• <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 ?

    Cathode infiltration with enhanced catalytic activity and durability for intermediate-temperature solid oxide fuel cells

    2022-06-18 03:00:10YinghuNiuWeirongHuoYundongYuWenjunLiYulinChenWeiqingLv
    Chinese Chemical Letters 2022年2期

    Yinghu Niu, Weirong Huo, Yundong Yu, Wenjun Li, Yulin Chen, Weiqing Lv,*

    a Yangtze Delta Region Institute (Huzhou) & School of Physics & School of Materials and Energy, University of Electronic Science and Technology of China,Huzhou 313001, China

    b School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384, China

    ABSTRACT To lower the operation temperature and increase the durability of solid oxide fuel cells (SOFCs), increasing attentions have been paid on developing cathode materials with good oxygen reduction reaction (ORR)activity at intermediate-temperature (IT, 500–750 °C) range.However, most cathode materials exhibit poor catalytic activity, or they thermally mismatch with SOFC electrolytes and undergo severe degeneration.Infiltrating catalysts on existing backbone materials has been proved to be an efficient method to construct highly active and durable cathodes.In this mini-review, the advantages of infiltration-based cathode compared with new material-based cathodes are summarized.The merits and drawbacks of different backbones are illustrated.Different types of catalysts for infiltration are depicted in detail.Suggestions on the material/structure optimization of the infiltrated cathodes of IT-SOFC are provided.

    Keywords:Infiltration Cathode Solid oxide fuel cell Oxygen oxidation reaction Durability

    1.Introduction

    Solid oxide fuel cells (SOFCs) are considered sustainable highefficient hydrogen-based energy production devices.The advantages of SOFCs include: (i) High power generation efficiency (>60%for electricity,>85% for electricity-heat cogeneration); (ii) Widely adaptable to a variety of fuels, such as H2, biogas, nature gas,and methane; (iv) Precious-metal catalysts are not necessary; (v)High volumetric power density and gravimetric power density (~10 W/cm3and ~3 kW/kg) [1].A SOFC consists of three key components: a dense electrolyte, a porous cathode and a porous anode.The working principle of SOFC is shown in Fig.1.The hydrogen oxidation reaction (HOR) occurs at the anode and releases electrons.The generated electrons move to the anode surface and travel along the external circuit to the cathode.The oxygen reduction reaction (ORR) occurs at the active sites of the SOFC cathode and produces O2-ions.The O2-ions transfer to the cathode/electrolyte interface, and migrate in the electrolyte to the anode/electrolyte interface.The dissociated H+ions in the active area of the anode combine with oxygen ions to finally produce H2O.

    Fig.1.Schematic of a SOFC based on an O2- conducting electrolyte.

    SOFCs are typically operated above 800 °C to ensure the good catalytic activity, acceptable ionic and electronic conductivity.High operating temperatures bring challenges on sealing issue, slow response to start up and cooling down, high total system cost and fast material degradation [2].To solve the challenges, SOFCs working at intermediate temperature range (500–750 °C) are desired(IT-SOFC).At IT temperature ranges, the performance and output power of SOFCs strongly depend on the ORR catalytic activity of cathode materials.In the ORR process, there are two critical steps, the reduction of oxygen at the surface active sites and the transport of oxygen ions away from the sites [3,4].In addition, the cathode materials should be chemically compatible, and have matched thermal expansion coefficient (TEC,α) with other components of SOFCs.Cathode materials should be in low cost and show long-term stability.There are two strategies to enhance the cathode performance: developing new materials and modifying the existing cathode materials.The conventional lanthanum strontium magnesium (LSM) cathode exhibits good performance above 800 °C, but cannot work at the IT temperature range.As shown in Fig.2, the TEC values of commonly used electrolytes such as yttrium stabilized zirconia (YSZ), strontium-/magnesiumdoped lanthanum gallate (LSGM), gadolinia doped ceria (GDC),samarium-doped cerium (SDC) and BaZr0.8-xCexY0.2O3-δ(BZCY) are in the range of 8.4 × 10-6~12.8 × 10-6K-1[5–10].Among the cathode materials developed [8,11–36], the commercial cathode of lanthanum strontium cobalt ferrite (LSCF) exhibits acceptable TEC (α100~600= 15.3 × 10-6K-1) [19,20] and good catalytic activity at the IT temperatures, but the performance of LSCF drops dramatically with decreasing temperature due to Sr segregation [37].Although new cathode materials with high ORR catalytic activity at low temperatures have been developed, such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) and Sm0.5Sr0.5CoO3-δ(SSC), their thermal stability and compatibility are far from satisfactory [38].Surface modification on some traditional commercialized cathode materials is considered to be a very promising strategy for ITSOFCs cathodes with high ORR activity and durability [39].

    Fig.2.The thermal expansion coefficient (bar chart in left), polarization resistance (bar chart in right) and electronic conductivity (blue star) of cathode materials at 600 .The cathode materials are Ba0.5Sr0.5Co0.8Fe0.2O3-δ [11,12], BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) [13], Ba1-xCo0.7Fe0.2Nb0.1O3-δ (0≤x≤0.1) (BCFN) [14,15]; La0.5Ba0.5CoO3-δ(LBC) [8,16], La0.2Ba0.8Co0.7Fe0.3O3-δ (LBCF) [17], LaBa0.5Sr0.5Co2O5+δ (LBSC) [18], La0.6Sr0.4Co0.2Fe0.8O3-δ (x = 0.4) [19,20], La2NiO4-δ (LNO) [21], NdBaCo2O5+δ (NBC) [22],NdBaCo1.5Fe0.5O5+δ (NBCF) [22], NdxBa1-xCo0.7Fe0.3O3-δ (NBCF) [17], NdBa0.5Sr0.5Co1.5Fe0.5O5+δ (NBSCF) [23,24], GdBaCo2O5+δ (GBC) [22], GdBa0.5Sr0.5Co2O5+δ (GBSC) [25],GdBaCo1.5Fe0.5O5+δ (GBCF) [22], GdBa0.5Sr0.5Co1.5Fe0.5O5+δ (GBSCF) [26], PrBa1-xCo2O5+δ (0≤x≤0.08)(PBC) [27], PrBa0.5Sr0.5Co2O5+δ(PBSC) [28], Pr0.1Ba0.9Co0.7Fe0.3O3-δ(PBCF)[17], PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) [29], Sm0.5Ba0.5CoO3-δ (SBC) [16,30], Sm0.45Ba0.05Sr0.5Co0.8Fe0.2 O3-δ (SBSCF) [31], Sm0.35Ba0.15Sr0.5Co0.8Fe0.2 O3-δ (SBSCF) [31],SmBa0.5Sr0.5Co2O5+δ (SBSC) [25,30], SrCo0.8Fe0.1Nb0.1O3-δ (SCFN) [32], SrCo0.9Ta0.1O3-δ(SCT) [33,34], and Sm0.5Sr0.5CoO3 (SSC) [30,35,36].The data for the thermal expansion coefficient of some common electrolyte materials are added in the bar chart in left.Electrolyte materials includes (Y2O3)0.08(ZrO2)0.92 (YSZ) [5], Ce0.8Sm0.2O2-δ (SDC)[6], GdxCe1-xO2-δ (GDC) (x = 0.1, 0.2) [5,7], La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) [8], and BaZr0.8-xCexY0.2O3-δ (0.1≤x≤0.5) [9].

