Thermal stability study of SDC/Na2CO3 nanocomposite electrolyte for low-temperature SOFCs

The novel core–shell nanostructured SDC/Na₂CO₃ composite has been demonstrated as a promising electrolyte material for low-temperature SOFCs. However, as a nanostructured material, stability might be doubted under elevated temperature due to their high surface energy. So in order to study the thermal stability of SDC/Na₂CO₃ nanocomposite, XRD, BET, SEM and TGA characterizations were carried on after annealing samples at various temperatures. Crystallite sizes, BET surface areas, and SEM results indicated that the SDC/Na₂CO₃ nanocomposite possesses better thermal stability on nanostructure than pure SDC till 700 °C. TGA analysis verified that Na₂CO₃ phase exists steadily in the SDC/Na₂CO₃ composite. The performance and durability of SOFCs based on SDC/Na₂CO₃ electrolyte were also investigated. The cell delivered a maximum power density of 0.78 W cm⁻² at 550 °C and a steady output of about 0.62 W cm⁻² over 12 h operation. The high performances together with notable thermal stability make the SDC/Na₂CO₃ nanocomposite as a potential electrolyte material for long-term SOFCs that operate at 500–600 °C.     

Preparation and characterization of nanocrystalline Ce0.8Sm0.2O1.9 for low temperature solid oxide fuel cells based on composite electrolyte

Nanocrystalline Ce_0.8Sm_0.2O_1.9 (SDC) has been synthesized by a combined EDTA–citrate complexing sol–gel process for low temperature solid oxide fuel cells (SOFCs) based on composite electrolyte. A range of techniques including X-ray diffraction (XRD), and electron microscopy (SEM and TEM) have been employed to characterize the SDC and the composite electrolyte. The influence of pH values and citric acid-to-metal ions ratios (C/M) on lattice constant, crystallite size and conductivity has been investigated. Composite electrolyte consisting of SDC derived from different synthesis conditions and binary carbonates (Li₂CO₃–Na₂CO₃) has been prepared and conduction mechanism is discussed. Water was observed on both anode and cathode side during the fuel cell operation, indicating the composite electrolyte is co-ionic conductor possessing H⁺ and O²⁻ conduction. The variation of composite electrolyte conductivity and fuel cell power output with different synthesis conditions was in accordance with that of the SDC originated from different precursors, demonstrating O²⁻ conduction is predominant in the conduction process. A maximum power density of 817 mW cm⁻² at 600 °C and 605 mW cm⁻² at 500 °C was achieved for fuel cell based on composite electrolyte.     

Upgrading the performance of La2Mo2O9-based solid oxide fuel cell under single chamber conditions

Various anode-supported solid oxide fuel cells (SOFC), based on 10 mol% Dy-doped La₂Mo₂O₉ (LDM) electrolyte, are prepared analytically and operated under single chamber conditions to explore the connections between electrode and power performance. The cathode of tested SOFCs is compositionally graded with three composites of samarium strontium cobaltite and Gd-doped ceria (GDC) to relax the thermal stress, because of sizable thermal expansion differences above 400 °C. We focus the research attention on varying the anode pore structure and composition to promote the power performance in methane/air mixture at 700 °C. For the one-layer support of GDC+NiO+LDM anode, addition of 10 wt% graphite minimizes its mass transport resistance through creating 8–5 μm long and ∼1 μm wide slit-shaped pores. The graphite pore former raises the peak power value by 80 mW cm⁻². Adopting a more porous and active outer layer, the double-layer support further enhances the cell power. The peak power was first raised by 48 mW cm⁻², using an outer layer that was prepared with 63 wt% NiO. Dosing 3% Pd on this outer layer uplifts another 59 mW cm⁻². In this study, with an improved anode, the peak power value reaches 437 mW cm⁻².     

