• <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 ?

    Morphological effect on electrochemical performance of nanostructural CrN?

    2021-12-22 06:43:42ZhengweiXiong熊政偉XuemeiAn安雪梅QianLiu劉倩JiayiZhu朱家藝XiaoqiangZhang張小強(qiáng)ChenchunHao郝辰春QiangYang羊強(qiáng)ZhipengGao高志鵬andMengZhang張盟
    Chinese Physics B 2021年12期
    關(guān)鍵詞:劉倩高志朱家

    Zhengwei Xiong(熊政偉) Xuemei An(安雪梅) Qian Liu(劉倩)Jiayi Zhu(朱家藝) Xiaoqiang Zhang(張小強(qiáng)) Chenchun Hao(郝辰春)Qiang Yang(羊強(qiáng)) Zhipeng Gao(高志鵬) and Meng Zhang(張盟)

    1Joint Laboratory for Extreme Conditions Matter Properties,Southwest University of Science and Technology,Mianyang 621010,China

    2Institute of Electronic Engineering,China Academy of Engineering Physics(CAEP),Mianyang 621900,China

    3Institute of Fluid Physics,China Academy of Engineering Physics,Mianyang 621900,China

    4Affiliated Hospital,Chengdu University of Traditional Chinese Medicine,Chengdu 611137,China

    Keywords: CrN,supercapacitors,metal nitride,nanostructures

    1. Introduction

    Supercapacitor is an important energy-storage device,presenting a longer lifetime (>105cycles), high power density (> 10 mW/cm2), and rapid charge/discharge capabilities safely. Nowsdays,commercial supercapacitors have been widely used in heavy-duty vehicles, load-leveling systems,and hybrid platforms. However, the common energy density of supercapacitors (~5 Wh/kg) was still lower than that of batteries (up to 200 Wh/kg) or fuel cells (up to 350 Wh/kg).[1]In the past decades, much efforts have been paid for improving the storage performance for supercapacitors. Transition metal nitrides (TMNs) were extensively investigated for many applications,such as electrocatalytic water splitting,[2]plasmonics,[3]and supercapacitors,[4]owing to their excellent conductivity, prominent thermal/chemical stability and outstanding electrochemical performance. Various TMNs, including nickel nitride,[5]titanium nitride,[6]vanadium nitride,[7,8]and molybdenum nitride,[9]have been explored as novel electrode materials for supercapacitors,showing superior specific capacitance and rate performance.In particular,chromium nitride(CrN)with a high resistance to wear and corrosion shows a promising advantage over conventional transition metal oxides in energy storage.[10–13]Lots of synthetic approaches to nanostructured CrN have been reported including physical vapor deposition, nanopatterning, and DC magnetron sputtering. Daset al.synthesized CrN nanoparticles with the size of 20 nm–30 nm by using the combination of a hydrothermal method and a nitridation process, showing a specific capacitance of 75 F/g at the current density of 30 mA/g.[11]Hayeet al.prepared CrN films by magnetron sputtering at glancing angle (GLAD), and obtained a high areal capacitance of 35.4 mF/cm2at 1.2 mA/cm2.[14]Weiet al.reported a high areal specific capacitance(12.8 mF/cm2at 10 mV/s)of CrN thin films prepared by DC magnetron sputtering technology, and the CrN thin film also exhibited high cycling stability with 92.1% capacitance retention after 2×104cycles in the H2SO4electrolyte(0.5 M).[10]However, the reported specific capacitance of CrN was still relatively low,as a disadvantage of TMNs based supercapacitor,comparing with metal oxides,mxenes or transition metal phosphides.[15]

    The morphology and size are critical factors in determining the electrochemical performance of the supercapacitor materials with a single component, due to the manifestation of the nanosize effect. As we know, the morphology, size, and synthetic method of TMNs may remarkably improve the number of redox centers and enhance their supercapacitor performance. For example, two-dimensional nanomaterials with a large specific surface area facilitate interfacial reactions in supercapacitors, rechargeable batteries, as well as catalysts.[16]Due to the unique structure, the obtained free-standing TiN nanosheet arrays have a large specific capacitance of 81.63 F/g and excellent cycling performance without capacitance decay after 2500 cycles.[17]Huoet al. synthesized VN nanoflakes from nitriding V2O5nanoflakes xerogel,resulting in the large nanoflake morphology of VN with porous structure. The VN material had a high specific capacitance of 152 F/g at 1 A/g in the alkaline solution.[18]However,the effect of morphology and size for the CrN material on the supercapacitor was rarely studied, as far as we know. Herien, three nanostructures of the CrN material were studies for their electrochemical properties in this work, basing on the Cr2O3precursors with different morphologies. The obtained CrN nanostructures, including (i) hierarchical microspheres assembled by nanoparticles, (ii) microlayers, and (iii) nanoparticles, were prepared by the combination of a thermal-nitridation process and a template (Cr2O3) technique. As a result, high-temperature nitridation could not only transform the hexagonal Cr2O3into cubic CrN completely, but also keep the template’ morphology unchanged. The electrochemical performance of CrN nanostructures assembling into supercapacitors was systematically tested and discussed.