    Surface modification can be achieved by several techniques, including atomic layer deposition (ALD) [40,41], pulsed laser deposition (PLD) [42] and solution infiltration.Among all the methods, infiltration/impregnation has been proved to be an effective method to construct SOFC in large scale without using any expensive equipment.The coating materials for infiltration are versatile and diverse [43].In a typical infiltration process, a liquid solution containing the desired electrocatalyst precursors is introduced into a previously sintered porous backbone formed on the electrolyte.Infiltrated phases are formed upon calcination at a certain temperature.Performing the process once or several times can achieve a desired electrocatalyst loading within the pores of the porous backbones.In this minireview, an overview of the infiltration method will be provided, including the advantages and the disadvantages,the developed backbones, the coating materials, the existing issues and the perspectives.

    2.The advantages of infiltration for IT-SOFC cathodes

    The main advantages of infiltration for IT-SOFC cathodes include: (1) A wide range of active materials for surface coating are allowed to be used, even for the material which is not intrinsic a good cathode material due to TEC mismatch [8,44].For instance, the electronic conductivity of La0.5Ba0.5CoO3-δ(LBC) at 600in air is relatively high (σ=1400 S/cm) as shown in Fig.2.However, the application of LBC (α100-900= 26.4 × 10-6K-1)has been limited since its thermal incompatibility to most electrolyte materials (e.g., the TEC of La0.8Sr0.2Ga0.8Mg0.2O2.8(LSGM)electrolyte is 12.0 × 10-6K-1) [8].LBC infiltrated LSGM is a thermally stable SOFC cathode.The TEC of LBC infiltrated LSGM(α100-900=12.5 × 10-6K-1) is close to that of the LSGM electrolyte, and even lower than LBC/LSGM composite (16.2 × 10-6K-1).(2) Both the surface composition and the surface structure can be altered after surface infiltration [45,46].The catalyst coating enables the formation of nano structures with high electrocatalytic activity due to the increased surface area and the enlarged triple-phase boundary (TPB) areas [43,47–50].(3) The infiltration method allows relatively low heat treatment temperatures (<900°C) which avoids the reduction of electrocatalyst/gas and electrocatalyst/ionic conductor (IC) interfacial areas induced by the crystal particle coarsening, and minimizes reactions between the infiltrated coating material and the backbone phase.(4) Infiltration can increase the durability of cathode and the tolerance to contamination as shown in Table 1 [20,44,51–60].The degradation of SOFC cathode is commonly caused by the formation of secondary phases or the reactions of the segregated phases with the gas species [56].These secondary phases result in decreased surface(bulk) electronic conductivity [61–65].The contaminants such as CO2[66], H2O [67], SO2and H2S [56,68] from environmental gas phases, the volatile chromium species [55,58] from interconnector and boron species from the sealing materials [69] will accelerate the degradation [68].The surface coating introduces a surface barrier layer, which suppresses the contamination to the surface of backbones.For instance, the segregated Sr on the LSCF cathode reacts with CrO3to form insulating SrCrO4, which blocks the cathode ORR active sites.Surface coating can effectively suppress the surface segregation and improve the tolerance to chromium [55–60,69–71].Yanget al.[44] found that SrCo0.9Ta0.1O3-δacted as a Cr getter on the LSCF surface, which can mitigate Cr poisoning.In our previous work, we found that the infiltrated BaCO3phase was almost inert to Cr species [20].Currently most studies are focused on the Cr contamination of the cathode (Table 1) [20,44,51–55,57–60].In addition to Cr contamination, water also influences dramatically the durability of IT-SOFCs, especially for SOFCs based on proton conductors [72].In future, more attentions should be paid on the water-tolerance performance of cathodes.

    Table 1 Summary of infiltrated cathodes with enhanced performance and durability in the literature from 2012 to 2021.

    3.Backbones for the surface infiltration

    The infiltration method is a multi-step preparation process,consisting of the formation of a pre-sintering porous backbone and the deposition of an active catalyst (the infiltrate).The electrode performance is influenced by the composition and the morphology of both the infiltrate and the backbone.Pre-sintering of backbones at high temperatures is important since it ensures the high effective electron or oxygen-ion conduction.Backbones with continuous pore structure are favorable for infiltration.In addition, the backbone material should be thermally and chemically compatible with electrolyte to achieve the structure and chemical stability.Three types of common backbones are widely used, including the singlephase electrolyte-based backbone, the single-phase cathode-based backbone and the multi-phase (MP) composite backbone, as shown in Fig.3.

    Fig.3.The schematics of (a) an electrolyte-based backbone, (b) a single-phase electrode-based backbone, (c) a multi-phase composite backbone.The dense box stands for the electrolyte of SOFC.The porous structure stands for the infiltration backbones.EC represents electronic conductor, MIEC represents mixed ionic and electronic conductor.

    3.1.Single-phase electrolyte-based backbones

    Many researchers have studied the infiltration based on the backbones of electrolyte materials.The advantages of the electrolyte backbones include the facile preparation process and the compatible TEC with electrolyte.For example, the porous-denseporous electrolyte backbone can be fabricated by one-step sintering of the green tape through pressing method or tape casting method [73].The commonly used electrolyte-based backbone materials in SOFCs are ionic conductors (IC) including YSZ [73–77],SDC [78], GDC [79–81], LSGM [8,82,83], scandia-stabilized zirconia (ScSZ) [84], (Bi0.8Er0.2)2O3(ESB) [2] and so on.Proton conductors (e.g., BaZr1-xYxO3-δ(BZY), BaCe1-xYxO3(BCY) and doped BZY (BCY)) are also used as backbones in SOFCs based on protonconducting electrolytes [85].The infiltrated cathodes based on electrolyte backbones show relatively lowRpas shown in Table 2[8,73–83,85,86].However, electrolyte-based backbones only conduct oxygen ions (or proton), sufficient amounts of electronically conductive materials must be infiltrated on electrolyte backbones by increasing the infiltration cycles to enhance the TPB length and to minimize the cathode electronic resistance.For instance, in some studies, researchers infiltrated up to 40 cycles or with catalyst amount over 45 wt% for sufficient loading [76,79].Therefore, the electrolyte backbone-based infiltration is typically a time-consuming multi-step process to infiltrate a considerable amount of material to ensure good electronic conductivity and sufficient TPB.The increased cost on raw materials such as some Cocontaining infiltrates should not be ignored [87–89].To reduce the infiltration time, new infiltration methods have been developed.For instance, The layer-by-layer (LbL)-assisted infiltration has been proposed to enhances surface wetting and to decrease the infiltration time [88].The ultrasonic spray infiltration and the inject printing infiltration techniques are viable in industrial or commercial level to produce large-area catalyst coated cathodes for SOFCs with high and stable performances [90,91].Atomic layer deposition (ALD) has been used to fabricate conformal and uniform catalyst coatings with atomic-scale thickness on backbones but still far from large-scale production [40,92].The infiltration followed by chemically-assisted electrodeposition allows us to achieve desired loading of cathode catalyst with reduced infiltration cycles and without using any expensive equipment [93,94].

    Table 2 The performances of electrolyte-backbone based infiltrated cathodes in the past 10 years.

    3.2.Single-phase cathode-based backbones

    The backbones made of cathode materials guarantee good electron transport.The infiltrations of various materials into either the porous electronic conductive (EC) or a mixed ionic–electronic conductive (MIEC) cathode backbones have been widely studied.Infiltrating ionic conductive materials into porous cathode backbones with low ionic conductivity, such as LSM or LaNi0.6Fe0.4O3-δ(LNF), can enhance the cathode ionic conduction and the effective three-phase boundary (TPB) area.At high temperatures (>800 °C),the LSM cathode has a high electronic conductivity, good chemical stability, high electrocatalytic activity, and matched TEC with many electrolyte materials [3,95–98].However, as the operating temperature decreases, the polarization resistance (Rp) of LSM and LSM/YSZ cathodes increases significantly due to the sluggish ORR kinetics.Infiltrating catalysts into porous LSM backbones can improve the cathode performance of IT-SOFCs.Akbariet al.[99] infiltrated La2NiO4into the LSM backbone, and found thatRpis reduced by 90.5% to 2.5Ωcm2at 650 °C and the ORR activation energy is decreased from 130 kJ/mol to 103 kJ/mol.However, the polarization resistance (or area specific resistance, ASR)is still much higher than the requirement for practical applications (<0.15Ωcm2) in IT-SOFCs [99,100].

