Degradation of La0.6Sr0.4Co0.2Fe0.8O3–δ–Ce0.8Sm0.2O1.9 Cathodes on Coated and Uncoated Porous Metal Supports

The degradation of composite LSCF‐SDC cathodes on porous 430 stainless steel supports was investigated. Two degradation mechanisms were observed: a multi‐layer oxide scale, believed to consist of Cr₂O₃ and SrCrO₄, formed at the support‐cathode interface, and small amounts of chromium were detected within the cathodes. To reduce degradation, La₂O₃ and Y₂O₃ reactive element oxide coatings were deposited on the internal pore surfaces of the metal supports. The reactive element oxide coatings reduced the amount of volatile chromium that deposited in the cathodes. As a result, the degradation rates of the cathodes on coated supports were significantly lower than the degradation rates of cathodes made on uncoated metal supports. In cathode symmetrical cells, polarization resistance degradation rates as low as 2.56 × 10⁻⁶ Ω cm² h⁻¹ were observed over 100 hours on coated metal supports, compared to an average of 1.23 × 10⁻⁴ Ω cm² h⁻¹ on uncoated supports.     

Evaluation of Using LaNi0.6Fe0.4O3–δ Contact Layer Between La0.6Sr0.4FeO3 Cathode and Crofer22APU Interconnect for Solid Oxide Fuel Cells

Interconnect‐cathode interfacial adhesion is important for the durability of solid oxide fuel cell (SOFC). Thus, the use of a conductive contact layer between interconnect and cathode could reduce the cell area specific resistance (ASR). The use of La_0.6Sr_0.4FeO₃ (LSF) cathode, LaNi_0.6Fe_0.4O_3–δ (LNF) contact layer and Crofer22APU interconnect was proposed as an alternative cathode side. LNF‐LSF powder mixtures were heated at 800 °C for 1,000 h and at 1,050 °C for 2 h and analyzed by X‐Ray power diffraction (XRD). The results indicated a low reactivity between the materials. The degradation occurring between the components of the half‐cell (LSF/LNF/Crofer22APU) was studied. XRD results indicated the formation of secondary phases, mainly: SrCrO₄, A(B, Cr)O₃ (A = La, Sr; B = Ni, Fe) and SrFe₁₂O₁₉. Scanning electron microscopy with energy dispersive X‐Ray spectroscopy (SEM‐EDX) and the X‐Ray photoelectron spectroscopy (XPS) analyzes confirmed the interaction between LSF/LNF and the metallic interconnect due to the Cr vaporization/migration. An increment of the resistance of ∼0.007 Ω cm² in 1,000 h is observed for (LSF/LNF/Crofer22APU) sample. However, the ASR values of the cell without contact coating, (LSF/Crofer22APU), were higher (0.31(1) Ω cm²) than those of the system with LNF coated interconnect (0.054(7) Ω cm²), which makes the proposed materials combination interesting for SOFC.     

Three‐Dimensional Reconstruction and Microstructure Modeling of Porosity‐Graded Cathode Using Focused Ion Beam and Homogenization Techniques

In this study, microstructure of a porosity‐graded lanthanum strontium manganite (LSM) cathode of solid oxide fuel cells (SOFCs) has been characterized using focused ion beam (FIB) and scanning electron microscopy (SEM) combined with image processing. Two‐point correlation functions of the two‐dimensional (2D) images taken along the direction of porosity gradient are used to reconstruct a three‐dimensional (3D) microstructure. The effective elastic modulus of the two‐phase porosity‐graded cathode is predicted using strong contrast (SC) and composite inclusion (CI) homogenization techniques. The effectiveness of the two methods in predicting the effective elastic properties of the porosity‐graded LSM cathode is investigated in comparison with the results obtained from the finite element model (FEM).     