    2. Experimental details

    2.1. Preparation of Cr2O3 precursor

    (i)The microspheres Cr2O3precursor was synthesized by a modified hydrothermal method.[19]Briefly, 0.8-mmol glucose and 0.1-mmol Cr(NO3)3·9H2O were dissolved in 40-ml and 20-ml deionized water, respectively. The two solutions were then mixed and placed in 100 ml of teflon liner coated with a stainless steel autoclave. After keeping the temperature at 180?C for 24 h,a black precipitate was obtained. Then,the powders were washed with deionized water and alcohol three times,and dried in a drying oven at 60?C for 5 h. Finally,the powders were heated up to 550?C for 4 h in a muffle furnace at an atmosphere. (ii)The Cr2O3microplates precursor was synthesized by a method reported previously.[20]Firstly, 15 mL of Cr(NO3)3solution (0.1 mol/L) was heated to 70?C under magnetic stirring. Then, the ammonia solution was added to the above solution dropwise,until the pH=9. The suspension was kept at room temperature for 1 h. Finally, it was washed with deionized water,and then dried under reduced pressure at 140?C in a drying cabinet. (iii)The Cr2O3nanoparticle precursor was synthesized by a simple annealing method. Firstly,1 mmol of CrCl3·6H2O and 3 mmol of propylene oxide were stirred in 40 mL of DI water in a breaker to form a gel. Then,the obtained gel was placed in an aluminum oxide crucible,and heated to 600?C. The state was kept for 1 hour in the atmosphere,and the product was obtained.

    2.2. Preparation of CrN nanostructures

    By using the above-mentioned three Cr2O3precursors with different morphologies, we obtained three different nanostructural CrNs respectively. Briefly, 2.0 g of the above three kinds of Cr2O3powders were loaded into a crucible,respectively,and heated to 800?C in an ammonia(NH3)atmosphere. The NH3flow rate was 0.06 m3/h, and the process was kept for 4 h. Then, the system was naturally cooled to room temperature. Note that NH3was introduced for 0.5 h before the temperature rise,ensuring that the air in the furnace was fully eliminated. The generated tail gas was absorbed by dilute H2SO4solution. The schematic diagram of CrN preparation was shown in Fig.1.

    Fig.1. Schematic diagram of CrN fabrication.

    2.3. Structure characterization

    All the samples used an x-ray diffractometer (XRD) to test the crystal structure of the material.The x-ray source is Cu targetKαradiation(λ=0.154 nm), the 2θmeasuring range is 10?–80?, and the scanning rate is 8?/min. The micromorphology of the samples was observed at high magnifications such as 104(10 kx)and 5×104(50 kx)with a high-resolution cold field emission scanning electron microscope(SEM).The chemical bond composition of the products was characterized by x-ray electron spectroscopy(XPS).A transmission electron microscope(TEM)with high-resolution transmission electron microscope(HRTEM)was used to observe the internal structure of the samples. With the Asap2020 chemical adsorption analyzer, the specific surface area of the sample was calculated by the Brunauer–Emmett–Teller (BET) equation of N2adsorption isotherm.

    2.4. Electrochemical characterization

    The working electrode was fabricated by a slurry-forging method with Ti sheet electrode. Briefly, CrN powders, conductive carbon powders, and polyvinylidene fluoride(PVDF)were mixed uniformly with a mass ratio of 8:1:1. Then,they were added with the N-methylpyrrolidone (NMP) until the mixed powder is ground into a thick slurry. The paste was uniformly coated on one side of the cleaned Ti sheet electrode and then dried in a drying box at 40?C for 12 h. The cyclic voltammetry curve (CV), constant current charge-discharge curve (GCD), impedance spectroscopy(EIS), and cyclic voltammetry stability of the CrN electrode material were tested through the electrochemical workstation(CHI660E) with a three-electrode system. The as-prepared CrN electrode, Hg/HgO and Pt sheets were used as working electrodes,the reference electrode,and the counter electrode,respectively. The electrolyte was 1-mol/L KOH.According to the CV and GCD curves, the specific capacitance (Cs) of the electrode material could be calculated separately by

    whereIis current,mis the material quality,?Vis the voltage window during the test,vis the scan rate of the CV curves,and?tis the discharge time. The energy density (E) and power density (P) of the CrN electrode materials was calculated by the following equations

    where ?Vand ?tare the voltage window and time of discharge,respectively.

    3. Results and discussion

    First, nanostructural Cr2O3precursors were synthesized with three kind of morphologies with nanoparticles, microlayer, and microsphere. The Cr2O3nanoparticles were generated by high-temperature sintering of the gel formed by chromium trichloride hexahydrate and propylene oxide. Dispersed nanoparticles were found with a relatively uniform size(Figs. 2(a) and 2(b)). The microlayered Cr2O3was obtained by drying chromium nitrate solution under reduced pressure in an alkaline environment(Figs.2(c)and 2(d)). Its surface was composed of Cr2O3nanoparticles bonded and stacked.Importantly, the microspherical Cr2O3was prepared by a reported hydrothermal method, and the spherical Cr2O3surface was loose and porous clearly(Figs.2(e)and 2(f)). Nanostructural CrN electrode materials were obtained by annealing different nanostructural Cr2O3in ammonia atmosphere as shown in the schematic diagram. During the reaction,the oxygen atoms in Cr2O3are replaced by nitrogen atoms,resulting in CrN materials with loose nanostructures. The whole high-temperature ammoniation process is presented by the following formula:

    By the combination of the construction of Cr2O3nanostructure precursors with the ammoniating process,CrN materials with different nanostructures were obtained. Compared with the morphologies of the Cr2O3precursors, there are the following differences of as-prepared CrN materials. The size of the CrN nanoparticles was reduced and has no clear edges from the observation of TEM test. The surface of the CrN microspheres is looser (Fig. 3(g)), and the CrN is observed as loose microspheres by TEM observation (Fig. 3(h)). In the cross-section, there are a lot of holes in the CrN microlayers(Fig.3(d)). For CrN nanoparticles,the HRTEM image shows the interplanar spacing of 0.24 nm and 0.21 nm,which is consistent with the cubic CrN (111) and (200) interplanar spacing.[13]For the microlayer and microspherical CrN,the corresponding (200) crystal plane was also found, confirming that high-temperature ammoniation could completely transform transition metal oxides into transition metal nitrides.These unique nanostructures may provide fast transmission channels for electronic transport, thereby improving energy storage performance.

    Fig.2. SEM images of Cr2O3 at different magnifications: (a)10 kx nanoparticles;(b)50 kx nanoparticles;(c)10 kx microlayers;(d)50 kx microlayers;(e)10 kx microspheres;(f)50 kx microspheres.

    The XRD patterns of CrN nanostructures with different morphologies were shown in Fig. 4(a). The prepared CrN nanostructures have a cubic crystal structure (JCPDS No. 03-065-2899) after hightemperature nitridation.[20,21]High-temperature ammoniation could completely convert hexagonal Cr2O3into cubic CrN,which is consistent with the HRTEM measurement results. Three peaks at 574.5, 575.6,and 586.5 eV were found in Figs. 4(b) and 4(c), which were attributed to the formation of CrN compounds by the reaction between Cr and N during the nitridation process.[22,23]The peak at 396.6 eV in the N 1s spectrum was derived from the Cr-N bond.[24]

    Fig. 3. Morphologies of CrN nanoparticles: (a) SEM, (b) TEM, (c) HRTEM. Morphologies of CrN microlayers: (d) SEM, (e) TEM, (f)HRTEM. Morphologies of CrN microspheres: (g) SEM, (h) TEM, (i) HRTEM. The insets at the upper right of figures [panels (d), (e), (g)]show the magnified view.

    XPS measurements were further employed to analyze the element composition and valence states of the CrN sample.XPS experiments confirmed that there were only two elements,Cr and N,in the synthesized CrN sample,which is consistent with XRD analysis. In the high-resolution XPS scan,Cr 2p core splits into 2p 3/2 and 2p 1/2 peaks(575.5 eV and 584.9 eV).The results indicated that Cr element exhibited+3 oxidation states in the sample. On the other hand, N 1s peak was fitted into 396.6 eV,and indexed to the Cr-N bond.[22–24]

    Fig.4. (a)XRD patterns of CrN with different nanostructures: nanoparticles(black line),microsphers(red line),and microlayers(blue line). XPS spectra of CrN with(b)Cr 2p and(c)N 1s.

    Initially,CrN materials with different morphologies were evaluated by the cyclic voltammetry and current chargedischarge curves in Fig. 5. It could be seen that the rectangular area of the CV curve of the CrN nanoparticles was small at different scan rates, resulting in its small capacitance. By combining with the GCD curve, it could be seen that there is oxidation–reduction reaction during the charge and discharge process. For the microlayered CrN, the CV curve is almost rectangular and has a weak redox peak. Combined with the GCD curve results, it shows that there is a redox pseudocapacitance behavior during the electrochemical behavior. Figure 5(e) shows the CV curve of porous spherical CrN.The redox peak was found obviously,indicating that there is a redox pseudocapacitance behavior during the electrochemical charging and discharging process, which is consistent with the result of the GCD curve. According to the CV and GCD curves,the specific capacitance of the electrode material was calculated (Eqs. (1) and (2)). The specific capacitance decreases with the increase of the scan rate,as CrN electrode material showed a slow transfer and charge diffusion in the KOH electrolyte at a higher scan rate. Within the scan rate range of 10 mV/s–500 mV/s, the specific capacitance drop range of CrN nanoparticles, microlayers, and microspheres were: 82.4 F/g→55.6 F/g, 126.7 F/g→63.2 F/g,213.2 F/g→106.3 F/g respectively, and the corresponding specific capacitance retention rates were 67.5%, 49.8%, and 49.9%,respectively.

    Fig. 5. The CV and GCD curves of CrN with different morphologies: (a) nanoparticles CV, (b) nanoparticles GCD, (c) microlayers CV, (d)microlayers GCD,(e)microspherical CV,and(f)microspherical GCD.

    Fig. 6. Specific capacitance of CrN with different nanostructures under (a)different scanning rates and(b)different current densities.

    The relationship between current density and specific capacitance was shown in the curves of Fig. 6. As the current density increases, the specific capacitance gradually decreases, which is consistent with the trend between the scan rate and specific capacitance curve. In the current density range of 0.75 A/g–10 A/g, the specific capacitance drop intervals of CrN nanoparticles, microlayers, and microspheres were 79.8 F/g→55.0 F/g, 118.0 F/g→63.8 F/g,208.1 F/g→113.5 F/g, respectively. The corresponding specific capacitance retention rates were 68.9%, 54.1%, and 54.5%, respectively. For the above three different nanostructures of CrN materials, although the CrN nanoparticles had a higher specific capacitance retention rate,the specific capacitance was smaller. In contrast,the porous microspherical CrN had a high specific capacitance with a scan rate of 500 mV/s and 10 A/g,showing a big advantage in the application of supercapacitors.