    Different from electrolyte-based backbones and EC cathodebased backbones, MIEC cathode-based backbones show both good ionic conduction and electronic conduction, which broaden the types of infiltrated materials to even some non-electronic and non-ionic conducting oxides (e.g., CaO, MgO, BaO).LSCF has already been a commercial cathode at the intermediate temperatures from 600 °C to 750 °C [101,102].LSCF is also one of the widely used MIEC cathode backbones with both high ionic conductivity and good electronic conductivity and exhibits much better electrochemical performance as compared with most other cathode materials due to the relatively good ORR activity and the enlarged electrochemical active areas than traditional TPBs [102].LSCF have matched TEC with most electrolyte materials [58].All these properties make LSCF one of the most popular cathode candidates.However, at low temperatures (<650 °C), the relatively slow ORR kinetics limits the performance of LSCF cathode, resulting in increasedRpof the electrodes (>0.15Ωcm2).Therefore, considerable efforts have been made to develop catalysts on LSCF surface with high electrocatalytic ORR activity through infiltration.In addition, the long-term durability is another challenge for LSCF.The surface SrO segregation/enrichment alters the structure and composition of LSCF and is detrimental to the electro-catalytic activity and durability [95].The segregated SrO readily reacts with contaminants such as vaporized Cr species from the Cr-containing alloy.The surface infiltration of LSCF can not only increase the surface activity, but also inhibit the segregation of Sr or radiality reaction of Sr with contaminants.Due to the good MIEC property of LSCF backbone, there is no need for multiple infiltration cycles for high-loading catalyst.For instance, Namgunget al.[103] reported a one-step-infiltration for discrete SSC nanoparticles on the LSCF backbone by adopting of cetrimonium bromide (CTAB)-amino acid(glycine) in the stock solution.Chenet al.[58,104] demonstrated that using one-step infiltration process can significantly reduce theRpof the LSCF cathode.

    There are also some studies based on the infiltration of other MIEC cathode backbones, such as BSCF [53], PrBa0.5Sr0.5Co1.5Fe0.5O5+δ(PBSCF) [60], and Ba1-xCo0.7Fe0.2Nb0.1O3-δ(BCFN) [105].These cathode backbones are not widely used due to the higher content of Co and mismatched TEC with electrolytes (Fig.2,α >20 × 10-6K-1).Ruddlesden-Popper perovskite like La2NiO4-δ(LNO) has matched TEC with common electrolytes [106,107], the low-temperature performance of LNO cathodes has been improved by infiltration,but the performance still cannot meet the pratical requirements due to the large polarization resistance of the pristine LNO at low temperatures (Fig.2,Rp=3.86Ωcm2at 600) [21].In addition to the oxide cathodes mentioned above, the metal cathodes such as Ag are also used as backbones for infiltration.Metal backbones own matched TEC with other parts, high electrical conductivity and good formability.However, metal backbones are chemically unstable in oxidative atmosphere.

    3.3.Multi-phase composite backbones

    The composite backbones include IC-EC, IC-MIEC and EC-MIEC composites [108].Compared with the single-phase IC electrolyte backbones and the single-phase EC cathode backbones, IC-EC composite backbones (e.g., LSM/YSZ [109–111]) have prolonged threephase boundary.Wanget al.[112] co-infiltrated PdO and ZrO2on the LSM/YSZ electrode and obtained a polarization resistance of 0.40Ωcm2at 750 °C, which was 1/10 of that for bare LSM/YSZ cathode.For composite backbones, the chemical compatibility between composite materials needs to be considered.For example, many researchers found that La from LSM reacts with Zr from YSZ phase, forming an electrically insulating pyrochlore phase(La2Zr2O7) as the sintering temperature is higher than 900 °C[113–116].In recent years, extensive studies on composite backbones are based on GDC or SDC.GDC and SDC show less active with La in IC-MIEC composites.The combination of LSCF and GDC as backbone has been proved to be an ideal backbone to reduce the operating temperature [44,117,118].

    In summary, different types of infiltrated backbones are introduced in this section.For the electrolyte backbones, reducing the infiltration time is desired by developing new infiltration methods.For the single-phase cathode-based backbones, most studies still focus on conventional cathode materials such as LSCF.Other MIEC backbones are restricted by either their high price or their intrinsic properties.For the multi-phase composite backbones, since this type of backbones have elongated TPBs, their performances are very promising.Since the research on such backbones are still inadequate, there is a huge space to develop high-performance cathodes by infiltrating on such backbones.

    4.Catalysts for surface infiltration

    Several types of catalysts have been developed, including precious metals, oxygen ion-conducting oxides [55,119,120], mixed ionic and electronic conductors [70,121,122], non-ionic and nonelectronic conducting oxides [57,123].Besides, according to the chemical composition of the electro-catalysts, the catalyst on the surface can be divided into single-phase catalysts and multi-phase catalysts [104,124].The morphologies of the infiltrated catalysts on the surface of cathodes are diverse, including uniform coating layers, discrete nanoparticles, and conformal coating with discrete particles, as shown in Fig.4.The discrete nanoparticles have larger surface area for ORR than conformal coatings.However, the conformal coating has better durability and contaminants tolerance than the discrete nanoparticles coating since the conformal coatings can cover the entire cathode surface and avoid the coarsening issue of nanoparticles [44,58].The conformal coating with nanoparticles can achieve both high activity and durability than the aforementioned coatings.

    Fig.4.Schematics of the structures of the backbone and coatings.From (a) an asfired electrode backbone to three typical morphologies of infiltrated electrode after thermal treatment: (b) particle deposition, (c) thin film coating, and (d) conformal coating with nanoparticles.

    4.1.Precious metals

    Noble metals (e.g., Ag, Pd, Rh and Pt) have been used as catalysts coating on the cathodes due to the high catalytic activity, high oxygen solubility and permeability [125,126].In addition, precious metals such as silver can minimize the ohmic resistance due to their excellent electronic conductivity.Ag infiltration is frequently reported to enhance the performance of the cathodes such as LSM[127], LSCF [128] and LSCF/YSZ [129].However, the agglomeration of low-melting-point Ag decreases metal surface area and deteriorates the long-term stability of Ag-impregnated cathodes [130].To solve the agglomeration problem, it is found that co-infiltration of Ag and CeO2is an efficient way to inhibit Ag agglomeration on the surface of cathodes [130,131].CeO2has a high melting point which makes it stable under high temperature.Hence, ceria nanoparticles serving as a physical barrier against Ag agglomeration to ensure the excellent long-term stability.Pd and Pt have also been infiltrated on cathode surfaces [127,131,132].Adding a small amount of Pd catalyst (0.08 mg/cm2) can reduce the overpotential of LSM cathodes.Jianget al.[127] found that co-infiltration of Pd with either Ag (Pd0.8Ag0.2) or Co (Pd0.95Co0.05) into porous LSM can enhance both the ORR activity and the stability.For instance, the initial overpotential for Pd0.8Ag0.2coated LSM (≈20 mV) is reduced by 8% as compared with the pure Pd coated LSM measured at 850°C and 200 mA/cm2.The co-infiltration shows negligible degradation within the initial 2500 minutes at 850 °C.The main drawbacks of precious metals are their high cost and the low tolerance to contaminations (e.g., CO and H2S) [133].In recent years, most studies are focused on noble-metal-free coating materials since the performances of the cathodes coated with noble metals are commonly not better than the performances of noble-metal-free cathodes.