The Effect of Adding Ce1–xSmxO2–x/2 with Different Sm Contents on the Electrochemical Performance of GdBaCo2O5+δ Based Composite Cathode

In this paper, the Ce_1–xSm_xO_2–x/2 (x = 0.025, 0.05, 0.1, 0.2) samples were synthesized and then mixed with GdBaCo₂O_5+δ (GBCO) to form GBCO–Ce_1–xSm_xO_2–x/2 composite cathodes. The electrochemical performance of the composite cathodes was investigated by the electrochemical impedance spectroscopy (EIS) as a function of temperature and oxygen partial pressure. The impedance spectra results demonstrated that the introduction of proper Ce_1–xSm_xO_2–x/2 phase remarkably enhanced the electrochemical performance of GBCO cathode and caused a reduction in the total polarization resistance (Rp). Furthermore, as the amount of Ce_1–xSm_xO_2–x/2 in composite cathode was fixed, the variation of Sm content in Ce_1–xSm_xO_2–x/2 also had a significant influence on the electrochemical performance of the GBCO–Ce_1–xSm_xO_2–x/2 cathodes. For example, the Rp of GBCO cathodes containing 10 wt.% Ce_1–xSm_xO_2–x/2 considerably reduced from 0.37 to 0.17 Ω cm² at 600 °C with the decreasing Sm content x from 0.2 to 0.025. The improvement in performance of the GBCO–Ce_1–xSm_xO_2–x/2 cathodes compared to pure GBCO cathode could be mainly attributed to the catalytic activity of Ce_1–xSm_xO_2–x/2 towards the surface diffusion related processes, which was an elementary step in oxygen reduction reaction at cathode.     

Mn‐Stabilised Microstructure and Performance of Pd‐impregnated YSZ Cathode for Intermediate Temperature Solid Oxide Fuel Cells

The effect of Mn alloying on PdO powder and Pd‐impregnated Pd + YSZ cathode for the O₂ reduction reaction in intermediate temperature solid oxide fuel cells has been studied in detail. The microstructure, thermal stability, electrochemical activity and performance stability of the powder and cathode were analysed using thermal gravimetric analysis, X‐ray diffraction, scanning electron microscopy/energy dispersive spectroscopy and electrochemical impedance spectroscopy. The results indicate that an addition of 5 mol.‐% Mn effectively inhibits the growth and coalescence of Pd and PdO particles at high temperatures and stabilises the microstructure of the powders and the electrode; as a consequence, the electrochemical performance and stability of the cathode are significantly improved. The electrochemical performance of the Pd + YSZ and Pd_0.95Mn_0.05 + YSZ cathodes so prepared is much better than that of the conventional LSM‐based cathodes and is also comparable with the mixed ionic and electronic conducting oxide cathodes such as LSCF.     

Decreasing the Polarization Resistance of BaCo0.7Fe0.2Nb0.1O3–δ Cathodes by Infiltration of Ce0.8Y0.2O2–δ

Ce_0.8Y_0.2O_2–δ (YDC) was infiltrated into a BaCo_0.7Fe_0.2Nb_0.1O_3–δ (BCFN) cathode of intermediate temperature sold oxide full cells (IT‐SOFCs) in order to decrease its cathodic polarization resistance. BCFN and YDC infiltrated BCFN electrodes were fabricated on dense Ce_0.8Gd_0.2O_2–δ (GDC) thin pellets to form symmetrical cells. The electrochemical impedance spectra of the symmetrical cells were investigated in this present study. Firstly, the thickness of BCFN electrodes was optimized, and controlled at 30 µm for further study. The effects of infiltrated YDC amount and firing temperature on electrode polarization resistance were studied. The symmetrical cells infiltrated with 30 μL YDC solution and fired at 900 °C exhibited the lowest electrode polarization resistance in all samples. It was suggested that infiltration of YDC resulted in more active sites and prolonged TPBs in electrodes, improving the surface oxygen exchange, and finally improved the electrode performance.     

Synthesis and Electrochemical Properties of BaFe1−xCuxO3−δ Perovskite Oxide for IT‐SOFC Cathode

A series of iron‐based perovskite oxides BaFe_1−xCu_xO_3−δ (x = 0.10, 0.15, 0.20 and 0.25, abbreviated as BFC‐10, BFC‐15, BFC‐20 and BFC‐25, respectively) as cathode materials have been prepared via a combined EDTA‐citrate complexing sol‐gel method. The effects of Cu contents on the crystal structure, chemical stability, electrical conductivity, thermal expansion coefficient (TEC) and electrochemical properties of BFC‐x materials have been studied. All the BFC‐x samples exhibit the cubic phase with a space group Pm3m (221). The electrical conductivity decreases with increasing Cu content. The maximum electrical conductivity is 60.9 ± 0.9 S cm⁻¹ for BFC‐20 at 600 °C. Substitution of Fe by Cu increases the thermal expansion coefficient. The average TEC increases from 20.6 × 10⁻⁶ K⁻¹ for BFC‐10 to 23.7 × 10⁻⁶ K⁻¹ for BFC‐25 at the temperature range of 30–850 °C. Among the samples, BFC‐20 shows the best electrochemical performance. The area specific resistance (ASR) of BFC‐20 on SDC electrolyte is 0.014 Ω cm² at 800 °C. The single fuel cell with the configguration of BFC‐20/SDC/NiO‐SDC delivers the highest power density of 0.57 W cm⁻² at 800 °C. The favorable electrochemical activities can be attributed to the cubic lattice structure and the high oxygen vacancy concentration caused by Cu doping.     

