Electrochemical performance and stability of Sr-doped LaMnO_(3)-infiltrated yttria stabilized zirconia oxygen electrode for reversible solid oxide fuel cells

Porous Sr-doped lanthanum manganite–yttria stabilized zirconia(LSM–YSZ)oxygen electrode is prepared by an infiltration process for a reversible solid oxide fuel cell(RSOFC).X-ray diffraction and SEM analysis display that perovskite phase LSM submicro particles are evenly distributed in the porous YSZ matrix.Polarization curves and electrochemical impedance spectra are conducted for the RSOFC at 800 and 850C under both SOFC and SOEC modes.At 850℃,the single cell has the maximum power density of~726 mW/cm^(2)under SOFC mode,and electrolysis voltage of 1.35 V at 1 A/cm^(2)under SOEC mode.Fuel cell/water electrolysis cycle shows the cell has good performance stability during 6 cycles,which exhibits the LSM–YSZ oxygen electrode has high electrochemical performance and good stability.The results suggest that netw ork-like LSM–YSZ electrode made by infiltration process could be a promising oxygen electrode for high temperature RSOFCs.

Electricity Storage With High Roundtrip Efficiency in a Reversible Solid Oxide Cell Stack

We theoretically investigate the electricity storage/generation in a reversible solid oxide cell stack. The system heat is for the first time tentatively stored in a phase-change metal when the stack is operated to generate electricity in a fuel cell mode and then reused to store electricity in an electrolysis mode. The state of charge （H2 frication in cathode） effectively enhances the open circuit voltages （OCVs） while the system gas pressure in electrodes also increases the OCVs. On the other hand, a higher system pressure facilitates the species diffusion in electrodes that therefore accordingly improve electrode polarizations. With the aid of recycled system heat, the roundtrip efficiency reaches as high as 92% for the repeated electricity storage and generation.

Progress on direct assembly approach for in situ fabrication of electrodes of reversible solid oxide cells

Reversible solid oxide cells(SOCs)are very efficient and clean for storage and regeneration of renewable electrical energy by switching between electrolysis and fuel cell modes.One of the most critical factors governing the efficiency and durability of SOCs technology is the stability of the interface between oxygen electrode and electrolyte,which is conventionally formed by sintering at a high temperature of~1000–1250℃,and which suffers from delamination problem,particularly for reversibly operated SOCs.On the other hand,our recent studies have shown that the electrode/electrolyte interface can be in situ formed by a direct assembly approach under the electrochemical polarization conditions at 800℃and lower.The direct assembly approach provides opportunities for significantly simplifying the cell fabrication procedures without the doped ceria barrier layer,enabling the utilization of a variety of high-performance oxygen electrode materials on barrier layer–free yttria-stabilized zirconia(YSZ)electrolyte.Most importantly,the in situ polarization induced interface shows a promising potential as highly active and durable interface for reversible SOCs.The objective of this progress report is to take an overview of the origin and research progress of in situ fabrication of oxygen electrodes based on the direct assembly approach.The prospect of direct assembly approach in the development of effective SOCs and in the fundamental studies of electrode/electrolyte interface reactions is discussed.

High performance and stability of double perovskite-type oxide NdBa0.5Ca0.5Co1.5Fe0.5O5+δas an oxygen electrode for reversible solid oxide electrochemical cell

In this study,we successfully synthesized double perovskite-type oxide NdBa0.5Ca0.5Co1.5Fe0.5O5+δ(NBCCF)using a conventional wet chemical method as the oxygen electrode for reversible solid oxide electrochemical cells(RSOCs).The polarization resistance(Rp)of the composite electrode NBCCFGd0.1Ce0.9O2(GDC)is only 0.079Ωcm^2 at 800℃under air.The single cell based on NBCCF-GDC electrode displays a peak power density of 0.941 W/cm^2 in fuel cell mode and a low Rp value of 0.134Ωcm^2.In electrolysis cell mode,the cell displays an outstanding oxygen evolution reaction(OER)activity and shows current density as high as 0.92 A/cm^2 with 50 vol%AH(Absolute Humidity)at 800℃and applied voltage of 1.3 V.Most importantly,the cell exhibits admirable durability of 60 h both in electrolysis mode and fuel cell mode with distinguished reversibility.All these results suggest that NBCCF is a promising candidate electrode for RSOC.

