中温固体氧化物燃料电池铁系阳极催化剂的性能研究

采用水系流延法制备多孔氧化钇稳定氧化锆(Yttria-Stabilized Zirconia,YSZ)流延片与有机流延法制备YSZ电解质薄膜,经叠压共烧后获得多孔YSZ/致密YSZ薄膜复合基体。通过化学浸渍法分别在复合基体多孔YSZ层内浸渍了Fe(NO_3)_3、Co(NO_3)_2和Ni(NO_3)_2溶液来制备浸渍阳极SOFC单电池(以LSM+YSZ为阴极)。初步研究了铁系阳极催化剂的性能,测试了不同阳极SOFC单电池在不同温度下的电性能并采用SEM观察了不同浸渍阳极的形貌。进一步对Co-YSZ和Ni-YSZ阳极单电池的抗积碳性能进行了测试与比较。结果表明:在氢气气氛中钴的催化活性最高,镍次之,铁最差;在乙醇气氛中钴的催化活性仍要好于镍,而且Co-YSZ阳极单电池的抗积碳性要明显优于Ni-YSZ阳极单电池。铁系催化剂中Co的催化性能和抗积炭性能最佳。     

BaO修饰的Ni_(0.5)Cu_(0.5)O_x-YSZ阳极的制备及性能

阳极积碳会导致直接氧化甲烷型固体氧化物燃料电池(SOFCs)的性能衰减,为增加甲烷燃料中电池的稳定性,采用硬模板法与分次浸渍法制备Ba O/Ni_(0.5)Cu_(0.5)O_x包覆柱状YSZ复合阳极材料,制作单电池BaO/Ni_(0.5)Cu_(0.5)O_x-YSZ/YSZ/LSM,并进行电性能与长期稳定性测试。用SEM(扫描电子显微镜)与EDS(能谱议)对实验后的阳极结构与表面成分进行观察与分析。结果表明:在800℃的甲烷环境下,单电池的最大功率密度为323m W/cm~2;运行100h后,电压降只有2.12%。实验后的阳极SEM像表明,阳极呈立体多孔结构,有利于燃料气体与反应废气的扩散;催化金属颗粒均匀包覆着柱状YSZ,扩大了电化学反应区域。EDS能谱分析表明,有少量积碳形成,阳极孔道未被堵塞,证明了阳极结构的稳定。单电池稳定性的增强归功于立体多孔阳极的制备与碱性氧化物BaO的加入。     

恒压电沉积 Pt-Ni 合金催化剂的形貌控制及其对催化剂性能的影响

目的通过对电沉积过程中基体亲水性及电解液温度参数的控制,实现对Pt-Ni催化剂的形貌及催化性能的控制。方法采用恒电压沉积技术制备Pt-Ni合金催化剂。利用5%(质量分数)Nafion对多孔碳布基体表面进行亲水修饰,并控制电解液温度,合成具有不同形貌的Pt-Ni合金催化剂。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、能量色散谱(EDS)、循环伏安(CV)、单电池极化性能等测试技术对制备的催化剂进行物理及电化学表征。结果碳布基体表面经适量的Nafion修饰后,电沉积制备的合金催化剂颗粒细小,分布均匀。当碳布基体表面修饰的Nafion含量达到0.8 mg/cm2时,催化剂单电池极化性能最佳。另外,较高电解液温度下制备得到的球状形貌具有更大的电化学活性表面积(ECSA),更高的催化活性,优于较低温下制备的"雪花"状催化剂的性能。其中,50℃下电沉积制备的Pt-Ni合金催化剂ECSA达到47.6 m2/(g Pt),单电池运行过程中最大功率密度达到77.8 m W/cm2,具有最高的催化活性。结论适量Nafion修饰后的亲水多孔碳布基体上电沉积Pt-Ni合金催化剂性能更加优越。电解液温度的控制对恒电压沉积的Pt-Ni合金表面形貌控制有重要意义。     