Synthesis and Characterization of Oxyanion‐Doped Cobalt Containing Perovskites

In this paper, we report the incorporation of borate, silicate and phosphate into La_0.6Sr_0.4Co_0.8Fe_0.2O_3–δ (LSCF) and Sr_0.9Y_0.1CoO_3–δ (SYC) cathode materials for solid oxide fuel cells (SOFCs). In the former, an increase in the electronic conductivity was observed, which can be correlated with electron doping due to the oxyanion doping favoring the introduction of oxide ion vacancies. The highest conductivity was observed for La_0.6Sr_0.4Co_0.76Fe_0.19B_0.05O_3–δ, 1190 S cm^–1 at 700 °C, in comparison with 431 S cm^–1 for undoped La_0.6Sr_0.4Co_0.8Fe_0.2O_3–δ at the same temperature. For Sr_0.9Y_0.1CoO_3–δ series the conductivity suffers a decrease on doping, attributed to any effect of electron doping being outweighed by the effect of partial disruption of the electronic conduction pathways by the oxyanion. Composites of these cathode materials with 50% CGO10 were examined on dense CGO10 pellets and the area‐specific resistances (ASR) in symmetrical cells were determined. The ASR values, at 800 °C, were 0.20, 0.08 and 0.11 Ω cm² for La_0.6Sr_0.4Co_0.8Fe_0.2O_3–δ, La_0.6Sr_0.4Co_0.76Fe_0.19B_0.05O_3–δ and La_0.6Sr_0.4Co_0.78Fe_0.195Si_0.025O_3–δ, respectively. For the SYC materials, the oxyanion‐doped compositions also showed an improvement in the ASR values with respect to the parent compounds, despite the lower electronic conductivity in these cases. This observation may be due to an increase in ionic conductivity due to oxyanion incorporation leading to the formation of oxide ion vacancies. In addition, the stability of these systems towards CO₂ was studied. For La_0.6Sr_0.4Co_0.8(1–x)Fe_0.2(1–x)M_xO_3–δ series, all compositions showed no evidence for reactivity with CO₂ between RT and 1000 °C. On the other hand, for the Sr_0.9Y_0.1Co_1–xM_xO_3–δ series, some reactivity was observed, although the CO₂ stability was shown to be improved on oxyanion doping. Thus, these results show that oxyanion doping can have a beneficial effect on the performance of perovskite cobaltite cathode materials.     

Fabrication and Performance of Solid Oxide Fuel Cells with La0.2Sr0.7TiO3–δ as Anode Support and La2NiO4+δ as Cathode

A novel fabrication process for solid oxide fuel cells (SOFCs) with La_0.2Sr_0.7TiO_3–δ (LST_A–) as anode support and La₂NiO_4+δ (LNO) as cathode material, which avoids complicated impregnation process, is designed and investigated. The LST_A– anode‐supported half cells are reduced at 1,200 °C in hydrogen atmosphere. Subsequently, the LNO cathode is sintered on the YSZ electrolyte at 1,200 °C in nitrogen atmosphere and then annealed in situ at 850 °C in air. The results of XRD analysis and electrical conductivity measurement indicate that the structure and electrochemical characteristics of LNO appear similar before and after the sintering processes of the cathode. By using La_0.6Sr_0.4CoO_3–δ (LSC) as current collector, the cell with LNO cathode sintered in nitrogen atmosphere exhibits the power density at 0.7 V of 235 mW cm⁻² at 800 °C. The ohmic resistance (R_S) and polarization resistance (R_P) are 0.373 and 0.452 Ω cm², respectively. Compared to that of the cell with the LNO cathode sintered in air, the sintering processes of the cell with the LNO cathode sintered in nitrogen atmosphere can result in better electrochemical performance of the cell mainly due to the decrease in R_S. The microstructures of the cells reveal a good adhesion between each layer.     