    4.2.Oxygen ion conducting oxides

    Ion-conducting oxides including YSZ [134], SDC [119] and GDC[55,120] were introduced as coating materials by the infiltration/impregnation techniques.When the electrolyte materials are used as coating materials, the backbones should be electronic conductive, or mixed ionic and electronic conductive.The introduction of the ionic conductor is expected to improve the electrode ionic conductivity of the cathode and increase the TPB.Wanget al.[134] infiltrated electrolytes (YSZ, SDC) into the LSM backbone and studied their effect on the surface exchange coefficient(Keff) by electrical conductivity relaxation (ECR).They found that IC nanoparticles on LSM promote the surface exchange kinetics.The oxygen surface exchange coefficient at 1000 °C for YSZ coated LSM is 2.45 × 10-4cm/s, which is 2.7 times higher than that for bare LSM.Moreover, theKefffor SDC coated LSM (7.92 × 10-4cm/s) is 3 times higher than that for YSZ coated LSM.Jiang group[55,135] and dos Santos-Gómezet al.[120] coated Gd0.2Ce0.8O1.9on the LSCF surface through infiltration.They found that the electrochemical performance and the Cr-tolerance property of the coated cathode were both improved [55,120].The GDC coating serves as a barrier layer to enhance the tolerance of LSCF against chromium deposition and poisoning, but the performance in wet air was not given.

    4.3.EC and MIEC conductors

    Infiltrated electronic conducting phases can act as catalysts for the ORR [122,136].Despite LSM is not applicable for IT-SOFC cathodes or backbones, the commercial cobalt-free LSM was found to be a good infiltrating catalyst.Huanget al.[2] infiltrated La0.85Sr0.15MnO3±δinto the Bi1.6Er0.4O3backbone.The cell with the coated cathode exhibited a maximum power density (MPD) of 1.18 W cm-2(1.8 times higher as compared with the non-coated cell)and a lowRp(0.107Ωcm2) at 600 °C.Kanget al.[51] infiltrated La1-xSrxMnO3-δinto the LaNi6Fe4O3-δbackbone.They found that theRpwas greatly reduced by 77.9% to 0.49Ωcm2at 700 °C.However, the infiltrated LSM catalyst shows the largestRpthan the infiltrated materials including LaNi1-xFexO3-δ, LaxSr1-xCoyFe1-yO3-δ(LSCF), Gd1-xCexO2-δ(GDC) and Pr6O11.

    Compared with IC materials, MIEC catalyst coated cathodes have been studied extensively (e.g., LSCF [121], Sm0.5Sr0.5CoO3-δ[121] and PrSrCoMnO6-δ[70]).MIEC materials such as Sm0.5Sr0.5CoO3-δ[121], SrCo0.9Ta0.1O3-δ(SCT) [44] and LnBaCo2O3-δ[8,137] have comparable electronic conductivity,higher oxygen diffusion/exchange coefficient, better ORR activity and durability than LSCF, but cannot be directly used as cathodes due to the mismatched TEC with most electrolytes [8].In addition,the use of above materials in large amounts is not cost competitive due to the expensive component (e.g., Co, Sm).But the low-loading infiltrated catalysts can reduce the TEC mismatch and save the cost on the materials [8].

    4.4.Non-electronic and non-ionic conducting oxide

    The non-electronic and non-ionic conducting phases, including alkali-earth metal compounds (CaO [138], MgO [139], BaO [57],BaCO3[123,140,141] and SrCO3[142,143]) or transition metal oxide (NiO [144], CuO [117]), have been reported as coating materials on the backbones of MIEC or composite materials.These infiltrating materials are considered ORR inactive, but they may influence backbones.Bidrawnet al.[145] fabricated (La,Sr)FeO3(LSF) infiltrated YSZ (LSF-YSZ) and calcined at 1100 °C.Then LSF-YSZ backbone is infiltrated by CaO (or K2O) and followed by re-calcined at 700 °C.They found that the CaO (or K2O) infiltrated cathodes exhibited better performance than the pristine cathode, but the mechanism is not clear.Xia groups infiltrated LSCF with several inert phase materials, which showed both decreased polarization resistance and improved stability in air or contaminants (e.g.,chromium, H2O) due to the increased chemical oxygen surface exchange coefficient [123,141,143].Mutoroet al.[146] proposed that the increased ORR kinetics is attributed to the hetero-interface of Ruddlesden–Popper (La,Sr)2CoO4-δbetween La0.8Sr0.2CoO3and inactive Sr-phases (SrCO3/Sr(OH)2/SrO).In the report of Liet al.[143],SrCO3was infiltrated on LSCF.As shown from the high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) images in Figs.5a-d, no obvious solid-state reactions or new phases occur at the interface between SrCO3and LSCF.The density functional theory (DFT) calculations in Fig.5e indicates that SrCO3can influence the charge density distribution of Fe and Co, which increases the O2adsorption energy from -0.32 eV to -0.74 eV and decreases the dissociation energy barrier of O2molecule from 1.01 eV to 0.33 eV on SrCO3coated LSCF.Chenet al.[92,147] investigated BaO coated PrBa0.8Ca0.2Co2O5+δ(PBCC) and found that barium cobaltitein-situformed on the PBCC surface,which contributed to the enhanced ORR kinetics.

    Inert oxide is in low cost compared with other infiltration species.However, inactive oxides must be coated as discrete particles rather than conformal coating, otherwise inert oxides will block ORR reactions.The Sr segregation from LSCF cannot be well suppressed by the discrete inert oxide particles.The inert oxides coated LSCF cathodes still suffer from high polarization resistances(>0.15Ωcm2at 650 °C) [148,149].

    Fig.5.(a,b) HRTEM images and (c, d) SAED patterns of SrCO3 coated LSCF.(e) The dissociated energy profiles of the O2 molecule on the SrCO3-modified LSCF.Blue balls and red balls represent the adsorbed oxygen molecules and the crystal oxygen.Copied with the permission [143].Copyright 2017, Royal Society of Chemistry.

    4.5.Multi-phase catalyst

    Multi-phase catalysts coatings have been proved to be more efficient than single-phase catalysts.The morphology of the multiphase catalyst infiltrated cathodes could be obtained by carefully controlling the composition and wettability of the solution, the drying rate of infiltrating process, as well as the firing temperature.There are mainly two ways for multi-phase catalyst infiltration: co-infiltrating different materials at once (or separately), andin-situdecomposing.Seyedet al.[131] co-infiltrated Ag-Ceria catalysts into the LSM backbone.The infiltrated cathode showed decreased polarization among all the single-phase catalysts (Ag, Ceria, LSF-coated LSM) due to the high electronic conductivity of Ag and oxygen vacancy rich ceria.Tonget al.[150] co-infiltrated GDC and Pr6O11into the porous cobalt-free (La0.6Sr0.4)0.98FeO3-δ(LSF)backbone.The solution for infiltration contains Pr(NO3)3and colloidal GDC nanoparticles.At 750, theRpof GDC and Pr6O11coinfiltrated LSF cathode (0.017Ωcm2) is about one tenth of the bare LSF (0.197Ωcm2), one fifth of GDC coated LSF (0.089Ωcm2),and 60% of the Pr6O11-coated LSF (0.028Ωcm2).The unique activity of the co-infiltrated LSF electrode is attributed to the accelerated oxygen surface exchange kinetics by Pr6O11, and enhanced active surface area by GDC nanoporous architecture.