    To probe the conductive property occurring at electrode/electrolyte interfaces, impedance spectra of different nanostructured CrNs were obtained. The impedance curves of CrN nanoparticles,microlayers,and microspheres were approximately vertical, indicating that the three types of CrN nanostructures all exhibit capacitance characteristics. The intercept between the impedance curve of the sample in the highfrequency region and theXaxis can reflect the internal resistance (Rs) of the electrode material. As shown in the insets of Figs.7(a)and 7(c),theRsfor CrN nanoparticles,microlayers, and microspheres were 1.5 ?, 2.9 ?, and 0.9 ?, respectively. Among them,the internal resistance of microlayer CrN was the largest, due to a large number of voids in the crosssection of the microlayered CrN.For microspheres CrN,Rsis significantly smaller than that of other nanostructures, proving porous spherical CrN has the best conductive property. It was even smaller than that of TMOs electrode materials,such as Cr2O3(Rs= 2.3 ?),[25]MoO3(Rs= 2.22 ?),[26]V2O5(Rs=1.3 ?).[27]

    Fig.7. EIS plots of CrN with different nanostructures: (a)nanoparticles,(b)microlayers and microspheres. The insets display the impedance spectra in the high-frequency region.

    Comparing CrN electrode materials with different nanostructures, the specific capacitance was as follows: 82.4 F/g(nanoparticles)>126.7 F/g (microlayers)<213.2 F/g (microspheres). They were higher than that of other reported CrN electrodes, such as CrN nanoparticles (75 F/g) and CrN film(41.6 F/g).[11,20]The porous microspherical CrN had the biggest specific capacitance, due to the large specific surface area. According to the results of nitrogen adsorption and desorption (Fig. 8(a)), the specific surface areas of as-obtained CrN nanoparticles,microlayers,and microspheres were 13.7,28.6, and 58.1 cm3/g, respectively. Compared with the other two nanostructures, the specific surface area of microspherical CrN was significantly increased. As shown in Fig. 8(b),the capacity retention rate of the porous spherical CrN nanostructure after 5000 cycles in 1-mol/L KOH solution is 96%,demonstrating its excellent cycle stability in strong alkaline electrolytes.

    Fig.8. (a)Nitrogen adsorption–desorption isotherms of CrN with different nanostructures. (b)Cycling stability of CrN microspheres at room temperature.(c)Ragone plot of supercapacitors for CrN microsphers,V2O5 nanofibers,[27] V2O5 nanosheets,[29] Co3O4 thin sheets,[30] Mo0.1Ti0.9O2 nanoparticles,[31]MoO2/Mo2N nanobelts,[32] Cr2O3/CrN nanoshells,[13] TiN nanotubes,[33] TiN nanospheres,[34] VN nanowires,[35] and Mo3N2 nanobelts.[28]

    By using the Eqs. (5) and (4), we calculated the power density (443.4 W/kg) and energy density (28.9 Wh/kg) of porous spherical CrN. By comparing the energy density and power density of other metal oxide and metal nitride electrode materials,[27–35]porous microspherical CrN had excellent supercapacitor characteristics (Fig. 8(c)). A large number of studies have shown that electrode materials with different nanostructures exhibit different electrochemical properties. In the samples we constructed,the porous spherical CrN exhibits remarkable electrochemical performance,and the reason was summarized:by the following points:(i)A smaller internal resistance can effectively promote the rapid transfer of charges and shorten the charge and discharge time;[36,37](ii)The porous microspherical nanostructure has a larger specific surface area and successfully constructed a three-dimensional electrical charge network to further enhance the charge transfer rate.[38]

    4. Conclusion

    In this work, we provide a new strategy for the design and development of nanostructural CrN electrode materials with different morphologies (nanoparticles, microlayers, and microspheres). The specific capacitances of the three nanostructured CrNs were: 213.2 F/g (microspheres)>126.7 F/g(microlayers)>82.4 F/g(nanoparticles). Importantly the capacity retention rate of porous CrN microspheres is 96%after 5000 cycles in 1-mol/L KOH solution, and its energy density and power density reached 28.9 Wh/kg and 443.4 W/kg.These characteristics could effectively improve the energy storage characteristics of the electrode material.