The Effect of Plasma Spraying Power on La0.58Sr0.4Co0.2Fe0.8O3–δ–La0.8Sr0.2Ga0.8Mg0.2O3–δ Composite Cathode Interlayer Microstructure and Cell Performance

The metal‐supported intermediate temperature solid oxide fuel cells with a porous nickel substrate, a nano‐structured LDC (Ce_0.55La_0.45O_2–δ)–Ni composite anode, an LDC diffusion barrier layer, an LSGM (La_0.8Sr_0.2Ga_0.8Mg_0.2O_3–δ) electrolyte, an LSCF (La_0.58Sr_0.4Co_0.2Fe_0.8O_3–δ)–LSGM composite cathode interlayer and an LSCF cathode current collector are fabricated by atmospheric plasma spraying. Four different plasma spraying powers of 26, 28, 30, and 34 kW are used to fabricate the LSCF–LSGM composite cathode interlayers. Each cell with a prepared LSCF–LSGM composite cathode interlayer has been post‐heat treated at 960 °C for 2 h in air with an applied pressure of 450 g cm^–2. The current‐voltage‐power and AC impedance measurements indicate that the LSCF–LSGM composite cathode interlayer formed at 28 kW plasma spraying power has the best power performance and the smallest polarization resistance at temperatures from 600 to 800 °C. The microstructure of the LSCF–LSGM composite cathode interlayer shows to be less dense and composed of smaller dense regions as the plasma spraying power decreases to 28 kW. The durability test of the cell with an optimized LSCF–LSGM composite cathode interlayer gives a degradation rate of 1.1% kh^–1 at the 0.3 A cm^–2 constant current density and 750 °C test temperature.     

Temperature and Impurity Concentration Effects on Degradation of Nickel/Yttria‐stabilised Zirconia Anode in PH3‐Containing Coal Syngas

Degradation of the Ni/yttria‐stabilised zirconia (YSZ) anode of the solid oxide fuel cell has been evaluated in the coal syngas containing different PH₃ concentrations in the temperature range from 750 to 900 °C. Thermodynamic equilibrium calculations show that PH₃ in the coal syngas gas is converted mostly to P₂O₃ at 750–900 °C. The phosphorous impurity reacts with the Ni‐YSZ anode to form phosphates. The P‐impurity poisoning leads to the deactivation of the Ni catalyst and to the reduction in the electronic conductivity of the anode. The impurity poisoning effect on the anode is exacerbated by increase in the temperature and/or the PH₃ concentration.     

Oxygen Dissociation and Interfacial Transfer Rate on Performance of SOFCs with Metal‐Added (LaSr)(CoFe)O3‐(Ce,Gd)O2 – δ Cathodes

A solid oxide fuel cell (SOFC) unit is constructed with Ni‐Ce_0.9Gd_0.1O_{2 – δ} (GDC) as the anode, yttria‐stabilised zirconia (YSZ) as the electrolyte and Pt, Ag or Cu‐added La_0.58Sr_0.4Co_0.2Fe_0.8O_{3 – δ} (LSCF)–GDC as the cathode. The current–voltage measurements are performed at 800 °C. Cu addition leads to best SOFC performance. LSCF–GDC–Cu is better than LSCF–GDC and much better than GDC as the material of the cathode interlayer. Cu content of 2 wt.‐% leads to best SOFC performance. A cathode functional layer calcined at 800 °C is better than that calcined at higher temperature. Metal addition increases the O₂ dissociation reactivity but results in an interfacial resistance for O transfer. A balance between the rates of O₂ dissociation and interfacial O transfer is needed for best SOFC performance.     

Microstructure and Polarization Studies on Interlayer Free La0.65Sr0.3Co0.2Fe0.8O3–δ Cathodes Fabricated on Yttria Stabilized Zirconia by Solution Precursor Plasma Spraying

