Alkaline metal doped strontium cobalt ferrite perovskites as cathodes for intermediate-temperature solid oxide fuel cells

Perovskite oxides Sr_0.9K_0.1Fe_xCo_1-xO_3-δ (SKFCx, x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) are investigated as potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) on Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte. The cubic phase of the SKFCx oxides is demonstrated by x-ray diffraction. The SKFCx cathode shows good compatibility with the SDC electrolyte up to 900 °C. Among the investigated compositions, SKFC0.1 displays the highest electrical conductivity of 443–146 S·cm^?1 from 350 °C to 800 °C in flow air. The area specific resistances (ASRs) of the SKFCx (x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) cathodes are 0.047, 0.058, 0.066, 0.101, 0.155 and 0.175 Ω cm² at 650 °C in air on an SDC electrolyte. Among the five tested cathodes, SKFC0.1 exhibits the lowest area specific resistances between 550 °C and 750 °C, when tested on its symmetric cell configuration of cathode|SDC|cathode. The thermally stabilized cubic perovskite structure of the SKFC0.1 powder is demonstrated by high-temperature XRD. The average linear thermal expansion coefficient α_L of SKFC0.1 is 18.9$\times$10^?6 K^?1. A peak power density of 1643 mW·cm^?2 is achieved on SKFC0.1|SDC|Ni-SDC anode supported fuel cell at 650 °C. These features, and excellent electrocatalytic activity and good stability, indicate the potential of alkaline metal doped strontium cobalt ferrite perovskites are promising cathode materials for IT-SOFCs.     

High-performance SOFC based on a novel semiconductor-ionic SrFeO3-δ–Ce0.8Sm0.2O2-δ membrane

The semiconductor-ionic composite membrane has been recently developed for a novel solid oxide fuel cell (SOFC), i.e., the semiconductor-ion membrane fuel cell (SIMFC). In this work, the perovskite-type SrFeO_3-δ (SFO) as semiconductor material was composited with ionic conductor Ce_0.8Sm_0.2O_2-δ (SDC) to form the SFO-SDC composite membrane for SIMFCs. The SFO-SDC SIMFCs using the optimized weight ratio of 3:7 SFO-SDC membrane obtained the best performances, 780 mW cm^?2 at 550 °C, compared to 348 mW cm^?2 obtained from the pure SDC electrolyte fuel cell. Introduction of SFO into SDC can extend the triple phase boundary and provide more active sites for accelerating the fuel cell reactions, thus significantly enhanced the cell power output. Moreover, SFO was employed as the cathode, and a higher power output, 907 mW cm^?2 was achieved, suggesting that SFO cathode is more compatible for the SFO-SDC system in SIMFCs. This work provides an attractive strategy for the development of low temperature SOFCs.     

The electrolyte-layer free fuel cell using a semiconductor-ionic Sr2Fe1.5Mo0.5O6-δ – Ce0.8Sm0.2O2-δ composite functional membrane

Commercial double Perovskite Sr₂Fe_1.5Mo_0.5O_6-δ (SFM), a high performance and redox stable electrode material for solid oxide fuel cell (SOFC), has been used for the electrolyte (layer) -free fuel cell (EFFC) and also as the cathode for the electrolyte based SOFC in a comprehensive study. The EFFC with a homogeneous mixture of Ce_0.8Sm_0.2O_2-δ (SDC) and SFM achieved a higher power density (841 mW cm^?2) at 550 °C, while the SDC electrolyte based SOFC, using the SDC-SFM composite as cathode, just reached 326 mW cm^?2 at the same temperature. The crystal structure and the morphology of the SFM-SDC composite were characterized by X-ray diffraction analysis (XRD), and scanning electron microscope (SEM), respectively. The electrochemical impedance spectroscopy (EIS) results showed that the charge transfer resistance of EFFCs were much lower than that of the electrolyte-based SOFC. To illustrate the operating principle of EFFC, we also conducted the rectification characteristics test, which confirms the existence of a Schottky junction structure to avoid the internal electron short circuiting. This work demonstrated advantages of the semiconductor-ionic SDC-SFM material for advanced EFFCs.     