    猜你喜歡
    劉倩高志朱家
    Anisotropic plasmon dispersion and damping in multilayer 8-Pmmn borophene structures
    欲訪江南媚,醉夢(mèng)朱家
    本期名家—高志祥
    高志剛
    Shallow-water sloshing motions in rectangular tank in general motions based on Boussinesq-type equations *
    Rethinking Emotional Branding: Challenges, Risks and Unintended Consequences of Emotional Branding
    商情(2018年10期)2018-03-29 07:14:58
    Jamais trop tard
    跟我學(xué)英語
    Un enfant ou deux?
    The dynamics of the floodwater and the damaged ship in waves*
    日韩av在线大香蕉| 国产精品九九99| 欧美日韩精品网址| 在线观看免费视频日本深夜| 丁香六月欧美| 亚洲精品久久午夜乱码| 高清在线国产一区| x7x7x7水蜜桃| 桃色一区二区三区在线观看| 热99re8久久精品国产| 国产成人一区二区三区免费视频网站| 一进一出抽搐动态| 一进一出抽搐动态| 精品无人区乱码1区二区| 麻豆国产av国片精品| 国产97色在线日韩免费| 亚洲第一欧美日韩一区二区三区| 成人黄色视频免费在线看| 久久久久久大精品| 老司机午夜福利在线观看视频| 18禁美女被吸乳视频| 国产亚洲av高清不卡| 午夜两性在线视频| 中文亚洲av片在线观看爽| 热re99久久精品国产66热6| 亚洲一区二区三区色噜噜 | 精品久久久久久久久久免费视频 | 12—13女人毛片做爰片一| 日韩精品青青久久久久久| 亚洲成人精品中文字幕电影 | 18禁美女被吸乳视频| 啪啪无遮挡十八禁网站| 亚洲一区二区三区欧美精品| 青草久久国产| 视频区图区小说| 亚洲成国产人片在线观看| 法律面前人人平等表现在哪些方面| 久久伊人香网站| 精品久久久久久久久久免费视频 | 久久久久亚洲av毛片大全| 国产成人系列免费观看| 美女大奶头视频| 在线永久观看黄色视频| 长腿黑丝高跟| 久久精品人人爽人人爽视色| 人成视频在线观看免费观看| 久久性视频一级片| 亚洲精品国产区一区二| 日本黄色视频三级网站网址| 日韩成人在线观看一区二区三区| 午夜福利,免费看| 国产伦人伦偷精品视频| 国产精品成人在线| 精品午夜福利视频在线观看一区| xxx96com| 不卡av一区二区三区| 一级a爱视频在线免费观看| 18禁观看日本| 午夜影院日韩av| 一二三四社区在线视频社区8| 91av网站免费观看| 青草久久国产| 夜夜夜夜夜久久久久| 正在播放国产对白刺激| 午夜91福利影院| 久热爱精品视频在线9| 人人妻,人人澡人人爽秒播| 丰满的人妻完整版| 日韩三级视频一区二区三区| av在线天堂中文字幕 | 欧美另类亚洲清纯唯美| 怎么达到女性高潮| 在线观看舔阴道视频| 午夜激情av网站| 女人被躁到高潮嗷嗷叫费观| 亚洲精品一区av在线观看| avwww免费| 亚洲av成人av| 一个人免费在线观看的高清视频| 老鸭窝网址在线观看| 无人区码免费观看不卡| 国产片内射在线| 色播在线永久视频| 黑人巨大精品欧美一区二区mp4| 亚洲精品中文字幕在线视频| 久久人人精品亚洲av| av欧美777| 亚洲中文av在线| 母亲3免费完整高清在线观看| 97超级碰碰碰精品色视频在线观看| 久久影院123| 亚洲欧美一区二区三区久久| 成人特级黄色片久久久久久久| 亚洲国产毛片av蜜桃av| 亚洲熟妇熟女久久| 在线观看午夜福利视频| 性欧美人与动物交配| 国产日韩一区二区三区精品不卡| 亚洲欧美一区二区三区久久| 99久久久亚洲精品蜜臀av| 亚洲激情在线av| 黑丝袜美女国产一区| 亚洲人成电影观看| 美女扒开内裤让男人捅视频| 成人精品一区二区免费| 精品一区二区三区视频在线观看免费 | 琪琪午夜伦伦电影理论片6080| 国产精品 国内视频| 十分钟在线观看高清视频www| 亚洲欧美日韩高清在线视频| 亚洲专区国产一区二区| 精品电影一区二区在线| 久热这里只有精品99| 免费女性裸体啪啪无遮挡网站| 嫁个100分男人电影在线观看| 亚洲avbb在线观看| 91在线观看av| 久久久久久人人人人人| 97碰自拍视频| 日本精品一区二区三区蜜桃| 国产一卡二卡三卡精品| 97人妻天天添夜夜摸| 18禁观看日本| 