+atom and O2pstates for O atoms,we present in Figs.3c,e and g that the energy levels of Ce3+majority f spin states involved in the interaction with p-spin orbitals of O atom with the energy ofαβ-states lower which becoming more stable.Obviously,the fx3orbitals electrons are donated to the O2porbitals,which proving up to the hilt that surface generated an OV possess the capability of redox.Also,for interaction between Ce3+,La2+and O atoms,we present in Figs.3d–f the spin densities are strongly localized on Ce4f,5d,La5dand 2p of N states,the energy levels of Ce3+majority 4f spin states and La2+5d-states involved in the interaction with2p-spin orbitals of N atom with the energy ofαβ-states lower which becoming more stable,too.Similarly,as our previous analysis,the 4fx3orbitals of Ce and 5dz3orbitals of La electrons are donated to the 2p orbitals of N indicates that surface-anchored La also owns the capability of redox.

    Critically,the investigation into the mechanism of ammonia synthesis over the defected surface with the raw material(NO)is essential.Hence,to explore the reaction path of NORR on La-doped CeO2catalysts,the associative hydrogenation of pathways,which the proton-electron pair(H++ e?)attacks the N atom firstly and then O atom continuously until the NH3is generated,was considered according to the analysis of the degree of activation mechanism between N and O atom and the horizontal adsorption configuration,thus the barrier of NO direct dissociation greater than associative hydrogenation.And the Gibbs free energy of each reaction intermediate was calculated as shown in Fig.4a.

    Different from the value on the O site,ΔG(?NHO)of ?0.62 eV is lower than theΔG(?NOH)of 0.59 eV as shown in Fig.4a which comparing with other theoretical calculation of positive value and showing the excellent performance[54,55].We further examine the “enzymatic” pathway that the applied potential forU=0 V andT=298.15 K to study the true condition[56,57].And the detailed thermodynamic date we calculated the Gibbs free energy of all the adsorption and desorption structures are considered as shown in Fig.4b,which the length of NO bond changes of 1.244,1.334,1.487 and 2.863 ?A in the process of hydrogenation until breaking.Remarkably,due to the degree of NO activation and its own activity,whose?NxOy(x=1,2 and 3;y=1,2)intermediate is substantially low,resulting in a smaller energy barrier of ?0.62 eV for the first hydrogenation of?NO into?NHO,which is an exothermic reaction.For the second and third step of?NHOH and?NH2OH,the reactions are both exothermic energies of ?0.09 and ?0.26 eV to promote the dissociation of NO,that the third step(?NH3+?OH with the NO bond splitting up)is also downhill.It is presented in Fig.4a that Vo with La doping favors the?NH3+?H2O stabilization with ?1.85 eV downhill for?HH2+?OH →?NH3+?OH substantially.By the step of fifth for?NH3+?H2O,we also found that NORR activity of La-CeO2-OV over surface(111)can construct H2O.For the last step,the reason that we ignored the consideration for NORR process is its form of NH4+.Thus,the NORR process we conclude is thermodynamically spontaneous.

    Fig.4.(a)Free energy diagram of the NORR on the surface of La-doped CeO2(111)with OV,and all the calculations of free energy are at U=0 V and T=298.15 K.(b)The top and side views of optimized structures of NO adsorption on the defect CeO2(111)following the NORR pathways.

    Based on the theoretical findings,the NORR performance of La-CeO2-OV on the associative hydrogenation reaction coordinate can be described as illustrated in Fig.4.Firstly,the direction of alternation is determined by the activation mechanisms between N and O atoms and the horizontal adsorption configuration.Second,the situations of La-dopants and OV will effectively push the orbitals electrons of the sites of Ce and La to the NO molecular orbitals,resulting in the accelerated transmission of proton-coupled electrons and the spontaneous reaction that synthesis of the ammonia and water.

    Subsequently,we find that the effect of atomic radii is a critical factor for altering and ensuring the appropriate size of the NO molecule adsorption.We have also recorded that the most active reduction surface predicted is OV site,and investigated the CeO2(111)with doping the La metals from the ab initio DFT calculations by studying geometric and electronic structure properties.The results show thatEadsis of ?1.12 eV with relative horizontal adsorption,the Bader charge analysis of N atom accepting the charge of 0.53|e| from the Ce and La cation and O atom receiving the charge of 0.17|e|.Importantly,ΔGis less than zero of NORR(NO + 5(H++ e?)→NH3+ H2O),which indicating thermodynamically spontaneous reaction to synthesize ammonia and water under ambient conditions.