High conductive (LiNaK)2CO3Ce0.85Sm0.15O2 electrolyte compositions for IT-SOFC applications

Composite electrolytes of lithium, sodium, and potassium carbonate ((LiNaK)₂CO₃), and samarium doped ceria (SDC) have been synthesized and the carbonate content optimized to study conductivity and its performance in intermediate-temperature solid oxide fuel cell (IT-SOFC). Electrolyte compositions of 20, 25, 30, 35, 45 wt% (LiNaK)₂CO₃–SDC are fabricated and the physical and electrochemical characterization is carried out using X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscope, and current–voltage measurements. The ionic conductivity of (LiNaK)₂CO₃–SDC electrolytes increases with increasing carbonate content. The best ionic conductivity is obtained for 45 wt% (LiNaK)₂CO₃–SDC composite electrolyte (0.72 S cm^?1 at 600 °C) followed by the 35 wt% (LiNaK)₂CO₃–SDC composite electrolyte (0.55 S cm^?1 at 600 °C). The symmetrical cell of the 35 wt% (LiNaK)₂CO₃–SDC composite electrolyte with lanthanum strontium cobalt ferrite (LSCF) electrode in air gives an area specific resistance of 0.155 Ω cm² at 500 °C. The maximum power density of the fuel cell using 35 wt% (LiNaK)₂CO₃–SDC composite electrolyte, composite NiO anode and composite LSCF cathode is found to be 801 mW cm^?2 at 550 °C.     

Electrochemical evaluation of double perovskite PrBaCo2-xMnxO5+δ (x = 0, 0.5, 1) as promising cathodes for IT-SOFCs

Mn-substituted double perovskites, PrBaCo_2-xMn_xO_5+δ (x = 0, 0.5, 1), are evaluated as cathode materials for intermediate-temperature solid oxide fuel cells. The effects of Mn substitution content on their structural and electrochemical properties including crystal structure, thermal expansion coefficient, and cathodic interfacial polarization resistance are investigated. The PrBaCo_2-xMn_xO_5+δ samples exhibit structural changes with increasing Mn contents from tetragonal (x = 0) to cubic (x = 0.5 and 1.0) symmetry. The thermal expansion coefficient decreases with the increasing Mn content while the cathodic performance increases with the increment of Mn content from x = 0 to x = 0.5 then decreases with the further increment of Mn content from x = 0.5 to x = 1.0. When using La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.05O₃ with 300 μm thickness as electrolyte and Sr₂Fe_1.4Ni_0.1Mo_0.5O_6-δ as anode, the maximum powder density of the x = 0.5 composite is 0.638 W cm^?2, which is higher than that of the other two samples with x = 0 (0.474 W cm^?2) and x = 1.0 (0.371 W cm^?2) at 800 °C.     

Electrochemical and thermal properties of SmBa0.5Sr0.5Co2O5+δ cathode impregnated with Ce0.8Sm0.2O1.9 nanoparticles for intermediate-temperature solid oxide fuel cells

SmBa_0.5Sr_0.5Co₂O_5+δ (SBSC55) impregnated with nano-sized Ce_0.8Sm_0.2O_1.9 (SDC) powder has been investigated as a candidate cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The cathode chemical compatibility with electrolyte, thermal expansion behavior, and electrochemical performance are investigated. For compatibility, a good chemical compatibility between SBSC55 and SDC electrolyte is still kept at 1100 °C in air. For thermal dilation curve, it could be divided into two regions, one is the low temperature region (100–265 °C); the other is the high temperature region (265–850 °C). In the low temperature region (100–265 °C), a TEC value is about 17.0 × 10^?6 K^?1 and an increase in slope in the higher temperatures region (265–800 °C), in which a TEC value is around 21.1 × 10^?6 K^?1. There is an inflection region ranged from 225 to 330 °C in the curve of d(δL/L)/dT vs. temperature. The peak inflection point located about 265 °C is associated to the initial temperature for the loss of lattice oxygen and the formation of oxygen vacancies. For electrochemical properties, the polarization resistances (R_p) significantly reduced from 4.17 Ω cm² of pure SBSC55 to 1.28 Ω cm² of 0.65 mg cm^?2 of SDC-impregnated SBSC55 at 600 °C. The single cell performance of SBSC55∣SDC∣Ni-SDC loaded with 0.65 mg cm^?2 SDC exhibited the optimum power density of 823 mW cm^?2 at operating temperature of 800 °C. Based on above-mentioned properties, SBSC55 impregnated with an appropriate SDC is a potential cathode for IT-SOFCs.     