国产av在哪里看| 一级毛片精品| 欧美成人午夜精品| 精品人妻1区二区| 亚洲成av片中文字幕在线观看| 精品福利永久在线观看| 首页视频小说图片口味搜索| av国产精品久久久久影院| 又紧又爽又黄一区二区| 亚洲精品一区av在线观看| 亚洲av美国av| 一个人观看的视频www高清免费观看 | av国产精品久久久久影院| 中文亚洲av片在线观看爽| 国产xxxxx性猛交| 香蕉丝袜av| av福利片在线| 国产精品永久免费网站| 中文字幕精品免费在线观看视频| 动漫黄色视频在线观看| 日本 av在线| 性色av乱码一区二区三区2| 欧美日韩福利视频一区二区| 国产片内射在线| 欧美精品亚洲一区二区| 亚洲国产精品999在线| 五月开心婷婷网| 亚洲五月婷婷丁香| 成熟少妇高潮喷水视频| 亚洲av片天天在线观看| 欧美日韩黄片免| 国产高清激情床上av| 国产伦人伦偷精品视频| 成人手机av| 多毛熟女@视频| 免费日韩欧美在线观看| 午夜影院日韩av| 午夜福利免费观看在线| 十八禁人妻一区二区| 亚洲欧美精品综合久久99| 91九色精品人成在线观看| 国产精品综合久久久久久久免费 | 老熟妇仑乱视频hdxx| 88av欧美| 亚洲一区二区三区欧美精品| 成年女人毛片免费观看观看9| 黑人操中国人逼视频| 国产精品综合久久久久久久免费 | 在线观看一区二区三区激情| 久久久精品欧美日韩精品| 欧美精品一区二区免费开放| 国产亚洲欧美精品永久| 91九色精品人成在线观看| 亚洲伊人色综图| av有码第一页| 久99久视频精品免费| 午夜免费鲁丝| 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| 日韩欧美免费精品| 操美女的视频在线观看| 亚洲国产欧美网| 亚洲少妇的诱惑av| 久久久久久大精品| 真人一进一出gif抽搐免费| 法律面前人人平等表现在哪些方面| 国产免费男女视频| 婷婷精品国产亚洲av在线| 久久久国产精品麻豆| 三级毛片av免费| 久久国产亚洲av麻豆专区| 成人av一区二区三区在线看| 国产精品二区激情视频| 欧美色视频一区免费| 精品国产乱子伦一区二区三区| 不卡一级毛片| 国产一区二区三区综合在线观看| 国产欧美日韩综合在线一区二区| 午夜免费鲁丝| 丰满饥渴人妻一区二区三| av视频免费观看在线观看| a级毛片在线看网站| 高清在线国产一区| 亚洲精品中文字幕在线视频| 十八禁网站免费在线| 男人操女人黄网站| 国产激情欧美一区二区| 中文亚洲av片在线观看爽| 91麻豆精品激情在线观看国产 | 亚洲精品成人av观看孕妇| 1024香蕉在线观看| 国产精品 国内视频| 夫妻午夜视频| 一级黄色大片毛片| 在线观看免费视频网站a站| 久久久久久久精品吃奶| 成人三级做爰电影| 成年版毛片免费区| 精品人妻在线不人妻| 亚洲aⅴ乱码一区二区在线播放 | 亚洲精品一卡2卡三卡4卡5卡| 国产高清激情床上av| 日日干狠狠操夜夜爽| 少妇的丰满在线观看| 99国产精品一区二区三区| 精品一区二区三卡| 久久精品91无色码中文字幕| 久久精品亚洲av国产电影网| 亚洲色图 男人天堂 中文字幕| √禁漫天堂资源中文www| 欧美日韩精品网址| 欧美黄色片欧美黄色片| 99久久国产精品久久久| 91老司机精品| 国产男靠女视频免费网站| 老汉色av国产亚洲站长工具| 日本vs欧美在线观看视频| 亚洲自偷自拍图片 自拍| 国产不卡一卡二| 精品久久久久久久毛片微露脸| 欧美日韩亚洲国产一区二区在线观看| 国产无遮挡羞羞视频在线观看| 黄色视频,在线免费观看| 级片在线观看| 99久久人妻综合| 久久久久久久午夜电影 | 亚洲中文日韩欧美视频| 午夜免费成人在线视频| 日韩高清综合在线| 国产成人啪精品午夜网站| 成人三级做爰电影| 国产无遮挡羞羞视频在线观看| 极品教师在线免费播放| 亚洲国产中文字幕在线视频| 亚洲 国产 在线| 日韩av在线大香蕉| 国产激情欧美一区二区| 久久国产精品男人的天堂亚洲| 欧美成狂野欧美在线观看| 超碰成人久久| 久久久水蜜桃国产精品网| 久久精品国产99精品国产亚洲性色 | 在线av久久热| 丰满饥渴人妻一区二区三| 亚洲九九香蕉| 国产精品永久免费网站| 亚洲 国产 在线| 啪啪无遮挡十八禁网站| 亚洲精品国产区一区二| 男女床上黄色一级片免费看| 一夜夜www| 色综合欧美亚洲国产小说| 亚洲av成人av| 极品教师在线免费播放| 亚洲第一欧美日韩一区二区三区| 看免费av毛片| 欧美日韩亚洲高清精品| 日本 av在线| 成年人免费黄色播放视频| 老司机靠b影院| 久久香蕉国产精品| 精品日产1卡2卡| 成人av一区二区三区在线看| 国产午夜精品久久久久久| 亚洲男人的天堂狠狠| 18禁观看日本| 男女下面插进去视频免费观看| 