Pd-La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)composite as active and stable oxygen electrode for reversible solid oxide cells

To promote the electrocatalytic activity and stability of traditional(a_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)oxygen electrodes in reversible solid oxide cells(RSOCs),conventional physical mixed method was used to prepare the Pd-LSCF composite oxygen electrode.The cell with Pd-LSCF|GDC|YSZ|Ni-YSZ configuration shows perfect electrochemical performance in both solid oxide fuel cell(SOFC)mode and solid oxide electrolysis cell(SOEC)mode.In the SOFC mode,the cell achieves a power density of 1.73 W/cm^(2)at800℃higher than that of the LSCF oxygen electrode with 1.38 W/cm^(2).In the SOEC mode,the current density at 1.5 V is 1.67 A/cm^(2)at 800℃under 50 vol%steam concentration.Moreover,the reversibility and stability of the RSOCs were tested during 192 h long-term reversible operation.The degradation rate of the cell is only 2.2%/100 h and 2.5%/100 h in the SOEC and the SOFC modes,respectively.These results confirm that compositing Pd with the LSCF oxygen electrode can considerably boost the electrochemical performance of LSCF electrode in RSOCs field.

A real proton-conductive,robust,and cobalt-free cathode for proton-conducting solid oxide fuel cells with exceptional performance

The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can increase fuel cell performance by extending the reaction active area.Although oxygen-ion and electron conductions can be measured directly,proton conduction in these oxides is usually estimated indirectly.Because of the instability of cathode materials in a reducing environment,direct measurement of proton conduction in cathode oxide is difficult.The La0.8Sr0.2Sc0.5Fe0.5O3–δ(LSSF)cathode material is proposed for H-SOFCs in this study,which can survive in an H_(2)-containing atmosphere,allowing measurement of proton conduction in LSSF by hydrogen permeation technology.Furthermore,LSSF is discovered to be a unique proton and electron mixed-conductive material with limited oxygen diffusion capability that is specifically designed for H-SOFCs.The LSSF is an appealing cathode choice for H-SOFCs due to its outstanding CO_(2)tolerance and matched thermal expansion coefficient,producing a record-high performance of 2032 mW cm^(−2)at 700℃and good long-term stability under operational conditions.The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H-SOFCs,opening the way for developing high-performance cathodes.

A high-entropy spinel ceramic oxide as the cathode for proton-conducting solid oxide fuel cells

A high-entropy ceramic oxide is used as the cathode for the first time for proton-conducting solid oxide fuel cells(H-SOFCs).The Fe_(0.6)Mn_(0.6)Co_(0.6)Ni_(0.6)Cr_(0.6)O_(4)(FMCNC)high-entropy spinel oxide has been successfully prepared,and the in situ chemical stability test demonstrates that the FMCNC material has good stability against CO_(2).The first-principles calculation indicates that the high-entropy structure enhances the properties of the FMCNC material that surpasses their individual components,leading to lower O_(2)adsorption energy for FMCNC than that for the individual components.The HSOFC using the FMCNC cathode reaches an encouraging peak power density(PPD)of 1052 mW·cm^(-2)at 700℃,which is higher than those of the H-SOFCs reported recently.Additional comparison was made between the high-entropy FMCNC cathode and the traditional Mn_(1.6)Cu_(1.4)O_(4)(MCO)spinel cathode without the high-entropy structure,revealing that the formation of the high-entropy material allows the enhanced protonation ability as well as the movement of the O p-band center closer to the Fermi level,thus improving the cathode catalytic activity.As a result,the high-entropy FMCNC has a much-decreased polarization resistance of 0.057Ω·cm^(2)at 700℃,which is half of that for the traditional MCO spinel cathode without the high-entropy design.The excellent performance of the FMCNC cell indicates that the high-entropy design makes a new life for the spinel oxide as the cathode for HSOFCs,offering a novel and promising route for the development of high-performance materials for H-SOFCs.