不同螯合剂对镍铁催化层的结构与抗积碳性能的影响

通过热分解法制备Ni0.75Fe0.25催化层,研究了不同螯合剂(柠檬酸,乙醇酸和D-葡萄糖酸)对催化层的结构及抗积碳性能的影响。结果表明:热分解法制得的晶相为Fe Ni3相,其结构及尺寸均与螯合剂有关。氧-程序升温氧化和拉曼光谱分析表明含D-葡萄糖酸的催化层具有最佳的抗积碳能力。采用D-葡萄糖酸改性催化层制作的单电池在650℃的甲烷燃料中最大功率达289 m W·cm-2。另外,该电池在甲烷燃料中以600 m A·cm-2的电流密度下运行9 h后电压仍保持初始电压的61%,而未改性的单电池电压相同运行条件下仅余53%。     

AuPd/C作为直接NaBH4-H2O2燃料电池阳极催化剂的性能

采用浸渍还原法制备不同比例的AuPd/C纳米粒子;分别采用X线衍射仪(XRD)和透射电镜(TEM)对催化剂进行结构和形貌分析;利用CHI660a电化学工作站对催化剂进行电化学测试,结果表明:催化剂材料均为面心立方结构,AuPd/C中纳米合金粒子的粒径为5 nm左右,比Au/C中的纳米Au粒子更小,且均匀分散在VXC-72R炭黑的表面;Au/C的峰电流密度为25.05 mA/cm2,与Au/C相比,AuPd/C明显提高NaBH4的电氧化催化活性;以纳米AuPd/C为阳极催化剂、Au/C为阴极催化剂制成直接NaBH4-H2O2燃料电池(DBHFC),发现以Au1Pd2/C为阳极催化剂的DBHFC拥有良好的电池性能;在温度为60℃、NaBH4浓度为1 mol/L时DBHFC的最大功率密度达到114.6 mW/cm2。     

阳极氧化铝模板为基底可控制备碳纳米棒

以不负载任何活性组分的阳极氧化铝模板为基底,采用化学气相沉积法在700℃下催化裂解乙炔可控制备纳米碳材料,反应气氛分别为氩气和氢气;产物通过扫描电镜和高分辨透射电镜进行表征.结果表明:当反应气氛为氩气时,阳极氧化铝模板表面沉积了棒体较直的碳纳米棒,这些碳纳米棒形貌规整,平铺在阳极氧化铝模板表面;当反应气氛为氢气时,碳纳米棒的生长方向变成了规整地直立状态;所制备的碳纳米棒为实心的,结构为断断续续的石墨片层组成的波纹状结构.     

SnS / ZnO 叠层太阳能电池的制备及性能研究

目的获得光电性能较佳的Sn S/Zn O叠层太阳能电池。方法通过磁控溅射法,采用不同的溅射参数在FTO玻璃上制备Sn S和Zn O薄膜,研究Sn S和Zn O薄膜的晶体结构、表面形貌和光学性能,最终获得制备叠层太阳能电池的最佳方案。结果沉积Sn S薄膜的溅射功率、沉积时间、工作气压为28W,40 min,2.5 Pa和36 W,25 min,2.3 Pa时,获得的两种Sn S薄膜均在(111)晶面具有良好的择优取向,晶粒较大,表面致密光滑,禁带宽度分别为1.48,1.83 e V。沉积Zn O薄膜的溅射功率、溅射时间、工作气压为100 W,10 min,2.5 Pa时,Zn O薄膜的结晶性能更优,透过率更大,适合作为太阳能电池的n层。以宽禁带Sn S(1.83 e V)为外p型吸收层,窄禁带宽度Sn S(1.48 e V)为内p型吸收层制备的FTO/n-Zn O/p-Sn S(1.83 e V)/n-Zn O/p-Sn S(1.48 e V)/Al叠层太阳能电池,其光电转化效率为0.108%,短路电流为0.90 m A,开路电压为0.40 V。结论制得的叠层太阳能电池性能较传统单层太阳能电池更优。     

太阳能电池光阳极的制备和光电性能研究

采用旋涂法制备TiO_2基底并摻入不同含量g-C_3N_4制备了g-C_3N_4/TiO_2复合光阳极,研究了不同g-C_3N_4掺杂量的复合光阳极对电池光电性能的影响。结果表明,g-C_3N_4/TiO_2复合光阳极相对于TiO_2光阳极更有利于量子点附着,并提高电池的光电转换效率;随着覆盖尿素含量的增加,g-C_3N_4会更多的沉积在TiO_2薄膜表面,电池的开路电压、短路电流密度、填充因子和光电转换效率均呈现先增加而后减小的趋势,在尿素添加量为15 g时取得最大值(V_(oc)=0.604 V,J_(sc)=16.97 mA/cm~2,FF=0.419,IPCE=4.15%)。     