    In-situexsolving, segregating or decomposing oxide from the bulk coating phase is another strategy for MP catalysts.Chenet al.infiltrated the catalyst precursor solution with a stoichiometric ratio of Pr2Ni0.5Mn0.5O4+δonto the porous LSCF cathode surface [58,124].A perovskite PrNi0.5Mn0.5O3(PNM) conformal coating with exsoluted PrOxnano-particles (PNM-PrOxMP) on LSCF are formed (Fig.6a) during the cell start-up process at the fire temperature of 800.The fast Fourier transform (FFT) pattern at location 1 indicates that PrOxnanoparticles are rich in oxygen vacancies.From the DFT calculations, the O vacancy energy for PrOxis 1.04 eV, which is smaller than that for LSCF (2.38 eV).The smaller O vacancy energy promotes the O2reduction and the diffusion of dissociated O as illustrated in Fig.6b.The O migration barrier for PNM structure with Pr deficiency is 0.45 eV, which is much lower than that for bulk PNM structure (1.26 eV).This indicates that PNM with Pr deficiency facilitates the oxygen-ion transfer (Fig.6b).EIS and ECR measurement reveal that the PNM-PrOxMP catalyst accelerates the oxygen-ion transfer and the oxygen dissociationabsorption processes [124,151].For example, by coating PNM-PrOxMP catalyst on bare LSCF, theRpis significantly reduced from 1.02Ωcm2to 0.25Ωcm2at 650 °C as shown in Fig.6c.The EIS spectra is fitted by the equivalent circuit, where the high frequency arc resistance (RH) and the low frequency arc resistance (RL) correspond to the oxygen-ion transfer process and the oxygen dissociation absorption process, respectively.Compared with bare LSCF, bothRHandRLis reduced in the cathode with PNM-PrOxMP coated.At 650 °C, theKefffor PNM-PrOxMP coated LSCF (1.51 × 10-5cm/s)is twice of that for bare LSCF (Fig.6d), indicating that the oxygen dissociation-absorption process (oxygen surface exchange) is accelerated.More importantly, the PNM-PrOxMP catalyst enhances significantly the tolerance to Cr poisoning even in humidified air with a degrading rate of 0.0434% h-1at 0.7 V in 3% H2O, which is 1/10 of that for the bare LSCF cathode [58].Similarly, PrCoO3-x(PCO) and BaCoO3-x(BCO) nanoparticles segregated from the conformal PBCC[104], SrMoO4(SM) phase exsolved from the Sr2MnMoO5-δ(SMM)phase have been reported [152].

    Fig.6.(a) High-resolution TEM image of PrOx exsoluted from PNM as SOFC cathode.The insets are the FFT patterns from the exsoluted nanoparticles (location 1) and the conformal coating (location 2), and the EELS spectra from location 1 and 2.(b) Schematic representation of the ORR mechanism on the MP (PrOx/PNM)coated LSCF cathode.(a,b) Copied with permission [104].Copyright 2018, Elsevier.(c) Impedance spectra of single cells at 650 °C and the equivalent circuit R1(RHCPEH)(RLCPEL) used to fit the spectra.(d) Plots of the surface exchange coeffi-cients (Keff) as function of temperatures.(c,d) Copied with permission [151].Copyright 2018, Elsevier.

    Fig.7a comparesRpfor LSCF cathodes infiltrated with various materials, including MP catalysts (PBCC MP catalyst [104],Ba1-xCoFe0.2NbO3-δ(BCFN) and BaCO3[20]), MIEC conductors (SSC[121], LSCF [121], BaCoOx[59]), ionic conductors (SDC [119], GDC[55,135]), electronic conductors (LSM [153]), inactive oxides (MgO[139], SrCO3[143], BaCO3[123]) and precious metal (Rh and Pd[126]).MP coated LSCF exhibits a lowerRpthan most of the cathodes.Improving factor (fp), the ratio of the polarization resistance of the bare cathode to that of the coated cathode [97], is used to describe the performance improvement.As shown in Fig.7b,among all the coated LSCF, MP coated LSCF shows much higherfpas compared with the other infiltration species.The improving factor for infiltrated LSCF follows the order: MP>MIEC>inactive oxide or precious metal.This indicates that multi-phase catalysts are advantageous over the other infiltration species.Among the MP coated cathodes, thefpfor BCFN and BaCO3coated LSCF at 650 °C(fp= 8.66) shows the highest value among all the catalysts.

    Fig.7.(a) The temperature dependance of Rp and (b) the improving factor for LSCF cathodes coated with different materials.PBCC MP coated LSCF is reproduced with permission [104].Copyright 2018, Elsevier.BCFN and BaCO3 multiphase coated LSCF is reproduced with permission [20].Copyright 2021, Wiley-VCH GmbH.Both SSC coated and LSCF coated are reproduced with permission [121].Copyright 2009, Elsevier.BaCoOx coated is reproduced with permission [59].Copyright 2020, Elsevier.SDC coated is reproduced with permission [119].Copyright 2010, Elsevier.GDC coated is reproduced with permission [55,135].Copyright Elsevier.LSM coated is reproduced with permission [153].Copyright 2013, Elsevier.MgO coated is reproduced with permission [139].Copyright 2018, Elsevier.SrCO3 coated is reproduced with permission [143].Copyright 2017, Wiley-VCH GmbH.BaCO3 coated is reproduced with permission [123].Copyright 2016, Wiley-VCH GmbH.Both Rh coated and Pd coated are reproduced with permission [126].Copyright 2008, Elsevier.

    The ORR activity and the tolerance to contaminations (Cr and H2O) are significantly improved by the MP coating.Another example through utilizing the instability of the coating materials on the backbone toin-situform MP catalyst was from Nicolletet al.[154] They infiltrated Pr2NiO4+δinto the GDC backbone and obtained Pr6O11and NiO phases at 900 °C in N2since GDC backbone inhibited the crystallization of Pr2NiO4+δ.The Pr6O11and NiO phases coated cathode exhibited a lowRpof 0.078Ωcm2at 600 °C[152,154].To date, there are few studies on how to control the distribution and size of the exsolved nanoparticles.Due to the complexity of the structure and the component of MP coating materials, it is difficult to reveal the ORR catalytic mechanism.In the future, more MP catalyst materials with different morphologies and compositions with specific properties need to be exploited.

    To summarize section 4, different types of infiltrated catalysts or materials are overviewed.The correlations among the composition, structure and performance of infiltrated catalysts or materials are illustrated according to the classification of the infiltrated catalysts.The MP catalysts are highly desired to developed high-performance and durable cathodes.The variety of backbones,morphologies and compositions greatly broaden the application of infiltrated cathodes.By careful design, the catalyst for surface infiltration can greatly enhance the catalytic activity at low and intermediate temperatures and improve the tolerance to contaminations.

    5.Summary and prospective

    Infiltration on the existing backbones has been proved to be an efficient method to construct highly active and durable cathodes.The infiltration process and the performance depend on many factors.In this mini-review, we emphases on the backbones and the coating materials.MIEC and composite backbones are more competitive as compared with the electrolyte backbones due to the increased TPB areas.The choice of the infiltrate material is versatile,including precious metals, oxygen ion-conducting oxides, mixed ionic and electronic conductors, and non-ionic and non-electronic conducting oxides.In particular, infiltrated multi-phase catalysts on LSCF backbone exhibit better ORR catalytic activity and thermal/chemical stability.The infiltration method allows us to use a wide range of infiltrated materials into various backbones, and endows the coated cathodes with desired properties.