High-performance proton-conducting solid oxide fuel cells using the first-generation Sr-doped LaMnO_(3) cathode tailored with Zn ions

Sr-doped LaMnO_(3)(LSM)which is the firstgeneration cathode for solid oxide fuel cells(SOFC;)has been tailored with Zn ions,aiming to achieve improved protonation ability for proton-conducting SOFCs(H-SOFCs).The new Sr and Zn co-doped LaMnO_(3)(LSMZ)can be successfully synthesized.The first-principle studies indicate that the LSMZ improves the protonation of LSM and decreases the barriers for oxygen vacancy formation,leading to high performance of the LSMZ cathode-based cells.The proposed LSMZ cell shows the highest fuel cell performance among ever reported LSMbased H-SOFCs.In addition,the superior fuel cell performance does not impair its stability.LSMZ is stable against CO_(2),as demonstrated by both in-situ CO_(2)corrosion tests and the first-principles calculations,leading to good long-term stability of the cell.The Zn-doping strategy for the traditional LSM cathode with high performance and good stability brings back the LSM cathode to intermediate temperatures and paves a new way for the research on the LSM-based materials as cathodes for SOFCs.

Visiting the roles of Sr-or Ca-doping on the oxygen reduction reaction activity and stability of a perovskite cathode for proton conducting solid oxide fuel cells

While double perovskites of PrBaCo_(2)O_(6)(PBC)have been extensively developed as the cathodes for proton-conducting solid oxide fuel cells(H-SOFCs),the effects of Sr-or Ca-doping at the A site on the activity and stability of the oxygen reduction reaction are yet to be fully studied.Here,the effect of A-site doping on the oxygen reduction reaction activity and stability has been studied by evaluating the performance of both symmetrical and single cells.It is shown that Ca-doped PBC(PrBa_(0.8)Ca_(0.2)Co_(2)O_(6),PBCC)shows a slightly smaller polarization resistance(0.076Ωcm^(2))than that(0.085Ωcm^(2))of Sr-doped PBC(PrBa0.8Sr0.2Co2O6,PBSC)at 700◦C in wet air.Moreover,the degradation rate of PBCC is 0.0003Ωcm^(2)h^(−1)(0.3%h−1)in 100 h,about 1/10 of that of PBSC at 700◦C in wet air.In addition,it is also confirmed that single cells with PBCC cathode show higher peak power density(1.22Wcm^(−2)vs.1.08Wcm^(−2)at 650◦C)and better durability(degradation rate of 0.1%h^(−1)vs.0.13%h^(−1))than those with PBSC cathode.The distribution of relaxation time analyses suggests that the better stability of the PBCC electrode may come from the fast and stable surface oxygen exchange process in the medium frequency range of the electrochemical impedance spectrum.

Efficient reversible CO/CO_(2) conversion in solid oxide cells with a phase-transformed fuel electrode

The reversible solid oxide cell(RSOC)is an attractive technology to mutually convert power and chemicals at elevated temperatures.However,its development has been hindered mainly due to the absence of a highly active and durable fuel electrode.Here,we report a phase-transformed CoFe-Sr_(3)Fe_(1.25)Mo_(0.75)O_(7)-δ(CoFe-SFM)fuel electrode consisting of CoFe nanoparticles and Ruddlesden-Popper-layered Sr_(3)Fe_(1.25)Mo_(0.75)O_(7)-δ(SFM)from a Sr_(2)Fe_(7/6)Mo_(0.5)Co_(1/3)O_(6)-δ(SFMCo)perovskite oxide after annealing in hydrogen and apply it to reversible CO/CO_(2)conversion in RSOC.The CoFeSFM fuel electrode shows improved catalytic activity by accelerating oxygen diffusion and surface kinetics towards the CO/CO_(2)conversion as demonstrated by the distribution of relaxation time(DRT)study and equivalent circuit model fitting analysis.Furthermore,an electrolyte-supported single cell is evaluated in the 2:1 CO-CO_(2)atmosphere at 800℃,which shows a peak power density of 259 mW cm^(-2)for CO oxidation and a current density of-0.453 A cm^(-2)at 1.3 V for CO_(2)reduction,which correspond to 3.079 and3.155 m L min-1cm^(-2)for the CO and CO_(2)conversion rates,respectively.More importantly,the reversible conversion is successfully demonstrated over 20 cyclic electrolysis and fuel cell switching test modes at 1.3 and 0.6 V.This work provides a useful guideline for designing a fuel electrode through a surface/interface exsolution process for RSOC towards efficient CO-CO_(2)reversible conversion.