阳极组分对热喷涂制备SOFC输出特性的影响

针对传统管状与板块结构SOFC的特点,提出了集两种结构设计的优点为一体的金属陶瓷支撑管状结构SOFC,并采用低成本的火焰喷涂与等离子喷涂制备电池各结构层.采用3种不同成分与结构的阳极探讨了阳极结构对电池输出特性的影响,结果表明,阳极结构对电池运行时的极化产生显著影响,采用小颗粒的NiO与YSZ的复合粉末制备的阳极,可以有效增加阳极的三相界面,从而降低阳极极化,显著提高电池的输出功率密度,1000℃时可达到最大值0.57 W/cm2.这些结果为优化电池阳极结构层的设计与制备提供了依据.     

基于纳米活性结构的不互溶W-Cu体系直接合金化及其热力学机制

利用纳米多孔活性结构诱导和促进W和Cu直接合金化，主要包括3步骤：首先，通过两步阳极氧化和还原退火在W表面制备纳米多孔结构；然后，在纳米多孔W上电沉积Cu层；最后，在近Cu熔点温度(980℃)下退火，得到W/Cu层状复合材料/连接件。W/Cu界面的表征结果表明，2种金属间的扩散距离约为27 nm,W和Cu之间成功实现直接合金化。同时，针对此前建立的不互溶金属直接合金化热力学模型存在的问题，改进了表面能和压力能的计算方法，解决了表面原子层数选用导致表面能结果具有随意性的问题和热力学计算中的单位尺度问题，实现了基于纳米活性结构的不互溶W-Cu直接合金化的热力学计算。热力学计算结果表明，W表面纳米多孔化之后W-Cu体系的表面能大幅提升，可以作为W和Cu直接合金化的热力学驱动力。分析认为，除具有高表面能的晶面增多之外，纳米结构形状也是W表面纳米化后表面能提高的主要原因之一。     

Ceramic materials containing rare earth oxides for solid oxide fuel cell

Materials for a solid oxide fuel cell were investigated aiming especially at low temperature operation of the cell. Although yttria-stabilized zirconia has been most popularly investigated as an electrolyte for the cell, the conductivity reaches the allowable level only around or higher than 1000 °C. The use of a ceria-based electrolyte, especially samaria doped ceria, significantly lowered the operation temperature of the cell due to its high oxide ion conductivity. The reduction of ceria with H₂ and resultant electronic conduction could be avoided by the coating of YSZ on to the anode side of the ceria. The ceria layer facing the air electrode is effective in reducing cathodic polarization. Ni-ceria cermet exhibited higher fuel electrode performance than Ni-YSZ cermet in lowering polarization.     

Dip coating technique in fabrication of cone-shaped anode-supported solid oxide fuel cells

A simple and cost-effective dip coating technique was successfully developed to fabricate NiO-YSZ anode substrates for cone-shaped anode-supported solid oxide fuel cells. A single cell, NiO-YSZ/YSZ/LSM-YSZ, was assembled and tested to demonstrate the feasibility of the technique applied. Using humidified hydrogen (75 ml/min) as fuel and ambient air as oxidant, the maximum power density of the cell was 0.78 and 1.0 W/cm² at 800 and 850 °C, respectively. The observed open-circuit voltages (OCV) was closed to the theoretical value and the scanning electron microscope (SEM) results revealed that the microstructures of the anode substrate and the cathode layer are porous and the electrolyte film is dense.     