    In summary,we have demonstrated the good structural engineering of reduction surface by ceria when La-doping with Vo.Comparing with NRR coordinates,NORR has lower energy consumption as confirmed by the theoretical results[46].And thus,we anticipate that such metals-La including oxygen vacancies can be extended over new ideas for efficient electrocatalytic NO to ammonia as a feedstock of nitrogen supplement.

    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 study was funded by the Natural Science Foundation of China(No.21603109),the Henan Joint Fund of the National Natural Science Foundation of China(No.U1404216),the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0676)and the Special Fund of Tianshui Normal University,China(No.CXJ2020-08).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2021.05.072.

    亚洲中文字幕日韩| 欧美成人免费av一区二区三区| 黄色视频,在线免费观看| 国产精品精品国产色婷婷| 视频区欧美日本亚洲| 亚洲av美国av| 国产一卡二卡三卡精品| 在线永久观看黄色视频| 午夜免费成人在线视频| 国产野战对白在线观看| 午夜影院日韩av| 日韩三级视频一区二区三区| 欧美人与性动交α欧美精品济南到| 精品第一国产精品| 亚洲三区欧美一区| 国产精品久久久人人做人人爽| 亚洲精品国产精品久久久不卡| 90打野战视频偷拍视频| 欧美黑人精品巨大| av欧美777| 亚洲一区二区三区色噜噜| 激情在线观看视频在线高清| av免费在线观看网站| 国产一区在线观看成人免费| 久久中文字幕人妻熟女| 很黄的视频免费| 男男h啪啪无遮挡| 丝袜在线中文字幕| 美女高潮到喷水免费观看| 1024视频免费在线观看| 人人妻人人澡人人看| 狠狠狠狠99中文字幕| 91国产中文字幕| 亚洲欧洲精品一区二区精品久久久| 757午夜福利合集在线观看| 国产精品久久久av美女十八| 搡老妇女老女人老熟妇| 亚洲男人的天堂狠狠| 曰老女人黄片| 久久精品国产清高在天天线| www.www免费av| 伦理电影免费视频| 欧美亚洲日本最大视频资源| videosex国产| 极品人妻少妇av视频| 国产在线精品亚洲第一网站| 亚洲国产欧美日韩在线播放| 久久精品人人爽人人爽视色| 夜夜夜夜夜久久久久| 91九色精品人成在线观看| 此物有八面人人有两片| 丝袜美腿诱惑在线| 自拍欧美九色日韩亚洲蝌蚪91| 成人永久免费在线观看视频| avwww免费| 免费人成视频x8x8入口观看| 国内久久婷婷六月综合欲色啪| 97人妻天天添夜夜摸| 男女下面进入的视频免费午夜 | 日韩欧美一区视频在线观看| 久久精品91无色码中文字幕| 成人18禁高潮啪啪吃奶动态图| 麻豆成人av在线观看| 两个人免费观看高清视频| 午夜福利在线观看吧| 高清在线国产一区| 国产亚洲av高清不卡| 亚洲第一青青草原| 大香蕉久久成人网| xxx96com| 