    Although the infiltrated cathodes have many advantages, these challenges should be addressed in future research: (1) The infiltration cycles should be largely reduced and large-scale infiltration techniques need to be developed.(2) Due to the limitations of the measurable scale, the underlying mechanism of the original performance improvement and the heterostructure between the infiltration materials and the backbones is still unclear.Further investigation onex-situandin-situcharacterization are needed to illustrate the reactions or catalytic mechanisms.(3) The composition and morphology of the infiltrated cathode surface should be rationally designed and well controlled, such as the thickness, the distribution of the particles and the multi-phase components.The correlation between the composition/structure of the infiltrated material and the cathode performance should be explored extensively.(4) New infiltrated materials should be explored, such as semiconductor materials.For instance, TiO2is found to enhance catalytic activity of the anode towards simulated biogas and the coking resistance due to the infrared light driven photocatalytic removal of deposited carbon [155].However, there are few studies on semiconductors as infiltration materials.(5) The infiltration concept can be expanded to other electrochemical energy devices.For example,the infiltrated electrodes can also be applied in solid electrolysis cells, metal-air batteries, photo-catalysis devices and so on.

    Declaration of competing interest

    The authors declare no competing financial interest.

    Acknowledgments

    This work was supported by the Natural Science foundation of China (No.51972043), Foundation of Yangtze Delta Region Institute (HuZhou) of UESTC, China (Nos.U03210010 and U03210028), the Sichuan-Hong Kong Collaborative Research Fund(No.2021YFH0184), the Application Fundamental Research Project of Sichuan Province (No.2019YJ0169), and the New Scholar Fund of UESTC.