Microstructure refinement of pulsed laser deposited La0.6Sr0.4CoO3−δ thin-film cathodes for solid oxide fuel cell

In this study, the microstructural modification of pulsed laser deposited La_0.6Sr_0.4CoO_3?δ (LSC64) thin-film cathodes for solid oxide fuel cells (SOFCs) to improve the lateral conduction and to reduce the surface composition degradation is investigated. A high-temperature deposited 100 nm-thick denser LSC64 layer is added over 2.4 μm-thick porous cathode to cover and bridge the cathode domains. According to the cell performance analyses using current-voltage-power measurements, the performance of the cell modified with an additional denser layer is increased compared with the cell without the denser layer in all operating temperature range. The degree of improvement of peak power density is bigger than 10% at 650–550 °C and is about 6% at 500 °C. This performance enhancement can be attributed to the electrochemical property improvement, especially oxygen surface exchange property, rather than to the conduction improvement, based on the electrochemical impedance analysis. Improved crystallinity and composition integrity of the denser LSC64 layer is considered to enhance the surface exchange property of the cathode.     

Electrochemical and microstructural characterization of cyclic redox behaviour of SOFC anodes

The oxidation of Ni to NiO in solid oxide fuel cell (SOFC) anode will result in large bulk volume change, which may change the interfaces of the two phases in the anode cermet and thus may cause significant performance degradation. The reduction and oxidation (redox) of the Ni/YSZ cermet were studied at 800 ℃. Anodic polarization measurements were performed before and after redox cycles. The anode current density at an overpotential of 100 mV kept decreasing during the whole redox treatment. It decreased from 19.11 to 7.95 mA·cm-2 after two redox cycles. Anode supported unit cell was assembled for cell's discharge measurements. Cell performance declined after each redox cycle. The maximum power density decreased from 126.28 to 40.32 mW·cm-2 . The microstructural changes after redox cycling were recorded using scanning electron microscopy (SEM). The results reveal that after re-oxidation, the Ni gets coarse and has a higher porosity; the nickel network structure turns to be desultory.     

Influence of the ratio between Ni and BaCe0.9Y0.1O3−δ on microstructural and electrical properties of proton conducting Ni-BaCe0.9Y0.1O3−δ anodes

Cermet anode substrates Ni-BaCe_0.9Y_0.1O_3−δ (Ni-BCY10) with varied ratios between Ni and BCY10 were prepared. BCY10 powders were prepared by the citrate-nitrate auto-combustion method and anode substrates were prepared by the method of evaporation and decomposition of solutions and suspensions. Sintered anode substrates were reduced and their properties were examined before and after reduction as a function of the ratio between Ni and BCY10. Microstructural properties of the pellets were investigated using X-ray diffraction analysis and field emission scanning electron microscopy. The influence of the Ni:BCY10 ratio on the microstructure of conducting paths through ceramic and metal parts was discussed. Impedance spectroscopy measurements were used for evaluation of electrical properties of the anode pellets. The high conductivity values of reduced anodes confirmed percolation through Ni particles even for an anode with a reduced amount of nickel. Fuel cell tests were carried out in order to examine the influence of the Ni:BCY10 ratio on fuel cell performance and to compare characteristics of cermet anodes with platinum electrodes. The ratio between Ni and BCY10 did have a slight influence on the power output of fuel cells. Fuel cells with a cermet anode demonstrated a higher power output compared to fuel cells with a platinum electrode.     

Compatibility between glass sealants and electrode materials of solid oxide fuel cells

BaO-CaO-Al2O3-SiO2-La2O3-B2O3 system glass materials were investigated as sealants for a solid oxide fuel cell (SOFC).The transition temperature (Tg) and the crystal temperature (Td) values decrease greatly with the increase of BaCO3 content when the other components do not change.For the thermal expansion coefficient (TEC) values,the trend is inverse.The sealant has superior thermal expansion coefficient matching properties with La(Sr)MnO3 (LSM) cathode,La(Sr)FeO3 (LSF) cathode,Ni-LDC (La doped CeO2) anode,and Ni-YSZ (yttria stabilized zirconia) cermet anode.The sealant also has superior stability,compatibility,and good bonding characteristic with these electrode materials at 800-900℃.The results indicate that the aluminosilicate system glass sealant possesses superior compatibility with electrode materials of the solid oxide fuel cell.     