Nano‐structured cathodes of La_0.65Sr_0.3Co_0.2Fe_0.8O_3–δ (LSCF) are fabricated by solution precursor plasma spraying (SPPS) on yttria stabilized zirconia (YSZ) electrolytes (LSCF‐SPPS‐YSZ). Phase pure LSCF is obtained at all plasma power. Performances of LSCF‐SPPS‐YSZ cathodes are compared with conventionally prepared LSCF cathodes on YSZ (LSCF‐C‐YSZ) and gadolinium doped ceria (GDC) (LSCF‐C‐GDC) electrolytes. High R_p is observed in the LSCF‐C‐YSZ (∼42 Ohm cm² at 700 °C) followed by LSCF‐C‐GDC (R_p ∼ 1.5 Ohm cm² at 700 °C) cathodes. Performance of the LSCF‐SPPS‐YSZ cathodes (R_p ∼ 0.1 Ohm cm² at 700 °C) is found to be even superior to the performance of LSCF‐C‐GDC cathodes. High performance in LSCF‐SPPS‐YSZ cathodes is attributed to its nano‐structure and absence of any interfacial insulating phase which may be attributed to the low temperature at the interaction point of LSCF and YSZ and low interaction time between LSCF and YSZ during SPPS process. In the time scale of 100 h, no change in the polarization resistances is observed at 750 °C. Based on the literature and from the present studies it can be stated that SOFC with YSZ electrolyte and LSCF‐SPPS‐YSZ cathode can be operated at 750 °C for a longer duration of time and good performance can probably be achieved.     

Effect of Contact between Electrode and Interconnect on Performance of SOFC Stacks

This work investigates the effect of contact between electrodes and alloy interconnects on output performance of solid oxide fuel cell (SOFC) stacks. The measured maximum output power density (p_max) of the unit cell increases from 0.07 to 0.1 W cm^–2 by increasing the tip area of the interconnect from 40 to 60 cm². The p_max increases from 0.07 to 0.15 W cm^–2 upon the addition of nickel foam and Ag mesh on the anode and cathode side, respectively. An additional (La_0.75Sr_0.25)_0.95MO_3–σ cathode current collecting layer is re‐printed on the original cathode current collecting layer, which aims to further improve the performance of the stack and individual cell. The performance of a 3‐cell short stack assembled by the cells with a new cathode current collecting layer is evaluated by measuring the current–voltage curve. The results indicate that the p_max values of the stack and individual cells are enhanced from 0.07 to 0.37 W cm^–2 and 0.15 to 0.5 W cm^–2 at 850 °C, respectively. The performance of the whole stack and individual cells is greatly improved due to the interconnect embedded in the re‐printed new cathode current collecting layer.     

Redox Tolerance of Thin and Thick Ni/YSZ Anodes of Electrolyte‐Supported Single‐Chamber Solid Oxide Fuel Cells under Methane Oxidation Conditions

Redox tolerance of 50 and 500 μm thick Ni/YSZ (yttria‐stabilized zirconia) anodes supported on YSZ electrolytes were studied under single‐chamber solid oxide fuel cell conditions. Open circuit voltage, electrochemical impedance spectra, and discharge curves of the cells were measured under different methane/oxygen ratios at 700 °C. For the cell with the thin anode, a significant degradation accompanying oscillatory behaviors was observed, whereas the cell based on the thick anode was much more stable under the same conditions. In situ local anode resistance (R_s) results indicated that the Ni/NiO redox cycling was responsible for the oscillatory behaviors, and the cell degradation was primarily caused by the Ni reoxidation. Reoxidation of the thick anode took place at a low methane/oxygen ratio, but the anode can be recovered to its original state by switching to a methane‐rich environment. On the contrary, the thin anode was unable to be regenerated after the oxidation. Microstructure damage of the anode was attributed to its irreversible degradation.     

Preparation and Electrochemical Properties of Sr‐doped K2NiF4‐type Cathode Material Pr1.7Sr0.3CuO4 for IT‐SOFCs

A novel K₂NiF₄‐type oxide Pr_1.7Sr_0.3CuO₄ (PSCu) is studied to obtain its electrochemical properties as the cathode for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). The PSCu cathode powder and Ce_0.8Sm_0.2O_1.9 (SDC) electrolyte powder were synthesized by sol‐gel method and glycine‐nitrate method, respectively. The crystal structure of PSCu powder and PSCu‐SDC composite powder were identified with X‐ray diffraction (XRD). It is shown that PSCu belongs to tetragonal K₂NiF₄‐type and has good chemical compatibility with SDC. The thermal expansion coefficient (TEC) of PSCu is close to that of SDC. The conductivity of PSCu tested with four‐probe method exhibits a semiconductor‐pseudometal transformation at 400–450 °C, where the maximum conductivity of 103.6 S cm⁻¹ is obtained. The polarization test indicates the area specific resistance (ASR) of PSCu decreases with increasing temperature, reaching 0.11 Ω cm² at 800 °C. The activation energy of oxygen reduction reaction during 600–800 °C is 1.19 eV. The single fuel cell performance test reveals the open circuit voltage (OCV) and resistivity of PSCu reduce with increasing temperature, but the power density ascends with increasing temperature. The maximal power density is 243 mW cm⁻² at 800 °C, and the corresponding current density and OCV are 633 mA cm⁻² and 0.77 V, respectively.     