    亚洲熟女毛片儿| 少妇被粗大的猛进出69影院| 极品教师在线免费播放| 免费在线观看黄色视频的| 高清在线国产一区| 一级黄色大片毛片| 国产精品香港三级国产av潘金莲| 男女之事视频高清在线观看| 久久久国产成人精品二区| 99国产精品99久久久久| 12—13女人毛片做爰片一| 国产欧美日韩一区二区三| 亚洲精品中文字幕一二三四区| 精品无人区乱码1区二区| 脱女人内裤的视频| 夜夜看夜夜爽夜夜摸| 巨乳人妻的诱惑在线观看| 国产成人精品在线电影| 99精品久久久久人妻精品| 人人澡人人妻人| 麻豆成人av在线观看| 日韩精品免费视频一区二区三区| 亚洲欧美一区二区三区黑人| 成熟少妇高潮喷水视频| 亚洲av五月六月丁香网| 精品国产一区二区三区四区第35| 大型av网站在线播放| 亚洲成a人片在线一区二区| 色播在线永久视频| 91成人精品电影| 天天添夜夜摸| 欧美一级毛片孕妇| 九色亚洲精品在线播放| 久久狼人影院| 免费女性裸体啪啪无遮挡网站| 免费在线观看亚洲国产| 亚洲中文日韩欧美视频| 久久久久亚洲av毛片大全| 国产黄a三级三级三级人| 国产精品自产拍在线观看55亚洲| 男人操女人黄网站| 国内久久婷婷六月综合欲色啪| 两个人看的免费小视频| 国产高清视频在线播放一区| 亚洲av电影在线进入| 无人区码免费观看不卡| 精品久久久精品久久久| 国产真人三级小视频在线观看| 午夜亚洲福利在线播放| 国产成人啪精品午夜网站| 欧美精品啪啪一区二区三区| 午夜福利一区二区在线看| 69av精品久久久久久| 精品久久蜜臀av无| 欧美精品亚洲一区二区| 免费在线观看完整版高清| 日韩大码丰满熟妇| 啦啦啦观看免费观看视频高清 | av超薄肉色丝袜交足视频| 亚洲欧美精品综合久久99| 欧美 亚洲 国产 日韩一| av中文乱码字幕在线| 久久久国产精品麻豆| 欧美日韩一级在线毛片| 波多野结衣巨乳人妻| 18禁观看日本| 制服丝袜大香蕉在线| 狂野欧美激情性xxxx| 成人永久免费在线观看视频| 欧美黑人精品巨大| 亚洲五月天丁香| 多毛熟女@视频| 欧美日韩瑟瑟在线播放| 丁香欧美五月| 中国美女看黄片| 国产高清videossex| 在线观看66精品国产| 少妇被粗大的猛进出69影院| 国产av又大| 免费观看精品视频网站| av中文乱码字幕在线| 国产亚洲欧美在线一区二区| 老司机午夜福利在线观看视频| 超碰成人久久| 18禁国产床啪视频网站| 日本一区二区免费在线视频| 色综合婷婷激情| 乱人伦中国视频| 俄罗斯特黄特色一大片| 午夜久久久在线观看| 日韩精品中文字幕看吧| 日韩欧美三级三区| 日本vs欧美在线观看视频| 国产亚洲精品一区二区www| 乱人伦中国视频| 香蕉丝袜av| 国产精品亚洲av一区麻豆| 亚洲va日本ⅴa欧美va伊人久久| 男女下面进入的视频免费午夜 | 在线观看免费日韩欧美大片| 看黄色毛片网站| 神马国产精品三级电影在线观看 | 亚洲av成人av| 亚洲一区高清亚洲精品| 亚洲欧美精品综合一区二区三区| www.999成人在线观看| 一级作爱视频免费观看| 熟妇人妻久久中文字幕3abv| 男女下面进入的视频免费午夜 | 热99re8久久精品国产| 欧美日本视频| 久热这里只有精品99| 日韩大码丰满熟妇| 韩国av一区二区三区四区| 久久久国产欧美日韩av| 99国产精品一区二区蜜桃av| 我的亚洲天堂| 涩涩av久久男人的天堂| 久久久久九九精品影院| 亚洲avbb在线观看| 一本综合久久免费| 国产一级毛片七仙女欲春2 | 99国产极品粉嫩在线观看| 国产精品爽爽va在线观看网站 | 中文字幕最新亚洲高清| 日韩精品青青久久久久久| 精品国产乱码久久久久久男人| 成人三级做爰电影| 亚洲成人久久性| 国产精品自产拍在线观看55亚洲| 欧美国产日韩亚洲一区| 日韩精品青青久久久久久| 一夜夜www| 国产精品永久免费网站| 男人舔女人的私密视频| 色精品久久人妻99蜜桃| 午夜日韩欧美国产| 少妇被粗大的猛进出69影院| 午夜精品在线福利| 免费一级毛片在线播放高清视频 | 天堂影院成人在线观看| 97碰自拍视频| 免费看十八禁软件| netflix在线观看网站| 97人妻精品一区二区三区麻豆 | 国产极品粉嫩免费观看在线| 无限看片的www在线观看| 男女下面进入的视频免费午夜 | 亚洲一区高清亚洲精品| 欧美精品亚洲一区二区| 国产成人精品在线电影| 国产aⅴ精品一区二区三区波| 色哟哟哟哟哟哟| 成在线人永久免费视频| 91大片在线观看| 日本免费一区二区三区高清不卡 | 一边摸一边做爽爽视频免费| 露出奶头的视频| 午夜福利成人在线免费观看| 老司机靠b影院| 99国产综合亚洲精品| 亚洲精品国产一区二区精华液| 亚洲精品在线美女| 51午夜福利影视在线观看| 午夜久久久久精精品| 亚洲成人久久性| 午夜亚洲福利在线播放| 久久午夜综合久久蜜桃| 色在线成人网| 午夜精品在线福利| 亚洲午夜精品一区,二区,三区| 国产三级在线视频| 香蕉丝袜av| 熟女少妇亚洲综合色aaa.| 色播在线永久视频| 日韩精品免费视频一区二区三区| 美女 人体艺术 gogo| 岛国在线观看网站| 亚洲av成人av| 久久伊人香网站| 色哟哟哟哟哟哟| 日韩视频一区二区在线观看| 两个人看的免费小视频| 一级a爱片免费观看的视频| 青草久久国产| 欧美 亚洲 国产 日韩一| 免费在线观看完整版高清| 非洲黑人性xxxx精品又粗又长| 美女国产高潮福利片在线看| av有码第一页| 亚洲第一电影网av| 涩涩av久久男人的天堂| 久9热在线精品视频| 国产伦一二天堂av在线观看| 久久久水蜜桃国产精品网| 自拍欧美九色日韩亚洲蝌蚪91| 亚洲 欧美 日韩 在线 免费| 51午夜福利影视在线观看| 精品久久久久久久久久免费视频| 国产真人三级小视频在线观看| 精品欧美国产一区二区三| 国产成+人综合+亚洲专区| 亚洲视频免费观看视频| 自拍欧美九色日韩亚洲蝌蚪91| 999精品在线视频| 亚洲av第一区精品v没综合| 精品一区二区三区av网在线观看| avwww免费| 国产极品粉嫩免费观看在线| 在线观看免费视频日本深夜| 男女之事视频高清在线观看| 午夜成年电影在线免费观看| 亚洲少妇的诱惑av| 久久久国产成人免费| 韩国av一区二区三区四区| 国产高清激情床上av| 麻豆国产av国片精品| 女人爽到高潮嗷嗷叫在线视频| 欧美黑人精品巨大| 非洲黑人性xxxx精品又粗又长| 免费无遮挡裸体视频| 亚洲熟妇中文字幕五十中出| 精品欧美一区二区三区在线| 亚洲一区二区三区色噜噜| 一个人免费在线观看的高清视频| 国产人伦9x9x在线观看| 国产亚洲精品第一综合不卡| 禁无遮挡网站| 757午夜福利合集在线观看| 午夜免费观看网址| 狂野欧美激情性xxxx| 夜夜看夜夜爽夜夜摸| 亚洲av电影在线进入| 国产激情久久老熟女| 欧美日韩黄片免| 日韩欧美免费精品| 99精品在免费线老司机午夜| 国产私拍福利视频在线观看| 国产亚洲欧美98| 国产精品一区二区精品视频观看| 久久久久久大精品| 成人18禁高潮啪啪吃奶动态图| 波多野结衣高清无吗| 人成视频在线观看免费观看| 中文字幕高清在线视频| 午夜免费观看网址| 可以免费在线观看a视频的电影网站| 亚洲欧美激情在线| 免费观看人在逋| 国产片内射在线| 大型黄色视频在线免费观看| 18禁裸乳无遮挡免费网站照片 | 欧美丝袜亚洲另类 | 久久精品亚洲熟妇少妇任你| 国产三级黄色录像| 9色porny在线观看| 久久亚洲精品不卡| 在线av久久热| av中文乱码字幕在线| 欧美成狂野欧美在线观看| 久久久久国产精品人妻aⅴ院| 啦啦啦 在线观看视频| 国产片内射在线| 日本五十路高清| 欧美成人性av电影在线观看| 欧美国产日韩亚洲一区| 国产精品乱码一区二三区的特点 | 精品国产一区二区久久| 麻豆久久精品国产亚洲av| 色播亚洲综合网| 午夜日韩欧美国产| 女生性感内裤真人,穿戴方法视频| 亚洲国产精品久久男人天堂| 国产成人系列免费观看| 亚洲欧美激情综合另类| 大型黄色视频在线免费观看| 欧美人与性动交α欧美精品济南到| 成年版毛片免费区| 男女下面插进去视频免费观看| 精品高清国产在线一区| 变态另类丝袜制服| 看免费av毛片| 美女高潮喷水抽搐中文字幕| 91大片在线观看| 久久狼人影院| 成熟少妇高潮喷水视频| 久久精品国产清高在天天线| 婷婷丁香在线五月| 波多野结衣av一区二区av| 99精品久久久久人妻精品| 久久香蕉精品热| 人成视频在线观看免费观看| 色老头精品视频在线观看| 国产精品精品国产色婷婷| 亚洲欧美日韩高清在线视频| 99热只有精品国产| 日韩欧美国产在线观看| 少妇被粗大的猛进出69影院| 欧美国产日韩亚洲一区| 日韩欧美一区视频在线观看| 亚洲国产中文字幕在线视频| 在线观看免费视频网站a站| 国产精品亚洲av一区麻豆| 黑人巨大精品欧美一区二区蜜桃| 国产麻豆成人av免费视频| 999久久久精品免费观看国产| 色精品久久人妻99蜜桃| 国产精品98久久久久久宅男小说| 久久亚洲真实| 国产精品98久久久久久宅男小说| 