久久久久亚洲av毛片大全| 日韩视频一区二区在线观看| 日韩一卡2卡3卡4卡2021年| 女人爽到高潮嗷嗷叫在线视频| av中文乱码字幕在线| 免费看美女性在线毛片视频| 亚洲国产精品久久男人天堂| 欧美日韩黄片免| videosex国产| 啪啪无遮挡十八禁网站| 久久久久国产一级毛片高清牌| 亚洲精品国产一区二区精华液| 高清黄色对白视频在线免费看| 18禁裸乳无遮挡免费网站照片 | 国产三级黄色录像| 最近最新免费中文字幕在线| 精品日产1卡2卡| 亚洲自偷自拍图片 自拍| 一进一出抽搐gif免费好疼| 亚洲伊人色综图| 欧美激情 高清一区二区三区| 欧美日本中文国产一区发布| 日韩av在线大香蕉| 极品人妻少妇av视频| 日日爽夜夜爽网站| 亚洲欧美激情在线| 午夜a级毛片| cao死你这个sao货| 成人国语在线视频| 美国免费a级毛片| 日韩精品青青久久久久久| 欧美黑人欧美精品刺激| 欧美成人性av电影在线观看| 免费在线观看亚洲国产| xxx96com| 国产亚洲精品综合一区在线观看 | 免费高清视频大片| 欧美日本中文国产一区发布| 国产高清有码在线观看视频 | 国产午夜福利久久久久久| 久热这里只有精品99| or卡值多少钱| 桃红色精品国产亚洲av| 久久草成人影院| 男男h啪啪无遮挡| 每晚都被弄得嗷嗷叫到高潮| 亚洲视频免费观看视频| 午夜福利在线观看吧| 正在播放国产对白刺激| 麻豆成人av在线观看| 久久精品国产清高在天天线| 大香蕉久久成人网| 精品久久久久久久久久免费视频| 国产一区二区三区视频了| 国产精品,欧美在线| 中国美女看黄片| 天堂影院成人在线观看| 国产精品一区二区精品视频观看| 精品人妻在线不人妻| 久久中文字幕人妻熟女| 欧美日韩福利视频一区二区| 精品一区二区三区av网在线观看| 欧美日韩精品网址| 亚洲国产精品sss在线观看| 淫秽高清视频在线观看| 国产av又大| 国产高清videossex| 国产亚洲精品一区二区www| 不卡一级毛片| 成在线人永久免费视频| 午夜久久久久精精品| 午夜激情av网站| 亚洲伊人色综图| 脱女人内裤的视频| 在线视频色国产色| 在线观看免费日韩欧美大片| 中文字幕av电影在线播放| 亚洲专区中文字幕在线| 亚洲精品美女久久av网站| 大香蕉久久成人网| 91麻豆av在线| 亚洲 欧美一区二区三区| 亚洲欧美激情在线| 天堂√8在线中文| 操美女的视频在线观看| 色婷婷久久久亚洲欧美| 亚洲精品一区av在线观看| 免费少妇av软件| 国产精品自产拍在线观看55亚洲| www.www免费av| 欧洲精品卡2卡3卡4卡5卡区| 欧美 亚洲 国产 日韩一| ponron亚洲| 美女高潮到喷水免费观看| tocl精华| 窝窝影院91人妻| 国产精品久久久久久亚洲av鲁大| 久久久精品欧美日韩精品| 波多野结衣一区麻豆| 国产精品永久免费网站| 精品少妇一区二区三区视频日本电影| 少妇被粗大的猛进出69影院| 亚洲av电影在线进入| 满18在线观看网站| 女人被狂操c到高潮| 欧美乱色亚洲激情| 天天躁狠狠躁夜夜躁狠狠躁| а√天堂www在线а√下载| 中文字幕色久视频| 久久精品亚洲熟妇少妇任你| 人人妻,人人澡人人爽秒播| 99在线人妻在线中文字幕| 青草久久国产| 国内精品久久久久精免费| 亚洲专区国产一区二区| 中文字幕人成人乱码亚洲影| 91麻豆精品激情在线观看国产| 精品久久久久久久毛片微露脸| 香蕉国产在线看| 制服人妻中文乱码| 啦啦啦韩国在线观看视频| 精品少妇一区二区三区视频日本电影| 欧美日本亚洲视频在线播放| 久久久久久国产a免费观看| 男人操女人黄网站| 不卡av一区二区三区| 99热只有精品国产| 精品日产1卡2卡| 麻豆久久精品国产亚洲av| 一夜夜www| xxx96com| 日韩欧美一区视频在线观看| 极品人妻少妇av视频| 又紧又爽又黄一区二区| 久久精品国产亚洲av高清一级| 黄片播放在线免费| 日韩精品免费视频一区二区三区| 久99久视频精品免费| 