Tailoring Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)with Sc as a new single-phase cathode for proton-conducting solid oxide fuel cells

Sc-doped Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)(SFMSc)was successfully synthesized by partially substituting Mo in Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)(SFM)with Sc,resulting in a higher proton diffusion rate in the resultant SFMSc sample.Theoretical calculations showed that doping Sc into SFM lowered the oxygen vacancy formation energy,reduced the energy barrier for proton migration in the oxide,and increased the catalytic activity for oxygen reduction reaction.Next,a proton-conducting solid oxide fuel cell(H-SOFC)with a single-phase SFMSc cathode demonstrated significantly higher cell performance than that of cell based on an Sc-free SFM cathode,achieving 1258 mW cm^(−2)at 700℃.The performance also outperformed that of many other H-SOFCs based on single-phase cobalt-free cathodes.Furthermore,no trade-off between fuel cell performance and material stability was observed.The SFMSc material demonstrated good stability in both the CO_(2)-containing atmosphere and the fuel cell application.The combination of high performance and outstanding stability suggests that SFMSc is an excellent cathode material for H-SOFCs.

Tailored Sr-Co-free perovskite oxide as an air electrode for high-performance reversible solid oxide cells

Sr-Co containing perovskite oxides are prospective air electrode candidates for reversible solid oxide cells(RSOCs).However,their efficiencies are limited by Sr segregation and the high thermal expansion coefficient(TEC)of Cobased perovskites.Herein,La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LCa FN)is tailored as an Sr-Co-free perovskite air electrode for highperformance RSOCs.Compared with La_(0.6)Sr_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LSFN)and La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCo F),LCa FN has a high electrical conductivity (297 S cm^(-1)),TEC compatibility(11.2×10^(-6)K^(-1)) and improved chemical stability.Moreover,LCa FN has high oxygen reduction reaction(ORR)activity with a low polarization resistance(0.06Ωcm^(2)) at 800℃.A single-cell NiYSZ/YSZ/gadolinium-doped ceria(GDC)/LCa FN-GDC operated at 800℃ yields a maximum power density of 1.08 W cm^(-2) using H_(2) as fuel.In the solid oxide electrolysis cell(SOEC)mode,the cell can achieve a current density of approximately 1.2 A cm^(-2) at 1.3 V with 70% humidity at 800℃.The cell exhibits good reversibility and remains stable in continuous SOEC and solid oxide fuel cell(SOFC)modes.These findings indicate the potential application of LCa FN as an air electrode material for RSOCs.

Electrochemical performance of La_(2)NiO_(4+δ)-Ce_(0.55)La_(0.45)O_(2−δ)as a promising bifunctional oxygen electrode for reversible solid oxide cells