电影成人av| 在线十欧美十亚洲十日本专区| 一个人免费在线观看的高清视频| 看黄色毛片网站| 天堂√8在线中文| 在线播放国产精品三级| 在线永久观看黄色视频| 国产高清videossex| 日韩精品免费视频一区二区三区| 亚洲精品国产一区二区精华液| 波多野结衣av一区二区av| 极品人妻少妇av视频| 亚洲 国产 在线| 欧美成狂野欧美在线观看| 一边摸一边做爽爽视频免费| 久久久久九九精品影院| 激情视频va一区二区三区| 日本 欧美在线| 亚洲最大成人中文| 欧美在线一区亚洲| 国产精品99久久99久久久不卡| 亚洲七黄色美女视频| 99久久99久久久精品蜜桃| 变态另类丝袜制服| 麻豆一二三区av精品| 国产精品一区二区三区四区久久 | 热re99久久国产66热| 亚洲av成人av| 中文字幕av电影在线播放| 天堂√8在线中文| 我的亚洲天堂| 日韩三级视频一区二区三区| 欧美最黄视频在线播放免费| 久久久水蜜桃国产精品网| 怎么达到女性高潮| 欧美日本中文国产一区发布| 久久国产亚洲av麻豆专区| 天堂√8在线中文| 欧美一级a爱片免费观看看 | 欧美老熟妇乱子伦牲交| 国产日韩一区二区三区精品不卡| 亚洲成av片中文字幕在线观看| 九色国产91popny在线| 18禁国产床啪视频网站| 国产精品一区二区在线不卡| 欧美黑人欧美精品刺激| 欧美最黄视频在线播放免费| 欧美日韩中文字幕国产精品一区二区三区 | 成人18禁高潮啪啪吃奶动态图| 国产精品久久久久久精品电影 | 欧美成人午夜精品| 禁无遮挡网站| 午夜视频精品福利| 久久这里只有精品19| 好男人电影高清在线观看| bbb黄色大片| 好男人电影高清在线观看| 18禁黄网站禁片午夜丰满| 日本免费一区二区三区高清不卡 | 午夜福利欧美成人| 色尼玛亚洲综合影院| 久久婷婷人人爽人人干人人爱 | 亚洲av日韩精品久久久久久密| 脱女人内裤的视频| 国产一区二区在线av高清观看| 久久中文字幕一级| 精品久久久精品久久久| 亚洲七黄色美女视频| www日本在线高清视频| 国产av精品麻豆| 91在线观看av| 性色av乱码一区二区三区2| 久久精品亚洲熟妇少妇任你| 满18在线观看网站| 少妇 在线观看| 久久久久久久久久久久大奶| 亚洲三区欧美一区| 久久香蕉激情| 午夜免费成人在线视频| 国产精品亚洲av一区麻豆| 国产在线观看jvid| 法律面前人人平等表现在哪些方面| 一a级毛片在线观看| 国产亚洲欧美精品永久| 亚洲视频免费观看视频| 看免费av毛片| 黄片小视频在线播放| 黄色a级毛片大全视频| 欧美黑人欧美精品刺激| 真人做人爱边吃奶动态| 久久中文字幕人妻熟女| 一边摸一边抽搐一进一出视频| av超薄肉色丝袜交足视频| 变态另类成人亚洲欧美熟女 | 18禁观看日本| 在线av久久热| 日韩欧美一区视频在线观看| 两个人看的免费小视频| 国产亚洲欧美在线一区二区| 亚洲专区字幕在线| 亚洲国产精品成人综合色| 日韩精品中文字幕看吧| av超薄肉色丝袜交足视频| 欧美成人午夜精品| 99香蕉大伊视频| 成人国产一区最新在线观看| 欧美中文日本在线观看视频| 精品人妻在线不人妻| 久久影院123| 国产精品免费一区二区三区在线| 免费观看精品视频网站| 国产精品精品国产色婷婷| 亚洲va日本ⅴa欧美va伊人久久| 国产精品久久久久久人妻精品电影| 变态另类成人亚洲欧美熟女 | 国产野战对白在线观看| www.精华液| 国产精品免费一区二区三区在线| 一级毛片精品| 香蕉丝袜av| 9热在线视频观看99| 久久精品成人免费网站| 一进一出抽搐gif免费好疼| 免费在线观看亚洲国产| 日韩精品免费视频一区二区三区| 久久人人爽av亚洲精品天堂| 国产成人精品在线电影| 成人国产综合亚洲| 香蕉国产在线看| 97碰自拍视频| 国产亚洲欧美精品永久| 人人妻人人爽人人添夜夜欢视频| 中文字幕高清在线视频| 国产成人精品久久二区二区91| 久热爱精品视频在线9| 日韩 欧美 亚洲 中文字幕| 免费在线观看黄色视频的| 国产午夜福利久久久久久| a级毛片在线看网站| 欧美绝顶高潮抽搐喷水| 国产精品日韩av在线免费观看 | 精品乱码久久久久久99久播| 一卡2卡三卡四卡精品乱码亚洲| 亚洲全国av大片| 国产av又大| 国产精品亚洲一级av第二区| 国产成人精品无人区| 黑人操中国人逼视频| 美女高潮到喷水免费观看| 亚洲天堂国产精品一区在线| 日韩欧美一区视频在线观看| www.精华液| 亚洲男人天堂网一区| 一区二区三区国产精品乱码| 大型av网站在线播放| 成人特级黄色片久久久久久久| 免费在线观看黄色视频的| 波多野结衣av一区二区av| 久久伊人香网站| 91精品三级在线观看| 欧美日本视频| 色精品久久人妻99蜜桃| 日本免费一区二区三区高清不卡 | 精品乱码久久久久久99久播| 人妻丰满熟妇av一区二区三区| 天天添夜夜摸| 99国产精品一区二区三区| 欧美在线一区亚洲| 亚洲国产欧美日韩在线播放| 久久精品国产99精品国产亚洲性色 | 国产精品久久久久久人妻精品电影| 成人特级黄色片久久久久久久| 女警被强在线播放| 男人舔女人下体高潮全视频| 人妻丰满熟妇av一区二区三区| 极品教师在线免费播放| 亚洲五月色婷婷综合| 日韩有码中文字幕| 久久狼人影院| 国产精品电影一区二区三区| 欧美成人性av电影在线观看| 变态另类成人亚洲欧美熟女 | 男人舔女人下体高潮全视频| 精品久久久久久久久久免费视频| 欧美激情极品国产一区二区三区| 99国产精品一区二区三区| 亚洲人成电影观看| 国产男靠女视频免费网站| 欧美国产日韩亚洲一区| 欧美日韩中文字幕国产精品一区二区三区 | 欧美av亚洲av综合av国产av| 久久国产精品人妻蜜桃| 国产成人精品在线电影| 一二三四在线观看免费中文在| 亚洲一卡2卡3卡4卡5卡精品中文| 国产又爽黄色视频| 精品久久久久久久久久免费视频| 精品国产乱码久久久久久男人| 黑人巨大精品欧美一区二区mp4| bbb黄色大片| avwww免费| 国产激情欧美一区二区| 69av精品久久久久久| 免费在线观看影片大全网站| 欧美成人免费av一区二区三区| 免费在线观看完整版高清| 搡老熟女国产l中国老女人| 亚洲国产欧美一区二区综合| 久久人人97超碰香蕉20202| 国产激情久久老熟女| 国产午夜精品久久久久久| 99国产精品一区二区三区| 欧美乱妇无乱码| 婷婷精品国产亚洲av在线| 在线播放国产精品三级| 精品久久久久久久毛片微露脸| 黄色成人免费大全| 国内精品久久久久久久电影| 国产蜜桃级精品一区二区三区| 波多野结衣巨乳人妻| 电影成人av| 成人国产一区最新在线观看| 丰满人妻熟妇乱又伦精品不卡| 亚洲无线在线观看| 女同久久另类99精品国产91| 两人在一起打扑克的视频| 他把我摸到了高潮在线观看| 韩国av一区二区三区四区| 国产成人影院久久av| 免费看a级黄色片| xxx96com| 亚洲av第一区精品v没综合| 老汉色∧v一级毛片| 精品午夜福利视频在线观看一区| 欧美日本中文国产一区发布| 激情在线观看视频在线高清| 免费在线观看黄色视频的| 国产主播在线观看一区二区| 色综合婷婷激情| 日韩大码丰满熟妇| 精品久久久久久,| 亚洲欧美日韩高清在线视频| 亚洲一码二码三码区别大吗| 男人舔女人的私密视频| 国产av一区在线观看免费| 大陆偷拍与自拍| 动漫黄色视频在线观看| 少妇的丰满在线观看| 男女床上黄色一级片免费看| 亚洲国产精品合色在线| 午夜精品久久久久久毛片777| avwww免费| 在线国产一区二区在线| 黄片大片在线免费观看| 国产又爽黄色视频| 看片在线看免费视频| 在线观看午夜福利视频| 亚洲成人精品中文字幕电影| 精品国内亚洲2022精品成人| 老鸭窝网址在线观看| 99国产极品粉嫩在线观看| xxx96com| 69av精品久久久久久| 日韩欧美国产一区二区入口| 九色国产91popny在线| 亚洲七黄色美女视频| 亚洲专区中文字幕在线| 亚洲天堂国产精品一区在线| 黄频高清免费视频| 午夜福利高清视频| 国产人伦9x9x在线观看| 一夜夜www| 18禁观看日本| av天堂久久9| 午夜亚洲福利在线播放| 国产欧美日韩一区二区三区在线| 高清在线国产一区| 国产伦人伦偷精品视频| 日本免费一区二区三区高清不卡 | 淫秽高清视频在线观看| 亚洲国产高清在线一区二区三 | 怎么达到女性高潮| 国内精品久久久久精免费| 大型av网站在线播放| 波多野结衣高清无吗| 久久人人爽av亚洲精品天堂| 69av精品久久久久久| 人人妻,人人澡人人爽秒播| 最近最新中文字幕大全电影3 | 如日韩欧美国产精品一区二区三区| 久久狼人影院| 久久精品国产综合久久久| 亚洲成av人片免费观看| 亚洲片人在线观看| 美国免费a级毛片| 别揉我奶头~嗯~啊~动态视频| 97人妻精品一区二区三区麻豆 | 岛国在线观看网站| 久久久精品国产亚洲av高清涩受| 88av欧美| 国产精品99久久99久久久不卡| 十分钟在线观看高清视频www| 国产黄a三级三级三级人| 亚洲人成网站在线播放欧美日韩| 欧美成人免费av一区二区三区|