Thermal stability study of La0.9Sr0.1Ga0.8Mg0.2O2.85–(Li/Na)2CO3 composite electrolytes for low-temperature solid oxide fuel cells

Novel composite materials based on La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 (LSGM) and a binary eutectic carbonates (52 mol% Li₂CO₃:48 mol% Na₂CO₃) are potential electrolytes for low-temperature solid oxide fuel cells (LTSOFCs) operating at 400–600 °C. However, thermal stability of the LSGM–(Li/Na)₂CO₃ composites remains in doubt due to the molten state of the carbonates at elevated temperature. In this paper, XRD, SEM, TGA and EIS were employed for thermal ageing and cycling studies of the LSGM–(Li/Na)₂CO₃ composites. XRD and SEM results showed that ageing induced a slight effect on the structure and morphology of the composites. TGA and EIS results indicated that the composites had a good stability during cycling. The LSGM–20 wt% (Li/Na)₂CO₃ sample showed a relatively stable conductivity (7–9 × 10⁻² S cm⁻¹) during a 650 h measurement under air at 600 °C. Single cell based on the composite electrolytes was reported for the first time, a maximum power density of 617 W cm⁻² and the open circuit voltage (OCV) of 1.01 V were achieved at 600 °C for the composite containing 20 wt% carbonates. The notable thermal stability together with fairly high performance emphasize the promise of LSGM–(Li/Na)₂CO₃ composite electrolytes for long-term LTSOFCs.     

La0.75Sr0.25Cr0.5Mn0.5O3 as hydrogen electrode for solid oxide electrolysis cells

La_0.75Sr_0.25Cr_0.5Mn_0.5O₃ (LSCM) has been applied as hydrogen electrode (cathode) material in solid oxide electrolysis cells operating with different steam concentrations (20, 40, 60 and 80 vol.% absolute humidity (AH)) using 40 sccm H₂ carrier gas at 800, 850 and 900 °C, respectively. Impedance spectra and voltage-current curves were measured as a function of cell electrolysis current density and steam concentration to characterize the cell performance. The cell resistance decreased with the increase in electrolysis current density while increased with the increase in steam concentration under the same electrolysis current density. At 1.6 V applied electrolysis voltage, the maximum consumed current density increased from 431 mA cm⁻² for 20 vol.% AH to 593 mA cm⁻² for 80 vol.% AH at 850 °C. Polarization and impedance spectra experiments revealed that LSCM-YSZ hydrogen electrode played a major role in the electrolysis reaction.     

Effect of CO2 partial pressure on the cathode lithiation in molten carbonate fuel cells

Nickel cathode is transformed to lithiated nickel oxide by oxidation and lithiation during the conditioning process for molten carbonate fuel cells. In the lithiation process, the amount of lithium inserted into nickel oxide depends on the oxygen and CO₂ composition and this affects the performance of nickel cathode. In this paper, CO₂ interruption technique was applied to investigate the effects of CO₂ interruption on the lithiation of nickel oxide. During the CO₂ interruption for 24 h in cathode operating at 20 mA/cm², the carbonate ion in electrolyte was decomposed into oxygen and CO₂. With the additional oxygen on cathode surface, Ni²⁺ is oxidized to Ni³⁺ with formation of cation vacancy in NiO. The lithium content of cathode increased from 3.0 at.% to 17.4 at.% (over-lithiation) and hence LiNiO₂ phase was formed in the cathode. Cathode surface area is increased by a decrease in NiO particle size with the formation of micropores. The morphological change in cathode enhanced its electrochemical performance in the single cell. Cell voltage of the single cell that has been subjected to CO₂ interruption at 120 mA/cm² was enhanced by 300 mV, due primarily to the reduction in the internal resistance from 2.0 to 0.8 Ω cm² and also in the charge transfer resistance from 3.0 to 1.1 Ω cm².     

Y2O3-promoted NiO/SBA-15 catalysts highly active for CO2/CH4 reforming

A series of Y₂O₃-promoted NiO/SBA-15 (9 wt% Ni) catalysts (Ni:Y weight ratio = 9:0, 3:1, 3:2, 1:1) were prepared using a sol–gel method. The fresh as well as the catalysts used in CO₂ reforming of methane were characterized using N₂-physisorption, XRD, FT-IR, XPS, UV, HRTEM, H₂-TPR, O₂-TPD and TG techniques. The results indicate that upon Y₂O₃ promotion, the Ni nanoparticles are highly dispersed on the mesoporous walls of SBA-15 via strong interaction between metal ions and the HO–Si-groups of SBA-15. The catalytic performance of the catalysts were evaluated at 700 °C during CH₄/CO₂ reforming at a gas hourly space velocity of 24 L g_cat⁻¹ h⁻¹(at 25 ^°C and 1 atm) and CH₄/CO₂molar ratio of 1. The presence of Y₂O₃ in NiO/SBA-15 results in enhancement of initial catalytic activity. It was observed that the 9 wt% Y–NiO/SBA-15 catalyst performs the best, exhibiting excellent catalytic activity, superior stability and low carbon deposition in a time on stream of 50 h.     