一级毛片女人18水好多| 国产在线观看jvid| 高清毛片免费观看视频网站 | 精品电影一区二区在线| 亚洲一码二码三码区别大吗| 欧美最黄视频在线播放免费 | 欧美在线一区亚洲| xxx96com| 日本五十路高清| 电影成人av| 国产99久久九九免费精品| 99久久人妻综合| 欧美激情高清一区二区三区| 国内久久婷婷六月综合欲色啪| 国产高清视频在线播放一区| 欧美日韩亚洲综合一区二区三区_| 色尼玛亚洲综合影院| 动漫黄色视频在线观看| 国产有黄有色有爽视频| xxxhd国产人妻xxx| 亚洲成人精品中文字幕电影 | 真人做人爱边吃奶动态| av在线播放免费不卡| 制服诱惑二区| 日韩免费高清中文字幕av| 亚洲国产精品999在线| 久久亚洲真实| 精品卡一卡二卡四卡免费| 亚洲久久久国产精品| 亚洲免费av在线视频| 国产99白浆流出| 亚洲av第一区精品v没综合| 丁香六月欧美| 亚洲精品久久成人aⅴ小说| 很黄的视频免费| 激情视频va一区二区三区| 男女之事视频高清在线观看| 亚洲 欧美一区二区三区| 欧美日本亚洲视频在线播放| 69精品国产乱码久久久| 色婷婷久久久亚洲欧美| 人人妻人人爽人人添夜夜欢视频| e午夜精品久久久久久久| 亚洲欧美日韩另类电影网站| 国产三级黄色录像| 精品欧美一区二区三区在线| 亚洲中文字幕日韩| 最近最新中文字幕大全免费视频| 黄片播放在线免费| 国产精品久久久av美女十八| 亚洲国产精品一区二区三区在线| 少妇的丰满在线观看| 国产免费男女视频| 国产av一区二区精品久久| 久久久精品国产亚洲av高清涩受| 丰满饥渴人妻一区二区三| 国产成人精品无人区| 黑人操中国人逼视频| 99精品欧美一区二区三区四区| 色综合欧美亚洲国产小说| 18禁观看日本| 久久午夜亚洲精品久久| 不卡av一区二区三区| 亚洲精品美女久久久久99蜜臀| 国产亚洲欧美精品永久| 午夜免费成人在线视频| 真人一进一出gif抽搐免费| 欧美日韩精品网址| 嫩草影院精品99| 黄片播放在线免费| 黄色女人牲交| 国产成人欧美在线观看| 久久久久国产精品人妻aⅴ院| 十八禁网站免费在线| 成人三级做爰电影| 亚洲 国产 在线| 十八禁人妻一区二区| 欧美日韩精品网址| 一夜夜www| 韩国av一区二区三区四区| 国产黄a三级三级三级人| 最新美女视频免费是黄的| 亚洲人成网站在线播放欧美日韩| av在线天堂中文字幕 | 亚洲精品久久午夜乱码| 男人舔女人下体高潮全视频| 精品一区二区三区四区五区乱码| 丰满饥渴人妻一区二区三| 最近最新免费中文字幕在线| 亚洲va日本ⅴa欧美va伊人久久| 美女高潮到喷水免费观看| www.熟女人妻精品国产| 日本欧美视频一区| 夜夜夜夜夜久久久久| 欧美日韩亚洲高清精品| 最近最新免费中文字幕在线| 国产熟女xx| 91精品三级在线观看| 校园春色视频在线观看| 91字幕亚洲| 桃红色精品国产亚洲av| 精品久久久精品久久久| 久久精品影院6| 久久午夜综合久久蜜桃| 午夜影院日韩av| 操出白浆在线播放| 亚洲中文字幕日韩| 欧美激情 高清一区二区三区| 欧美日本中文国产一区发布| 精品欧美一区二区三区在线| 亚洲全国av大片| 大香蕉久久成人网| 欧美国产精品va在线观看不卡| 国产av一区二区精品久久| 午夜老司机福利片| 久久精品91蜜桃| 满18在线观看网站| 99国产精品99久久久久| 欧美激情 高清一区二区三区| 免费久久久久久久精品成人欧美视频| 黑人巨大精品欧美一区二区蜜桃| 国产麻豆69| 最好的美女福利视频网| 成人三级做爰电影| 久久中文看片网| 夜夜躁狠狠躁天天躁| 啦啦啦 在线观看视频| 午夜日韩欧美国产| 久久99一区二区三区| 亚洲精品久久成人aⅴ小说| 亚洲男人的天堂狠狠| 一进一出好大好爽视频| 亚洲情色 制服丝袜| 日韩欧美一区二区三区在线观看| 自拍欧美九色日韩亚洲蝌蚪91| 九色亚洲精品在线播放| 999精品在线视频| 51午夜福利影视在线观看| 国产成人av激情在线播放| 少妇被粗大的猛进出69影院| 精品日产1卡2卡| av中文乱码字幕在线| 国产国语露脸激情在线看| 国产成人欧美| 中文欧美无线码| 亚洲精品成人av观看孕妇| 国产精品久久视频播放| 久久精品亚洲熟妇少妇任你| 亚洲人成77777在线视频| 午夜免费鲁丝| 人人妻人人爽人人添夜夜欢视频| 中文字幕最新亚洲高清| 日韩欧美一区视频在线观看| 久久久久国产一级毛片高清牌| 纯流量卡能插随身wifi吗| 久久久久国内视频| 美女国产高潮福利片在线看| 狠狠狠狠99中文字幕| 久久精品国产综合久久久| 国产精品一区二区三区四区久久 | 又黄又爽又免费观看的视频| 香蕉丝袜av| 亚洲av片天天在线观看| 99在线人妻在线中文字幕| 亚洲情色 制服丝袜| 久久中文看片网| 