Evaluation of a Cu/YSZ and Ni/YSZ Bilayer Anode for the Direct Utilization of Methane in a Solid‐Oxide Fuel Cell

Carbon deposition is an issue when operating solid oxide fuel cells (SOFC) on fuels other than hydrogen, and so a variety of strategies have been used to prevent carbon accumulation on the anodes. In this paper, we describe a bilayer anode that contains a functional layer consisting of Ni/YSZ and a conduction layer consisting of Cu/YSZ. The anode‐supported button cells were fabricated using a uni‐axially pressing technique to produce the anode, followed by impregnation with Cu. The cells were tested at 1,023 K in dry CH₄ and their performance compared to that of a typical Ni/YSZ anode. The Cu does not catalyze the cracking of methane and as such less carbon deposits in the conduction layer resulting in anode stability for over 100 h. The limitation with using Cu in the anode is the temperature of operation.     

Effects of PH3 and CH3Cl Contaminants on the Performance of Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) have been considered as one of the most efficient power generators that can directly convert chemical energy in the natural gas, biomass, or coal‐derived gas to electrical energy. Various contaminants in syngas are capable to cause catalyst malfunction and cell performance drop, limiting fuel cell to a wide application. The effects of PH₃ and CH₃Cl fuel impurities on the electrochemical performance of SOFCs are investigated at various testing conditions. Performance drop caused by the addition of 10 ppm PH₃ remains identical in pure hydrogen and simulated coal‐derived syngas at 750 °C, but a slight increase is observed when the cells are fueled syngas at 850 °C. The presence of CH₃Cl in syngas causes cell degradation to a larger extent at 850 °C. Moreover, the cooperative influences of PH₃ and CH₃Cl impurities in hydrogen are also studied at 750, 800, and 850 °C. The addition of CH₃Cl can stop and remove PH₃ poisoning behavior, which is associated with each contaminant concentrations and operational temperatures. The related mechanism has been deeply analyzed and diagnosed.     

Integration of Spin‐Coated Nanoparticulate‐Based La0.6Sr0.4CoO3–δ Cathodes into Micro‐Solid Oxide Fuel Cell Membranes

Thin cathodes for micro‐solid oxide fuel cells (micro‐SOFCs) are fabricated by spin‐coating a suspension of La_0.6Sr_0.4CoO_3–δ (LSC) nanoparticulates obtained by salt‐assisted spray pyrolysis. The resulting 250 nm thin LSC layers exhibit a three‐dimensional porous microstructure with a grain size of around 45 nm and can be integrated onto free‐standing 3 mol.% yttria‐stabilized‐zirconia (3YSZ) electrolyte membranes with high survival rates. Weakly buckled micro‐SOFC membranes enable a homogeneous distribution of the LSC dispersion on the electrolyte, whereas the steep slopes of strongly buckled membranes do not allow for a perfect LSC coverage. A micro‐SOFC membrane consisting of an LSC cathode on a weakly buckled 3YSZ electrolyte and a sputtered Pt anode has an open‐circuit voltage of 1.05 V and delivers a maximum power density of 12 mW cm^–2 at 500 °C.     

Effect of Ethane and Propane in Simulated Natural Gas on the Operation of Ni–YSZ Anode Supported Solid Oxide Fuel Cells

Solid oxide fuel cells with Ni–yittria‐stabilised zirconia (YSZ) anode supports were tested on surrogate natural gas fuels (methane containing 2.5–10% ethane and 1.25–5% propane) and compared with results for pure methane. Inert anode‐side diffusion barriers were found to help suppress coking on the Ni–YSZ anodes. However, carbonaceous deposits were observed on anode compartment surfaces and the barrier layers for all of the natural gas compositions tested. The addition of air to the natural gas was shown to suppress this coking. For natural gas with 5% ethane and 2.5% propane, the addition of 33% air yielded stable, coke‐free operation at 750 °C and 800 mA cm^–2. Cell performance on this fuel was only slightly worse than for the same cell operated with dry hydrogen.