Assembling single cells to create a stack: The case of a 100 W microtubular anode-supported solid oxide fuel cell stack

Microtubular solid oxide fuel cell systems have many desirable characteristics compared with their planar counterparts; however, there are many obstacles and difficulties that must be met to achieve a successful and economically viable manufacturing process and stack design. Anode-supported tubes provide an excellent platform for individual cells. They allow for a thin electrolyte layer, which helps to minimize polarization losses, to be applied to the outside of the tube, thus avoiding the difficulty of coating the inside of an electrolyte or cathode-supported tubes, or the stack design problem of having a fuel chamber if the anode is on the outside of the tube. This article describes the fabrication of a traditional (Ni-YSZ) anode tube via extrusion of a plastic mass through a die of the required dimensions. The anode tubes were dried before firing, and tests were performed on the tubes to determine the effects of prefiring temperature on porosity. The porous tubes had a vacuum applied to the inside while being submerged in aqueous electrolyte slurry. Various parameters were examined, including vacuum pressure, submergence time, and drying conditions, and were studied using microscopy. Cathode coatings (based on both doped lanthanum manganite and doped lanthanum cobaltite) were applied using a brush-painting technique, and were optimized as a function of paint consistency, drying conditions, and firing temperatures. The finished tubes were then stacked in an array to provide the specific current/voltage requirements, using a brazing technique. This article will describe the output characteristics of a single cell and a small stack (of 100 W designed power output). This paper was presented at the ASM Materials Solutions Conference & Show held October 18–21, 2004 in Columbus, OH.     

Progress in Metal-Supported Axial-Injection Plasma Sprayed Solid Oxide Fuel Cells Using Nanostructured NiO-Y0.15Zr0.85O1.925 Dry Powder Anode Feedstock

A composite NiO-Y_0.15Zr_0.85O_1.925 (YSZ) agglomerated feedstock having nanoscale NiO and YSZ primary particles was used to fabricate anodes having sub-micrometer structure. These anodes were incorporated into two different metal-supported SOFC architectures, which differ in the order of electrode deposition. The composition of the composite Ni-YSZ anodes is controllable by selection of the agglomerate size fraction and standoff distance, while the porosity is controllable by selection of agglomerate size fraction and addition of a sacrificial pore-forming material. A bi-layer anode was fabricated having a total porosity of 33% for the diffusion layer and 23% porosity for the functional layer. A power density of 630 mW/cm² was obtained at 750 °C in humidified H₂ with cells having the bi-layer anode deposited on the metal support. Cells having the cathode deposited on the metal support showed poor performance due to a significant number of vertical cracks through the electrolyte, allowing excessive gas cross-over between the anode and the cathode compartments.     

流延法制备的SOFC阳极及其性能

研究了以流延法成型中温平板式固体氧化物燃料电池(IT-SOFC)Ni-YSZ阳极基底金属陶瓷,并成功地制备出厚度为200-500μm的该金属陶瓷基底材料.在其中添加不同种类的成孔剂以增加孔隙率.对以该流延工艺制备的素坯及复合陶瓷的性能进行了研究,其中,素坯膜的热烧结性能通过热重-差示扫描分析进行了研究;复合陶瓷基体材料的孔隙率以阿基米德排水法进行了测试;并以扫描电子显微镜观察了其微观形貌.确定了NiO-YSZ基底材料的预烧及成瓷烧结温度范围.随着烧结温度的升高,孔隙率逐渐下降.其中,有机成孔剂和无机成孔剂在造孔性能方面还存在着某些方面的差异.     

Analysis of macro segregation in twin-roll cast aluminium strips via solidification curves

A porous NiO/yttria-stabilized zirconia (YSZ) anode substrate for zirconia-based tubular solid oxide fuel cells (SOFCs) was prepared by the gelcasting. The effect of the impregnation of SDC in the substrate was studied. Electrochemical impedance spectroscopy and I–V and I–P curves of the cells were measured. Scanning electron microscopy (SEM) was used to observe the microstructures. The results indicate that the performance of the cell can be significantly improved by incorporating the nano-structured SDC particles in the substrate. The peak power density of the cell is increased by about 60% and the area specific resistance (ASR) decreased by about 47% at 700 °C, compared with the unmodified cells. It is explained as the extended triple-phase boundary (TPB) in the anode substrate and the excellent electrocatalytic property of SDC. It is also found that the nano-scale SDC particles change a lot during the reduction of the anode substrate, and the morphology of the resultant SDC particles on the metal Ni is significantly different from that on the YSZ. After the long-term operation, the morphology of the SDC particles on the Ni changes again, but that on the YSZ keeps almost unchanged.