Preparation and characterization of Sm0.2Ce0.8O1.9/Na2CO3 nanocomposite electrolyte for low-temperature solid oxide fuel cells

Sm_0.2Ce_0.8O_1.9 (SDC)/Na₂CO₃ nanocomposite synthesized by the co-precipitation process has been investigated for the potential electrolyte application in low-temperature solid oxide fuel cells (SOFCs). The conduction mechanism of the SDC/Na₂CO₃ nanocomposite has been studied. The performance of 20 mW cm⁻² at 490 °C for fuel cell using Na₂CO₃ as electrolyte has been obtained and the proton conduction mechanism has been proposed. This communication demonstrates the feasibility of direct utilization of methanol in low-temperature SOFCs with the SDC/Na₂CO₃ nanocomposite electrolyte. A fairly high peak power density of 512 mW cm⁻² at 550 °C for fuel cell fueled by methanol has been achieved. Thermodynamical equilibrium composition for the mixture of steam/methanol has been calculated, and no presence of C is predicted over the entire temperature range. The long-term stability test of open circuit voltage (OCV) indicates the SDC/Na₂CO₃ nanocomposite electrolyte can keep stable and no visual carbon deposition has been observed over the anode surface.     

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.     

Cathode materials for La0.995Ca0.005NbO4 proton ceramic electrolyte

The study presents the chemical and mechanical compatibility of the proton conducting electrolyte La_0.995Ca_0.005NbO₄ (LCNO) with the LSM, LSCM and BSCF cathodes and the electrochemical performance of symmetrical cells based on LCNO. After annealing at high temperature the electrolyte-cathode mixtures in air and wet air, the obtained products were analyzed by X-ray powder diffraction (XRPD). The microstructure of the cathode and electrolyte materials and the interfaces were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The results show that LSCM cathode is chemically and mechanically stable with the LCNO electrolyte although the BSCF cathode reacts with it. Cation diffusion was observed between LSM cathode and LCNO electrolyte after the heat treatment of their mixture at T = 1150 °C. The electrochemical study performed on symmetrical cells revealed that the LSCM cathode presents the lowest value of area specific resistance (ASR) compared to the ones of the LSM and BSCF cathodes: ASR_LSCM = 35 Ω cm²; ASR_LSM = 57 Ω cm²; ASR_BSCF = 416 Ω cm² (in humidified air at 750 °C). Finally, a CER-CER approach was used in order to minimize the polarisation resistance of the LSM cathode by mixing LSM and LCNO in different volumetric ratios. The lowest value of ASR for LSM-based composite cathode was obtained by adding 50 vol.% of LCNO to LSM cathode (ASR_LSM/LCNO = 22 Ω cm² in humidified air at 750 °C).     

Enhancing Ni anode performance via Gd2O3 addition in molten carbonate-type direct carbon fuel cell

Recently, there is a consensus that a limited performance in direct carbon fuel cell (DCFC) using molten carbonate electrolyte is caused by the limited triple phase boundaries (TPB) formation. In order to solve this problem, we added Gd₂O_3, a well-known lanthanide oxide material for the improvement of wettability in the Ni anode. As a result, it was clearly shown that the voltage drop level and charge transfer resistance was decreased, and therefore the peak power density was increased by almost two times that of solely Ni anode to reach up to 106.7 mW/cm² with carbon black and 114.1 mW/cm² with actual coal fuel. The increased wettability led to the improvement of triple phase boundary (TPB) formation and consequently the enhancement of DCFC performance. While the wettability was increased with oxide content in Ni anode, the proportion of Ni at the surface of anode and the electronic conductivity was gradually decreased. With this reason, the peak power density showed the volcano type change with the amount of Gd₂O₃ addition. Finally, it was revealed that the optimum composition for the anode was Ni:Gd₂O₃ = 1:5 in weight ratio.     