Effects of co-doped barium cerate additive on morphology,conductivity and electrochemical properties of samarium doped ceria electrolyte for intermediate temperature solid oxide fuel cells

The composite of samarium doped ceria (Sm_0.2Ce_0.8O_2-δ, SDC) and co-doped barium cerate (BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ, BZCYYb) is prepared by mechanical mixing and investigated as electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). Coexistence of SDC and BZCYYb are observed for composite electrolyte by X-ray diffraction after sintering at 1500 °C for 5 h, while the slight deviation of the diffraction peak indicating the element diffusion between two phases. The scanning electron microscope and electron probe microanalyzer results demonstrate that small BZCYYb grains disperse uniformly around the grains of SDC, limiting the growth of SDC grains and decreasing the average grain size of composite electrolyte. Impedance spectroscopy measurement reveals that the grain boundary resistance can be significantly reduced by about an order of magnitude through adding 15–30 wt. % BZCYYb to SDC. Single cells based on the composite electrolyte are fabricated using nickel cermet (Ni-SDC) anode and perovskite (La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ, LSCF) cathode.Relatively high open circuit voltage (OCV), much lower polarization resistance and encouraging high power density are obtained for cells with composite electrolyte compared to those with single SDC electrolyte. Among all of the samples, single cell based on 15 wt. % BZCYYb-85 wt. % SDC composite electrolyte exhibits the lowest total resistances of 0.641 Ω·cm² and the highest peak power densities of 0.56 W·cm^?2 at 600 °C.     

La0.1SrxCa0.9−xMnO3−δ-Sm0.2Ce0.8O1.9 composite material for novel low temperature solid oxide fuel cells

Lowering the operating temperature of the solid oxide fuel cells (SOFCs) is one of the world R&D tendencies. Exploring novel electrolytes possessing high ionic conductivity at low temperature becomes extremely important with the increasing demands of the energy conversion technologies. In this work, perovskite La_0.1Sr_xCa_0.9?xMnO_3?δ (LSCM) materials were synthesized and composited with the ionic conductor Sm_0.2Ce_0.8O_1.9 (SDC). The LSCM–SDC composite was sandwiched between two nickel foams coated with semiconductor Ni_0.8Co_0.15Al_0.05LiO_2?δ (NCAL) to form the fuel cell device. The strontium content in the LSCM and the ratios of LSCM to SDC in the LSCM-SDC composite have significant effects on the electrical properties and fuel cell performances. The best performance has been achieved from LSCM-SDC composite with a weight ratio of 2:3. The fuel cells showed OCV over 1.0 V and excellent maximum output power density of 800 mW cm^?2 at 550 °C. Device processes and ionic transport processes were also discussed.     

A novel La2NiO4+δ-La3Ni2O7-δ-Ce0.55La0.45O2-δ ternary composite cathode prepared by the co-synthesis method for IT-SOFCs

A novel La₂NiO_4+δ-La₃Ni₂O_7?δ-Ce_0.55La_0.45O_2?δ (L2N1-L3N2-LDC) ternary composite with a weight ratio of 0.3:2.5:2.2 was prepared by a one-step co-synthesis method and employed as cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). X-ray diffraction (XRD) profiles confirmed the successful synthesis of the composite consisted of L2N1, L3N2 and LDC phases, without any other impurity. Compared with the cathode prepared by the physical mixing method, the co-synthesized composite cathode possessed a porous microstructure with the smaller particle size and more uniform distribution of various elements. The ternary composite cathode on Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte revealed improved electrochemical performance, achieving the polarization resistance value of 0.06 Ω cm² at 800° C in stationary air. Electrochemical impedance spectra under various oxygen partial pressures indicated the charge transfer process was the rate limiting step for oxygen reduction reaction. Furthermore, a SDC electrolyte (about 350 μm) supported single cell with L2N1-L3N2-LDC as cathode and Ni-SDC as anode demonstrated a maximum power density of 253 mW cm^?2 at 800° C. These results confirmed that L2N1-L3N2-LDC ternary composite prepared by co-synthesized method is a very promising cathode material for IT-SOFCs.     