In this work,La_(2)NiO_(4+δ)-Ce_(0.55)La_(0.45)O_(2−δ)(denoted as LNO-xLDC)with various LDC contents(x=0,10,20,30,and 40 wt%)were prepared and evaluated as bifunctional oxygen electrodes for reversible solid oxide cells(RSOCs).Compared with the pure LNO,the optimum composition of LNO-30LDC exhibited the lowest polarization resistance(Rp)of 0.53 and 0.12Ω·cm^(2)in air at 650 and 750℃,respectively.The enhanced electrochemical performance of LNO-30LDC oxygen electrode was mainly attributed to the extended triple phase boundary and more oxygen ionic transfer channels.The hydrogen electrode supported single cell with LNO-30LDC oxygen electrode displayed peak power densities of 276,401,and 521 mW·cm^(−2)at 700,750,and 800℃,respectively.Moreover,the electrolysis current density of the single cell demonstrated 526.39 mA·cm^(−2) under 1.5 V at 800℃,and the corresponding hydrogen production rate was 220.03 mL·cm^(−2)·h^(−1).The encouraging results indicated that LNO-30LDC was a promising bifunctional oxygen electrode material for RSOCs.

基于可逆固体氧化物电池的电氢耦合微电网全生命周期规划-运营研究

为促进实现“双碳”目标,新能源将成为未来能源供应的主体。考虑到高比例新能源对电力系统容量规划和调度运营带来的巨大挑战以及电氢能源需求量的持续增长对电力系统的影响,以微电网为研究对象,设计基于可逆固体氧化物电池的考虑源荷不确定性的电氢耦合微电网全生命周期规划-运营优化模型及其求解算法。首先,针对风光产电、电氢负荷等多种不确定因素,设计包含微电网全生命周期内各年份不同典型日的数据,以构成随机场景。其次,对电氢耦合微电网容量规划成本、全生命周期调度运营成本以及新能源年均渗透率等多个优化目标进行数学表达,并对各发电机组、可逆固体氧化物电池以及储氢库的规划-运营约束进行线性描述。然后,设计一种改进的增广ε约束算法求解模型的Pareto解集,并提出一种平衡决策方法从解集中获取最佳规划-调度方案。最后,仿真结果表明,所提方法能均衡各优化目标,在保证新能源高渗透率的同时提升电氢耦合微电网的可靠性以及规划-运营经济性。

基于可逆固体氧化物电池的气电双向耦合统一调度优化

传统多能市场模型一般将异质能源转换装置视作市场主体,例如燃气电厂等。能源互联网理念下,异质能源的综合利用要求打破种类壁垒,形成统一能源传输系统。计量的能源形式不统一,能源转换方向单一,限制了能源互联网的应用场景。基于实验数据推导可逆固体氧化物电池(reversal solid oxide cells,r SOC)等效物理模型,提出一种rSOC双向能源传输管道的电力-天然气统一市场模型,并将节点边际价格(locational marginal price,LMP)推广到异质能源的统一能价机制,验证rSOC异质能价双向传递作用。研究表明应用rSOC双向传输管道有助于节省供能成本,提高综合能源市场经济效益和调度效率。所提异质能源市场统一价格理论,以及气电统一市场模型为综合能源联合交易提供理论基础和模型参考。

双向可逆的集中式电氢耦合系统容量优化配置

针对风光富集地区大型新能源发电厂的弃风弃光问题,利用可逆固体氧化物燃料电池(reversible solid oxide fuel cell,RSOC)结合氢储能的双向转换特性消纳多余风光资源,提出一种双向可逆的集中式RSOC电氢耦合系统容量优化配置方法。首先构建集中式RSOC电氢耦合系统架构,建立发电系统、电氢转换系统等模型;其次考虑燃料电池特性建立RSOC性能衰减模型,考虑特高压通道可用传输能力不确定性生成典型场景;进而建立集中式RSOC双层容量规划模型,上层以运营期收益最大为目标优化RSOC、储氢库容量配置,下层以综合成本最低为目标优化各设备出力,联合粒子群算法与Cplex求解器进行求解。最后通过算例分析,验证RSOC的加入提高了系统经济性及环境效益,同时投资灵敏度分析表明电池单位容量成本是制约系统经济运行的重要因素。