又黄又爽又免费观看的视频| 一个人免费在线观看的高清视频| 亚洲情色 制服丝袜| 国产男靠女视频免费网站| 这个男人来自地球电影免费观看| 国内精品久久久久精免费| 波多野结衣高清无吗| 亚洲五月天丁香| 热re99久久国产66热| 日韩 欧美 亚洲 中文字幕| 电影成人av| 看片在线看免费视频| 男人舔女人下体高潮全视频| 女人精品久久久久毛片| 午夜福利高清视频| 18禁裸乳无遮挡免费网站照片 | 亚洲自偷自拍图片 自拍| 国产精品一区二区三区四区久久 | 人人澡人人妻人| 日韩成人在线观看一区二区三区| 女警被强在线播放| 精品少妇一区二区三区视频日本电影| 高清黄色对白视频在线免费看| 国产激情欧美一区二区| 色综合亚洲欧美另类图片| av片东京热男人的天堂| 国产欧美日韩一区二区三区在线| 亚洲五月婷婷丁香| 国产精品免费视频内射| 精品免费久久久久久久清纯| 一级毛片女人18水好多| 他把我摸到了高潮在线观看| 成熟少妇高潮喷水视频| 村上凉子中文字幕在线| 国产极品粉嫩免费观看在线| 欧美亚洲日本最大视频资源| 高清毛片免费观看视频网站| 亚洲自偷自拍图片 自拍| 亚洲精品美女久久av网站| www.精华液| 日韩精品青青久久久久久| 日韩大码丰满熟妇| 亚洲自偷自拍图片 自拍| 亚洲精品美女久久av网站| 日韩欧美在线二视频| 午夜免费成人在线视频| 18禁黄网站禁片午夜丰满| 亚洲五月色婷婷综合| 欧美激情高清一区二区三区| 丝袜美足系列| 黄色视频不卡| 夜夜躁狠狠躁天天躁| 欧美在线黄色| 亚洲免费av在线视频| 亚洲中文字幕一区二区三区有码在线看 | 日本 欧美在线| 精品国产国语对白av| 中文字幕人妻丝袜一区二区| 正在播放国产对白刺激| 欧美黑人精品巨大| 校园春色视频在线观看| 亚洲欧美激情在线| 欧美av亚洲av综合av国产av| 麻豆一二三区av精品| 欧美一级a爱片免费观看看 | 亚洲精品美女久久av网站| 日本撒尿小便嘘嘘汇集6| 亚洲精品国产区一区二| 高清毛片免费观看视频网站| 亚洲专区国产一区二区| a级毛片在线看网站| 成人永久免费在线观看视频| 久久中文字幕人妻熟女| 咕卡用的链子| 90打野战视频偷拍视频| 成人精品一区二区免费| 99国产精品免费福利视频| 首页视频小说图片口味搜索| 久久久久亚洲av毛片大全| 欧美乱妇无乱码| 欧美精品亚洲一区二区| 久久久久久久久久久久大奶| 9热在线视频观看99| 俄罗斯特黄特色一大片| 9191精品国产免费久久| 午夜福利免费观看在线| 日韩大尺度精品在线看网址 | 黑人欧美特级aaaaaa片| 国产精品免费一区二区三区在线| 国内久久婷婷六月综合欲色啪| 精品久久久久久,| 国产成人一区二区三区免费视频网站| 女人被躁到高潮嗷嗷叫费观| 午夜精品久久久久久毛片777| 少妇 在线观看| 51午夜福利影视在线观看| 久久国产亚洲av麻豆专区| 国产91精品成人一区二区三区| 精品久久久久久成人av| av欧美777| 中出人妻视频一区二区| 国产精品影院久久| 日韩一卡2卡3卡4卡2021年| 欧美一区二区精品小视频在线| 黄片大片在线免费观看| 亚洲人成网站在线播放欧美日韩| 18美女黄网站色大片免费观看| 国产亚洲精品av在线| 在线天堂中文资源库| 久久久久久久久免费视频了| 午夜福利,免费看| 亚洲欧洲精品一区二区精品久久久| 一a级毛片在线观看| 亚洲成国产人片在线观看| 亚洲精品在线观看二区| 两人在一起打扑克的视频| 大型黄色视频在线免费观看| 久9热在线精品视频| 夜夜看夜夜爽夜夜摸| 日本 欧美在线| 曰老女人黄片| 国产精品久久久久久人妻精品电影| 日韩国内少妇激情av| 免费高清在线观看日韩| 亚洲av片天天在线观看| 嫩草影院精品99| 波多野结衣巨乳人妻| 亚洲熟妇熟女久久| 国产精品电影一区二区三区| 久久久久久国产a免费观看| 免费在线观看日本一区| 19禁男女啪啪无遮挡网站| 91老司机精品| 老汉色av国产亚洲站长工具| 