国产日韩一区二区三区精品不卡| 欧美黑人精品巨大| 久久精品国产99精品国产亚洲性色 | 色尼玛亚洲综合影院| 一a级毛片在线观看| 国产aⅴ精品一区二区三区波| 长腿黑丝高跟| 欧美乱色亚洲激情| 18禁裸乳无遮挡免费网站照片 | 国产成人免费无遮挡视频| 18禁美女被吸乳视频| 日韩av在线大香蕉| 99久久99久久久精品蜜桃| 嫩草影院精品99| 精品卡一卡二卡四卡免费| 国产一区二区在线av高清观看| 正在播放国产对白刺激| 丰满的人妻完整版| 国产高清国产精品国产三级| 免费少妇av软件| 精品国产一区二区久久| 身体一侧抽搐| 在线观看午夜福利视频| 女性被躁到高潮视频| 18禁美女被吸乳视频| 久久精品亚洲精品国产色婷小说| 国产一区二区三区在线臀色熟女 | 亚洲国产看品久久| 狂野欧美激情性xxxx| 91成人精品电影| 女人被狂操c到高潮| 久久国产乱子伦精品免费另类| 精品国产一区二区久久| 国产欧美日韩一区二区三区在线| 中文字幕人妻熟女乱码| 午夜精品国产一区二区电影| 久久性视频一级片| 91字幕亚洲| 校园春色视频在线观看| 国产欧美日韩一区二区三| 亚洲 欧美一区二区三区| 一夜夜www| 天堂俺去俺来也www色官网| 无人区码免费观看不卡| 一级a爱片免费观看的视频| 可以免费在线观看a视频的电影网站| 在线观看一区二区三区激情| 黑人欧美特级aaaaaa片| 成在线人永久免费视频| 在线观看免费视频日本深夜| 亚洲欧美激情综合另类| 久久天堂一区二区三区四区| 精品国产国语对白av| 久久99一区二区三区| 欧美日韩黄片免| 桃色一区二区三区在线观看| 1024香蕉在线观看| 香蕉久久夜色| 国产精华一区二区三区| 97碰自拍视频| 久久久久久亚洲精品国产蜜桃av| 亚洲国产精品sss在线观看 | 国产精品久久久久久人妻精品电影| 成人三级做爰电影| 热re99久久精品国产66热6| 欧美精品一区二区免费开放| 一二三四在线观看免费中文在| 人成视频在线观看免费观看| 97人妻天天添夜夜摸| 午夜福利在线免费观看网站| av天堂久久9| 国产精品免费一区二区三区在线| √禁漫天堂资源中文www| 嫩草影视91久久| 69精品国产乱码久久久| 精品电影一区二区在线| 国产精品秋霞免费鲁丝片| 国产男靠女视频免费网站| 亚洲一区高清亚洲精品| 国产精品香港三级国产av潘金莲| 国产精品一区二区三区四区久久 | 国产在线观看jvid| 亚洲成国产人片在线观看| 久久精品国产亚洲av香蕉五月| 黄片播放在线免费| 亚洲狠狠婷婷综合久久图片| 免费日韩欧美在线观看| 18禁裸乳无遮挡免费网站照片 | 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲全国av大片| 日韩一卡2卡3卡4卡2021年| 久久人人精品亚洲av| 夫妻午夜视频| www.999成人在线观看| 91在线观看av| 一级片免费观看大全| 麻豆久久精品国产亚洲av | 精品电影一区二区在线| 国产精品美女特级片免费视频播放器 | 色综合婷婷激情| 久久精品国产亚洲av高清一级| 国产亚洲av高清不卡| 日韩有码中文字幕| 美女大奶头视频| www.熟女人妻精品国产| 亚洲熟妇中文字幕五十中出 | 一夜夜www| 午夜两性在线视频| 无人区码免费观看不卡| 国产精品久久久av美女十八| 久久午夜综合久久蜜桃| 久久精品人人爽人人爽视色| 热99国产精品久久久久久7| a级毛片在线看网站| 亚洲精品国产区一区二| 色婷婷av一区二区三区视频| 国产又色又爽无遮挡免费看| 国产成人精品在线电影| 9191精品国产免费久久| 亚洲国产精品一区二区三区在线| 一边摸一边抽搐一进一出视频| 超色免费av| 成人国产一区最新在线观看| 性欧美人与动物交配| 欧美午夜高清在线| 精品高清国产在线一区| 交换朋友夫妻互换小说| 色哟哟哟哟哟哟| 色婷婷av一区二区三区视频| 亚洲国产看品久久| 久久人人爽av亚洲精品天堂| 国产精品爽爽va在线观看网站 | 18禁美女被吸乳视频| 亚洲三区欧美一区| 日本wwww免费看| 日韩精品免费视频一区二区三区| xxx96com| av在线天堂中文字幕 | 亚洲精品美女久久av网站| 午夜福利影视在线免费观看| 中亚洲国语对白在线视频| 国产欧美日韩一区二区三区在线| 性欧美人与动物交配| a级片在线免费高清观看视频| 精品卡一卡二卡四卡免费| 中文字幕人妻丝袜制服| 亚洲欧美日韩另类电影网站| 欧美日韩福利视频一区二区| 精品久久久久久,| √禁漫天堂资源中文www| 日本黄色日本黄色录像| 美国免费a级毛片| 这个男人来自地球电影免费观看| 日韩精品青青久久久久久| 国产激情久久老熟女| 久久精品影院6| 无限看片的www在线观看| 大香蕉久久成人网| 国产三级在线视频|