Effect of Ce on 5 wt% Ni/ZSM-5 catalysts in the CO2 reforming of CH4 reaction

The aim of this study is to investigate the promotional effect of Ce on Ni/ZSM-5 catalysts in the CO₂ reforming of CH₄ reaction. The evaluation of the catalytic performances of the composite catalysts was conducted in a fixed-bed reactor at atmospheric pressure. The influencing factors, including temperature, Ni and Ce loadings, molar feed ratio of CO₂/CH₄, and time-on-stream (TOS), were investigated. The characteristics of the catalysts were checked with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The reduction and the basic properties of the composite catalysts were elucidated by temperature-programmed reduction by H₂ (H₂-TPR) and temperature-programmed desorption of CO₂ (CO₂-TPD), respectively. The reactivity of deposited carbon was studied by sequential temperature-programmed surface reaction of CH₄ (CH₄-TPSR) and temperature-programmed oxidation using CO₂ and O₂ (CO₂-TPO and O₂-TPO). Results indicate that higher CH₄ conversion, H₂ selectivity, and desired H₂/CO ratio for 5 wt% Ni & 5 wt% Ce/ZSM-5 could be achieved with CO₂/CH₄ feed ratio close to unity over the temperature range of 500–900 °C. Moreover, the addition of Ce could not only promote CH₄ decomposition for H₂ production but also the gasification of deposited carbon with CO₂. The dispersion of Ni particles could be improved with Ce presence as well. A partial reduction of CeO₂ to CeAlO₃ was observed from XPS spectra over 5 wt% Ni & 5 wt% Ce/ZSM-5 after H₂ reduction and 24 h CO₂–CH₄ reforming reaction. Benefiting from the introduction of 5 wt% Ce, the calculated apparent activation energies of CH₄ and CO₂ over the temperature range of 700–900 °C could be reduced by 30% and 40%, respectively.     

Experimental and modeling kinetic study of the CO2 absorption by Li4SiO4

Nowadays, research aims to produce H₂ efficiently through modifying conventional processes by removing CO₂ at high temperature (T ≥ 500 °C). The sorption enhanced reforming (SER) is an example of such a process where CO₂ capture offers significant energy savings (≈23%). Besides, feedstock to this process may include different sources of biofuels. An essential part of this new reaction system is the use of a solid CO₂ absorbent. Among absorbents stands lithium orthosilicate (Li₄SiO₄) for its high absorption capacity and thermal stability. Therefore, the present research aims to study and model the kinetics of CO₂ absorption by Li₄SiO₄ in a temperature range of 550–650 °C. Results were consistent with a first order reaction dependence with respect to CO₂ concentration. Apparent activation energy of the gas–solid reaction (22.5 kcal/mol) is approximately equal the intrinsic activation energy (28.6 kcal/mol), suggesting that the surface reaction resistance determines the overall reaction rate.     

Enhanced hydrogen storage performance of LiAlH4-MgH2-TiF3 composite

The mutual destabilization of LiAlH₄ and MgH₂ in the reactive hydride composite LiAlH₄-MgH₂ is attributed to the formation of intermediate compounds, including Li-Mg and Mg-Al alloys, upon dehydrogenation. TiF₃ was doped into the composite for promoting this interaction and thus enhancing the hydrogen sorption properties. Experimental analysis on the LiAlH₄-MgH₂-TiF₃ composite was performed via temperature-programmed desorption (TPD), differential scanning calorimetry (DSC), isothermal sorption, pressure-composition isotherms (PCI), and powder X-ray diffraction (XRD). For LiAlH₄-MgH₂-TiF₃ composite (mole ratio 1:1:0.05), the dehydrogenation temperature range starts from about 60 °C, which is 100 °C lower than for LiAlH₄-MgH₂. At 300 °C, the LiAlH₄-MgH₂-TiF₃ composite can desorb 2.48 wt% hydrogen in 10 min during its second stage dehydrogenation, corresponding to the decomposition of MgH₂. In contrast, 20 min was required for the LiAlH₄-MgH₂ sample to release so much hydrogen capacity under the same conditions. The hydrogen absorption properties of the LiAlH₄-MgH₂-TiF₃ composite were also improved significantly as compared to the LiAlH₄-MgH₂ composite. A hydrogen absorption capacity of 2.68 wt% under 300 °C and 20 atm H₂ pressure was reached after 5 min in the LiAlH₄-MgH₂-TiF₃ composite, which is larger than that of LiAlH₄-MgH₂ (1.75 wt%). XRD results show that the MgH₂ and LiH were reformed after rehydrogenation.     