欧美最黄视频在线播放免费| АⅤ资源中文在线天堂| 日日摸夜夜添夜夜添小说| 天堂√8在线中文| 我的亚洲天堂| 欧美激情极品国产一区二区三区| 黄色毛片三级朝国网站| 国产亚洲欧美在线一区二区| 看片在线看免费视频| 亚洲精品国产精品久久久不卡| 脱女人内裤的视频| 亚洲av日韩精品久久久久久密| 50天的宝宝边吃奶边哭怎么回事| 天天躁狠狠躁夜夜躁狠狠躁| 真人一进一出gif抽搐免费| 亚洲一区二区三区不卡视频| 久久婷婷人人爽人人干人人爱 | 免费高清视频大片| 丁香六月欧美| 亚洲无线在线观看| 女人爽到高潮嗷嗷叫在线视频| 亚洲性夜色夜夜综合| 一区二区三区国产精品乱码| 大陆偷拍与自拍| 咕卡用的链子| 叶爱在线成人免费视频播放| 中文字幕精品免费在线观看视频| 男女下面插进去视频免费观看| 成人国产综合亚洲| 免费看十八禁软件| 国产亚洲精品久久久久久毛片| 久久精品91无色码中文字幕| 亚洲电影在线观看av| 禁无遮挡网站| 每晚都被弄得嗷嗷叫到高潮| 美女 人体艺术 gogo| 久久久久亚洲av毛片大全| 老司机午夜十八禁免费视频| 国产在线观看jvid| 国产精品 欧美亚洲| 色综合亚洲欧美另类图片| 亚洲精品国产色婷婷电影| 亚洲激情在线av| 亚洲天堂国产精品一区在线| 日韩欧美三级三区| 欧美最黄视频在线播放免费| 精品久久久久久久毛片微露脸| 韩国av一区二区三区四区| 欧美日韩亚洲综合一区二区三区_| 久久精品亚洲精品国产色婷小说| cao死你这个sao货| 久久香蕉精品热| 久久亚洲真实| 一本综合久久免费| 国产一区二区三区综合在线观看| 中出人妻视频一区二区| 亚洲全国av大片| 亚洲欧美一区二区三区黑人| 国内精品久久久久精免费| 亚洲自拍偷在线| 又大又爽又粗| 波多野结衣巨乳人妻| 一进一出好大好爽视频| 免费在线观看亚洲国产| 激情在线观看视频在线高清| 美女高潮到喷水免费观看| 久久久久国产一级毛片高清牌| 久久久久久免费高清国产稀缺| 国产一区二区三区在线臀色熟女| 成人18禁高潮啪啪吃奶动态图| 在线视频色国产色| 久久性视频一级片| 老熟妇乱子伦视频在线观看| 18美女黄网站色大片免费观看| 成人特级黄色片久久久久久久| 99在线视频只有这里精品首页| 999久久久国产精品视频| 久久这里只有精品19| 国产野战对白在线观看| 午夜久久久在线观看| 精品国产美女av久久久久小说| 久久国产精品人妻蜜桃| 亚洲精品国产精品久久久不卡| 亚洲午夜理论影院| 欧美日韩亚洲综合一区二区三区_| 天天一区二区日本电影三级 | 一区二区三区高清视频在线| 亚洲人成伊人成综合网2020| 丁香欧美五月| 亚洲精品国产色婷婷电影| 人人妻人人爽人人添夜夜欢视频| 久久久久久久久中文| 叶爱在线成人免费视频播放| 97人妻天天添夜夜摸| 桃红色精品国产亚洲av| 91字幕亚洲| 国产区一区二久久| 在线观看一区二区三区| 91老司机精品| 成在线人永久免费视频| 午夜激情av网站| 在线观看免费日韩欧美大片| 韩国精品一区二区三区| 色av中文字幕| 亚洲 欧美 日韩 在线 免费| 中文字幕另类日韩欧美亚洲嫩草| 国产熟女xx| 满18在线观看网站| 久久精品91蜜桃| bbb黄色大片| 最好的美女福利视频网| 多毛熟女@视频| 免费在线观看完整版高清| 黄色毛片三级朝国网站| 亚洲七黄色美女视频| 变态另类成人亚洲欧美熟女 | av天堂在线播放| 精品日产1卡2卡| 亚洲第一青青草原| 男男h啪啪无遮挡| 亚洲精品中文字幕一二三四区| 又紧又爽又黄一区二区| 日本一区二区免费在线视频| 国产真人三级小视频在线观看| 日韩欧美国产在线观看| 国产一区二区激情短视频| 亚洲国产欧美日韩在线播放| 桃色一区二区三区在线观看| 日韩欧美一区二区三区在线观看| 国产精品野战在线观看| 免费女性裸体啪啪无遮挡网站| 久热爱精品视频在线9| 亚洲一卡2卡3卡4卡5卡精品中文| 精品久久久久久,| 伦理电影免费视频| videosex国产| 午夜激情av网站| 麻豆国产av国片精品| 国产野战对白在线观看| 亚洲天堂国产精品一区在线| 久久久久久大精品| 777久久人妻少妇嫩草av网站| 国产av又大| 久久人人精品亚洲av| 午夜久久久在线观看| 亚洲av成人av| 亚洲午夜理论影院| 国产精品久久视频播放| 男人舔女人的私密视频| 亚洲av电影不卡..