可逆固体氧化物电池流场设计及优化的研究进展与展望

氢能作为一种清洁能源,不但具备清洁的利用过程,还能够与间歇性可再生能源有效结合,达到节能减排的重要效果。作为一种能够有效利用和制造氢能的装置,可逆固体氧化物电池(reversible solid oxide cell,RSOC)拥有燃料电池和电解槽两种运行模式,引起了广泛关注。RSOC的流场结构对其性能具有重要影响,具体表现为流道形状、尺寸及气体配置对RSOC内部气体流动特性的影响,均匀的气体分布及优异的扩散过程有利于电池输出性能及稳定性的提升。本综述总结了RSOC平行、蛇形、交指等传统流场与X形、三维网状等新型流场的结构特点及其电池输出特性,并对现有相关流场优化方式的研究进行了详细的分析和讨论,以全面概述该领域的最新进展。结果显示,针对RSOC内部气体流动特性可以通过优化温度、压强、气体流量等运行条件,选择合适的电解质、电极结构参数,阴阳极气流配置,以及设置流道障碍物等方式改进传统流场,促进气体传质与扩散过程;同时设计新型流场结构及多孔介质流场也是改善气体流动状态的一种方式。

开路状态下固体氧化物电解槽制备合成气的模型设计与验证

固体氧化物电解槽(SOEC)可将H_(2)O和CO_(2)通过共电解转化为合成气(H_(2)和CO),从而实现CO_(2)的捕集与利用。然而,除了电化学反应,反应气体在高温下的逆水汽反应(RWGS反应)对该过程也存在一定影响。为了探究RWGS反应在合成气制备中的作用,建立了一种纽扣型SOEC在开路状态下制备合成气的二维模型,研究了开路状态下进气组分和操作温度对SOEC支撑层中RWGS反应的影响。将模型仿真结果与实验数据进行对比验证,确保了模型的可靠性。结果表明,入口气体中还原性气体H_(2)含量(物质的量分数,下同)是影响RWGS反应速率的首要因素,H_(2)含量越高,RWGS反应速率越快。当H_(2)含量为30%时,CO_(2)转化率在29%以上;当H_(2)含量为10%时,CO_(2)转化率仅为9%~10%。此外,在H_(2)含量一定的情况下,RWGS反应速率主要与CO_(2)含量呈正相关,在入口气体中提高CO_(2)或者H_(2)含量,可不同程度提高开路状态下的CO_(2)转化率。更高的操作温度有利于RWGS反应更快进行,且在H_(2)含量一定的情况下,进气组分中CO_(2)含量越高,RWGS反应速率的变化率也越大。

太阳能耦合固体氧化物电池热电氢联产系统技术经济性分析

固体氧化物电池可在燃料电池发电模式和电解制氢模式间切换,且工作温度为650~850℃,具有高品位余热回收利用的潜力,将固体氧化物电池用于热、电、氢联产可大幅提高设备利用率及能量利用效率。提出了光伏、光热驱动的固体氧化物电池热电氢联产系统,并耦合了蓄电池及熔盐蓄热保障系统连续稳定运行。以总成本最低为目标,构建系统容量配置及运行策略优化的混合整数线性规划模型,并基于品位对口、梯级利用的用能原则,采用夹点分析方法优化全系统多品位能流的梯级利用,揭示耦合系统物质和能量高效集成机理。针对某工业园区太阳能资源及热电氢需求实际案例,固体氧化物电池年满负荷运行小时数高于6 000 h,耦合系统平准化用能成本为0.28元/kW。

可逆固体氧化物电池电极材料的研究进展

可逆固体氧化物电池电极材料在应对能源挑战和降低环境污染方面具有重要作用。文章介绍了固体氧化物燃料电池和电解电池的工作原理及它们结合成可逆固体氧化物电池的优点。着重讨论了电极材料选择对电池性能的重大影响,并深入分析了钙钛矿氧化物材料在氧电极氧还原/氧析出反应动力学提升方面的作用。此外,探讨了采用掺杂、离子缺陷引入、合成方法改进以及机器学习等策略来优化电极性能。同时,指出了燃料电极在不同运行模式下面临的挑战,如结构劣化和碳沉积等,为高效、稳定的可逆固体氧化物电池发展提供了新视角和方法。