Development of LSCF–GDC composite cathodes for low-temperature solid oxide fuel cells with thin film GDC electrolyte

La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) powder was prepared by glycine–nitrate combustion method. The electrochemical properties of porous LSCF cathodes and LSCF–Gd_0.1Ce_0.9O_1.95 (GDC) composite cathodes were evaluated at intermediate/low temperatures of 500–700 °C. The polarization resistance of pure LSCF cathode sintered at 975 °C for 2 h was 1.20 Ω cm² at 600 °C. The good performance of pure LSCF cathode is attributed to its unique microstructure—small grain size, high porosity and large surface area. The addition of GDC to LSCF cathode further reduced the polarization resistance. The lowest polarization resistance of 0.17 Ω cm² was achieved at 600 °C for LSCF–GDC (40:60 wt%) composite cathode. An anode-supported solid oxide fuel cell (SOFC) was prepared using LSCF–GDC (40:60 wt%) composite as cathode, GDC film (49-μm-thick) as electrolyte, and Ni–GDC (65:35 wt%) as anode. The total electrode polarization resistance was 0.27 Ω cm² at 600 °C, which implies that LSCF–GDC (40:60 wt%) composite cathode used in the anode-supported SOFC had a polarization resistance lower than 0.27 Ω cm² at 600 °C. The cell generated good performance with the maximum power density of 562, 422, 257 and 139 mW/cm² at 650, 600, 550 and 500 °C, respectively.     

Hydrogen storage properties of flexible and porous La0.8Mg0.2Ni3.8/PVDF composite

A study on the hydrogen storage properties of flexible and porous La_0.8Mg_0.2Ni_3.8/PVDF (polyvinylidene fluoride) composite was reported. In this composite, PVDF acted as a binder to connect the alloy powders and (NH₄)₂CO₃ as a pore-forming agent to create void space. Increasing PVDF content, the hydrogen absorption kinetics of the composite gradually decreased. Increasing (NH₄)₂CO₃ from 1% to 5%, the capacity firstly increased and then decreased. 0.08–0.13 wt% increased capacity for the composite was observed at 70 °C by comparison with the intrinsic composite (La_0.8Mg_0.2Ni_3.8/1%PVDF). Varying temperature from 0 °C to 100 °C, 0.1–0.15 wt% increased capacity were obtained for the typical porous composite (La_0.8Mg_0.2Ni_3.8/1%PVDF/3%(NH₄)₂CO₃). The PVDF-assisted composite showed the flexible/solidified characteristic in hydriding/dehydriding, which maybe lowed down the oxidation of the alloy powders and preserved the void space. Finally, ∼0.1 wt% increased capacity remained after ten hydriding/dehydriding cycles.     

Effects of salt composition on the electrical properties of samaria-doped ceria/carbonate composite electrolytes for low-temperature SOFCs