Partially reduced Ni0.8Co0.15Al0.05LiO2-δ for low-temperature SOFC cathode

Nowadays, Ni_0.8Co_0.15Al_0.05LiO_2-δ (NCAL) has been increasingly applied into the solid oxide fuel cell (SOFC) field as a promising electrode material. Here, the performances of NCAL cathode were investigated for low-temperature SOFCs (LT-SOFCs) on Ce_0.8Sm_0.2O_2-δ (SDC) electrolyte. After on-line reduction of NCAL for 30 min, the partially reduced NCAL, i.e., NCAL(r), was employed as the new cathode and its performances were also investigated. The area specific resistances of NCAL and NCAL(r) cathodes on SDC electrolyte are 7.076 and 1.214 Ω cm² at 550 °C, respectively. Moreover, NCAL(r) exhibits the activation energy of 0.46 eV for oxygen reduction reaction (ORR), which is much lower than that of NCAL (0.88 eV). The fuel cell consisted of NCAL electrodes and SDC electrolyte shows an open circuit voltage (OCV) of 0.95 V and power output of 436 mW cm^?2 at 550 °C. After cathode on-line optimization, the cell's OCV and power output are significantly increased to 1.01 V and 648 mW cm^?2, which mainly attributed to the accelerated ORR and decreased electrode polarization resistance. These results demonstrate that NCAL(r) is a promising cathode material for LT-SOFCs.     

Novel,cobalt-free,and highly active Sr2Fe1.5Mo0.5−xSnxO6−δ cathode materials for intermediate temperature solid oxide fuel cells

One of the technical hurdles to commercialization of intermediate temperature solid oxide fuel cells (IT-SOFCs) is the requirement of highly efficient cathode materials. Herein, we report the evaluation of Sr₂Fe_1.5Mo_0.5?xSn_xO_6?δ (x = 0, 0.1, 0.3 and 0.5, abbreviated as SFM, SFMS1, SFMS3, and SFS) oxides as cobalt-free cathode materials of IT-SOFCs. XPS analysis demonstrates the presence of variable valences among Fe, Mo and Sn elements, suggesting a small polaron hopping mechanism for electronic conduction. First principle calculations reveal that SFMS3 provides the lowest average formation energy of oxygen vacancy (E_vacO*) among these perovskites. The relatively low area specific resistances are obtained with SFMS3 electrode based on La_0.8Sr_0.2Ga_0.8Mg_0.2O_3?δ electrolytes, indicating its high activity for oxygen reduction reaction. Power density of the single cell using SFMS3 cathode as high as 618 mW cm^?2 at 800 °C is achieved, and operation lasts for 200 h without obvious degradation. The encouraging results promise SFMS3 as an alternative cathode material for IT-SOFCs.     

Electrochemical performance of a solid oxide fuel cell based on Ce0.8Sm0.2O2−δ electrolyte synthesized by a polymer assisted combustion method

A polyvinyl alcohol assisted combustion synthesis method was used to prepare Ce_0.8Sm_0.2O_2−δ (SDC) powders for an intermediate temperature solid oxide fuel cell (IT-SOFC). The XRD results showed that this combustion synthesis route could yield phase-pure SDC powders at a relatively low calcination temperature. A thin SDC electrolyte film with thickness control was produced by a dry pressing method at a lower sintering temperature of 1250 °C. With Sm_0.5Sr_0.5Co₃-SDC as the composite cathode, a single cell based on this thin SDC electrolyte was tested from 550 to 650 °C. The maximum power density of 936 mW cm⁻² was achieved at 650 °C using humidified hydrogen as the fuel and stationary air as the oxidant.     

Rare-earth oxide–Li0.3Ni0.9Cu0.07Sr0.03O2-δ composites for advanced fuel cells

Recent development on electrolyte-free fuel cell (EFFC) holding the same function with the traditional solid oxide fuel cell (SOFC) but with a much simpler structure has drawn increasing attention. Herein, we report a composite of industrial grade rare-earth precursor for agriculture and Li_0.3Ni_0.9Cu_0.07Sr_0.03O_2-δ (RE–LNCS) for EFFCs. Both structural and electrical properties are investigated on the composite. It reveals that the RE–LNCS possesses a comparable ionic and an electronic conductivities, 0.11 S cm^?1 and 0.20 S cm^?1 at 550 °C, respectively. An excellent power output of 1180 mW cm^?2 has been achieved at 550 °C, which is much better than that of the conventional anode/electrolyte/cathode based SOFCs, only around 360 mW cm^?2 by using ionic conducting rare-earth material as the electrolyte. Engineering large size cells with active area of 25 cm² prepared by tape-casting and hot-pressing gave a power output up to 12 W. This work develops a new functional single layer composite material for EFFCs and further explores the device functions.     