在线观看| 国产欧美日韩精品亚洲av| 国产亚洲精品一区二区www| 欧美成人一区二区免费高清观看 | 久久草成人影院| 亚洲第一青青草原| 久久精品国产综合久久久| 国产精品久久久久久人妻精品电影| 亚洲精品中文字幕在线视频| 女人被狂操c到高潮| 欧美午夜高清在线| 午夜日韩欧美国产| 麻豆av在线久日| 久久人人97超碰香蕉20202| 色av中文字幕| 在线天堂中文资源库| 亚洲av片天天在线观看| 午夜福利在线观看吧| 久久人人97超碰香蕉20202| 亚洲精品国产一区二区精华液| 久久精品影院6| 熟妇人妻久久中文字幕3abv| 嫁个100分男人电影在线观看| 亚洲伊人色综图| 国产av一区在线观看免费| 视频区欧美日本亚洲| 老司机在亚洲福利影院| 亚洲人成电影免费在线| 午夜a级毛片| 日日爽夜夜爽网站| 免费人成视频x8x8入口观看| 精品电影一区二区在线| 亚洲av电影不卡..在线观看| 19禁男女啪啪无遮挡网站| 色老头精品视频在线观看| 欧美人与性动交α欧美精品济南到| 国产成人系列免费观看| 人妻丰满熟妇av一区二区三区| 男女之事视频高清在线观看| 999精品在线视频| 老司机午夜福利在线观看视频| 男女床上黄色一级片免费看| 欧美乱色亚洲激情| 午夜精品在线福利| 久久国产精品男人的天堂亚洲| 亚洲欧美日韩高清在线视频| 国产亚洲精品久久久久5区| 亚洲精品在线美女| 亚洲第一欧美日韩一区二区三区| 国产精品二区激情视频| 在线十欧美十亚洲十日本专区| 真人一进一出gif抽搐免费| 巨乳人妻的诱惑在线观看| 淫妇啪啪啪对白视频| 一夜夜www| 悠悠久久av| 自拍欧美九色日韩亚洲蝌蚪91| 亚洲精品美女久久av网站| 一边摸一边抽搐一进一出视频| 欧美日韩福利视频一区二区| avwww免费| 精品高清国产在线一区| 亚洲精品久久国产高清桃花| 午夜影院日韩av| 国产成人av激情在线播放| 51午夜福利影视在线观看| 亚洲成人久久性| 午夜久久久在线观看| 成人亚洲精品一区在线观看| 国产亚洲av高清不卡| 欧美黄色淫秽网站| 深夜精品福利| 国产精品乱码一区二三区的特点 | 美女午夜性视频免费| 日韩大尺度精品在线看网址 | 12—13女人毛片做爰片一| 欧美另类亚洲清纯唯美| 国产成人精品在线电影| 成人特级黄色片久久久久久久| 少妇的丰满在线观看| 亚洲熟妇熟女久久| 九色亚洲精品在线播放| 日本撒尿小便嘘嘘汇集6| 美女高潮喷水抽搐中文字幕| 亚洲最大成人中文| bbb黄色大片| 91麻豆精品激情在线观看国产| 中文字幕精品免费在线观看视频| 欧美人与性动交α欧美精品济南到| 亚洲片人在线观看| 久久久久久久久中文| 一区二区三区精品91| 国产xxxxx性猛交| 中文字幕久久专区| 男女下面插进去视频免费观看| 97碰自拍视频| 9色porny在线观看| 69av精品久久久久久| 久久欧美精品欧美久久欧美| 亚洲情色 制服丝袜| 男女下面插进去视频免费观看| 此物有八面人人有两片| 国产在线精品亚洲第一网站| 99国产精品一区二区蜜桃av| 久久欧美精品欧美久久欧美| 人人澡人人妻人| 一个人观看的视频www高清免费观看 | 久久久水蜜桃国产精品网| 国产精品98久久久久久宅男小说| 亚洲免费av在线视频| 久久久水蜜桃国产精品网| 亚洲五月色婷婷综合| 老司机午夜福利在线观看视频| 国产精品日韩av在线免费观看 | 无人区码免费观看不卡| 日韩欧美三级三区| 手机成人av网站| 国产亚洲欧美98| 亚洲精品国产精品久久久不卡| 欧美成人午夜精品| 成熟少妇高潮喷水视频| 日韩视频一区二区在线观看| 老司机靠b影院| 日韩欧美国产在线观看|