Samaria-doped ceria (SDC)/carbonate composite electrolytes were developed for low-temperature solid oxide fuel cells (SOFCs). SDC powders were prepared by oxalate co-precipitation method and used as the matrix phase. Binary alkaline carbonates were selected as the second phase, including (Li–Na)₂CO₃, (Li–K)₂CO₃ and (Na–K)₂CO₃. AC conductivity measurements showed that the conductivities in air atmosphere depended on the salt composition. A sharp conductivity jump appeared at 475 °C and 450 °C for SDC/(Li–Na)₂CO₃ and SDC/(Li–K)₂CO₃, respectively. However, the conductivities of SDC/(Na–K)₂CO₃ increase linearly with temperature. Single cells based on above composite electrolytes were fabricated by dry-pressing and tested in hydrogen/air at 500–600 °C. A maximum power density of 600, 550 and 550 mW cm⁻² at 600 °C was achieved with SDC/(Li–Na)₂CO₃, SDC/(Li–K)₂CO₃ and SDC/(Na–K)₂CO₃ composite electrolyte, respectively, which we attribute to high ionic conductivities of these composite electrolytes in fuel cell atmosphere. We discuss the conduction mechanisms of SDC/carbonate composite electrolytes in different atmospheres according to defect chemistry theory.     

Durable high-performance Sm0.5Sr0.5CoO3–Sm0.2Ce0.8O1.9 core-shell type composite cathodes for low temperature solid oxide fuel cells

Sm_0.5Sr_0.5CoO₃ (SSC)-Sm_0.2Ce_0.8O_1.9 (SDC) core-shell composite cathodes are synthesized via a polymerizable complex method, and the durability of a cell incorporating the cathodes is examined. Nanocrystalline SSC powders have been coated onto the surfaces of SDC cores to enable the formation of a rigid backbone structure, over which the catalyst phase is effectively dispersed. A symmetrical SSC-SDC |SDC| SSC-SDC half-cell exhibits a polarization resistance of 0.098 Ω cm² at 650 °C. The durability and microstructure of the cathode are investigated by electrochemical impedance spectroscopy and thermo-cycle tests at temperatures in the range of 100 °C-650 °C. After 30 cycles, the polarization resistance is found to increase by 9.04 × 10⁻² Ω cm², a 3.56% rise with respect to the initial resistance. Coarsening of the SSC catalyst phase has been prevented with the use of core-shell type powders, as confirmed by a nearly constant low frequency polarization resistance and a microstructural analysis. The performance of a unit cell comprised of the core-shell type cathode exhibits 1.07 W cm⁻² at 600 °C and 0.62 W cm⁻² at 550 °C.     

Thermal cycle stability of Al2O3-based compressive seals for planar intermediate temperature solid oxide fuel cells

Al₂O₃-based compressive seals were fabricated by tape casting with Al₂O₃ and 0-30 wt% aluminum powders, and their sealing effectiveness, thermal cycle stability between 200 and 750 °C and applicability in planar intermediate temperature solid oxide fuel cells were evaluated. The results indicate that increasing the aluminum content from 0 to 30 wt% in the seals decreases the leakage rate and increases the thermal cycle stability under various inlet gas (N₂) pressures of 3.5, 7.0 and 10.5 kPa. Especially, with the seal containing 30 wt% of aluminum (ACS3), the initial leakage rate was below 0.03 sccm cm⁻¹ under an inlet pressure of 10.5 kPa, and the leakage rates during 96 thermal cycles were below 0.04 sccm cm⁻¹ under the same inlet gas pressure. The interfaces in the interconnect/seal/cell assembly with the ACS3 seal retained integrity after 50 thermal cycles, demonstrating the applicability of the Al₂O₃-based compressive seals in the planar intermediate temperature SOFCs.     

Electrochemical performance of a copper-impregnated Ni–Ce0.8Sm0.2O1.9 anode running on methane

Ni–Cu–Ce_0.8Sm_0.2O_1.9 anode-supported single cells were developed for the direct utilization of methane. An yttria-doped zirconia and Ce_0.8Sm_0.2O_1.9 bi-layer electrolyte and a La_0.6Sr_0.4Co_0.2Fe_0.8O_3 − δ cathode layer were fabricated by slurry spin-coating. Cu was added to the anode by impregnation with a nitrate solution. The effects of Cu on the electrochemical performance of the anode were investigated in dry methane with respect to times of impregnation. Impregnation with Cu twice was determined to be optimal. Incorporating Cu into the anode improved electrochemical performance of the cells, reducing ohmic resistance and suppressing carbon deposition. At 700 °C, the single cell exhibited a maximum power density of 406 mW/cm² in dry methane. At a current density of 500 mA/cm², the cell maintained 98.6% of its initial voltage after operation for 900 min.