An ionic conductor Ce0.8Sm0.2O2−δ (SDC) and semiconductor Sm0.5Sr0.5CoO3 (SSC) composite for high performance electrolyte-free fuel cell

An advanced electrolyte-free fuel cell (EFFC) was developed. In the EFFC, a composite layer made from a mixture of ionic conductor (Ce_0.8Sm_0.2O_2?δ, SDC) and semiconductor (Sm_0.5Sr_0.5CoO₃, SSC) was adopted to replace the electrolyte layer. The crystal structure, morphology and electrical properties of the composite were characterized by X-ray diffraction analysis (XRD), scanning electron microscope (SEM), and electrochemical impedance spectrum (EIS). Various ratios of SDC to SSC in the composite were modulated to achieve balanced ionic and electronic conductivities and good fuel cell performances. Fuel cell with an optimum ratio of 3SDC:2SSC (wt.%) reached the maximum power density of 741 mW cm^?2 at 550 °C. The results have illuminated that the SDC-SCC layer, similar to a conventional cathode, can replace the electrolyte to make the EFFC functions when the ionic and electronic conductivities were balanced.     

Cobalt-free layered perovskite GdBaFe2O5+x as a novel cathode for intermediate temperature solid oxide fuel cells

A cobalt-free layered perovskite oxide, GdBaFe₂O_5+x (GBF), was investigated as a novel cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Area-specific resistance (ASR) of GBF was measured by impedance spectroscopy in a symmetrical cell. The observed ASR was as low as 0.15 Ω cm² at 700 °C and 0.39 Ω cm² at 650 °C, respectively. A laboratory sized Sm_0.2Ce_0.8O_1.9 (SDC)-based tri-layer cell of NiO-SDC/SDC/GBF was tested under intermediate temperature conditions of 550-700 °C with humidified H₂ (∼3% H₂O) as a fuel and the static ambient air as an oxidant. A maximal power density of 861 mW cm⁻² was achieved at 700 °C. The electrode polarization resistance was as low as 0.57, 0.22, 0.13 and 0.08 Ω cm² at 550, 600, 650 and 700 °C, respectively. The experimental results indicate that the layered perovskite GBF is a promising cathode candidate for IT-SOFCs.     

Synthesis and characterization of Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ cathode for intermediate-temperature solid oxide fuel cells

Perovskite Ba_0.5Sr_0.5Co_0.8Fe_0.1Ni_0.1O_3-δ (BSCFNi) oxide is synthesized and characterized as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The X-ray diffraction (XRD) spectra show that BSCFNi is chemical compatible with La_0.9Sr_0.1Ga_0.83Mg_0.17O_2.865(LSGM) electrolyte below 950 °C, but weak reaction is observed between BSCFNi cathode and Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte after calcined at 950 °C for 10 h. The XPS results indicate that transition metal cations in BSCFNi sample exist two different valence states, i.e., Co^4+/3+, Fe^4+/3+ and Ni^3+/2+. The average thermal expansion coefficient (TEC) of BSCFNi is 18.7 × 10^?6 K^?1 between 200 °C and 850 °C in air. The maximum electrical conductivity reaches 35.3 Scm^?1 at 425 °C in air. The polarization resistance of BSCFNi cathode on LSGM and SDC electrolytes are 0.033 and 0.066 Ωcm² at 800 °C, respectively. The maximum power density of LSGM electrolyte-supported single cell with BSCFNi cathode reaches 690 mWcm^?2 at 800 °C. These primarily results indicate that BSCFNi is a candidate cathode material for IT-SOFCs.     

Stability considerations of semiconductor ionic fuel cells from a LNCA (LiNi0.8Co0.15Al0.05O2-δ) and Sm-doped ceria (SDC; Ce0.8Sm0.2O2-δ) composite electrolyte

Recent advances in composite materials, especially semiconductor materials incorporating ionic conductor materials, have led to significant improvements in the performance of low-temperature fuel cells. In this paper, we present a semiconductor LNCA (LiNi_0.8Co_0.15Al_0.05O_2-δ) which is often used as electrode material and ionic Sm-doped ceria (SDC; Ce_0.8Sm_0.2O_2-δ) composite electrolyte, sandwiched between LNCA thin-layer electrodes in a configuration of Ni-LNCA/SDC-LNCA/LNCA-Ni. The incorporation of the semiconductor LNCA into the SDC electrolyte with optimized weight ratios resulted in a significant power improvement, from 345 mW cm^?2 with a pure SDC electrolyte to 995 mW cm^?2 with the ionic-semiconductor SDC-LNCA one where the corresponding ionic conductivity reaches 0.255 S cm^?1 at 550 °C. Interestingly, the coexistence of ionic and electron conduction in the SDC-LNCA membrane displayed not any electronic short-circuiting but enhanced the device power outputs. This study demonstrates a new fuel cell working principle and simplifies technologies of applying functional ionic-semiconductor membranes and symmetrical electrodes to replace conventional electrolyte and electrochemical technologies for a new generation of fuel cells, different from the conventional complex anode, electrolyte, and cathode configuration.     

High performance BaFe1−xBixO3−δ as cobalt-free cathodes for intermediate temperature solid oxide fuel cells

Bi₂O₃ doped BaFeO_3?δ on the B-site as a cobalt free perovskite cathode for intermediate temperature solid oxide fuel cells is evaluated. The BaFe_1?xBi_xO_3?δ (BFBx) powders are synthesized by solid state reaction. It is found that Bi₂O₃ doping stabilizes the BaFeO₃ cubic phase. The new cathode is compatible with Gd_0.1Ce_0.9O_1.95 even calcined at 1000 °C for 10 h. The electronic conductivity shows a transformation from semiconductor to metal conductor, and achieves its maximum value of 28.1 S cm^?1 for BFB10 at 800 °C. The δ is as high as 0.408 for BFB10 determined by iodometric titration. This leads to the free volume in crystal lattice of BFB10 21.60% higher than that of BaNb_0.05Fe_0.95O_3?δ. The area specific resistance is only 0.133 Ω cm² for BFB10 at 750 °C and the average TEC is 26.697 × 10^?6 K^?1 measured from room temperature to 800 °C. The peak power density of Ni-YSZ|YSZ|GDC|BFB10 cell is 646.28 mW cm^?2 at 750 °C, higher than that of single cell using LSCF as cathode. These show that BFBx perovskite oxides with cubic phase are promising cathodes for intermediate temperature solid oxide fuel cells.     

High performance of protonic solid oxide fuel cell with BaCo0.7Fe0.22Sc0.08O3−δ electrode

Solid oxide fuel cells (SOFCs) have attracted tremendous attention for their combination of environmental power generation and fuel flexibility. Proton conducting SOFCs (P-SOFCs) demonstrate advantages over oxygen-ion conducting SOFCs, such as less activation energies on ionic transport and higher fuel utilization efficiency. Central to the devices is a suitable cathode with high catalytic activity. Herein, a cubic perovskite BaCo_0.7Fe_0.22Sc_0.08O_3?δ (BCFSc) has been applied as the cathode in proton-conducting solid state fuel cell (SOFC) with BaZr_0.1Ce_0.7Y_0.2O_3?δ (BZCY) electrolyte. Peak power densities of 760, 591, 452 and 318 mW cm^?2 are obtained at 650, 600, 550 and 500 °C with humidified hydrogen as the fuel and air as the oxidant. A low polarization resistance of 0.05 Ω cm² under open circuit at 650 °C is observed.     

High-performance PrBaCo2O5+δ-Ce0.8Sm0.2O1.9 composite cathodes for intermediate temperature solid oxide fuel cell

PrBaCo₂O_5+δ-Ce_0.8Sm_0.2O_1.9 (PBCO-SDC) composite material are prepared and characterized as cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction result proves that there are no obvious reaction between the PBCO and SDC after calcination at 1100 °C for 3 h. AC impedance spectra based on SDC electrolyte measured at intermediate temperatures shows that the addition of SDC to PBCO improved remarkably the electrochemical performance of a PBCO cathode, and that a PBCO-30SDC cathode exhibits the best electrochemical performance in the PBCO-xSDC system. The total interfacial resistances R_p is the smallest when the content of SDC is 30 wt%, where the value is 0.035 Ω cm² at 750 °C, 0.072 Ω cm² at 700 °C, and 0.148 Ω cm² at 650 °C, much lower than the corresponding interfacial resistance for pure PBCO. The maximum power density of an anode-supported single cell with PBCO-30SDC cathode, Ni-SDC anode, and dense thin SDC/LSGM (La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ)/SDC tri-layer electrolyte are 364, 521 and 741 mW cm⁻² at 700, 750 and 800 °C, respectively.